Fast and Efficient Removal of Oil from Water Surface Through Activated Carbon and Iron Oxide-Magnetic Nanocomposite
Tasnia Hassan Nazifa*
A S M Shanawaz Uddin
Faculty of Civil Engineering Universiti Teknologi Malaysia Skudai, Johor, Malaysia e-mail:
[email protected]
Faculty of Civil Engineering Universiti Teknologi Malaysia Skudai, Johor, Malaysia e-mail:
[email protected]
Rashidul Islam
Tony Hadibarata
Faculty of Built Environment Universiti Teknologi Malaysia Skudai, Johor, Malaysia
[email protected]
Faculty of Engineering and Science Curtin University, CDT 250 Miri, Sarawak, Malaysia e-mail:
[email protected]
Salmiati*
Azmi Aris
Centre for Environmental Sustainability and Water Security, Research Institute for Sustainable Environment Universiti Teknologi Malaysia Skudai, Johor, Malaysia. e-mail:
[email protected]
Centre for Environmental Sustainability and Water Security, Research Institute for Sustainable Environment Universiti Teknologi Malaysia Skudai, Johor, Malaysia e-mail:
[email protected]
Abstract—An efficient magnetized nanocomposite material adsorbent is made from agricultural waste like banana stem based activated carbon and combined with iron oxide nanoparticles. The composite adsorbents show excellent lubrication oil absorption capacity with rapid kinetics. Banana stem based activated carbon and composite materials is compared with commercial activated carbon and its magnetic composite to remove oil from aqueous environment. The banana stem based activated carbon was capable to adsorb oil up to 2.99 times of its weight and composite from commercial activated carbon could adsorb 5 times of its weight within 30 min and interestingly both composite could be removed from water body by applying external permanent magnet. The kinetic data were best fitted to the pseudo second order model and thermodynamic parameter was also estimated.
Extensive application of activated carbons as adsorbents are frequently seen in separation or catalysis process. However, activated carbons are not cost effective because of costly raw materials like coal (non-renewable). Later, a rising attention has come forward on the usage of waste biomass as raw materials for activated carbon. Banana peel and pseudo stem, palm shell or kernel shell, coconut shell etc. [2]. The application of activated carbon derived from agricultural waste is more economical since they can be obtained easily. Moreover, it provides an added profit to the generated biomass waste, as this way leads to the reduction of agricultural by product waste disposal, thus adding byproduct functionality. Although widely used in practical application and research, these adsorbents still have some limitations. For instance, porous materials and activated carbon have few disadvantages like difficulties during collection time because of small particles, high generation temperature for activated carbon (500 -800 0C), low separation competence caused by water co-adsorption (6-10). The ordinary polymeric membranes are likely to decompose at high temperatures and less substantial selectivity. Moreover, membranes are less suitable for the large oil spill clean-up or organic contaminants in aquatic surface. Acknowledging that an oil spillage will make massivearea water contamination over a short time as for example, 1 ton of spilled oil will instantly spread over the surface to form a 12 km2 film area. In that case, efficient and fast removal of spilled oil from aquatic surface as fast as possible should become a most essential task for the oceanic
Keywords-oil spill; activated carbon; magnetic nanoparticle; banana stem; agricultural waste
I. INTRODUCTION Due to increased attention on the topic of environmental protection, there found a growing demand for those materials which are capable to remove different forms of organic/inorganic pollutants or oil spills from the aquatic environment. The oil spillage occurrences on marine environment have caused many negative impacts on the marine ecosystem. The common materials used to attain this target include fabricated polymer, membrane, activated carbon, high adsorption capacities porous materials, zeolites, collagen fibers etc. [1].
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environment and living protection. Oil-adsorbent components can be distributed as well as collected fast will reduce the intended ecological impact. Currently, it has been reported that adsorbents with super oleophilic and super hydrophobic properties could selectively gather organic chemicals or oils from water body, which suggests a novel strategy for the oil-water separation techniques [3]. Nowadays, magnetic porous sorbents were proved to demonstrate a rapid separation of oil/organic pollutants from water by applying a suitable external magnet [4]. Nevertheless, little concentration was paid on the materials united with magnetic particles. We admit that, these types of combined materials might be used to the selective and fast clean-up of large oil spilled area under an external magnetic field. Here, the manuscript reports the adsorption capacity of banana stem based activated carbon and commercial activated carbon to remove lubrication oil from water body. This research also explores the adsorption potentiality of magnetically modified activated carbon made from above two mentioned activated carbon. The activated carbon was able to absorb oil from water body. More interestingly, the magnetically modified activated carbon could be thoroughly and quickly collected after oil adsorption by using external magnetic bar, which broadens the possibility to rapid removal of oil. II.
