Flocculation of combined contaminants of dye and heavy metal by nano-chitosan flocculants

Abstract

In this study, two multifunctional nano-chitosan flocculants (CPAM-NCS1 and CPAM-NCS2) were made through the graft modification of cationic monomer and carboxymethylchitosan (CMCTS) to remove combined contaminants. The effects of various factors (pH, flocculant dosage and hydraulic mixing conditions) on the flocculation performance under single and composite pollution conditions were systematically investigated, the optimal chemical oxygen demand (COD) and the chromaticity removal rates in the dye wastewater were 79.9% and 83.9% at wastewater pH 7, the fast stirring rate 300 rpm, the fast stirring time 8 min, and the dosage of CPAM-NCS1 80 mg/L, respectively. The optimal removal rates of Cu (II) obtained by CPAM-NCS1 and CPAM-NCS2 at were 80.3% and 75.2% at 60 mg/L and the wastewater pH 7, respectively. The optimal removal rates of Cu (II) and disperse orange were 85.3% and 89.4%, respectively, in a composite pollutant system in which Cu (II) and disperse orange coexisted when the pH of the composite system was 9 and the dosage of CPAM -NCS1 was 60 mg/L. This study proved that nanoflocculants made by modifying CMCTS with different structures can demonstrate ideal flocculation removal performance for dye and heavy metal wastewaters.