Adsorption-coagulation for the decolorisation of textile dye solutions

Abstract

Studies were undertaken for the removal of colour from different types of synthetic dye solutions by using powdered activated carbon (PAC) and bentonite clay (BC) as adsorbents. The different types of dyes (direct, mordant and basic) studied were Direct Orange, Eriochrome Black T and Malachite Green. The synthetic dye solutions behaved differently with the two adsorbents. The effect of adsorption by PAC and the further addition of a very small dose of a coagulant polyaluminium chloride (PAIC) on the settling and/or reuse of adsorbents used was studied. PAC and BC, though effective adsorbents, remained suspended in the solution for a long time. PAIC not only enhanced dye removal, but also formed a sludge that settled very quickly and which could also be reused effectively for dye removal.