EXPERIMENTAL
A. Materials AR grade iron(III) chloride, ferrous sulphate, zinc chloride (ZnCl2) and sodium hydroxide were brought from Merck, Germany. Commercial activated carbon (labelled as C-AC) was supplied by local chemical supplier. Banana stems were collected from orchard area of University Teknologi, Skudai, Johor, Malaysia. For oil spill study, lubrication oil was purchased from BHPetrol, Skudai. B. Activated Carbon (AC) Preparation Dry banana leaf stems were collected, then cut into small pieces and washed with tap water to clear away visible dirt and sands. Then soaked into 1:1 ZnCl2 solution for 24 Hrs. The impregnated stems were oven dried for whole night and pyrolyzed using horizontal furnace under constant nitrogen flow at 400 0C for 2 hours. Later the pyrolyzed stems were crushed to powder form (labelled as B-AC) and stored in air tight jar for further use. C. Magnetic Activated Carbon (MAC) Preparation The prepared B-AC and C-AC were magnetized following the procedure showed by [5] with slight adjustment. AC (35-40) g, was suspended in de ionized water (500 mL). Freshly prepared ferric chloride (FeCl3) solution mixed with ferrous sulphate (FeSO4) solution and stirred vigorously at 80-900C. Aqueous suspension of AC was then added with the ferrous and ferric chloride mixture. The mixture was stirred slowly for approximately 40 min. Lastly, freshly prepared NaOH (10M) was added drop wise to attain final pH of the solution 10 to 11. The suspension was aged at 25ºC temperature overnight and before oven dry
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at 1050C the magnetized activated carbon (MAC) was washed with distilled water followed by ethanol. D. Adsorbent Characterization Technique Infrared spectrum of the prepared MACs and ACs were studied using Fourier-transform infrared spectrometer (FTIR, Perkin Elmer, Spectrum GX, USA). The sampling was set up as KBr pellets and scanned over the range of 400-4000 cm-1 to detect the possible functional groups which are involved with adsorption. Surface morphology of AC and MAC was examined using a field-emission scanning electron microscope (FE-SEM, JEOL JSM 6710F). X-ray diffraction (XRD) patterns for MACs were evaluated on a powder X-ray diffraction system using a Bruker D8 diffractometer system (40 kV, Cu αradiation, 30 mA) for angle 2θ between 5º to 90º. E. Calculation of oil Adsorption Capacity The lubrication oil adsorption capacity of B-AC, C-AC, B-MAC and C-MAC were determined by weight basis. In case of magnetic composite B-MAC and C-MAC, the oil adsorbed particles were recovered by using an external permanent magnet and later dried at 80 0C to evaporate the water. However, in case of AC, the adsorbents after oil adsorption were filtered and dried in the same condition to evaporate water. The amount of oil that was absorbed (k) by specific AC and MAC were calculated by the following formula: K=(m2-m1)/(m1)
(1)
where, m1 and m2 are the weights (gm) that was determined before and after oil adsorption. III.
RESULTS AND DISCUSSION
A. Characterization of Adsorbent 1) Surface Analysis through FESEM: Fig. 1 A demonstrates the micrograph of raw banana stem before the carbonization process. The micrograph portrays a flat and even surface without the presence of any pores after analysis at a higher magnification. Fig.1B shows the surface morphology of B-AC after the impregnation with 1:1 ZnCl2. As observed from the morphology, there are plenty of pores has been developed on the B-AC and C-AC surface. These pores are formed randomly onto the activated carbon surface with different width and diameters. Hence, BAC shows a larger pore volume and surface area on its external surface in compare to raw one. Micrograph (1C & E) demonstrates the morphological transformation due to iron particles impregnation into the carbon matrix pores. It is noticed that few pores of B-AC and C-AC are partially occupied with iron oxide nanoparticles developing a porous spongy texture. Most of the carbon pores appear to encompass iron oxide. Therefore, resulting the surface area as well as pore volume of B-MAC and C-MAC becoming lower in compare to that of B-AC and C-AC. The reduction in surface area after magnetizing the parent carbon materials has been reported earlier [6]. 2) FTIR spectroscopy
The FTIR spectrum of B-AC, B-MAC, C-AC and CMAC are shown in Fig. 2 (A, B, C, D). The B-AC displays absorption peak at 3454, 1628, 1320 and 782 cm-1 which are assigned to O-H, C=C, C-N and C-C stretching modes respectively. The shape and position of the peak at 3454 cm1 O-H bonded hydroxyl groups Free OH functional goups
are marked as phenols at ~3605 cm-1, as alcohols at ~3625 cm-1 and as carboxylic acids at 3530 cm-1. Based on these four types hydrogen-bonded structures mentioned earlier [7]. In case of C-AC, adsorption peak of at 3418, 1585 and 1164 cm-1 revealed the presence of O-H stretching, O-H bending and C-O broad band respectively.
