Effective removal of zinc from an aqueous solution using Turkish ...

Environ Earth Sci (2013) 70:3031–3041 DOI 10.1007/s12665-013-2364-5

ORIGINAL ARTICLE

Effective removal of zinc from an aqueous solution using Turkish leonardite–clinoptilolite mixture as a sorbent Go¨khan Zengin

Received: 14 August 2012 / Accepted: 28 February 2013 / Published online: 15 March 2013 Ó Springer-Verlag Berlin Heidelberg 2013

Abstract In this study, the feasibility of using a low-cost adsorbent mixture composed of leonardite (L) and clinoptilolite (C) was evaluated by batch adsorption method using different parameters such as mixing ratio, contact time, pH, temperature, and adsorbent amount for the removal of Zn (II) ions from an aqueous solution. The adsorbents were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. Additionally, leonardite–clinoptilolite mixture was analyzed by scanning electron microscopy coupled with energy dispersive X-ray. The Zn (II) adsorption along with an unprecedented adsorption capacity of 454.55 mg g-1 for unmodified natural sorbents was obtained by mixing leonardite and clinoptilolite (LC) without any pretreatment at a ratio of 3:1, using 0.1 g of sorbent at a pH 6, for 2 h of contact time. The experimental data showed a good fit for the Langmuir isotherm model. The thermodynamic parameters revealed that the present adsorption process was spontaneous and exothermic in nature (25–50 °C). The kinetic results of the adsorption showed that the Zn (II) adsorption onto the LC follows pseudo-second-order model. The resultant LC mixture has an excellent adsorption capacity of a Zn (II) aqueous solution, and data obtained may form the basis for utilization of LC as an unpretreated low-cost adsorbent for treatment of metalliferous industrial wastewater. Keywords Zinc (II) adsorption Clinoptilolite Leonardite Fourier transform infrared spectroscopy Raman spectroscopy Scanning electron microscopy coupled with energy dispersive X-ray G. Zengin (&) Leather Engineering Department, Engineering Faculty, Ege University, Bornova, 35100 Izmir, Turkey e-mail: [email protected]

Introduction Contamination of aquatic ecosystems with pollutants such as cadmium, chromium, copper, lead, nickel and zinc is one of the most important environmental concerns due to their toxic effects on humans and aquatic organisms. They can be found in wastewater with varying concentrations as a result of industrial activities such as mining, metallurgy and galvanizing industry, chemical industry, textile printing and dyeing, and leather tanning operations (Bailey et al. 1999; Kilic et al. 2011; Kragovic´ et al. 2012). Zinc is an essential element in plant and animal metabolism and regulates many biochemical processes in the human body; however, higher concentrations of zinc can be detrimental and cause serious health problems and it is considered as one of the priority pollutants by the US Environmental Protection Agency (Montilla et al. 2003; USEPA 2005; Rao et al. 2006; Trgo et al. 2006; Ozdes et al. 2011). Hence, the removal of zinc from water and wastewater in a safe and cost-effective manner has essential importance in terms of the protection of public health and the environment. A number of methods have been developed for the removal of zinc (Bailey et al. 1999; Çoruh 2008; Kragovic´ et al. 2012) and adsorption onto sorbents is one of the most promising methods for zinc removal due to its stoichiometric structure, lower pollutant contraction, inertness to water pH and chemistry, confining the pollutant in a volume reduced by a factor 103–104 (Colella 1998). A literature survey on zinc removal reveals that researchers generally used synthetic materials and their combinations as sorbent (Hamadi et al. 2001; Zawani et al. 2009). Although the commercially available synthetic adsorbents such as polymeric resins and activated carbons are more effective than the natural materials, they are relatively expensive and

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appropriate to apply for larger scales. On the other hand, natural sorbents are abundantly available, inexpensive, chemically inert, porous, non-toxic, and environmentally acceptable. Thus, numerous low-cost natural materials and adsorbents such as natural zeolites (clinoptilolite), which provide advantage over other adsorbents for removing zinc in terms of their combination of ion exchange and molecular sieve characteristics (Colella 1998; Erdem et al. 2004) and humic substances like leonardite, which have a high cation exchange capacity (Sole´ et al. 2003; Hanzlı´k et al. 2004; Li et al. 2010) have been successfully employed for the removal of zinc and other toxic metals from aqueous solutions. Although clinoptilolite has been documented as a promising adsorbent by various researchers (Hernandez et al. 2000; Cincotti et al. 2006; Trgo et al. 2006), limited work has been reported on the utilization of leonardite (Stevenson 1994; Ouki and Kavannagh 1997; Stathi and Deligiannakis 2010). To our knowledge, no studies have been published to date that attempt to determine the zinc removal efficiency of Turkish leonardite–clinoptilolite mixture. In the present study, the utilization of an unmodified leonardite–clinoptilolite mixture as a sorbent for Zn (II) removal was evaluated by a batch adsorption process. The effect of various parameters on adsorption process such as mixing ratio, contact time, pH, adsorbent amount, and temperature on Zn (II) adsorption were studied, and the optimum conditions for the maximum adsorption were determined. In order to describe the solute uptake rate, and obtain information for designing and modeling the water treatment processes (Hamadi et al. 2001), the adsorption capacity and kinetics of the leonardite and clinoptilolite mixture with respect to the aqueous solution of Zn (II) under batch conditions were also investigated. The prominent features of this study is the preparation of a mixture of zeolite and an underutilized adsorbent, leonardite, and the application of this mixture without prior treatment which is one of the major factors influencing the cost of the adsorption process.

