(tsp), granular ammonium sulphate and ammonium nitrate are known to have a high water ..... treated with 5 ml of phosphate reagent (27.7 g sodium molybdate and 1 g ammonium ..... ACS Sustainable Chemistry & Engineering · June.
BINDURA UNIVERSITY OF SCIENCE EDUCATION FACULTY OF SCIENCE CHEMISTRY DEPARTMENT
TWO DIMENSIONAL LAYERED NANOMATERIAL: A POTENTIAL CONTROLLED RELEASE FERTILIZER BY SHADRECK MTAMBO B1438746 SUPERVISOR: DR C MACHINGAUTA DISSERTATION SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE BACHELOR OF SCIENCE HONOURS DEGREE (HBSc CHT) IN CHEMICAL TECHNOLOGY.
JUNE 2018
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APPROVAL FORM The undersigned certify that they have supervised, read and recommend to the Bindura University of Science Education for acceptance of a research project entitled:
TWO DIMENSIONAL LAYERED NANOMATERIAL: A POTENTIAL CONTROLLED RELEASE FERTILIZER
Submitted By SHADRECK M TAMBO
In partial fulfilment of the requirements for the BACHELOR OF SCIENCE HONOURS DEGREE IN CHEM ICAL TECHNOLOGY
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DEDICATION
I would like to dedicate my project to my beloved lovely wife Dzidzai and our two jewels Jerry Anashe and M ukudzeiishe.
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ACKNOWLEDGEMENTS
Firstly, l thank Almighty God for His guidance and completion of the research project successfully. I express my profound gratitude to Dr. M achingauta for his endless and wise guidance during the course of this study who despite of his busy schedule was able to find some time for me and imparted the researcher the knowledge that paved a way for better understanding of the research and organizing analysis of the samples at external institutions. I duly acknowledge the help, direct or indirect of M r. T Chihota my Superior at work and Laboratory M anager of FSG Superfert Bindura Plant for his unwavering support. I extend my gratitude to the University laboratory staff in Chemistry department for their support and sharpening our research skills.
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ABS TRACT HDS are two dimensional layered anionic clays or hydrotalcite-like nanomaterials having diversified applications in catalysis, electrochemistry, separation technology and medicine because of their layered structure and high anion exchange capacity. These nanomaterials are abbreviated by formulae: [M 2+ –M 3+–X] where the M 2+ and M 3+ are cations and X - is an anion. The net positive charge, which is due to substitution of trivalent by divalent metal ions in the brucite-like layers M (OH)2, is stabilized by an equivalent negative charge of the interlayer solvated anions. These weakly bound anions on the layers are exchangeable by other anionic species resulting in vital variants in the interlayer space. The study aimed at synthesis of a layered nanomaterial and testing for controlled release. The ZnHNP was prepared by exchange of nitrate by orthophosphate ions in ZnHN synthesized by coprecipitation technique using zinc nitrate and zinc oxide. Both the precursors and the phosphate-exchanged phases were characterized by Fourier transformation infrared spectroscopy (IR) and slow release both nitrates and phosphates monitored by UV-vis spectroscopy. The anionic exchange showed that carbonate ions displaced both nitrates and phosphates in the ZnHNP. The nanosheets exhibited slow release properties hence a potential slow release fertilizer. This research applies nanotechnologies in use of slow/controlled release (SR/CR) fertilizers to the improvement of nutrient supply management while minimizing environmental, ecological and health hazards in agriculture as the whole nanosheets specie is fully degradable
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ABBREVIATIONS AND ACRONYMS
ICP
Inductive Coupled Plasma spectroscopy
FT-IR
Fourier Transform Infrared spectroscopy
HDS
Hydroxyl Double Salt
LDH
Layered Double Hydroxides
LDS
Layered Double Salts
SR/CR
Slow / Controlled release
UV
Ultra Violet
UV-Vis
Ultra Violet-Visible spectroscopy
XANES
X Ray Near Edge Spectroscopy
XRD
X-Ray Diffraction
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TABLE OF CONTENTS Contents APPROVAL FORM...................................................................................................................... 2 DEDICATION ................................................................................................................................. 3 ACKNOWLEDGEMENTS ................................................................................................................. 4 ABSTRACT .................................................................................................................................... 5 ABBREVIATIONS AND ACRONYMS.................................................................................................. 6 TABLE OF CONTENTS .................................................................................................................... 7 LIST OF TABLES ............................................................................................................................. 9 LIST OF FIGURES ..................................................................................................................... 10 Figure 4.2 ............................................................................................................................... 10 1.1 Introduction...................................................................................................................... 11 1.2 Background....................................................................................................................... 12 1.3 Problem statement............................................................................................................ 13 1.4 Aim:.................................................................................................................................. 13 1.5 Objectives:........................................................................................................................ 13 CHAPTER 2: LITERATURE REVIEW................................................................................................. 14 2.1 Introduction...................................................................................................................... 14 2.2 Anion Exchange Capacity of HDS materials.......................................................................... 15 2.3 Methods for HDS synthesis ................................................................................................ 16 2.4 Structure of HDS................................................................................................................ 18 2.5 Applications of HDS ........................................................................................................... 19 2.6 Mechanism of Slow Release ............................................................................................... 20 2.7 Modifications to Slow Release............................................................................................ 20 2.8 Characterization Techniques .............................................................................................. 21 2.8.1 Fourier Transform Infrared spectroscopy (FT-IR) ........................................................... 21 2.8.2 Ultraviolet Visible spectroscopy (UV-Vis) ...................................................................... 21 2.8.3 Scanning Electron Microscopy (SEM) ............................................................................ 22 2.8.5 Transmission Electron Microscopy (TEM)...................................................................... 22 2.8.7 Powder X-ray Powder Diffraction (PXRD) ...................................................................... 22 CHAPTER 3: METHODOLOGY ............................................................................................ 23 3.1 Chemicals ........................................................................................................................ 23 3.2 Preparation ZnHN and ZnHNP....................................................................................... 23 3.4 Characterization of prepared ZnHN AND ZnHNP ......................................................... 23 7
3.5 Slow release of phosphate and nitrates ions ..................................................................... 24 3.6 Preparation of nitrate standards and method of used. ..................................................... 24 3.7 Preparation of phosphate standards and method used. ................................................... 24 CHAPTER 4: RESULTS .......................................................................................................... 25 4.1 FT-IR Results ..................................................................................................................... 25 4.2 UV Vis spectroscopy results for the desorption of the HDS (ZnHNP) .............................. 26 CHAPTER 5: DISCUSSION .................................................................................................... 27 5.3 Conclusion ....................................................................................................................... 29 5.4 Recommendations ........................................................................................................... 30
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LIST OF TABLES Table 4.1: Concentrations of P and N measured by UV-vis
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LIS T OF FIGURES Figure 3.1: Calibration curve of nitrates Figure 4.1: FT-IR results for synthesized ZnHN Figure 4.2: FT-IR results for phosphate intercalated ZnHNP Figure 4.3: Slow release of nitrates and phosphates
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1.1 Introduction M ost studies have suggested phosphate containing layered double hydroxide (LDH) is applicable as a slow release phosphate fertilizer (Hadis et al., 2018) but no mentioning of nitrates and phosphates in one HDS. HDSs have been synthesized using the co-precipitation method and also the urea hydrolysis method Hadis (et al., 2018). The most common method for LDH preparation is co-precipitation method because it is easier, cheap and less time consuming. The layered double hydroxides (LDH) family of nanomaterials are essential composites with the general formula of [M 2+ 1–xM 3+ x (OH)2]x+ [An–]x/n·mH2O where M 2+ and M 3+ are di- and trivalent metals, and A n– is an anion. Altered LDH, hydroxide double salts (HDS) with a general formula of [M 2+ 1-xM 2+2x(OH)2]2x+ [An–]2x/n·mH2O comprise two divalent cations. HDS salts containing same cations are branded basic salts (Ivanov et al.; 2017).HDS have been study of interests as potential long-term foliar fertilizers especially the most promising Zinc hydroxide nitrate (Zn5(OH)8(NO 3)2·2H 2O). The literature states: Zn5(OH)8(NO 3)2·2H2O, Zn5(OH)8(NO 3)2, Zn3(OH)4(NO 3)2 and Zn(OH)(NO 3)2·H2O as the known forms of zinc hydroxide nitrate with the last listed not having layered structure (M achingauta, 2013).