Figure 1. FESEM photograph of raw banana stem (A), B-AC (B), B-MAC (C), C-AC (D), and C-MAC (E)
A
782cm-1
3434 cm-1
D
C
Figure 2. FTIR spectrum of B-AC (A), B-MAC (B), C-AC (C) and C-MAC (D)
However, two additional, intense peaks at 554 cm-1 and 586 cm-1, proves the presence of Fe3O4 (iron oxides) in BMAC and C-MAC sample [6]. 3) XRD analysis: Fig. 3(A&B) depicts the XRD pattern of B-MAC and CMAC. The amorphous phase of carbon in both the samples were observed at 2θ of 10 to 300. Chemical activation has lead the parent material adsorbent (i.e. AC) to decompose organic components at the time of carbonization. The carbon
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bonding restructuring is responsible to form such type of amorphous phase [8]. Some numbers of peaks are prominent at 2θ= 30.25, 35.6, 43.8, 57.4, 62.90 in B-MAC and 30.28, 35.1, 43.35, 57.45, 62.6, 85.80 in C-MAC which are consistent with the existence of Fe3O4 (magnetite) and γFe2O3 (maghemite). These iron particles were probably formed during the MAC preparation as a result of hydrolysis, precipitation, adsorption and process [9]. According to [10], production of γ-Fe2O3 and Fe3O4 is hard to distinguish even
after analysis. Both the species may have the similar peak in analysis. However, their properties are accepted as both the species contain magnetic phase. These results are rational
with the micrograph from FESEM analysis where it proves the high impregnation of magnetic nanoparticles onto B-AC and C-AC.
Figure 3. XRD pattern of (A) B-MAC, (B) C-MAC
B. Oil Removal Lubrication oil was used to create artificial oil spill. The adsorption capacity of B-AC and C-AC for lubrication oil were determined following the procedure discussed above. One-gram B-AC and C-AC were found to absorb 2.29 gm and 3.8 gm of lubrication oil within half an hour (Fig. 4A). On the other hand, one gram of activated carbon when used in a form of composite material B-MAC retains 2.99 gm and 4
B-AC C-AC
3
6 5 4 3 2 1 0
A
2 1 0
0
10
20 30 Time (min)
40
B-MAC C-MAC
Oil Adsorption (g/g)
Oil adsorption (g/g)
5
C-MAC retains 5 gm of oil almost in the same duration. The oil adsorption ability of B-MAC and C-MAC, with respect to the activated carbon weight exist in them, using the lubrication oil is presented in Fig. 4B. The oil removal capacity is too large to that of activated carbon made from palm shell, where only 99 mg oil/g retention capacity was measured even after chemical activation [1].
0
50
10
B
20 30 Time (min)
40
50
Figure 4. Oil retention capacity by (A) B-AC and C-AC, (B) B-MAC and C-MAC.
The removal of oil applying ACs were tedious and time consuming due to the filtration technique involved in the separation of adsorbent. Nevertheless, this major disability was overcome by using B-MAC and C-MAC. In addition, the instantaneous pulling force on the magnetized nanoparticles facilitate a developed oil retention capability of the carbon by dragging much oil on the adsorbed component when used as magnetic composite. The characteristics of the oil adsorption curves found are quite analogous for the composite material and activated carbons. This indicate that the kinetics of adsorption is quite same, suggesting the role of surface area and porosity of used activated carbon to determine the adsorption capacity of oil. In case of B-AC and B-MAC, the process of adsorption was not spontaneous in compare to that of C-AC and CMAC. The oil adsorption in pores of absorbing materials is comparatively slow process. Because, a sufficient time is needed for viscous natured fluids like lubrication oil to infiltrate into the adsorbent pores by the action of capillary force. However, the highest retention capacity was achieved by C-MAC in 35 min which demonstrate a better report compared to previously reported magnetized sorbent composites, for example epoxidized rubber-based composite, whose highest retention was attained after 2 h [11]. Table I represents the retention capacity of lubrication oil by various adsorbent.