Environ Earth Sci (2013) 70:3031–3041

to improve their efficiency, since a larger surface area implies a greater adsorption capacity (Kenney and Keeping 1962). The characteristics of clinoptilolite leonardite and, leonardite–clinoptilolite mixture used in the study are given in Table 1. LC (3:1) used in further experiments was characterized by SEM/EDX (Philips XL-30S FEG) (Fig. 1) and the surface area of the mixture was determined by BET method (Micromeritics, Gemini V.Series). Al, SiO2 and Si/Al ratio of clinoptilolite used in the study were comparable with the cited literature; however, pore diameter size and surface area is lower than the previously reported values obtained by C ¸ oruh (2008). Table 1 Chemical composition and characteristics of clinoptilolite, leonardite and leonardite–clinoptilolite (3:1) mixture Characteristics of the adsorbents Clinoptilolitea 11.84 %

Si/Al

5.12

K2O CaO

3.44 %

Appearance porosity

35–40 %

2.18 %

Bulk density

0.6–1.0 g/cm3

MgO

1.15 %

Crystalline dimension

5–15 lm

Na2O

0.38 %

Specific weight

2.1 g/cm3

K

2.3 %

Pore diameter size (mean)

0.041 lm

Ca

1.1 %

Surface area

40.79 m2/g

Na Mg

0.35 % 0.35 %

pH

7.5

C

50–60 %

Organic matter

min 65 %

O

30–50 %

Humic acid

70–75 %

H

2.5–5.0 %

Density

1.65 g/ml

N

2.0–3.0 %

Moisture

25–30 %

S

0.3–0.5 %

Specific weight

0.8 ± 0.1 g/ cm3

pH

6–6.5

Leonardite–clinoptilolite mixtureb

Adsorbents

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67.11 %

Al2O3

Leonarditea

Experimental

Clinoptilolite and leonardite were provided by Gordes Mining Company, Manisa, Turkey. Samples were cleaned with distilled water to remove the surface dust and then dried in an oven at 110 °C prior to the batch adsorption experiments. Clinoptilolite and leonardite were ground and passed through a standard sieve with a 1 mm pore diameter

SiO2

C

25.01 %

N

2.66 %

Si/Al

4.17

O Na

50.23 % 0.07 %

BET surface area

14.32 m2/g

Mg

0.42 %

Pore volume

0.0380 cm3/g

Al

3.41 %

Average pore diameter size

11.8 nm

Si

14.23 %

S

0.59 %

Moisture

9.79 %

K

1.10 %

pH

6.4

Ca

1.42 %

Fe

0.86 %

a

The physico/chemical compositions of clinoptilolite and leonardite samples were provided by Gordes Mining Company, Manisa, Turkey

b

LC mixture was characterized by SEM/EDX and the surface area and pore diameter of the mixture was determined by BET method


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Fig. 1 SEM-EDX analysis of LC (3:1) mixture

Adsorbate All chemicals were of analytical reagent grade and purchased from Merck (Darmstadt, Germany). A standard Zn (II) stock solution was prepared by using ZnSO47H2O salt and ultrapure water and then diluted to the required concentrations before being used. Adsorbent characterization X-ray diffraction (XRD) of adsorbent Mineralogical analyses of the adsorbents were carried out by means of a Rigaku Ultima IV X-ray diffraction system. The patterns were collected at 30 kV and 40 mA for 45 min, in the angular range from 2° to 90° in 0.05° steps. The identification of the patterns was performed with software containing data maintained by the International Centre for Diffraction Data Files. Fourier transform infrared spectra (FTIR) of adsorbent The spectra of the clinoptilolite, leonardite, and leonardite– clinoptilolite (LC) were collected by transmitted light FTIR (Perkin Elmer Spectrum 100 with ATR) at a resolution of 4 cm-1 at the interval of 4,000–600 cm-1 at room temperature. All spectra were rationed against a background air spectrum and stored as absorbance values at each data point. Raman spectra of adsorbent Perkin Elmer Raman Station 400 coupled with a 300 mV laser output at a wavelength of 785 nm was used for the structure determination of clinoptilolite, leonardite, and leonardite–clinoptilolite (LC). The Raman spectra of the

