Adsorption of Indium(III) from aqueous solutions using SQD-85 resin

Size: px

Start display at page:

Download "Adsorption of Indium(III) from aqueous solutions using SQD-85 resin"

Vivien Cobb
5 years ago
Views:

1 Indian Journal of Chemical Technology Vol., May-July 015, pp Adsorption of Indium(III) from aqueous solutions using SQD-85 resin Hao Zhang 1, Xinyi Chen 1, Chunhua Xiong 1, *, Caiping Yao 1, Jiandin Li 1, Xuming Zheng & Jianxiong Jiang 3 1 Department of Applied Chemistry, Zhejiang Gongshang University, Hangzhou, 31001, China Engineering Research Center for Eco-Dying & Finishing of Textiles, Ministry of Education, Zhejiang Sci-Tech University, Zhejiang Province, , China 3 Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education, Hangzhou Normal University, Zhejiang Province, 31001, China xiongch@163.com Received 3 May 013; accepted 16 January 014 The feasibility of using SQD-85 resin as an adsorbent for indium(iii) has been investigated. Various conditions such as solution ph, temperature and contact time on the adsorption of indium(iii) has also been examined. The results show that the optimal adsorption condition of SQD-85 resin for indium(iii) is achieved at the ph value of 5.5 in acetic acid-sodium acetate (HAc-NaAc) buffer solution. The maximum uptake capacity of indium(iii) is 97. mg/g at 98K at an initial ph value of 5.5. The isotherms data fits well with Langmuir model better than Freundlich model. Kinetics on the adsorption of indium(iii) has been studied. The apparent activation energy Ea and adsorption rate constant k 98 values are 1.11 kj/mol and min -1, respectively. The thermodynamic parameters with the S value of J/(K mol) and H value of kj/mol indicate that the adsorption process is endothermic in nature. While the decrease of Gibbs free energy ( G) with the temperature increasing indicates that the process occurred spontaneously. Finally, indium(iii) can be eluted using 0.1 mol/l HCl solution and the elution percentage was relatively high (97%). Resins before and after indium(iii) and adsorbed and characterized by IR spectroscopy and thermo-gravimetric analysis. Keywords: Adsorption, Indium(III), Kinetics, SQD-85 resin, Thermodynamics Indium is a rare and valuable metal which is widely used in a variety of industries, such as liquid crystal displays (LCDs) 1-, semiconductors, low-temperature solders and infrared photodetectors 3. Though it is widely distributed in the earth's crust, the reserves of indium are very small and often appear in low concentrations. Considering the current indium metal consumption rates, it is estimated that the global reserves of indium metal can only last for another 0 more years. Therefore, there is a growing interest in the development of new indium metal recovery methods 6. Most studies related to the extraction of indium(iii) have employed chemical precipitation 7-9, solvent extraction 10, and liquid membrane 11. However, for solutions of low concentrations of indium(iii), these conventional methods have a lot of disadvantages, such as high reagent/energy requirements, the generation of toxic sludge or other waste products, and high capital costs. Compared with the other methods, ion exchange has received a considerable attention in recent years because of its relatively low- cost, effectiveness and easy handling. SQD-85 resin, as one of the typical ion exchange resins, contain functional group of COOH, which possesses not only protons that can exchange with cations, but also oxygen atoms that can coordinate directly with metal ion and form stable coordinate compound. Also, it is easy to obtain since it s commercially produced. Due to the above mentioned properties, SQD-85 resin has been preferred in indium(iii) sorption for metal recovering. In this work, SQD-85 resin was used for the recovery of indium(iii) from aqueous solution using batch and column adsorption methods. Some factors affecting adsorption, such as initial ph of solution, temperature and contact time have been examined. Kinetics and isotherm adsorption experiments were carried out. Thermodynamic parameters of adsorption for indium(iii) ion were calculated. The Thomas model was applied to the experimental data that is obtained from the column experiments. The experimental results may provide a new pathway to the recovery of indium(iii) from aqueous solutions in the hydrometallurgical systems.