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1.2 Background Slow release mechanisms of HDSs release phosphates and nitrates in response to specific signals (carbonate from dissolved carbon dioxide from respiration of roots) from the plant roots, which we term controlled release. This is triggered by rhizosphere conditions as well plant strategies to overcome phosphorus deficiencies, such as acidification, excretion of organic anions, and a higher carbonate concentration around the respiring roots. Release from HDSs may be spatiotemporally controlled (M aarten et al): phosphates and nitrates release is not only slow, as is the case for common slow release fertilisers, but it may also be localized near the plant roots. Against this background, this study was set up to develop a synthesis and exchange protocol for HDS with both nitrates and phosphates and test its fertilizer value. A diversity of layered inorganic/organic blend compounds with nanodimensional interlayer spacing containing exchangeable anions have been synthesized and applied in catalysis, water purification, ion exchange, fire retardancy, and controlled release of anions. The layered double hydroxides (LDHs) and basic metal hydroxides have been the substance of interest in several studies (M achingauta, 2013).LDHs, with a generic formula of [M 2+ (1 – x) M 3+ x(OH)2] x + Ax- zH2O, consist of positively charged metal hydroxide layers containing divalent and trivalent metal ions and inorganic or organic anions, A - that serve to balance the charge as well as control the interlayer spacing. LDHs can be considered complementary to cationic, or smectite, clays, and the ability to exchange intercalated ions has been a key factor in optimizing these materials for different applications. Similarly, anion exchange reactions have been utilized with basic metal hydroxides such as intercalated zinc hydroxide, Zn (OH) 2 X, where X is an intercalated anion. Hydroxyl double salts, HDSs, are another more recently emerging class of compounds that hold similar promise for development as new nanostructured materials for a wide range of applications. HDSs are similar to LDHs except that the metal hydroxide layer contains two divalent metals. The identity of the metal ions controls the details of the intralayer structure. The exchangeable anion can either be monovalent, for example, Cl-, NO 3-, or CH3COO -, or divalent, such as SO 42- or CO 32-. Different synthetic routes for obtaining HDSs have been reported, and there have been several studies that characterize anion-exchanged materials. Although there has been some work reported on the synthesis and characterization of HDSs, no studies to date have focused on the kinetics and mechanism of the anionic exchange reactions and much progress on agricultural application on herbicides and fertilizer.
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However, in the case of LDHs and other related lamellar materials, time-resolved energydispersive X-ray diffraction, (EDXRD) and XANES has been utilized to obtain in situ kinetic data on the evolution of the solid-phase structures during intercalation and/or anion exchange reactions. 1.3 Problem statement Phosphorus and nitrogen are essential plant nutrient s ess ential for leaf and roots , fruits development res pectively. Nitrogen is taken up from the soil by crops' root structures as NH 4+ and NO 3- chiefly through mass transfer (Krzysztof et al.; 2007).They are available and only present at very low concentrations in the s oil solution due to strong leaching, sorption or precipitation of the phosphates and nitrates anions. T here is a need to develop fertilis ers with better p hosp hate and nitrogen efficiency us e, which prevents was ting through leaching, sorption, precipitation and runoff water. In acid weathered soils, s trong and largely irreversible phosphorus fixation (formation of insoluble phos phates) on (oxy) hydroxides of Iron and Aluminum occurs, whereas in calcareous s oils phosphates reacts with calcium and iron cations to form poorly soluble precipitates. Current commercial p hosphate and nitrogenous fertilisers s uch as diammonium hydrogen phos phate (DAP) triple s uperphosphate (tsp ), granular ammonium sulphate and ammonium nitrate are known to have a high water solubility. In phosphorus and nitrogen deficient weathered or calcareous soils, the phosphate and nitrate anions readily react after amendment and, as a result, their use efficiency and residual values are low. A slow releas e of phos phates and nitrates from the HDS fertilizer may overcome this issue by gradually s upplying nutrients in the rhizosp here, thereby limiting fixation into soil. 1.4 Aim: Prep aration of HDS controlled release fertilizer with nitrate and phos phate exchanged anions . 1.5 Objectives: (i) To p repare zinc hy droxyl nitrate. (ii) To incorp orate phosphate in the HDS. (iii) To tes t its s low release capacity of the HDS fertilizer.