samples were obtained at a resolution of 4 cm-1 at an interval frequency of 3,250–200 cm-1. Adsorption experiments Batch adsorption experiments were performed with the selected Zn (II) concentration, pH, and contact times using a constant mass of LC mixture and 100 mL of adsorbate solution. Samples were shaken in 250-ml Erlenmeyer flasks at 150 rev min-1 on orbital shaker at room temperature. The pH values were adjusted using either an HCl or NaOH solution. At various time intervals, the suspensions were filtered through a Whatman No. 1 filter paper to completely remove solid particles and then the filtrates were analyzed for Zn (II) concentration by an ICP-OES (inductively coupled plasma-optical emission spectrometer). The instrument was calibrated using a standard reference solution for zinc, and the quality control solution was run during analysis to confirm calibration. For the control of any leaching interference during the test period, a sample was prepared by adding leonardite and clinoptilolite adsorbent mixture to deionized water as a blank sample and conducted under similar conditions of concentration, pH, and temperature. Adsorption capacity The effects of various parameters such as the mixing ratio of leonardite and clinoptilolite, contact time, pH, amount of LC mixture, and temperature were investigated in a batch adsorption model to determine the adsorption capacity. Varied mass proportions (1:1, 1:3, and 3:1) of leonardite and clinoptilolite (LC) were applied at different contact time intervals such as 2, 4, 6, and 24 h to determine the optimum mixing ratio and contact time. The effects of different pH values such as 2, 3, 4, 5, and 6 during the 2 h of contact time were investigated for different proportions

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of LC. Following the determination of the optimum pH value, the effects of 0.1, 0.5, 1 and 2 g of adsorbents were also examined. Subsequent experiments were carried out with only the optimized parameters. The effect of temperature on the equilibrium adsorption capacity was investigated at 25, 30, 35, 40, 45, and 50 °C using 0.1 g of LC (3:1) with 300 mg L-1 initial metal concentration at a pH of 6 for 2 h. The Langmuir adsorption isotherm model was applied to describe the isotherms of Zn (II) adsorption onto the LC (3:1). For this experiment, various concentrations of Zn (II) from 20 to 400 mg L-1 were added to the 100 ml of adsorbate solutions at a pH of 6, using 0.1 g of adsorbent amount for the 2 h of contact time. Duplicate experiments with triplicate samples were performed and the average values were reported. Kinetic studies The kinetic parameters of Zn (II) adsorption onto LC (0.1 g) were determined with 100 ml solutions containing 400 mg L-1 Zn (II) concentrations at 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 150, 180, 210, and 240 min at 25 ± 2 °C. Results and discussion Characteristics of adsorbents X-ray diffraction of adsorbents The structures of each adsorbent and the mixture were characterized with X-ray diffraction. XRD patterns of the

Fig. 2 XRD patterns of clinoptilolite, leonardite and LC

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clinoptilolite, leonardite, and LC (3:1) are presented in Fig. 2. The characteristic strong and weak peaks of clinoptilolite can be clearly seen at angle 9.88°, 11.20°, and 22.49° theta (2h) which were assigned to Si/Al. The patterns acquired from clinoptilolite were found identical to that of reported in literature (Çoruh 2008; Ostrooumov et al. 2012). Leonardite exhibits strong diffraction peaks at 2h = 18.45°, 20.95°, 21.95°, 24.10°, and 26.60°. Similarly, the leonardite:clinoptilolite mixture (3:1) shows both the characteristic peaks for leonardite and clinoptilolite (Sardashti and Alidoost 2008). FTIR spectra of adsorbents Fourier transform infrared spectra of clinoptilolite, leonardite, and LC (before and after adsorption) are presented in Fig. 3. The intensity of the adsorbent peaks varied from 600 to 1,600 cm-1. The band 600–1,200 cm-1: The stretching mode (650–820 cm-1) in the FTIR spectroscopy was found to be sensitive to the Si/Al ratio of the framework for clinoptilolite (Breck 1974). The Si/Al bands were observed in the range of 670, 720, and 792 cm-1 for the clinoptilolite adsorbent, with the leonardite showing three bands of Si/Al at 670, 779, and 796 cm-1. The typical band at 1,020 cm-1 was attributed to the Si–O vibrations of silicate, which confirms the existence of the mineral part and silicate molecule in the structure of the clinoptilolite and leonardite. A very sensitive band between 950 and 1,100 cm-1 belonging to the hydrated/anhydrous silicates or their derivatives was detected for LC. The FTIR peaks of LC were seen within the wave of numbers from 650 to 800 and 1,000 to 1,025 cm-1 due to the possible interference of silicate and aluminate in the LC adsorbent in each spectrum (Fig. 3). Lastly, the band occurring at 695 cm-1 for LC after adsorption could be the result the insertion of Zn (II) ions into the LC structure. A similar change was also reported by Krol and Mozgawa (2011). The band 1,200–1,800 cm-1: The FTIR band of clinoptilolite at 1,626 cm-1 belongs to the O–H deformation of water. It is clearly seen that the FTIR spectrum given in Fig. 3 is a typical spectrum for clinoptilolite (Ostrooumov et al. 2012). The –COOH groups, O–H deformation, and stretch frequency of the carboxyl group (–COOH) of leonardite were observed at 1,700–1,400, 1,379, and 1,581 cm-1, respectively. The bands at 1,395 and 1,615 cm-1 corresponding to the OH deformation of water was observed for the LC adsorbent (Salem and Sene 2011). A similar spectrum confirming the presence of organic matter in the leonardite was also previously reported (Breck 1974; Stevenson 1994; Olivella et al. 2002). In addition, the band at 1,615 cm-1 for LC and the band at 1,616 cm-1 for leonardite were thought to be the possible non-ionized