2 114 INDIAN J. CHEM. TECHNOL., MAY-JULY 015 Experimental Section Apparatus The concentrations of metal ion were determined with Shimadzu UV-550 ultraviolet-visible spectrophotometer. The resin dosage was measured by electronic balance of Sartorius BS 4s. Mettler Toledo delta 30 ph meter was used for measuring the ph values of solutions. The samples were shaken in the DSHZ-300A and THZ-C-1 temperature constant shaking machine. The water used in the present work was purified using Mol Research analysis-type ultra-pure water machine. The thermogravimetric analysis was investigated using Mettler TGA/DSCl simultaneous thermal analyzer (with a temperature range of C, heating rate of 0 C/min, atmosphere of N ). The sample for IR spectroscopy was described by Nicolet 380 FT-IR. Materials SQD-85 resin was supplied by Jiangsu Suqing Water Treatment Engineering Group Co., Ltd (Jiangsu, China). And the properties were shown in Table 1. The standard stock solutions were prepared by dissolving an appropriate amount of indium (AR) in 6 mol/l HCl. HAc-NaAc (1 mol/l) solutions with ph 3.5~6.0 and C 6 H 1 N 4 -HCl buffer solutions with ph 5.4 were prepared from the HAc, NaAc, C 6 H 1 N 4 and HCl solutions. The chromophoric reagent of 0.% xylenol orange solution was obtained by dissolving g xylenol orange powder into 100 ml purified water. All other chemicals were of analytical grade and purified water was used throughout. Batch experiments Experiments were conducted in a certain range of ph, temperature and contact time. The operation for the adsorption of indium(iii) is usually carried out in batch vessels 1. Batch experiments were performed under kinetic and equilibrium conditions. A desired amount of Resin Table 1 General description and properties of resin Macroporous weak acid resin Functional group COOH Structure Macroporous Containing moisture/% 45~50 Capacity/(mmol g 1 ) 14.0 Wet superficial density/(g ml 1 ) 0.70~0.80 True wet density/(g ml 1 ) 1.10~1.0 pretreated SQD-85 resin was weighed and added into a conical flask, in which a desired volume of buffer solution with ph 5.5 was added. After 4 h, a required amount of standard solution of indium(iii) was put in. The flask was shaken in a shaker at a given constant temperature. The upper layer of clear solution was taken for analysis until adsorption equilibrium was reached. The procedure of kinetic tests was identical to that of the equilibrium tests. The aqueous samples were taken at preset time intervals and the concentrations of indium(iii) were similarly measured. Column experiments In the column experiments, continuous packed bed studies were performed in a fixed bed mini glass column ( 6 mm 30 cm) with 300 mg resin. The SQD-85 resin in the column was pre-soaked for 4 h before starting the experiment. The indium(iii) solution at a known concentration and flow rate was passed continuously through the stationary bed of sorbent in up-flow mode to avoid diluting the effluent. The experiment was continued until a constant indium(iii) ions concentration was obtained. The column studies were performed at the optimum ph value determined from batch studies and at a constant temperature of 5 C to be representative of environmentally relevant condition. Analytical method A solution containing of indium(iii) was accurately added into a 10 ml colorimetric tube, and then 1.0 ml visualization reagent of 0.% xylenol orange and 4 ml C 6 H 1 N 4 -HCl buffer solution were added. After the addition of purified water to the mark of colorimetric tube, the absorbency was determined in a 1 cm colorimetric vessel at a wavelength of 515 nm and compared with the blank test. The adsorption capacity (Q) and distribution coefficient (D) were calculated according to the following formulas: Q D C C W 0 e = V (1) C C V C W 0 e = () e where C 0 is the initial concentration in solution (mg/ml); C e is the equilibrium concentration in solution (mg/ml); V is the total volume of solution (ml); W is the dry mass of resin (g).