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CHAPTER 2: LITERATURE REVIEW 2.1 Introduction Two-dimensional (2D) nanosheets material have recently received much focus and interest owing to their distinctive physical and chemical properties. Superb intercalation properties of 2D layered material bid a new platform for emerging hybrid materials called nanocomposite. This class of nanomaterials have wide applications in industries and the environment such as anion-exchanger, catalysis, delamination, medical science and more (Luiz et al.; 2016). Layered double hydroxides (LDHs) and hydroxyl double salts (HDSs) have been broadly explored and are renowned for their anion-exchangeable properties (Kandare, 2005). LDHs consist of brucite-type layers of mixed metal hydroxide with formula [M +21-x M +3x(OH)2](A−n)x/n·yH 2O where M +2and M +3 are the divalent and trivalent metal cations, respectively. A n− is the exchangeable anion and y denotes the water content of the interlayer section. HDSs are identical to LDHs but differ in metal hydroxide inorganic layers of the earlier which are composed of two divalent metal cations (M ajoni 2011). Layered hydroxide salts (LHS) for example zinc layered hydroxide (ZLH) are analogous to the HDS structure which is related to that of brucite. The LHS the inorganic layers consist of only one kind of metal cation such as M g2+ , Cu2+ , Zn2+ and Ni2+ formulized M +2(OH)2−x(A−n)x/n·yH2O with OH − anions on the brucite hydroxide layer substituted by water molecules and counter anions (M ohd et al .;2012) The layered structure of HDSs is expandable, if the visitant anion is larger in size than the interlayer anion existing in the LDHs, or the three-dimensional positioning of the visitant permits the enlargement. Different visitant anions can be intercalated into the HDS’s layered structure, thus a variety of hybrid layered nanomaterials can be synthesized (M ohd et al.; 2012). Zinc Layered Hydroxides (ZHL) participate in anion-exchange reaction, by replacing anionic organic molecules for the interchangeable interlayer anions in the lattice forming layered hybrid nanosheets. The use of ZLH as matrices in controlled release (CR) formulations, has rarely been studied. M ultiple studies already reported the uptake of P from synthetic solutions by HDSs (M ajoni, 2011). However, the stability of the HDS-structures during phosphate exchange is uncertain and not reported. No reports were found on the kinetics of concurrent release off both phosphates and nitrates from HDS. In this study zinc HDS was synthetized by the method of coprecipitation and tested for controlled release of nitrates and phosphates.
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2.2 Anion Exchange Capacity of HDS materials Kandare (2005) described anionic exchange reactions are generally as topotactic solid state methods of modifying existing layered materials while maintaining their overall structural integrity. Ion exchange reactions that take place within the d-spacing of layered metal hydroxides are said to be topotactic Kandare (2005), since the overall structural integrity of the materials will be maintained even after the exchanges have taken place. Several factors including structural morphology, intrinsic and extrinsic defects, lattice vacancies, lines and planes of deformation, interstitials, and grain boundaries play an important role in the reactivity of these materials (M ajoni, 2011). In addition to following the evolution of the solid structure, there have been a few reports where similar exchange reactions have been examined from the perspective of determining the temporal profiles of anion release into solution mentioned by Kandare (2005). Characterizing anion release rates is a critical aspect in the design of nanostructured materials for applications such as the controlled release of drugs (Kandare 2005).By analogy to LDH compounds, some key factors in HDS anion exchange reactivity are expected to be reactant structural parameters (metal ion identity and intralayer structure), crystallite size and structural disorder, and the identity/structure of the replacement anion (Kandare, 2009). The goal of this study is to determine nitrate and phosphate controlled release from the HDSs and characterization . Anion exchange in hydroxyl double salts (HDSs) depends on the arrangement of the intercalated anions, and there is a robust link between thermodynamics and kinetics of their discharge reactions. Several factors affect the rates of release include interactions between the metal hydroxide layers and the anions, anion-anion interactions intralayer and in the exchange medium, and solvent-anion interaction (M ajoni et al.; 2014). T hese factors are expected to have a multifarious effect on the reaction rates since they affect each isomer differently. The complex interaction of the aforementioned factors habitually make it tough to come up with a simple relationship amid the rate of release and the aforesaid factors (M ajoni et al.; 2014). It is essential realize that these factors are anticipated to be governed by the types and positions of chemical groups on the anion. The existence of hydrogen bonding inside the interlayer space decreases the Gibbs free energy of formation of the hybrid nanomaterials hence stabilizes the system (M ajoni et al.; 2014). The release rate of ions thus depends on the variances in the energy of nanomaterial and the barriers to reaction.
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M achingauta (2009) mentioned topotactic incorporation of divalent cations. It has been shown that when zinc hydroxyl nitrate, Zn5(OH)8(NO 3)2, is added to metal chloride solutions such as M Cl2 (M 2+ =Co2+, Ni2+ or Zn2+ ), a compound with general formula (Zn, M )5(OH)8Cl2 is formed. This reaction shows that HDSs can also replace cations located in their main hydroxide layers, a process called “diadochy”. This phenomenon has also been described for LDHs such as M g6Al(OH)6+ [NO 3.2H 2O] - and [M g6Al2(OH)16]2+ [CO 3.4H2O]2- (M achingauta, 2009). In these LDHs a solution of Cu, Ni, Co and Zn in the presence of NaCl was able to replace M g2+ from the hydroxide layers. A diadochy reaction is also selective; attempts to incorporated M n2+ (from M nCl2) resulted only in anion exchange. This highly selective uptake of cations allows for these materials to be applied in soil or water treatment (M achingauta, 2009). 2.3 Methods for HDS synthesis HDS occur naturally but can also be synthesized at low cost and by environmentally clean chemistry (green chemistry). For the synthesis several factors must be considered, e.g., the degree of cation substitution of M 2+ by M 3+, cation and interlayer anion nature, synthesis pH, and, in some cases, atmosphere control. M oreover, for more crystalline materials, the following factors must be controlled: solutions concentration, the rate of addition of one solution over the other, stirring degree, final pH of the resulting suspension (for variable-pH methods), pH during the addition (for constant-pH method), and temperature of the final solution, that is usually carried out at room temperature. Luiz, (et al., 2005) discussed the following methods of synthesis; a) Coprecipitation The coprecipitation method has three routes that is increasing pH, decreasing pH, and constant pH. The first one is called as titration method which involves simultaneous precipitation (coprecipitation) with alkaline solution containing the anion to be intercalated added on a solution with cations. Trivalent cations have a tendency to precipitate at lower pH than bivalent ones hence crystalline LDH would be scarcely obtained by this method. The experimental technique of coprecipitation at decreasing pH involves adding a solution with the cation onto a solution with the alkaline solution and the anion to be intercalated and has shown to give good results. LDH preparation by coprecipitation at constant pH is the most extensively used method of synthesis to obtain pleasing results, obtaining LDH with good structural arrangement and phase pureness (Nalawade et al., 2009).