3035

Fig. 3 FTIR spectrums between 3,900 and 600 cm-1 for clinoptilolite, leonardite and LC

functional group in the humic acid which is comparable with previous studies (Gossart et al. 2003; Terkhi et al. 2008). The band 1,800–4,000 cm-1: The wide absorption band within the range of 3,200–3,700 cm-1 was characterized by the hydrogen bonded hydroxyl or amino groups. The band at 3,695 cm-1 was the symmetric stretching m(O–H) vibration of the OH groups for leonardite and LC. The band

at 3,615 cm-1 was stretching m(–OH) vibrations of the inner –OH groups for all adsorbents. The inner hydroxyl groups in clinoptilolite and LC (before and after adsorption), lying between the tetrahedral and octahedral sheets, began the absorption at 3,625 cm-1 (Madejova 2003). The band at 3,400 cm-1 is assigned to the stretching and bending vibration of the hydroxyl functional groups. The band at

Fig. 4 Raman spectra of the leonardite, clinoptilolite and LC (before and after adsorption)

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3,380 cm-1 was attributed to the stretching and bending vibration of the hydroxyl functional groups for all the adsorbents. The bands between 2,920–2,850 and 2,918–2,850 cm-1 were observed due to the presence of the aliphatic C–H vibration in the structure of LC (before and after adsorption) and leonardite, respectively (Fig. 3). Raman spectra of adsorbents Figure 4 shows the Raman spectra of LC (before and after adsorption), leonardite, and clinoptilolite samples between 200 and 3,250 cm-1. The Raman scattering for the H2O molecule was very low, due to the rotational and translational vibration in the Raman spectroscopy for all adsorbents. The vibration bands of the hydroxyl groups were observed over 2,900 cm-1 H-stretch bands for all the adsorbents. Zeolites are characterized with an intense Raman band between 450 and 670 cm-1 (Ostrooumov et al. 2012). The strong bands of clinoptilolite samples were observed in the region of 450–1,000 cm-1, although zeolite types generally show little or no bands in the region of the asymmetric stretching bands in the FTIR spectra. The bands observed at 496, 544, 960, and 964 cm-1 were thought to be the natural sodalite of clinoptilolite (Angell 1973). In the zeolite spectrums, bands and their intensity in various regions can be different depending on their Si/Al ratio. The strong bands observed in the 960 and 964 cm-1 range were due to Si–O asymmetric stretch that depends on the Si/Al ratio for clinoptilolite and LC (Fig. 4). The bands at 496 and 544 cm-1 could be considered as Si–O–Si for clinoptilolite and LC. As can be seen in Fig. 4, leonardite exhibits lower bands than clinoptilolite. The band at 2,908 cm-1 may be assigned to the C–H stretching of

Fig. 5 Zn (II) adsorption capacity of different leonardite:clinoptilolite mixing ratio as a function of contact time (L leonardite, C clinoptilolite)

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alkane, alkene, or the aromatic structure for leonardite (Francioso et al. 2001). The Raman spectra of LC obtained before and after adsorption, exhibit significant differences in terms of band intensities (Fig. 4). In addition, the bands belonging to Si– O–Si for clinoptilolite were not detected after the adsorption of Zn (II) on LC, as a consequence of its ion exchange or adsorption characteristics. This may be attributed to the deformation of the four-membered rings that were observed at the wavelength of 464 cm-1 (Mozgawa et al. 2004; Mozgawa and Bajda 2006). Adsorption experiments Effect of adsorbent mixing ratio and contact time Various proportions of leonardite–clinoptilolite were investigated to determine the effect of the mixing ratio on the adsorption of Zn (II) using 2 g of LC, at a pH 2 with 100 mg L-1 initial metal solution concentration for different time intervals (Fig. 5). Adsorption capacities were observed to increase with an increase in the leonardite amount. A ratio of 3:1 LC was considered as an optimal value for high Zn (II) adsorption. The ion exchange of Zn (II) was rapid and the equilibration was attained after 2 h of contact time. This was considered as the optimum contact time, due to the insignificant increase of adsorption capacity after 2 h and minimum energy consumption (Buasri et al. 2008). Effect of pH The adsorption of Zn (II) onto leonardite–clinoptilolite mixture at different initial pH values (between 2 and 6) for

Fig. 6 Zn (II) adsorption capacity of various leonardite:clinoptilolite mixing ratios as a function of pH


