Studies on the Removal of Turbidity and Physicochemical Remediation of Wastewater Using Anionic Cross-Linked and Carboxymethyl Starch Hydrogel

Abstract

In this sorption-based water treatment versatility study, cross-linked carboxymethyl starch phosphate (CCSP) hydrogel was reproduced via modification of native legume starch (NS) using sodium trimetaphosphate and sodium monochloroacetate. The swelling capacity and the point zero charge pH (pH_PZC) of the hydrogel were evaluated before the studies for the removal of turbidity and the physicochemical remediation of wastewater. The modification increased the swelling capacity from 156% (NS) to 473% (CCSP) and decreased pH_PZC from 5.66 (NS) to 4.77 (CCSP). This indicated enhancements in sorption and coagulation characteristics with the incorporation of negatively charged groups on CCSP. The equilibrium studies on turbidity removal (coagulation) using simulated turbid water showed that CCSP can serve as an efficient (>80%) coagulant at optimum conditions (pH: 6, agitation time: 15 min, temperature: 30°C, agitation speed: 50 rpm, and hydrogel dosage: 1000 mg/L). The treatment of wastewater samples with CCSP reduced turbidity (95–96%), chemical oxygen demand (42–46%), and total dissolved solids (12–21%), among other remediated conditions that indicated that the treated water was safer for discharge or utility.