Effective clay material enriched with thiol groups for Zn(II) removal from aqueous media: A statistical approach based on response surface methodology

In the present work, the removal of Zn(II) ions from aquatic environments onto 3-mercaptopropyl trimethoxysilane modified kaolin (MK) was investigated in a batch system. Moreover, the optimization and effects of independent parameters such as pH, initial Zn(II) concentration (Co, mg/L) and contact time (min) on the uptake of Zn(II) onto MK were examined by response surface methodology (RSM). Central composite design (CCD) in RSM, the most popular statistical technique, was successfully applied to optimize and model the selected parameters (pH, Co, contact time) for Zn(II)% adsorption onto MK. The number of experiments based on CDD was 20, a total of 20 sets which included fourteen factorial points and six center points were performed to obtain the maximum Zn(II) uptake from aqueous solutions. The optimum points obtained from CCD were 6.39, 50.09 mg/L and 76.10 min for pH, Co, and contact time, in their given order. In these optimal conditions, the maximum removal percentage was found to be 86.19%. The results indicated that the removal yield of Zn(II) from aqueous media onto MK was successfully performed by CCD in RSM. It can be concluded that MK is also a promising material for the uptake of other heavy metals similar to Zn.