'Waste' coir pith - a potential biomass for the treatment of dyeing wastewaters

Removal of acid dyes (acid violet and acid brilliant blue) and basic dyes (rhodamine B and methylene blue) was carried out using 'waste' coir pith as adsorbent. Parameters like agitation time, adsorbent dosage and pH effect were studied. Adsorption followed the first-order rate expression. The equilibrium data fit well with both Langmuir and Freundlich models of adsorption. Desorption experiments confirmed that major mode of adsorption is ion-exchange for the dyes acid brilliant blue and methylene blue whereas acid violet showed mainly physical adsorption. Chemisorption seems to be the major mode of adsorption for rhodamine B. (C) 2001 Elsevier Science Ltd. All rights reserved.