DYE REMOVAL FROM WASTE-WATER BY ADSORPTION ON WASTE FE(III) CR(III) HYDROXIDE/

Agricultural and industrial solid wastes can be recycled as nonconvent ional adsorbents if they are inert and harmless to reduce the cost of the wastewater treatments. Waste Fe(III)/Cr(III) hydroxide, generated in the treatment of Cr(VI) bearing wastewaters in a fertilizer industr y, was used for the adsorption of Congo red (direct dye) from aqueous solution. The parameters studied include agitation time, initial dye c oncentration, pH and adsorbent dosage. The adsorption capacity was eva luated by using both the Langmuir and Freundlich adsorption isotherm m odels. Removal of the dye was maximum, 91% at pH 3. Low desorption (9% ) with water seems to indicate that the dye is mostly held by the adso rbent through ion-exchange.