Optimization of The Starch Chitosan-based Flocculant Crosslinked by Ethylene Glycol Dimethacrylate on Removing Dypro 19 Textile Dye from Wastewater

Dyes used in industry, especially textile dyes, are one of the water pollutants that receive much attention because they are potentially toxic, carcinogenic, mutagenic, and generally challenging to decompose naturally. Textile dyes from wastewater can be removed through coagulation-flocculation. However, conventional coagulation-flocculation based on Fe and Al salts and synthetic polymers often leaves residual pollution. In this research, the performance of the new biopolymer-based flocculant, namely starch-ethylene glycol dimetacrylate-chitosan (SEC), which can act as coagulants and flocculants in solid-liquid separation of textile dyes, has been optimized using response surface methodology (RSM) approach. The influences of several independent variables, such as initial pH, SEC dosage, and rapid stirring time, were studied. The design experiment was the box-Behnken design (BBD), which involved three factors, three levels, and 15 treatment combinations. Based on the fitting results, the quadratic model is significant and accurate in predicting the solid-liquid separation of Dypro 19 (p-value 0.0002, F-value 51.94, and R2 0.9894). Numerical optimization based on the desirability function shows that using initial pH variables of 8, SEC dosage of 2.2 mL L-1, and rapid stirring time of 3 minutes can produce a predicted removal of Dypro 19 of 97.01%. Model validation through experiments on these variables shows that 95.71% of Dypro 19 can be removed. These results indicate that the proposed model's validity, accuracy, and acceptability are good.