Pb2+ adsorption by ethylenediamine-modified pectins and their adsorption mechanisms

Ethylenediamine-modified pectins (EPs) with different degrees of amidation (DA) were prepared and characterized by Fourier Transform Infrared spectra (FTIR), elemental analysis, X-ray photoelectron spectroscopy (XPS). The prepared EPs were then used to remove Pb2+ from the aqueous solution. It was found that EPs with the highest DA (EP48) exhibited great removal efficiency of Pb2+ (≥94 %) at low concentrations of 40-80 mg/L. The zeta potential analysis showed that EP48 had the fastest increase in zeta potential when Pb2+ was continuously added and was the first to be electroneutralized. Particle size analysis further confirmed that EP48 was the first precipitated and formed a larger EP48-Pb2+ complex. The FTIR and XPS analyses indicated that Pb2+ was adsorbed via the ion exchange of carboxylic groups and chelation with acylamino and amino groups. These results suggested that the EP48 might be a promising adsorbent for the removal of low concentrations of Pb2+ in contaminated water.