Adsorption behavior of Cd(II) from aqueous solutions onto gel-type weak acid resin

The adsorption and desorption behaviors of Cd(II) on gel-type weak acid resin (GTWAR) have been investigated. The influence of operational conditions such as contact time, initial concentration of Cd(II), initial pH of solution and temperature on the adsorption of Cd(II) has also been examined. The results show that the optimal adsorption condition of GTWAR for Cd(II) is achieved at pH = 5.95 in HAc–NaAc medium. The maximum uptake capacity of Cd(II) is 282 mg/g GTWAR at 298 K. The adsorption of Cd(II) follows the Langmuir isotherm and Freundlich isotherm, and the correlation coefficients have been evaluated. Even kinetics on the adsorption of Cd(II) has been studied. The apparent activation energy Ea and adsorption rate constant k298 values are 2.95 kJ/mol and 3.02 × 10− 5 s− 1, respectively. The calculation data of thermodynamic parameters which ΔS value of 110 J/(mol K) and ΔH value of 13.1 kJ/mol indicate the endothermic nature of the adsorption process. Whilst, a decrease of Gibb's free energy (ΔG) with increasing temperature indicates the spontaneous nature of the adsorption process. Finally, Cd(II) can be eluted by using 0.5 mol/L HCl solution and the gel-type weak acid resin can be regenerated and reused. The sample was described by IR spectroscopy and scanning electron micrographs (SEM).