Sorption performance of cysteine-modified bentonite in heavy metals uptake

Abstract

A local clay, bentonite (N-Ben), was modified by the biologically--based ligand, cysteine (Cys), through a simple sorption technique. The modified sorbent (Cys-Ben) demonstrated affinity for soft and moderately soft heavy metal ions (HMI), such as Cd(II) and Pb(II), probably as a result of the soft basic character of the thiol ligand side chains. The resulting modified system was effective for metal binding with capacities of 0.503 and 0.525 mmol g -1 , for Pb(II) and Cd(II), respectively. Comparative batch experiments were performed for removing lead and cadmium from aqueous solutions. The sorption parameters were derived from a Langmuir fit to the sorption isotherms of the studied ions. The study showed that the sorption capacity of Cys-Ben was higher than that of N-Ben for these ions. The effect of pH was examined over the range 2.0-6.0. The sorption capacities of Cys-Ben showed that this modified clay is a good sorbent for the examined heavy metal ions.

Adsorption study of cadmium ions on kaolinite modified by histidine and cysteine

“…Histidine has three amino groups that can potentially present additional binding sites for Cd ions from wastewater. Cysteine (C3H7NO2S) has thiol group which has a high affinity for heavy metals [23] and plays a vital role in the synthesis of peptides and proteins and in the detoxification of heavy metals such as cadmium and mercury in living organisms [24][25][26].…”