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b) Salt-oxide M ethod In this method bivalent metal oxide suspension is reacted with a trivalent metallic cation solution and the anion to be intercalated maintaining pH considerably acidic to hydrolyze the divalent cation oxide slowly. It is required that the divalent cation oxide undergoes slow hydrolysis and the anion to be intercalated must form a soluble salt with the trivalent cation stable in acidic media. (Luiz et al., 2005). c) Hydrothermal Synthesis M ethod The method utilize suspension of oxides or hydroxides of M 2+ and M 3+ cations or both. The suspension is injected into a solution with acid or salt. The reaction takes place at high pressure and temperature. The main advantage of this method, when compared with other coprecipitation ones, is its avoidance of detrimental waste discard, which may be harmful to the environment containing nitrates, chlorides and hydroxyl anions (M ajoni, 2011 and Luiz et al., 2005). d) Induced Hydrolysis Method It involves precipitation of M 3+ cation hydroxide at pH slightly below that in which M 2+ cation hydroxide precipitation befalls. The aqueous suspension of M 3+ is added into the M 2+ one Luiz (et al., 2015) keeping pH at a fixed value by concurrent addition of sodium hydroxide solution. e) Sol-Gel M ethod The reaction take place in an alcohol solution of magnesium ethoxide dissolved in HCl with a solution comprising Al tri-sec-butoxide. The blend is heated to reflux and agitated until gel materialization. The material prepared through this technique has controlled pore size and highly precise surface area. The sol-gel method has been used in the HDS synthesis as it has a great advantage of producing materials with higher pureness (M ajoni, 2011). The HDS produced by direct methods are the forerunner materials for indirect synthesis techniques. The high kinesis that some anions present when inserted within the interlayer enables new nanomaterial synthesis by substitution reactions (Kandare, 2005). This replacement can be achieved in several ways and involves the capability of the host anions to steady the lamellar structure. The steadying ability of some anions in HDS layers follows the order: M onovalent anions: OH − > F− > Cl− > Br− > NO −3> I− Bivalent anions: CO 32-> C10H4N2O8S2- > SO 42- (Luiz et al., 2005).
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a) Ion Exchange in Solution M ethod The process involves of adding a LDH precursor containing interlayer anions typically chlorides or nitrates in a concentrated solution with the anion of attention. The exchange competence differs a lot, the exchanged anion should have the highest ability to stabilize the lamella (more probable to be intercalated) or be in a higher quantity than the LDH precursor anion or both. b) Ion Exchange in Acidic M edium M ethod In this method, the LDH precursor must have an interlayer anion capable of undergoing acid attack. LDH precursor suspension is mixed with weak acid solution whose conjugate base is preferred to be intercalated. The reaction is based on balance dislodgment because the precursor anion is protonated and “exists” the interlayer space, which is now occupied by the conjugate base of the acid retaining the system electro neutrality (Luiz et al.; 2015). c) Regeneration This technique is based on “memory effect” of some layered materials. The HDS with carbonate anion is usually used as precursor, due to its behavior during calcination. Calcination must be executed at appropriate temperature to breakdown partly the hydroxyls from lamellae and transform interlamellar anion into volatile which produce double oxyhydroxide explained Luiz (et al.; 2015). After calcination a solution comprising the targeted anion is added, regenerating the HDS by hydrolysis and the new intercalated anion. The pH raised during the regeneration process must be corrected to avoid hydroxyl from occupying the interlayer space (M ohd et al.; 2012). 2.4 S tructure of HDS Structure of LDH is steadied by electrostatic attraction and hydrogen bonding between the layered hydroxyl groups and interlayer anions. The structure of hydroxyl double salts can generally be represented as [(M 2+ 1-xMe2+ 1+x) (OH)3 (1-y)/n]An- 1+3y)/n.mH2O where M 2+ and M e2+ represent different divalent metal ions. In layered hydroxyl salts, which are closely related to HDSs, M 2+ = M e2+ (thus they contain a single type of divalent metal ion). The differences in the ionic radii of the divalent M e 2+ and M 2+ metal ions in the brucite-like metal hydroxide layers of HDSs should be within 0.05 Å. The structure formed and the relative composition of the ions in the metal hydroxide layers depends on the preparation technique and the character of the metal ions.
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HDSs and LHSs can be classified broadly into two structural types based on the structure of either zinc hydroxyl nitrate (ZHN) with the formula Zn5(OH)8(NO3)2.2H2O or copper hydroxyl nitrate (CHN) with the formula Cu 2(OH)3NO3 (Kandare, 2005). 2.5 Applications of HDS (i)
Water treatment
CrO4 was removed from dirtied water by Ca3.8Al2 (OH)11.6Cl2(H2O) 5. The adsorption throughout the synthesis was used for removal of Zn 2+/CrO 42− from waste water. Cement, containing Al2O3, was mixed with Ca(OH) 2 to provide Ca/Al and then used to treat the mixture of Zn2+ /CrO 42− . The subsequent product was a Zn/Al-CrO 4 HDS. Li-Al-HDS was produced through the co-precipitation and homogeneous precipitation techniques (Luiz et al.; 2015) and used to eliminate fluoride from water. Li-Al-LDH demonstrated high fluoride adsorption capability.
(ii)
Anticorrosion agent
Intercalation of the benzoate anion (a corrosion protection agent) into the Zn/Al-LDH boosted its anti-corrosion ability of HDS nanomaterials, significantly decreasing corrosion rate in Q235 carbon. P-aminobenzoate (pAB) was intercalated into M g2Al-CO 3-LDH to produce M g2Al-pAB, which significantly decreases corrosion in virtual concrete by reducing the free chloride concentration in simulated concrete mix via anionic exchange between free chloride and pAB anions in the M g2Al-pAB structure (M ohd et al.;2012). The layered zinc hydroxide with sulphate as the pawn anion showed elevated protective capability for corrosion resistance of steel and iron substrates. The zinc hydroxide sulphate layer is produced by exposing galvanic Zn and Zn-M n alloys to a freely aired solution of aqueous sodium sulphate (Luiz et al.; 2015).
(iii)
Catalysis
Thiamine pyrophosphate-Mg/Al and Thiamine pyrophosphate-Zn/Al-LDH nanocomposites are used as heterogeneous catalysts for decarboxylation of pyruvic acid and boosts catalytic activity of thiamine pyrophosphate (TPP) due to the incorporation of thiamine pyrophosphate into the interlayer gallery of LDH.
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M g/Al-LDH synthesized at Mg/Al ratio (R) of 2 demonstrated higher catalytic efficiency in the transformation of fatty acid methyl esters to monoethanolamides in comparison to M g/Al synthesized at R of 3 prepared by the same technique (M ohd et al.; 2012 and Luiz et al.; 2015). Zinc hydroxide nitrate was intercalated with anionic iron porphyrin and the resulting nanocomposite showed significant catalytic activity for the oxidation of cyclohexane to tertbutyl alcohol. (iv)
Flame retardants
Incorporation of acrylonitrile-butadiene-styrene (ABS) resin into M g/Al and ZnM g/Al-LDHs leads to significant improvement in smoke suppression and reduction in flammability rate. Intercalation of flame retardants, namely ammonium polyphosphate, pentaerythritol, or melamine cyanurate M ohd (et al.; 2012)into Zn/Al-LDH enhanced the fire retardant property of polylactic acid (PLA) and the PLA-FR-Zn/Al-LDH nanocomposite showed higher flame retardant efficiency. Low-density polyethylene (LDPE) has been intercalated into M g/AlLDH, which improved flame retardant property of LDPE. (v)
Sensors and electrodes
M g/Al-LDH intercalated with cobalt-ethylenediaminetetraacetate (Co(II)-EDTA) complex was used as a chemical/biological sensor for H 2O2 detection and showed great selectivity for H2O 2.Hemin-Fe/Ni-LDH nanocomposite-modified electrodes could accomplish the role of the natural enzyme, peroxidase, and could also be used in H 2O2 detection (Luiz et al.; 2015). 2.6 Mechanism of S low Release Calcareous soils and acid weathered soils have a low P fertilization efficiency due to fast and irreversible P precipitation/sorption. Slow and controlled released P fertilizer may supply P to plants and circumvent the soil fixation reactions HPO 42- can be released in response to plant signals (CO 32- from respiration, organic anions). (M aarten et al.; 2014) 2.7 Modifications to S low Release The synthesized HDS had both nitrate and phosphate ions. The study tested controlled release of both nitrates and phosphates unlike other studies which only focused on phosphate. The slow release was done with hydrogencarbonate which mimic the real soils. (Everaert, al., 2014; M aarten, al., 2016).
