Simultaneous adsorption of Cu(II) and SO42− ions by a novel silica gel functionalized with a ditopic zwitterionic Schiff base ligand

Abstract A novel silica gel based absorbent SG-H 2 L 1 , capable of simultaneous adsorption of cations and anions from aqueous solution, was prepared by immobilization of a ditopic zwitterionic Schiff base ligand H 2 L 1 onto a modified silica gel. The functionalized silica gels were characterized by Fourier transform infrared spectroscopy, elemental analysis, thermogravimetric analysis and porous structure analysis. The results showed a degree of functionalization of 0.32 mmol H 2 L 1 per gram of SG-H 2 L 1 . The effect of pH, contact time and initial Cu(II) and SO 4 2− concentration parameters on the simultaneous adsorption of Cu(II) and SO 4 2− ions were investigated. The adsorption was fast and the effective pH range for simultaneous adsorption of Cu(II) and SO 4 2− was neutral region. The adsorption study showed that SG-H 2 L 1 had good adsorption efficiency for Cu(II) and SO 4 2− , and the maximum adsorption capacity for Cu(II) and SO 4 2− , respectively, was the same of 0.65 mmol g −1 at 25 °C. Langmuir and Freundlich isotherm models were employed to analyze the experimental data, and the Langmuir model fitted better for both Cu(II) and SO 4 2− . Due to the zwitterionic feature, desorption and regeneration of the absorbent was readily realized by adjusting the pH of the regenerating media with diluted H 2 SO 4 (0.5 mol L −1 ) and ammonia solution (pH = 10), respectively. The new type absorbent SG-H 2 L 1 exhibited good recyclability and reusability for 5 cycles use without deterioration in its functionality. Therefore, the adsorbent can be used effectively for efficient and simultaneous adsorption of Cu(II) and SO 4 2− from waste water. The mechanism for simultaneous adsorption of cation and anions on SG-H 2 L 1 was also discussed. This study provides a strategy for the development of new absorbents for simultaneous adsorption of hazardous metal ions and anions from waste water effluents.