Functionalization of chitosan by grafting sulfhydryl groups to intensify the adsorption of arsenite from water

Arsenic pollution with high toxicity is widely distributed and needs to be addressed urgently. Sulfhydryl-functionalized chitosan (Chi-SH) was prepared by the reaction of 3-mercaptopropyltrimethoxysilane with chitosan in ethanol-water solution and used to remove As(III) from water. The prepared absorbent was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), thermo gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The results confirmed the successful grafting of sulfhydryl groups with chitosan. The adsorption performance of Chi-SH was studied systematically. The Chi-SH showed excellent As(III) removal efficiency of over 99% from 10 mg/L As(III) solution in the pH range of 3.0–10.0. The adsorption behavior of As(III) on Chi-SH accorded with the pseudo-second-kinetic (R2 ≥ 0.972) model and Langmuir adsorption isotherm (R2 ≥ 0.959). The maximum adsorption capacity of Chi-SH was 21.01 mg/g at 298 K and pH 7. The background electrolyte (NaNO3) concentration and the presence of co-existing ions almost do not affect the adsorption process. The Chi-SH was successfully regenerated by 0.5 mol/L oxalic acid for 1.5 h. The removal efficiency of As(III) is over 80% in two cycles.