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2.8 Characterization Techniques This section gives a brief outline of the analytical techniques that are required for the characterization of the nanoparticles synthesized in this study. 2.8.1 Fourier Transform Infrared spectroscopy (FT-IR) The Fourier transform infrared spectroscopy is one of the most popular spectroscopic techniques that have been successfully used by chemists to identify organic and inorganic compounds. In this study the Perkin Elmer System 2000 Fourier transform infrared (FTIR) was used to determine the newly formed functional groups in HDS. Fourier transform infrared (FTIR) spectroscopy is based on the absorption, by covalent bonds in molecules, of electromagnetic radiation in the infrared region of the electromagnetic spectrum. In attenuated total reflectance -Fourier transform infrared (ATR-FTIR) spectroscopy, an ATR accessory with a highly refractive prism is used as a sampling tool. In ATR sampling, the IR beam is totally reflected from the internal surface of the prism at the prism-sample interface if the incident beam angle is larger than the critical angle for internal reflection. (M ajoni, 2009) The internal reflectance creates an evanescent wave that extends beyond the surface of the crystal into the sample, which is in intimate contact with the crystal, leading to some of the energy of the evanescent wave being absorbed by the sample. In regions of the infrared spectrum where the sample absorbs energy, the evanescent wave will be attenuated (Kaouther et al.; 2017). 2.8.2 Ultraviolet Visible spectroscopy (UV-Vis) The UV-Vis is a great tool for quantitative analysis. It is based on the correlation between the degree of absorption and the concentration of the absorbing material. Concentrations of species in samples, mainly solutions, are often measured using UV/Vis absorption spectrometry or fluorescence spectrometry. The light’s wavelength that a compound will absorb from the light emitting source mentioned by Kandare (2005) is characteristic of its chemical structure. Absorption of ultraviolet radiation and visible radiation is associated with the excitation of electrons, in both molecules and atoms to higher energy states. Kandare (2005) explained that total amount of light (I) transmitted through a solution of an absorbing chemical in a clear solvent can be related to its concentration by Beer-Lambert law:
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Once the Beer-Lambert law is followed, a plot of absorbance against concentration will give straight line, the gradient of which is the molar absorptivity (Farahnaz et al.; 2014) 2.8.3 S canning Electron Microscopy (S EM) HDS size and shape vary with the preparation technique and chemical structure of the materials. Scanning Electron M icroscopy (SEM ) examines and verify HDS morphological properties. HDS materials have low electrical conductivity to generate good images hence silver or carbon coating is applied on the samples before imaging. Observation of lamellar crystals formation and superposition of the layers on SEM is used to determine the particle size and morphology (Yunbo et al.; 2015). 2.8.5 Transmission Electron Microscopy (TEM) TEM has been used to examine HDS morphology. HDS are crystalline and their interlayer distances are determined through the TEM images. Lamellae distance measured by TEM complements PXPD (X-ray powder diffraction) measurements (Salleh et al.; 2017) 2.8.7 Powder X-ray Powder Diffraction (PXRD) M aterial crystallinity and baseline distances (the d-spacing between planes in a crystal lattice) are measured Powder X-ray diffraction (PXRD). X-ray diffraction pattern show 00l baseline peaks related to the lamellae stacking sequence. Non-baseline peaks, considered nonharmonic, are related to lamellae structure. Powder X-ray diffraction (PXRD) is one of the primary tools of chemical analysis and it’s a rapid analytical technique primarily used for phase identification of crystalline or amorphous materials. PXRD is the widely used instrument for elucidating crystal structures and atomic spacing. This method is relies on constructive interference of monochromatic radiation and a crystalline sample. Diffraction takes place when X-rays are scattered by a periodic array with long-range ordering, producing constructive interference at specific angles. Electrons in an atom coherently scatter the X-rays; the strength with which an atom scatters the X-rays is proportional to the number of electrons around the atom (M achingauta, 2013). X-rays constructively interfere when conditions satisfy the Bragg’s Law (nλ=2dsinθ), where λ is the wavelength of incident X-rays, θ is the angle between the incident ray and the scattering planes, while d is the d-spacing between the planes in the lattice. Conversion of diffraction peaks to d-spacing allows for the identification of diverse minerals since every mineral has a set of distinctive d-spacing. The experimental technique relies on three main components; the X-ray tube, sample holder, and X-ray detector (M achingauta, 2013 and M ajoni 2011).
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CHAPTER 3: METHODOLOGY 3.1 Chemicals Chemicals used for different experiments in this research were of analytical grade. Sodium molybdate (99%), ammonium metavanadate (99%), nitric acid (70%), hydrochloric acid (37%) sodium hydrogencarbonate (99.8%), zinc nitrate (99.5%), zinc oxide (99.8), potassium nitrate (99%) and disodium hydrogen orthophosphate (99.5) were purchased from ACE Associated Chemical Enterprises of South Africa. In all experiments deionized water was used. 3.2 Preparation ZnHN and ZnHNP 18.94 g Zn(NO3)2.6H2O was dissolved in 100 ml de-ionized water and then added 8.1 g ZnO into the mixture. The white solution was placed on shaker for 10 minutes and left for 24 hours at room temperature. The white precipitate ZnHN was filtered, washed with deionized water and dried for 24 hours at room temperature (M achingauta, 2009). 10 g of ZnHN was placed on shaker for 12 hours in a beaker containing 100 ml of 10 mM Na2HPO 4, at 120 rpm, filtered and dried in oven at 70 degrees. (Legrouri et al.; 1999) 3.3 Instruments A drying oven was used to dry samples before surface analysis on FT -IR. A Thermo Fisher M IR iS5 FT-IR spectrophotometer was used to record spectra of to find functional groups within the HDS compounds. Finally the concentration of the slow release for phosphates and nitrates in solution was analyzed according to the calibration method using UV-Vis spectrophotometer (Genesys 10S). 3.4 Characterization of prepared ZnHN AND ZnHNP Functional group elucidation was done using Thermo Fisher M IR iS5 FT -IR spectrophotometer. The layered structure of the synthesized HDSs was characterized using FTIR.