2 h of contact time is shown in Fig. 6. The pH values were chosen in the range of 2–6 due to the formation of precipitation above pH 7. The removal of Zn (II) actually increased by increasing the pH values. The maximum adsorption capacities of Zn (II) were obtained at higher pH values because of the dissolution of the crystal structure and the competition between protons and Zn (II) ions for the exchange sites on the clinoptilolite particles (Peric´ et al. 2004; Motsi et al. 2009). Thus, the adsorption capacity was found low below pH 6, which indicates that pH is a significant factor affecting the speciation of the metals and their adsorption extent (Motsi et al. 2009). Additionally, the removal efficiency of metal ions generally increased at higher pH values because clinoptilolite was highly selective for H3O? ions when their concentration was high. Therefore, at lower pH values, H3O? ions competed with metal ions for the exchange sites on clinoptilolite (Çoruh 2008). The optimum pH value was determined as 6, which is comparable with previously published literature (Buasri et al. 2008). Effect of adsorbent amount The effect of various adsorbent amounts of LC (3:1) on the removal efficiency of Zn (II) was investigated for 2 h of contact time, at a pH 6, using a 100 mg L-1 initial Zn (II) concentration. The difference between the removal efficiency values obtained for 0.1 and 1.0 g adsorbent amounts was found approximately 5 % (Fig. 7). Adsorbent amount used for further experiments were selected as 0.1 g, because increase in removal efficiency with higher adsorbent amounts is not significant, and have negligible effect on removal efficiency. The previously reported low-cost adsorbent amounts used for zinc removal are presented in Table 2. It is notable that the adsorbent amount of LC used

3037

in the present study is significantly lower than the other studied adsorbents except in Srivastava et al. (1994), where the adsorbent capacity was five times lower than the results obtained in this study. Effect of temperature The thermodynamic parameters that must be considered to determine the adsorption processes are the changes in standard enthalpy (DH°), standard entropy (DS°), and standard free energy (DG°) due to the transfer of a unit mole of solute from the solution onto the solid–liquid interface (Tan et al. 2008). The thermodynamic parameters can be calculated using Eqs. 1 and 3, where KL is the Langmuir isotherm constant, R (8.314 J/mol K) is the universal gas constant, and T (K) is the absolute solution temperature. DG ¼ RT ln KL

DG ¼ DH TDS

ð1Þ

ln KL ¼ DS =R DH =RT

ð2Þ ð3Þ

The plot of ln K against 1/T (Vant’s Hoff plot) of the Zn (II) solution was carried out as indicated in Fig. 8, in which the DH° and DS° values are calculated from the slope and intercept of the plot (Yousef et al. 2011). The thermodynamic parameters, standard free energy change (DG°), enthalpy change (DH°), and entropy change (DS°) were calculated from Fig. 8 and the results are presented in Table 3. The adsorption of Zn (II) slightly decreased with an increase in temperature from 25 to 50 °C. The negative value of DH° reveals that the adsorption of Zn (II) ions onto the LC was exothermic in nature. The system’s free energy (DG°) decreased with the increase in temperature. The negative DG° values at all temperatures indicate that the adsorption process was less favorable at higher temperature (Horsfall and Abia 2003) and that the adsorption of Zn (II) was spontaneous. The adsorption mechanism and the metal uptake on the LC could be considered as chemical, since the values of DG° are higher than -20 kJ mol-1 (Kennedy et al. 2007). Furthermore, the positive DS° of the Zn (II) adsorption processes indicates decreased randomness at the adsorbent/solution interface during the adsorption (Tan et al. 2008). Adsorption isotherms

Fig. 7 Effect of LC mixture amount on zinc removal

The Langmuir model was found to fit well with the experimental data for all the adsorbents, although natural adsorbents exhibit a chemical heterogeneity represented by different functional groups. The Langmuir equation describes adsorption on strongly homogeneous surfaces and is represented by the following equation;

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Table 2 Reported Zn (II) adsorption capacities for various adsorbent amounts

Adsorbent

Adsorbent amount (g)

NaCl-modified clinoptilolite

2.0

9.43

2.5

21.20

Çoruh (2008)

Algerian sheep hoof

2.0

73.53

Souag et al. (2009)

Maize crop

2.0

57.47

Kaolinite

B1.0B 1.0

25.10

Qi and Aldrich (2008)

0.04

95.00

Srivastava et al. (1994)

Waste tea leaves

0.5

11.4

Ahluwalia and Goyal (2005)

Cassava waste

1.0

55.82

Horsfall and Abia (2003)

Modified cassava waste

1.0

559.74

Horsfall and Abia (2003)

Leonardite–clinoptilolite mix.

0.1

454.55

Present study

Fig. 9 The Langmuir adsorption isotherm of Zn (II) on LC

-1

-1

DS° J k

-1

DG° kJ mol

298

-60.63

303 308

-58.40 -56.16

210.00 205.78

313

-53.93

203.55

318

-51.70

198.93

323

-49.46

193.10

Ce =qe ¼ 1=KL SM þ Ce =SM ;

-446.68

mol

qe mg g-1 212.31

ð4Þ

where SM (mg g-1) is the maximum amount of adsorption corresponding to a complete monolayer coverage on the surface, qe (mg g-1) is the amount of metal ion, KL (l g-1) is the Langmuir constant, and Ce is the equilibrium liquid phase concentrations of the metal ion solution.