3 ZHANG et al.: ADSORPTION OF INDIUM(III) FROM AQUEOUS SOLUTIONS USING SQD-85 RESIN 115 Results and Discussion Influence of ph on the adsorption for indium(iii) The ph of aqueous solution has been identified as the most important variable governing the adsorption capacity of resins. In order to investigate the effect of ph on the adsorption of indium(iii) ions on the SQD- 85 resin, the adsorption experiments were carried out by varying the initial ph value of the solution over range of 3.5~6.0. The distribution coefficient was very small in the ph range of 3.5~5.0 and a sharp increase of the distribution coefficient occurred in the ph range of 5.0~5.5. The ph value affected the surface charge of the adsorbent and the degree of ionization and speciation of the adsorbate in aqueous solution 13. The indium(iii) uptake increased as the ph went up, and it can be explained based on a decrease in competition between protons (H + ) and indium(iii) for the same adsorption sites and by the decrease of the positive surface charge on the resin resulting in a lower electrostatic repulsion between the surface of resin and indium(iii). While at ph 6.0, the metal ion was prone deposit. Hence the adsorption ph value was optimized as 5.5. Determination of adsorption rate constant and apparent activation energy The influence of contact time on the adsorption of indium(iii) onto SQD-85 resin (Fig. 1) was investigated at the temperature of 88, 98 and 308 K. It is clear that the adsorption amount of indium(iii) increased as the contact time elapsed. The adsorption amount of metal ions increased rapidly during the first few hours, and then increased slowly until equilibrium state was reached. The equilibrium for the adsorption of indium(iii) was reached in 13 h. Due to the existence of greater number of resin sites available for metal ions adsorption, the initial adsorption rate was very fast. As the remaining vacant surface sites decreased and due to formation of repulsive forces between the metals on the solid surface and in the liquid phase, the adsorption rate slowed down. The kinetic curves are single, smooth, and continuous, indicating the possible monolayer coverage of metal ions on the surface of the resins 14. The kinetics of adsorption can be described by the first-order kinetic model expression 15 that is given by: k1 log( Qe Qt ) = logq1 t (3).303 The second-order kinetic model equation is given as 16 : t Qt 1 t = + (4) k Q Q where Q t and Q e are the adsorption amounts of indium(iii) at certain time and at equilibrium time (mg/g), Q 1 and Q are the calculated adsorption capacities of first-order kinetic model and secondorder kinetic model (mg/g), respectively, and k 1 and k are is the adsorption rate constant of first-order kinetic model and second-order kinetic model (g/(mg min)). As shown in Table, the correlation coefficient (R 1 ) for the first-order kinetic model is better than the the correlation coefficient (R ) for the second-order kinetic model. Moreover, the calculated adsorption capacity of first-order kinetic model produces good fittings which indicated that the interactions would follow the first-order kinetic model. This meant that the liquid film spreading was the predominating step of the adsorption process 17. According to the Arrhenius equation 18 : E a lg k = + lg A... (4).303RT Fig. 1 Effect of contact time on adsorption where E a is the Arrhenius activation energy for the adsorption process indicating the minimum energy that reactants must have for the reaction to proceed, A is the Arrhenius factor, R is the gas constant (8.314 J/(mol K), k is the adsorption rate constant and T is the solution temperature. E a and A values can be

