Appraisal of Cassava Starch as Coagulant Aid in the Alum Coagulation of Congo Red from Aqua System

Abstract

Cassava starch (CS) was evaluated as coagulant aid in the alum coagulation of an acid dye, Congo red (CR), from aqua system. The use of CS, as coagulant aid reduced the value of the optimum alum dose, required for coagulation of CR, by 50%. The abilities of alum and CS were assessed, separately, on the coagulation of varying concentrations of CR contaminated water by method of continuous variation of the alum and CS dosages. Alum coagulated the CR while the CS performed poorly. Varying dosages of the CS were combined with half the optimum alum dose, for each concentration, and reduction in the aqua CR concentration was observed. The percentage of CR removed was appreciable at all the pH studied and the amount of CR removed increased with increase in the flocculation time. The kinetics of the flocculation process was studied by fitting the data obtained to a kinetic model and the flocculation rate constant increased with increase in the initial CR concentration.