23
3.5 S low release of phosphate and nitrates ions M ethod was adopted from experiments by M aarten (et al., 2016) and Everaert (et al., 2014) was slightly modified. The release of phosphates and nitrates was determined in a zero sink system at pH=8.3 in 2 mM NaHCO 3. These conditions mimic those in the rhizosphere of a calcareous soil: a total dissolved hydrogencarbonate concentration around 2 mM and a constant withdrawal of phosphates and nitrates from soil solution by plant roots (M aarten et al., 2016). The 0.1 g ZnHNP mixed in 50 ml of 2 mM NaHCO 3 solution in a beaker was placed on shaker for 15 minutes and process repeated for 30, 60, 320 and 720 minutes, measuring the desorption of both nitrates and phosphates with UV-Vis (Koilraj.; et al 2013). 3.6 Preparation of nitrate standards and method of used. The nitrate is absorbed at 220 nm. This follows Beer’s law with linear behavior in solution. Dissolved organic hydroxyl and carbonate ions may also absorb at 220 nm, one must be able to distinguish between the absorbance of nitrate. The acidification with 1 M HCI reduces the interferents, hydroxyl ions forms water on reacting with acid p roton and carbonate relinquishes carbon dioxide. This is accomplished by making a measurement of the sample’s absorbance at 220 and 275 nm. The blank and standard solutions of 2 ppm, 4 ppm, and 6 ppm were prepared using KNO 3. The calibration curve was established. 3.7 Preparation of phosphate standards and method used. Standards of phosphate were prepared using 0.1917 g KH 2PO 4 into 1 L distilled water to form 1000 ppm. Dilution was done to obtain 1, 2, 3 and 5 ppm in 50 ml volumetric flasks. The UV-VIS was calibrated with standards and analysis was done at 418 nm wavelength and concentrations of phosphates was read on blank and samples (0.1 g of synthesized HDS fertilizer shaken in beaker containing 100 ml of 2 mM sodium hydrogen carbonate solution) treated with 5 ml of phosphate reagent (27.7 g sodium molybdate and 1 g ammonium metavanadate dissolved in 100 ml distilled water and top up with 417 ml nitric acid).
24
CHAPTER 4: RES ULTS 4.1 FT-IR Results
80
641.55
1370.32
85
ZnHN
90
3476.13
95
75
%T
70 65 60 55 50 45 40 35 400 0
350 0
300 0
250 0
200 0
150 0
100 0
500
W av enu mber s ( c m- 1)
%T
75
634.14641.55
80
1006.07 943.99
ZnHN
85
ZnHNO3PO4
90
3477.36 3476.13
95
1370.321370.27
1636.27
Figure 4.1: FT-IR results for synthesized ZnHN
70
65
60
55
50
45
400 0
350 0
300 0
250 0
200 0
W av enu mber s ( c m- 1)
Figure 4.2: FT-IR results for phosphate intercalated ZnHNP 25
150 0
100 0
500
4.2 UV Vis spectroscopy results for the desorption of the HDS (ZnHNP) Table 4.1: Concentrations of P and N measured by UV-vis
Slow release of P and N 0.005
0.0045 0.004 0.0035
0.003 0.0025 0.002
0.0015 0.001
0.0005 0 0
100
200
300
400 Conc P
Conc N
Figure 4.3: Slow release of nitrates and phosphates
26
500
600
700
800
CHAPTER 5: DIS CUSSION 5.1 FTIR Results IR spectra confirmed the formation of zinc hydroxide nitrate in the precursor material. The peak at 643.55cm-1 was in noble agreement with previous stated works by Assadawoot (et al.; 2013) the IR peaks 676 cm−1 allotted to hydrogen bonding frequencies related to Zn-O H. Peak at 1370.32 cm-1was confirmed by the Assadawoot (et al.; 2013) listing 1340 cm−1 ascribing it to the vibration modes of NO3- ions. The 1340 cm−1 peak also endorsed asymmetric stretching mode of NO 3- indicating the presence of NO3- between zinc hydroxide layers. ZnHN peak at 3476.13 cm-1 was within range stated by Assadawoot (et al.; 2013) mentioning 3543 cm−1 and 3433 cm−1 indicating more than one type of hydroxyl groups in the structure to a bunch of double flower. The IR spectrum of the starting material ZnHN prepared at pH 7 look a lot like those exhibited by all hydrotalcite-like phases. Characteristic large band at 3440 cm-1 was similar to the obtained 3476 cm-1 which correspond to the valence vibration of hydroxyl groups. The well-defined and very intense band located at approximately 1380 cm near to obtained result of 1370.27cm-1 can be attributed to the nitrate vibration (Legrouri et al.; 1999). The band and the shoulder located around 665 cm-1 similar to the obtained peak at 641.55 cm-1 accredited to the º4 vibrations of nitrate groups mentioned by Legrouri (et al.; 1999). Adjustments were detected on the IR spectra of the exchanged HDS phases, the presence of characteristic bands of the orthophosphate around 1050, 870 and 550 cm-1 in line with obtained 1006.07, 943.90 and 634.14 cm-1 corresponding to º3(PO4 3-), º1(PO4 3-) and º4(PO4 3-
) vibrations and broadening as well dissymmetry of the band characteristic of hydroxyl
groups. This is clarified by the formation of hydrogen bonding between the phosphate groups and water or hydroxyl groups (Legrouri et al.; 1999). The intensity of the band situated at 943 cm-1 increased, which are attributed to the PO 3 - valence vibrations These latter observations are in good agreement with the fact that when the pH increases, the concentration of the phosphate ion PO4 3- in the solution increases at the expense of the hydrogen phosphate ions (HPO4 2- and H 2PO4 -) (Legrouri et al.; 1999). M aarten (eat al.; 2016) stated the absorption band at 1037–1043 cm−1 similar to obtained results at 1006.07cm-1 revealing that phosphate was adsorbed by inner and outer-sphere surface complex mechanisms. The exchange of phosphate with OH – groups was probably another mechanism in phosphate uptake by studied HDS. Incomplete phosphate intercalation in the HDS was expected to have fertilizer with both nitrates and phosphates. 27