4 116 INDIAN J. CHEM. TECHNOL., MAY-JULY 015 Table Kinetics model constants for adsorption of indium(iii) by SQD-85 resin T (K) Q e (mg/g) First-order kinetic model Second-order kinetic model Q 1 ( mg/g) k 1 (min 1 ) R Q (mg/g) k 1 ( min 1 ) R estimated from slope and intercept value of this plot lgk vs 1/T, respectively. The correlation coefficient of the straight line R = was achieved. The apparent activation energy E a was 1.11 kj/mol, which could be considered as a low energy barrier in this study. It can be deduced that the adsorption speed accelerated when the temperature rose within the scope of experimental temperature. Isotherm adsorption curve The Langmuir and Freundlich models are the most frequently employed models that have been published in the literature to describe experimental data of adsorption isotherms. The Langmuir and Freundlich isotherms are studied in 30 ml solutions with the initial metal ions concentration varying in the range of 6 mg/30 ml~1 mg/30ml with 15.0 mg resin at desired ph, 100 rpm and 88, 98 and 308 K. The adsorption data are analyzed to see whether the isotherm obeyed the Langmuir 19 and Freundlich 0 isotherm models. The linear forms of the Langmuir and Freundlich isotherms are represented by the following equations: Langmuir isotherm: Ce Ce 1 = +... (5) Q Q bq e m m Freundlich isotherm: 1 log = log K f + log Ce... (6) n where Q e is the equilibrium indium(iii) ions concentration on the adsorbent (mg/g), C e is the equilibrium indium(iii) ions concentration in solution (mg/ml), Q m is the monolayer capacity of the adsorbent (mg/g), b is the Langmuir constant and related to the free energy of adsorption, K f is Freundlich constant and n (dimensionless) is the heterogeneity factor. According to the results, higher R values (R 88K =0.990, R 98K =0.971, R 308K =0.9945) were obtained from Langmuir model than from the Freundlich model (R 88K =0.9881, R 98K =0.9671, R 308K =0.9875), suggesting the applicability of Langmuir model to this system. The Langmuir isotherms model assumes that adsorption takes place at specific homogeneous sites within the adsorbents and has been successfully applied to many other real adsorption processes. It is evident that the adsorption of indium(iii) ion onto SQD-85 resin is fitted better to the Langmuir isotherm than that of the Freundlich isotherm models. Thermodynamic parameters In any adsorption procedure, both energy and entropy considerations should be taken into account in order to determine which process will take place spontaneously. Values of thermodynamic parameters are the actual indicators for practical application of a process. The effect of temperature on the adsorption characteristics of indium(iii) onto SQD-85 resin was investigated in the range of 88~308 K. Thermodynamic parameters such as standard free energy change ( G), standard enthalpy changes ( H) and standard entropy changes ( S) were calculated by using the following equation: S H lg D =... (7).303R.303RT G = H T S... (8) where D is distribution coefficient; R is the gas constant (8.314 J/(mol K)); and T is the absolute temperature. The plot of lgd vs 1/T gives the straight line from which H and G is estimated by the slope and intercept of the linear form and the G values at different temperatures were calculated using Eq.(8), respectively. Table 3 shows the values of thermodynamic parameters of indium(iii) ions adsorption on SQD-85 resin. As presented in the table, the negative G values at given temperatures indicate the spontaneous nature of the adsorption and confirm the feasibility of the adsorption process. The positive values of S referred to the increased

