Abstract: A novel compound flocculant was prepared using one-step process with the natural bentonite and cationic starch adsorbed for each other, in order to increase the color removal efficiency of bentonite and cationic starch, respectively. The mixture of cationic starch and bentonite had a large specific surface area and loose structure, which increased the effect of adsorption for dye. An indicator of the percentage of color removal was used to determined the optimal application conditions of cationic starch –bentonite compound through experiments: the dosage of adsorbent was 1.25g.L-1 with a mass ratio of 1:1, the pH of dyeing wastewater was 7, without additional sodium chloride, and its color removal rate from wastewater of reactive red X- 3B was more than 90%. On this basis, the adsorption isothermal line of the cationic starch-bentonite compound was set, which belonged to L-model, and the adsorbent’s adsorption of the reactive red X- 3B is coordinated surface adsorption.

Key words: bentonite, cationic starch, composite flocculant, dyeing wastewater, color removal