There are two regions of interest on ZnHN; 1300-1500 cm-1 and 2900-3600 cm-1. By first focusing on the region 1300 – 1500 cm-1, it can be seen that the nitrates in these groups exhibit two different binding interactions. For the non-reactive compounds, two bands of comparable intensity are observed, which is consistent with bound nitrates (which bind by two oxygen atoms, the negatively charged bind electrostatically and the other bind weakly through hydrogen bonding), while the single intense peak at about 1370.32 cm -1, is consistent with free or unbound nitrates. Free nitrates are known to have a D3h point group symmetry, while bound nitrates can either be in a C2v or Cs symmetry. It is however difficult, to separate structures exhibiting C2v symmetry from those showing Cs symmetry using vibrational spectroscopy since the symmetry of the nitrate differs very little between the two. X-ray crystallography can be applied to successfully differentiate between the two (M achingauta, 2013). The slow release of nitrates anions shows that they are grafted into the hydroxide layers and that ZnHNP contain both bound and unbound nitrates, but mostly the unbound nitrates. The region 2900-3600 cm-1 has information about CH and OH stretches and reveals the nature of binding interactions of hydroxyl groups at 3476.13cm-1. The broad peaks indicate that the hydroxyl groups are experiencing intense hydrogen bonding, while sharp peaks show that some of the hydroxyl groups are free. 5.2 UV Vis results on slow release The electrolyte concentration in this experiment was similar to ionic strength of soil solutions as the sodium hydrogen carbonate mimicking soil solutions mentioned by M aarten (et al.; 2016). The synthesized HDS can be utilized as slow release nitrate-phosphate fertilizer. The low amount of phosphate and nitrate desorption from synthesized HDS were observed compared to conventional fertilizers, Ammonium Nitrate (AN) and M ono Ammonium Phosphate (M AP) particles which dissolves within 10 minutes (M aarten et al.; 2014). This may have implications for use as a slow release phosphate fertilizer. The synthesized HDS contain Zn element, further research on their application in zinc deficient calcareous soils is recommended. The slow release of nitrates and phosphate ions shows that they are grafted into the hydroxide layers and that ZnHNP possesses both bound and unbound nitrates, but mostly the unbound nitrates. From results, it was observed that NO -3 in the solution, at low or high concentrations, did not affect phosphate desorption. M ost studies in the literature mention usage of HDS as matrices for slow release of nutrients or agrochemicals in terms of its physical-chemical properties with no major studies of its agricultural applications. 28
The chemical characterization of HDS is highly evolved, with the use of a wide range of analytical techniques. However, the agronomic studies of these nanohybrids do not present the same level of complexity to support agricultural applications. The development of innovative agronomic techniques compatible with studying the chemistry of nanomaterials is crucial to application of nanotechnology in agriculture. The current interface of chemistry and agronomy is still in its infantry. The chemistry of HDSs has a large space in current studies to develop new fertilizers based on the demands of plants and soils and increasing crop yields. The study also aimed to decrease this gap and improve synergism between chemists and soil scientists. Zinc hydroxide nitrate suspension is a promising feedstock for the production of foliar fertilizer. The CRFs release their nutrients slowly and gradually during the whole farming period and need to be applied once which significantly reduces both time and energy consumption. M ore efficient use of nutrients leads to a reduction of waste material produced by the fertilizers industry and natural gas consumption. It is also pointed out that using the CRFs increases the crops' yield. The CRFs are the fertilizers which gradually release their mineral nutrients, while at the same time providing proper nutrition to plants. HDS fertilizers form distinct category of the CRFs systems in which there is no physical barrier in the form of a polymer material, and in which the release rate decisive factor is either solubility or degradability of a given fertilizer. 5.3 Conclusion The release of P and N by the HDS is clearly slower confirming that it can act as a slow release compound. Despite the incomplete P release, the observed slow release is encouraging, and suggests that P-N HDS may have potential as slow release fertilisers. The results obtained in this study attests that the synthesized HDS has potential use as slow release fertilizer since the whole salt is degrade to molecules and elements useful to plants in solution. Zinc oxide can degrade in water as it is soluble and zinc ions will be available to plants as well on top of nitrates and phosphates.
29
5.4 Recommendations Since researches on HDS potential application in agriculture and fertilizer nanotechnology are very few, the researcher would recommend studies based on I.
Finding the effectiveness of HDS fertilizer in pot scale of soils so as to check it on the effectiveness over the season of crops compared to conventional fertilizers.
II.
To test for controlled release with citrate anions and compare with traditional fertilizer and HDS without citrate ions and kinetics studies using Avrame model determine the rate and see whether it prevents leaching of nutrients.
III.
To effect of ageing on the HDS as it has not been studied in detail; for example, effect of carbon dioxide and pH changes with time to help in storage of the fertilizer and modifications to counter effect of high carbonate concentration if it negatively affect in the rhizosphere.
IV.
To load potassium on the HDS using memory effect of ions so that an NPK fertilizer can be developed.
V.
Granulating and coating the HDS fertilizer so that it can easily be applied and further enhance controlled release with coating polymer.
VI.
Analysis of the HDS using ICP-M S, XRD, TEM and XANES to check the elemental composition of the fertilizer, the penetration of different ions in the interlayer sites to study the bound and unbound ions in the layered structure of the fertilizer. ICP M S gives elemental quantity while XRD and TEM confirms and gives clear interlayer sites occupied by the exchanged anions while XANES can penetrate deeply interlayer to confirm the depth of anion penetration affected by factors such as anion geometry, interaction to each other, their size and the relationship between their size and charge.
VII.
Further testing can be done to determine the residual value of P and degradation of Zn from the soils treated with a P-N HDS to check the present of zinc ions on final degradation of the fertilizer in solution.