5 ZHANG et al.: ADSORPTION OF INDIUM(III) FROM AQUEOUS SOLUTIONS USING SQD-85 RESIN 117 Table 3 Thermodynamic parameters calculated for adsorption of indium(iii) on SQD-85 resin at different temperatures H kj/mol S G (kj/mol) J/K mol T = 88 K T = 98 K T = 308 K randomness at the solid-solution interface. The positive values of H reveal that the adsorption is endothermic in nature. The enthalpy change value is kj/mol, indicating that physisorption and chemisorption coexist during adsorption process 1,. Elution test Whether an adsorbent is economically attractive in removal of metal ions from aqueous solution depends not only on the adsorptive capacity, but also on how well the adsorbent can be regenerated again. For repeated use of an adsorbent, adsorbed metal ions should be easily desorbed under suitable conditions. In this work, desorption of indium(iii) ions with various concentration of HCl eluent solution was carried out. The percentages of elution are 89, 97, 95 and 91% for 0.05, 0.1, 0. and 0.3 mol/l HCl concentration, respectively. The results show that the indium(iii) adsorbed by SQD-85 resin can easily be desorbed, which indicates that SQD-85 resin can be employed repeatedly in indium(iii) adsorption. Column study Dynamic adsorption curve The breakthrough curve shows the loading behavior of indium(iii) to be removed from solution in a fixed bed 3. Total adsorbed indium(iii) quantity (Q; mg/g) in the column for a given feed concentration and flow rate is calculated from equation 4 : Q ( C C e ) m v = 0 dv... (9) 0 where C 0 and C e are metal ion concentrations in the influent and effluent, respectively, m is the total mass of the sorbent loaded in the column and V is the volume of metal solution passed through the column. Q is the experimental maximum sorption capacity value obtained by graphical integration. The experimental breakthrough curves of indium(iii) by SQD-85 resin are shown in Fig.. Successful design of a column adsorption process requires prediction of the concentration vs time profile or breakthrough curve for the effluent. The maximum sorption Fig. Breakthrough curve for indium(iii) on SQD-85 resin Fig. 3 Thomas model for the continuous adsorption of indium(iii) capacity of resin is also needed in design. Traditionally, the Thomas model is used to fulfill the purpose. The model has the following form 5 : Ce 1 = (10) C 1 + exp K ( Qm C V ) / θ [ ] 0 T 0 where K T is the Thomas rate constant (ml min 1 mg 1 ) and is the volumetric flow rate (ml min 1 ). The linearized form of the Thomas model is as follows: C 0 KTQm KTC0 ln 1 = V Ce θ θ (11) The kinetic coefficient K T and the adsorption capacity of the column Q can be determined from a plot of ln[(c 0 /C e -1] vs t at a certain flow rate as shown in Fig. 3. The outlet time t is from V/. The Thomas equation coefficients for indium(iii) adsorption were K T = ml/(min mg) and Q = mg/g.

6 118 INDIAN J. CHEM. TECHNOL., MAY-JULY 015 Dynamic desorption curve Efficient elution of adsorbed solute from SQD-85 resin in column was essential to ensure the reuse of SQD-85 for repeated adsorption/desorption cycles. With respect to the stripping of indium(iii) from SQD-85, 0.1 mol/l HCl eluant was employed. A sharp increase of indium(iii) concentration at the beginning of acid elution was observed. Desorption curve was plotted the effluent concentration (C e ) vs elution volume (V) from the column at a certain flow rate. It is seen that, 60 ml 0.1 mol/l HCl eluent solution provided effectiveness of the desorption of indium(iii) from SQD-85, after which further desorption was negligible. These results show that efficient elution of indium(iii) from SQD-85 in column is practical, which indicates that the resin has a potential repeatedly in removing indium(iii) from aqueous solutions. TG analysis The thermo-gravimetric analysis (TGA) curves for SQD-85 resin before and after adsorption of indium(iii) were detected at the range of 0~1000 C and the TGA curves are illustrated in Fig. 4. When the temperature is lower than 50 C, the SQD-85 resin presents an outstanding thermal stability. However, at the temperature range of 100 C to 500 C, SQD-85- indium(iii) demonstrate two decomposition steps: one is at 00 C and the other one is at 450 C. These results mentioned above indicate that the SQD-85 resin within the adsorption of indium(iii) ions can lower the thermal stability and accelerate the decomposition rate. The higher residue (38.6%) of SQD-85-indium(III) compared with that of SQD-85 (10.%) revealed that indium(iii) ions were adsorbed onto SQD-85 resin. IR Spectra IR analysis is an important analytical tool determination of adsorption mechanism. The results about structural caused by SQD-85 resin loading with indium(iii) was given by FTIR spectra. From the experimental results above, the functional groups of SQD-85 resin, COOH and indium(iii) were supposed to form bonds. In order to confirm this, the spectra of resin, before and after indium(iii) was adsorbed, were compared. It was found that the characteristic adsorption peak of bond C=O (171 cm -1 ) decreased in intensity after indium(iii) adsorption, and the new peak 167 cm -1 formed. After the adsorption, the characteristic peak of the bond Fig. 4 Thermo-gravimetric analysis (TGA) for the SQD-85 resin before and after the adsorption of indium(iii) ions OH shifts from 3437 to 340 cm 1. The results showed that the hydrogen and oxygen atoms in the OH and C=O groups were involved in indium(iii) adsorption. The adsorption mechanism might be partly a result of the ion exchange or complexation between the ions and carboxyl groups of SQD-85 resin. Conclusion The adsorption onto SQD-85 resin is highly dependent on the ph value. In addition, contact time and system temperature also influences the adsorption processes. The maximum adsorption capacity of the resin for indium(iii) is 97. mg/g in ph 5.5 HAc- NaAc system at 98 K. And it is found that 0.1 mol/l HCl solution provides effectiveness for desorption of indium(iii) from SQD-85 resin. Isotherm studies show that the adsorption process of SQD-85 resin for indium(iii) follows both the Langmuir and Freundlich isotherm model. The apparent activation energy E a was 1.11 kj/mol, indicating that the adsorption had a low potential barrier. Thermodynamic parameters ( H, S, G) indicate that the adsorption of indium(iii) on SQD-85 resin is a spontaneous reaction and is endothermic in nature. Column experiments show that it is possible to remove indium(iii) ions from aqueous medium dynamically. And the resin can be used in the environmental protection and hydrometallurgical system. Acknowledgement The project was supported by the National Natural Science Foundation of China (No.17635) and the

