Dye removal using low cost adsorbents

Dyestuff production units and dyeing units have always had a pressing need for techniques that allow economical pretreatment for color in the effluent. The effectiveness of adsorption for dye removal from wastewaters has made it an ideal alternative to other expensive treatment options. The current paper deals with an investigation on four low-cost adsorbents locally available in Saskatchewan, Canada for dye removal. Feat, steel plant slag, bentonite clay and fly ash were utilized for this study and their performance evaluated against that of granular activated carbon. Batch kinetic and isotherm studies, and column studies were undertaken, and the data evaluated for compliance with the Langmuir, Freundlich and BET isotherm models. Synthetic dye wastewaters prepared from commercial grade acid, basic and disperse dyes were used in this study and the results showed high removals of acid dyes by fly ash and slag while peat and bentonite exhibited high basic dye removals. For the acid and basic dyes, the removals were comparable with that of granular activated carbon, while for the disperse dyes, the performance was much better than that of granular activated carbon. The results obtained point towards viable adsorbents which are both effective as well as economically attractive for color removal from wastewaters. (C) 1997 IAWQ. Published by Elsevier Science Ltd.