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Igwe and Abia (2007) Shahmohammadi-Kalalagh et al. (2011)

Tobacco dust

T (K)

-19.38

4.95

Buasri et al. (2008)

Lignin

Table 3 Thermodynamic parameters of Zn (II) adsorption on LC at different temperatures DH° kJ mol

References

Clinoptilolite

Fig. 8 Effect of temperature on Zn (II) adsorption

-1

qm (mg g-1)

As can be seen in Fig. 9, the adsorption isotherm data fit well with the Langmuir model (R2 C 0.95). This implies the formation of monolayer coverage of metal ions on the surface of the adsorbent. The maximum adsorption capacity (SM) and the Langmuir constant (KL) was determined as 454.55 mg g-1 and 4.58 9 10-4 g-1, respectively, at 25 ± 2 °C. The Zn (II) adsorption capacity of the LC was compared with the various adsorbents listed in Table 2. The results showed that adsorption capacity of the LC mixture was considerably higher when compared with the other reported values of clinoptilolite. C ¸ oruh (2008), Buasri et al. (2008), Peric´ et al. (2004), Cincotti et al. (2001), Panayotova and Vekilov (2002) and Shahwan et al. (2005) found the adsorption capacity of clinoptilolite for zinc as 21.3, 9.43, 5.9, 4.6, 2.3, and 1.2 mg g-1, respectively. In the present study considering the adsorbent amount used for the removal of zinc, it is evident that the LC mixture exhibited


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significantly higher zinc removal efficiency than the other cited values in the literature. The combination of the leonardite with clinoptilolite appears to act synergistically and exhibited higher adsorption capacity, which resulted from the complexation of the leonardite with zinc with highly stable coordinate linkages. This is due to the complex heterogeneous nature of the leonardite and the ionization degree of multiple functional groups such as carboxyl and hydroxyl (Hanzlı´k et al. 2004; Katanyoo et al. 2012). Adsorption kinetics The kinetics of adsorption based on the overall adsorption rate by adsorbents is calculated using the Lagergren’s firstorder kinetic equation and pseudo-second-order (Zawani et al. 2009). The first-order rate expression of Lagergren is given as: dq=dt ¼ k1 ðqe qt Þ

ð5Þ

where qe and qt are the amount of Zn (II) adsorbed on the adsorbent at equilibrium and time t, respectively (mg g-1), and k1 is the rate constant of the first-order adsorption (min-1). Integrating equation (L) for the boundary conditions t = 0 to t = t is the following: ln (qe qt Þ ¼ lnqe k1 t

ð6Þ

The plot of log (qe - qt) versus t will give a straight line and the value of k1 can be obtained from the slope of the graph. The second-order kinetic model is expressed as: 2

dq=dt ¼ k2 ðqe qt Þ ;

ð7Þ

where k2 is the pseudo-second-order rate constant of adsorption (g mg-1 min-1). The linearized integrated form of (7) is given as: ðt=qt Þ ¼ 1=ðk2 q2e Þ þ 1=ðqe tÞ

ð8Þ

If the pseudo-second-order kinetics is applicable to the system, then the plot of t/qt versus t will give a linear relationship with 1/qe and 1/(k2 q2e ), respectively (Zawani et al. 2009). The values of qe and k2 can be determined from the slope and intercept from Eq. (8) (Hamadi et al. 2001). The ion exchange of Zn (II) was found to be rapid and the equilibrium was achieved within 2 h. The linear regression correlation coefficient (R2) value was determined below 0.95 from the plot between log (qe - qt) versus time (t) that disables the application of Lagergren’s first-order to predict the sorption kinetic model. The k2 value was calculated as 0.020786528 g mg-1 min-1 from the plot between t/q versus t. The r2 value was found to be 0.999 confirming that the adsorption data are well presented by pseudo-second-order kinetics. This supports

the assumption behind the model that the adsorption is due to chemisorption (Cúrkovic´ et al. 1997).

Conclusion In the present study, the potential usage of a low-cost, natural adsorbent mixture composed of Turkish leonardite and clinoptilolite, was investigated by the batch adsorption method for removal of Zn (II) ions from an aqueous solution with respect to different experimental parameters including mixing ratio, contact time, pH, adsorbent amount, and temperature. The removal efficiency of Zn (II) was increased by increasing the leonardite proportion and pH value. The uptake equilibrium was ideally described by the Langmuir sorption isotherm and equations gave satisfactory correlation coefficients. The values of DG° and DH° revealed the spontaneous and exothermic nature of the sorption process. The kinetic data were fitted to the pseudo-second-order kinetic model which is important for designing and modeling the water treatment processes. The maximum adsorption amount of Zn (II) onto the LC was 454.55 mg g-1 which is significantly higher than the other reported natural unmodified adsorbents. The results demonstrated that LC can be effectively utilized as an unpretreated inexpensive adsorbent to remove zinc from industrial wastewater. Acknowledgments The author wishes to acknowledge the Turkey Prime Ministry State Planning Organization for the equipment supplied (Project no: 2007DPT001) and The Company Gordes Mining, Manisa, Turkey, for providing the clinoptilolite and leonardite samples.

