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 w
ere studied. Adsorption followed the first-order rate expression. The equil
ibrium data fit well with both Langmuir and Freundlich models of adsorption
. Desorption experiments confirmed that major mode of adsorption is ion-exc
hange for the dyes acid brilliant blue and methylene blue whereas acid viol
et showed mainly physical adsorption. Chemisorption seems to be the major m
ode of adsorption for rhodamine B. (C) 2001 Elsevier Science Ltd. All right
s reserved.