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TABLE I.
COMPARISON OF MAXIMUM ADSORPTION CAPACITIES OF VARIOUS ADSORBENTS FOR OILS
Adsorption (g/g) 2.6 Rice husks 6.4 Oleic acid grafted sawdust 5.79 Castor oil grafted sawdust 0.61 Horn shell residues 3.01 Coconut shell based magnetic activated carbon 3.8 Fe2O3 -C nanoparticle 2.29 Banana stem based activated carbon 2.99 Banana stem based magnetic activated carbon Adsorbent
Reference [14] [15] [15] [16] [1] [4] This Study This Study
The oil adsorption capacity of B-MAC and C-MAC are studied using various kinetic models [12], to determine the adsorption capacity at equilibrium state. Among the studied kinetic models, all experimental data was found to fit well to the pseudo-second-order kinetic equation given by t/qt = 1/k2qe2+t/qe [12] as reported previously for the treatment of dyes in aqueous solution. Where qe and qt are the amount of lubrication oil adsorbed (g g⁻¹) at equilibrium state and at any time t (min) and k2 are second order adsorption rate constant (g g⁻¹ min⁻¹), the value of qe (g/g) and k2 for each kinetic model were estimated by plotting a graph t/qt versus t for pseudo second order. Table II demonstrates the obtained kinetic parameters for both B-MAC and C-MAC from the graph plot.
TABLE II.
RESULTS OF THE ANALYSIS OF THE ADSORPTION KINETICS OF B-MAC AND C-MAC.
Adsorbent material B-MAC C-MAC
R2 0.9744 0.9796
Slope 0.2225 0.1569
Intercept 3.7582 1.6071
qe (g/g) 4.494 6.37
K2 0.0132 0.0153
Oil retention (g/g)
C. Temperature Dependence Thermodynamic parameters were assessed to affirm the adsorption nature. The effect of temperature (K) on adsorption of lubrication oil onto MACs were studied over a range of 28 0C to 50 0C. The oil containing dish was placed in a water bath set to pre-determined temperature for 30 min to maintain a thermal equilibrium. Then both the magnetic composite was smeared onto the oil layer. Next, the oil adsorbed composite was separated by a permanent magnet. Fig. 5 demonstrates the amount of oil retained by B-MAC and C-MAC for 30 min at three different temperature. 6
28ºC
35ºC
We are grateful to the AUN/SEED Net collaborative research program for Common Regional Issue (CRC) for financial assistance. REFERENCES [1]
[2]
[3]
[4]
50ºC
4
[5]
2 0
[6] B-MAC
C-MAC
Figure 5. Oil retention capacity at various tempertaure
As the temperature increased from 28 0C to 50 0C, the oil adsorption capacity decreased from 2.99 to 1.1 gm for per gram of B-MAC and from 5 to 3.2 gm for per gram of CMAC. Thus, when compared to the result at 28 0C (room temperature), the oil adsorption capacity decreased nearly 36% at 500C. The decrease of the oil retention capacity with the increase of temperature can be explained like weakening of physio sorption, mediated by water repellent interactions. Nevertheless, the decrease of adsorption capacity with the increase of temperature, the retention capacity at 500C was higher than the result reported previously for various composites at 28 0C. Hence, the adsorbent proves more effective and efficient [13].
[7]
IV. CONCLUSIONS Two types of magnetized nanocomposite have been prepared from banana stem based activated carbon and commercial activated carbon. The studies proved that both the non-magnetized and magnetized adsorbents is a wonderful material for efficient oil removal and can be separated by external magnet application (for composite). The magnetic separation technique is instantaneous and less tedious since magnetic nanoparticle interactions are involved for recovery of water-oil mixture. The technique may also be appropriate for retainment of oil immediately after the spill accident to prevent further contamination. The additional benefits like simplicity of the process, cost effectiveness along with good adsorption capacity can allow the materials to be implied for the oil removal in conjugation with the other currently applicable technologies.
[11]
ACKNOWLEDGEMENT
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