References Ahluwalia SS, Goyal D (2005) Removal of heavy metals by waste tea leaves from aqueous solution. Eng Life Sci 5(2):158–162 Angell CL (1973) Raman spectroscopic investigation of zeolite and adsorbed molecules. J Phys Chem 77(2):222–227 Bailey SE, Olin TJ, Bricka RM, Adrian DD (1999) A review of potentially low-cost sorbents for heavy metals. Wat Res 33(11):2469–2479 Breck D (1974) Physical properties of crystalline zeolites. In: Breck DW (ed) Zeolite molecular sieves: structure, chemistry, and use. John Wiley & Sons Buasri A, Yongbut P, Chaiyut N, Phattarasirichot K (2008) Adsorption equilibrium of zinc ions from aqueous solution by using modified clinoptilolite. Chiang Mai J Sci 35(1):56–62 Cincotti A, Lai N, Orru R, Cao G (2001) Sardinian natural clinoptilolites for heavy metals and ammonium removal: experimental and modeling. Chem Eng J 84(3):275–282 Cincotti A, Mameli A, Locci MA, Orru R, Cao G (2006) Heavy metal uptake by Sardinian natural zeolites: experiment and modeling. Ind Eng Chem Res 45:1074–1084 Colella C (1998) Environmental applications of natural zeolitic materials based on their ion exchange properties. In: Misaelides

123

3040 P, Macasek F, Pinnavaia TJ, Colella C (eds) Natural microporous materials in environmental technology. Kluwer Academic Publishers, Dordrecht Çoruh S (2008) The removal of zinc ions by natural and conditioned. Desalination 225:41–57 Cúrkovic´ L, Cerjan-Stefanovic´ S´, Filipan T (1997) Metal ion exchange by natural and modified zeolites. Water Res 31(6): 1379–1382 Erdem E, Karapinar N, Donat R (2004) The removal of heavy metal cations by natural zeolites. J Colloid Interf Sci 280:309–314 Francioso O, Sanchez-Cortes S, Tugnoli V, Marzadori C, Ciavatta C (2001) Spectroscopic study (DRIFT, SERS and 1H NMR) of peat leonardite and lignite humic substances. J Mol Struct 565–566: 481–485 Gossart P, Semmoud A, Ruckebusch C, Huvenne JP (2003) Multivariate curve resolutions applied to Fourier transform infrared spectra of macromolecules: structural characterisation of the acid form and the salt form of humic acids in interaction with lead. Anal Chim Acta 477:201–209 Hamadi NK, Chen XD, Farid MM, Lu MGQ (2001) Adsorption kinetics for the removal of chromium (VI) from aqueous solution by adsorbents derived from used tyres and sawdust. Chem Eng J 84:95–105 Hanzlı´k P, Jehlicˇka J, Weishauptova´ Z, Sˇebek O (2004) Adsorption of copper, cadmium and silver from aqueous solutions onto natural carbonaceous materials. Plant Soil Environ 50(6):257–264 Hernandez MA, Corona L, Rojas F (2000) Adsorption characteristics of natural erionite, clinoptilolite and mordenite zeolites from Mexico. Adsorption 6:33–45 Horsfall M, Abia AA (2003) Sorption of cadmium(II) and zinc(II) ions from aqueous solutions by cassava waste biomass (Manihot sculenta Cranz). Water Res 37:4913–4923 Igwe JC, Abia AA (2007) Adsorption isotherm studies of Cd (II), Pb(II) and Zn (II) ions bioremediation from aqueous solution using unmodified and EDTA-modified maize crob. Ecl Quı´m Saõ Paulo 32(1):33–42 Katanyoo S, Naksata W, Sooksamiti P, Thiansem S, Arquero OA (2012) Adsorption of zinc ion on leonardite prepared from coal waste. Orient J Chem 28(1):373–378 Kennedy LJ, Vijaya JJ, Sekaran G, Kayalvizhi K (2007) Equilibrium, kinetic and thermodynamic studies on the adsorption of m-cresol onto micro- and mesoporous carbon. J Hazard Mater 149: 134–143 Kenney JF, Keeping ES (1962) Root mean square in mathematics of statistics, 3rd edn. Van Nostrand, Princeton Kilic E, Font J, Puig R, Colak S, Celik D (2011) Chromium recovery from tannery sludge with saponin and oxidative remediation. J Hazard Mater 185(1):456–462 Kragovic´ M, Dakovic´ A, Sekulic´ Z, Trgo M, Ugrinab M, Peric´ J, Gatta GD (2012) Removal of lead from aqueous solutions by using the natural and Fe(III)-modified zeolite. Appl Surf Sci 258:3667–3673 Krol M, Mozgawa W (2011) The spectroscopic study of building composites containing natural sorbents. Spectrochim Acta A 79:743–748 Li Y, Yue Q, Gao B (2010) Adsorption kinetics and desorption of Cu (II) and Zn(II) from aqueous solution onto humic acid. J Hazard Mater 178:455–461 Madejova J (2003) FTIR techniques in clay mineral studies. Vib Spectrosc 31:1–10 Montilla I, Parra MA, Torrent J (2003) Zinc phytotoxicity to oilseed rape grown on zinc-loaded substrates consisting of Fe oxidecoated and calcite sand. Plant Soil 257(1):227–236 Motsi T, Rowson NZ, Simmons MJH (2009) Adsorption of heavy metals from acid mine drainage by natural zeolite. Int J Miner Process 92:42–48

