O-Acylation of chitosan by l-arginine to remove the heavy metals and total organic carbon (TOC) from wastewater

Abstract

Chitosan has acylated with l-arginine in the presence of H2SO4 as a catalyst to the aim of increasing the adsorption efficiency. Chitosan (CS) and chitosan-O-arginine (CS-Arg) were characterized and investigated by elemental analysis, Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The results obtained from elemental analysis exhibited presence of sulfur content, indicate that sulfuric acid still a crosslinker between CS-Arg chains, also the degree of substitution (DS) of l arginine in CS backbone was 1.83, indicate the acylation process has took place in both C3-OH and C6-OH of CS. XRD results exhibited that CS-Arg is more crystalline than CS, due to the formation of intra and inter molecular hydrogen bonds between amino and hydroxyl groups. The removal of heavy metals (Mn2+, Pb2+and Al3+) and total organic carbon (TOC) from wastewater by CS and CS-Arg in batch mode has been studied at different adsorbent dosages, temperatures and contact times. The maximum removal efficiency for three metal ions using CS achieved 99.6%, 99.1% and 98.9%, respectively, while by using CS-Arg were 97.1%, 94.3% and 99%. However, the maximum adsorption capacity of TOC by CS achieved 50 mg/g and 40.35 mg/g by CS-Arg. The total maximum adsorption capacity of CS-Arg is lower than CS.