Performance and mechanism of adsorption and desorption for copper(II) on corn straw modified with sulfhydryl group

The pollution of water bodies by Cu(II) is a significant environmental concern. In this paper, we developed a novel straw-based adsorbent, mercaptopropionyl corn straw (MPCS), by the pretreatment with alkali and the modification sulfhydryl group for effectively removing Cu(II) in aqueous solutions. Some characterization results revealed that the abundant functional groups (—OH, —SH, —NH₂, —COOH) on straw played a crucial role in facilitating Cu(II) adsorption onto MPCS. Adsorption experiments were carried out to assess the performance of MPCS for removing Cu(II) through static adsorption. Under optimized conditions including 150 rpm of oscillation rate, 35 °C of adsorption temperature, and 80 min of adsorption time with 50 mg/L of Cu(II) at pH 5.0 in aqueous solution, the removal efficiency reached as high as 98.86 %, and the maximum adsorption capacity was 8.25 mg/g. The adsorption process exhibited conformity with both Langmuir model and pseudo-second-order kinetic model. Thermomechanical analysis indicated that the adsorption was an endothermic spontaneous process. Furthermore, desorption kinetics demonstrated that HCl and EDTA could effectively desorb MPCS-Cu with an endothermic process following pseudo-second-order kinetic model. Five consecutive cycles confirmed the excellent regeneration performance of MPCS. Finally, based on experimental data and analysis results presented herein, a potential adsorption mechanism was proposed.