7 ZHANG et al.: ADSORPTION OF INDIUM(III) FROM AQUEOUS SOLUTIONS USING SQD-85 RESIN 119 Special Major Science and Technology Project of Zhejiang Province, China (No. 011C11098). References 1 Yang J X, Retegan T & Ekberg C, Hydrometallurgy, 137 (013) 68. Lee C H, Jeong M K & Kilicaslan M F, Waste Manage, 33 (013) Chou W L & Yang K C, J. Hazard. Mater, 154 (008) Gupta B, Mudhar N & Singh I, Sep Purif Technol, 57 (007) Chou W L & Huang Y H, J Hazard Mater, 17 (009) Liu H M, Wu C C & Lin Y H, J Hazard Mater, 17 (009) Barakat M A, Hydrometallurgy, 49 (1998) Jiang J B, Liang D Q & Zhong Q D, Hydrometallurgy, 106 (011) Li Y H, Liu Z H & Li Q H, Hydrometallurgy, 105 (011) Virolainen S, Ibana D & Paatero E, Hydrometallurgy, 107 (011) Guerriero R, Meregalli L & Zhang X, Hydrometallurgy, 0 (1988) Xiong C H & Yao C P, J Hazard Mater, 166 (009) Imamoglu M & Tekir O, Desalination, 8 (008) Aroua M K, Leong S P P & Teo L Y, Bioresource Techmol, 99 (008) Plazinski W, Appl Surf Sci, 56 (010) Ofomaja A E, Naidoo E B & Modose S J, Desalination, 51 (010) Boyd G E, Adamson A W & Myers L S, J Am Chem Soc, 69 (1947) Kandelbauer A, Wuzella G & Mahendran A, Chem Eng J, 15 (009) Langmuir I, J Am Chem Soc, 40 (1918) Freundlich H M F, Z Phys Chem, 57 (1906) Jing X S, Liu F Q & Yang X, J Hazard Mater, 167 (009) 589. Xiong C H, Pi L L & Chen X Y, Carbohyd Polym, 98 (013) 1. 3 Xiong C H, Chen X Y & Yao C P, Curr Org Chem, 16 (01) Tabakci M & Yilmaz M, J Hazard Mater, 151 (008) Mathialagan T & Viraraghavan T, J Hazard Mater, 94 (00) 91.

a variety of living species. Therefore, elimination of heavy metals/dyes from water and

Chapter IV Studies on the adsorption of metal ions and dyes The presence of heavy metals/dyes in the aquatic environment can be detrimental to a variety of living species. Therefore, elimination of heavy