‘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.