Reactive dyes removal from wastewaters by adsorption on eucalyptus bark: Variables that define the process

An attempt to help solving the pollution problem caused by the presence of reactive dyes in textile effluents, was undertaken. Owing to the fact that eucalyptus bark is a very abundant, inexpensive, forest residue in the auth ors' country, Portugal, it was decided to experiment with it as a potential adsorbent for a certain type of the supracited pollutants used in cellulos e fibers dyeing (Remazol BE). In order to study the variables that define t he process, 2(4) and 2(5) factorial experimentations were carried out, in t wo stages. In the first one, the variables selected were: temperature, init ial pH, sodium chloride concentration and initial dye concentration/bark co ncentration ratio. As tests showed that the last parameter did not describe the adsorption process, another stage followed, keeping the first three va riables and substituting initial dye concentration and bark concentration s eparately for their ratio. It was verified that all the variables studied h ad significant influence on the adsorption process at the level of 1% proba bility. The influence order was: initial dye concentration > bark concentra tion > initial pH > sodium chloride concentration > temperature. Parallel a dsorption tests, under similar conditions, carried out with a commercial ac tivated carbon and with eucalyptus bark, showed for the last one an adsorpt ion capacity about half of that of the first one. It is considered that the obtained results are quite encouraging, though there is still a long way t o go before definitive conclusions may be withdrawn. (C) 1999 Elsevier Scie nce Ltd. All rights reserved.