A novel integrated treatment system for coal wastewaters

Abstract

The aims of this study are to develop, characterize and optimize a novel treatment scheme that would be effective simultaneously against the toxic organics and heavy metals present in coal conversion wastewaters. To remove and recover heavy metals from wastewaters, four different types of surfactant-clay complexes have been prepared using hectored or montmorillonite as the base clays. The adsorbent is prepared by first coating the clay surface, upto a monolayer, with a cationic surfactant, CBDA, to which an amine, (DT), or a carboxylic acid (Palmitic acid, PA) is anchored using hydrophobic effect to form a mixed bilayer. Such an arrangement is expected to locate the functional groups in metal adsorption at the solid-solution interface. Complexes based on hectored are shown to adsorb Cu{sup 2+} ions more strongly than the ones based on montmorillonite. The rate of adsorption of Cu{sup 2+} ions is quite rapid and the adsorbed amount levels off in less than 2 hrs. The optimum pH for metal adsorption is around 6.5 and the amount of metal adsorbed declines sharply on the lower pH side of the pH optimum, suggesting that removal and recovery of adsorbed metal ions can be effected by a slight pH shift.