Synthesis of silica supported thiosemicarbazide for Cu(II) and Zn(II) adsorption from ethanol: A comparison with aqueous solution

Abstract Silica supported thiosemicarbazide (SG-GPTS-ATS) was synthesized for adsorption of Cu(II) and Zn(II) from ethanol and aqueous solutions, respectively. SG-GPTS-ATS was fully characterized and the adsorption property was systematically investigated. Result illustrates the adsorption capacity of SG-GPTS-ATS for both Cu(II) and Zn(II) in ethanol solution is superior than that in aqueous solution. The equilibrium adsorption time for Cu(II) is 150 min in both solutions, while these for Zn(II) are 130 and 160 min in ethanol and aqueous solution. Adsorption kinetic illustrates the adsorption is controlled by film diffusion step and follows pseudo-second-order model. The adsorption isotherm shows the uptake of Cu(II) and Zn(II) can be increased by increasing the initial concentration of metal ion and temperature in both ethanol and aqueous solution. The adsorption is proceeded by monolayer behavior and is endothermic, spontaneous, and entropy increased in nature. The adsorption mechanism analysis illustrates the capture of Cu(II) and Zn(II) by SG-GPTS-ATS is mainly dominated by hydroxyl O, secondary amine N, and S atoms.