30
REFERENCES
Assadawoot Srikhaowa, Siwaporn M eejoo Smith (2013). Preparation of Cu2(OH)3NO 3/ZnO, A Novel Catalyst for M ethyl Orange Oxidation under Ambient Conditions, Applied Catalysis B: Environmental 130– 131 (2013) 84– 92 Badreddine. M , Legrouri. B, Barroug. A, De Roy. A, Besse. J P (1999). Ion Exchange of Different Phosphate Ions into the Zinc–Aluminum–Chloride Layered Double Hydroxide M aterials Letters 38 _1999. 391–395 Chow Hui Hoon (2011/12) .The Removal M ethods of Phosphorus/Phosphate and Nitrogen/ Nitrate from Water and Wastewater. Campbell University, U.S.A., School Of Arts and Science, Tunku Abdul Rahman College, Kuala Lumpur, M alaysia Everson Kandare, Jeanne Hossenlopp. (2005) Hydroxyl Double Salt Anion Exchange Kinetics: Effects of Precursor Structure and Anion Size. Journal of Physical Chemistry B, Vol 109, No. 17 (February 2005): pg. 8469-8475 Farahnaz Barahuie, M ohd Zobir Hussein, Sharida Fakurazi and Zulkarnain Zainal. (2014). Development of Drug Delivery Systems Based on Layered Hydroxides for Nanomedicine Int. J. Mol. Sci. 2014, 15, 7750-7786; doi: 10.3390/ijms15057750 Hadis Hatami, Amir Fotovat, Akram Halajnia. (2018).Comparison of adsorption and desorption of phosphate on synthesized Zn-Al LDH by two methods in a simulated soil solution. Applied Clay Science 152 (2018) 333–341. Hafezeh Nabipour, M oayad Hossaini Sadra and Nygil Thomas (2016). Synthesis, Controlled Release And Antibacterial Studies Of Nalidixic Acid–Zinc Hydroxide Nitrate Nanocomposites, New J.Chem. 2016, 40, 238 Ivanov. K I, Kolentsova. E N, Nguyen. Cao N, Peltekov. A B, Angelova. V R (2017). Synthesis and Stability of Zinc Hydroxide Nitrate Nanoparticles. Bulgarian Chemical Communications, Volume 49 Special Issue G (pp.225 –230) 2017
31
Kaouther Abderrazek, Najoua Frini Srasraa and Ezzeddine Srasraa (2017). Synthesis and Characterization of [Zn-Al] Layered Double Hydroxides: Effect of the Operating Parameters. J. Chin. Chem. Soc. 2017, 64, 346–353. Koilraj. P, Churchil A. Antonyraj, Vishal Gupta, Reddy. C.R.K., Kannan. S (2013). Novel Approach for Selective Phosphate Removal Using Colloidal Layered Double Hydroxide Nanosheets and Use of Residue as Fertilizer. Applied Clay Science 86 (2013) 111–118 Krzysztof Lubkowski, Barbara Grzmil (2007). Controlled Release Fertilizers. Polish Journal of Chemical Technology, 9, 4, 81- 84, 2007, 10:2478/v10026-007-0096-6 Legrouri. A, Badreddine. M , Barroug. A, De Roy. A, Bess. J P (1999). Influence of pH on The Synthesis of the Zn–Al–Nitrate Layered Double Hydroxide and the Exchange of Nitrate by Phosphate Ions, Journal of M aterials Science Letters 18 (1999) 1077-1079 Luíz Paulo Figueredo Benício, Rejane Alvarenga Silva, Júnia Aparecida Lopes, Denise Eulálio, Rodrigo M orais M enezes dos Santos, Leonardo Angelo de Aquino, Leonardus Vergütz, Roberto Ferreira Novais, Liovando M arciano da Costa, Frederico Garcia Pinto and Jairo Tronto. (2015). Layered Double Hydroxides: Nanomaterials For Applications in Agriculture. R. Bras. Ci. Solo, 39:1-13, 2015. M aarten Everaert, Fien Degryse, M ike J. M cLaughlin, Dirk De Vos, Erik Smoldersa (2017). Agronomic Effectiveness of Granulated and Powdered P-Exchanged M g-Al LDH Relative to Struvite and M AP. Journal of Agricultural and Food Chemistry, July 2017 DOI:10.1021/acs.jafc.7b01031 M aarten Everaert, Ruben Warrinniera, Stan M akenna, Jon-Petter Gustafssonb, Dirk De Vows, Erik Smoldersa (2016). Phosphate-Exchanged M g-Al Layered Double Hydroxides: A New Slow Release Phosphate Fertilizer. ACS Sustainable Chemistry & Engineering · June 2016 DOI:10.1021/acssuschemeng.6b00778 M achingauta, Cleopas, (2013) "Synthesis, Characterization and Application of TwoDimensional Layered M etal Hydroxides for Environmental Remediation Purposes". Dissertations (2009 - ). Paper 305. http://epublications.marquette.edu/dissertations_mu/305
32
M ajoni, Stephen. (2011) "Development, Kinetic Analysis and Applications of 2-D Nanostructured Layered M etal Hydroxides" (2011).Dissertations (2009 - ). Paper 162. http://epublications.marquette.edu/dissertations_mu/162 M ajoni Stephen and Hossenlopp Jeanne. M (2014). Controlled Release Kinetics in Hydroxyl Double Salts: Effect of Host Anion Structure Advances in Physical Chemistry, Volume 2014, Article ID 710487, http://dx.doi.org/10.1155/2014/710487 M ohd Zobir Hussein, Nor Shazlirah Shazlyn, Abdul Rahman, Siti H. Sarijo and Zulkarnain Zainal (2012). Herbicide-Intercalated Zinc Layered Hydroxide Nanohybrid for a Dual-Guest Controlled Release Formulation. Int. J. M ol. Sci. 2012, 13, 7328-7342; doi:10.3390/ijms13067328 Nalawade. P, Aware. B, Kadam. V J and Hirlekar. R S (2009). Layered Double Hydroxides: A Review. Journal of Scientific & Industrial Research Vol. 68, April 2009, Pp.267-272 Salleh. N M , M ohsin.SM N, Sarijo H.S and Ghazali. S A I S M (2017). Synthesis and Physio-Chemical Properties of Zinc Layered Hydroxide-4-Chloro-2-M ethylphenoxy Acetic Acid (ZM CPA) Nanocomposite. IOP Conf. Series: M aterials Science and Engineering 204 (2017) 012012 doi:10.1088/1757-899X/204/1/012012. Shaviv. A. (2000). Advances in Controlled Release of Fertilizers. “Advances in Agronomy”, 71:1-49 Varadachari Chandrika and Goertz Harvey M (2010). Slow-release and Controlled-release Nitrogen Fertilizers, In ING Bulletins on Regional Assessment of Reactive Nitrogen, Bulletin No. 11, (Ed. Bijay Singh), SCON-ING, New Delhi, pp i-iv & 1-42. Vollmer. N and Ayers. R (2012). Decomposition Combustion Synthesis of Calcium Phosphate Powders for Bone Tissue Engineering. ISSN 1061_3862, International Journal of Self Propagating High Temperature Synthesis, 2012, Vol. 21, No. 4, pp. 189–201. Allerton Press, Inc. Yunbo Wang and Deshuai Sun (2015). Phosphate Removal from Aqueous Solutions on Fly Ash with M edium Calcium Content. International Korean J. Chem. Eng., 32(7), 1323-1326 (2015) DOI: 10.1007/s11814-014-0342-6.
33
APPENDIX Table 4.1: Slow release of the anions in solution of sodium hydrogen carbonate measured using UV-Vis spectroscopy. TIM E in minutes
[P] ppm
[N] ppm
720
0.0043
0.0026
360
0.0018
0.0011
180
0.0012
0.0008
60
0.0007
0.00078
30
0.0005
0.00046
15
0.0002
0.00029
Table 4.2: FT-IR peaks for ZnHN and ZnHNP
M aterial
Peak ( cm-1)
ZnHN
3476.13
Description
1370.32 641.55 ZnHNP
3477.36 1370.27 1006.07 943.90 634.14
34
