Use of activated clays in the removal of dyes and surfactants from tannery waste waters

A method is tested to reduce the pollution of effluents produced in the hide transformation process. Adsorption processes with clays could constitute a simple, selective and economical alternative to conventional physical-chemical treatments. The adsorption capacity of natural and acid-activated bentonite and sepiolite for anionic dyes normally used in the tannery was compared with that of a conventional adsorbent such as activated carbon. Natural bentonite with a different level of acid activation was used to adsorb a non-ionic surfactant such as nonylphenol ethoxylated with 8 mol of ethylene oxide. The capacity of sepiolite and acid-activated bentonite to adsorb anionic dyes normally used in the tannery was much greater than that of conventional adsorbents. A surfactant removal of 90% was achieved in approximately 10 min because of the high affinity between surfactant and adsorbent. Natural bentonite activated with 0.5 M H2SO4 was the most effective adsorbent for ethoxylated nonylphenol. (C) 2003 Elsevier B.V. All rights reserved.