Esterification of chitosan with L-alanine and a study on their effect in removing the heavy metals and total organic carbon (TOC) from wastewater

Abstract

Abstract In this work, chitosan was modified by the esterification with L-alanine in the presence of H2SO4 as a catalyst to increase the number of amino groups with the aim of increasing the adsorption efficiency. Chitosan (CS) and chitosan-O-alanine (CS-Aln) were characterized and investigated by elemental analysis, Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The results obtained from elemental analysis and IR indicated the presence of sulfuric acid after neutralization as a crosslinker between CS-Aln chains. Also CS-Aln is more amorphous than CS due to the ionic bonds of crosslinker. The removal of three heavy metals (Mn2+, Pb2+ and Al3+) and total organic carbon (TOC) from wastewater by CS and CS-Aln in the batch mode has been studied at different adsorbent dosages, temperatures and contact times. The maximum metal ions removal efficiency using CS achieved 99.6%, 99.1% and 98.9%, respectively, while by using CS-Aln 95.3%, 99.3% and 98.9% were achieved. However, the maximum adsorption capacity of TOC by CS achieved 50 mg/g and 89 mg/g by CS-Aln. The total maximum adsorption capacity of CS-Aln is higher than CS.