123

Environ Earth Sci (2013) 70:3031–3041 Mozgawa W, Bajda T (2006) Application of vibrational spectra in the studies of cation sorption on zeolites. J Mol Struct 792–793: 170–175 Mozgawa W, Handke M, Jastrzebski W (2004) Vibrational spectra of aluminosilicate structural clusters. J Mol Struct (704):247–257 Olivella MA, del Rıò JC, Palacios J, Vairavamurthy AM, de las Heras FXC (2002) Characterization of humic acid from leonardite coal: an integrated study of PY-GC-MS, XPS and XANES techniques. J Anal Appl Pyrol 63:59–68 Ostrooumov M, Cappelletti P, de Gennaro R (2012) Mineralogical study of zeolite from New Mexican deposits (Cuitzeo area, Michoacan, Mexico). Appl Clay Sci 55:27–35 Ouki SK, Kavannagh M (1997) Performance of natural zeolites for the treatment of mixed metal contaminated effluents. Waste Manage Res 15:383–394 Ozdes D, Duran C, Senturk HB (2011) Adsorptive removal of Cd(II) and Pb(II) ions from aqueous solutions by using Turkish illitic clay. J Environ Manage 92(12):3082–3090 Panayotova MI, Vekilov B (2002) Kinetics of heavy metal ions removal by use of natural zeolite. J Environ Sci Health A 37(2):127–136 Peric´ J, Trgo M, Medvidovic´ NV (2004) Removal of zinc, copper and lead by natural zeolite—a comparison of adsorption isotherms. Water Res 38:1893–1899 Qi BC, Aldrich C (2008) Biosorption of heavy metals from aqueous solutions with tobacco dust. Bioresour Technol 99:5595–5601 Rao GPC, Satyaveni S, Ramesh A, Seshaiah K, Murthy KSN, Choudary NV (2006) Sorption of cadmium and zinc from aqueous solutions by zeolite 4A, zeolite 13X and bentonite. J Environ Manage 81(3):265–272 Salem A, Sene RA (2011) Removal of lead from solution by combination of natural zeolite–kaolin–bentonite as a new lowcost adsorbent. Chem Eng J 174:619–628 Sardashti AR, Alidoost M (2008) From molecular understanding to innovative applications of humic substances. In: Permikova IV, Kulikova NA (eds) Studies of the structure of extracted humic acid from Naharhoran forest Gorgan’s soil, vol I. Moscow – Saint Petersburg Russia, pp 117–120 Shahmohammadi-Kalalagh S, Babazadeh H, Nazemi AH, Manshouri M (2011) Isotherm and kinetic studies on adsorption of Pb, Zn and Cu by kaolinite. Casp J Env Sci 9(2):243–255 Shahwan T, Zu¨nbu¨l B, Eroglu AE, Yilmaz S (2005) Effect of magnesium carbonate on the uptake of aqueous zinc and lead ions by natural kaolinite and clinoptilolite. Appl Clay Sci 30(3–4):209–218 Sole´ M, Casas JM, Lao C (2003) Removal of Zn from aqueous solutions by low-rank coal. Water Air Soil Poll 144:57–65 Souag R, Touaibia D, Benayada B, Boucenna A (2009) Adsorption of heavy metals (Cd, Zn and Pb) from water using keratin powder prepared from Algerien Sheep Hoofs. Eur J Sci Res 35(3): 416–425 Srivastava SK, Singh AK, Sharma A (1994) Studies on the uptake of lead and zinc by lignin obtained from black liquor—a paper industry waste material. Environ Technol 15:353–361 Stathi P, Deligiannakis Y (2010) Humic acid-inspired hybrid materials as heavy metal absorbents. J Colloid Interf Sci 351:239–247 Stevenson FJ (1994) Humus chemistry (genesis, composition, reactions), function of organic matter in soil, 2nd edn. Wiley, New York Tan IAW, Ahmad AL, Hameed BH (2008) Adsorption of basic dye on high-surface-area activated carbon prepared from coconut husk: equilibrium, kinetic and thermodynamic studies. J Hazard Mater 154:337–346 Terkhi MC, Taleb MC, Gossart P, Semmoud MC, Addoua A (2008) Fourier transform infrared study of mercury interaction with

Environ Earth Sci (2013) 70:3031–3041 carboxyl groups in humic acids. J Photoch Photobio A 198:205–214 Trgo M, Peric´ J, Vukojevic´ Medvidovic´ N (2006) Investigations of different kinetic models for zinc ions uptake by a natural zeolitic tuff. J Environ Manage 79(3):298–304 USEPA (2005) Priority pollutants, code of federal regulations. Title 40: protection of environment, chap I. Appendix A to 40 CFR Part 423. Environmental Protection Agency

3041 Yousef RI, El-Eswed B, Al-Muhtaseb AH (2011) Adsorption characteristics of natural zeolites as solid adsorbents for phenol removal from aqueous solutions: kinetics, mechanism, and thermodynamics studies. Chem Eng J 171:1143–1149 Zawani Z, Luqman Chuah A, Choong TSYT (2009) Equilibrium, kinetics and thermodynamic studies: adsorption of Remazol Black 5 on the Palm Kernel Shell Activated Carbon (PKS-AC). Eur J Sci Res 37(1):67–76

123