An eco-friendly wheat straw adsorbent functionalized with mercaptopropionyl for the removal of Cu(II) from aqueous solution

A novel absorbent called mercaptopropionyl wheat straw (MPWS) was prepared through alkali pretreatment and mercaptopropionyl modification for efficient removal of Cu(II) from aqueous solutions. Single factor experiments were conducted to investigate various parameters affecting the adsorption of Cu(II) with MPWS. Adsorption experiments including kinetics, isotherms, thermodynamics, as well as various characterization methods were employed to discuss the mechanism of Cu(II) uptake by MPWS in this study. The results showed that MPWS exhibited high removal capacity for Cu(II), achieving a maximum removal efficiency of 97.28 % under optimal conditions: oscillation rate at 150 rpm, temperature at 303 K, duration at 2 h, pH value at 6.0, and initial concentration of Cu(II) at 100 mg/L. The fitting results indicated that pseudo-second-order kinetic model better described the experimental data while Freundlich model provided a better fit for isothermal data. Thermodynamic calculations confirmed that the adsorptive process was spontaneous and endothermic. Characterization techniques such as FTIR spectroscopy SEM imaging, and EDS analysis confirmed chemisorption between Cu(II) ions and functional groups present on MPWS including sulfhydryl groups, amine groups, hydroxyl groups, and carboxyl groups. Overall, the main mechanisms governing Cu(II) uptake onto MPWS included coordination, ion exchange, electrostatic adsorption, and physical adsorption.