The flocculation performance of Tamarindus mucilage in relation to removal of vat and direct dyes

A food grade natural mucilage, extracted from the seeds of Tamarindus indica pods, is used as a flocculant for removal of solubilised vat (golden yellow) and direct dye (direct fast scarlet) in aqueous solutions. The maximum removal obtained was 60% for golden yellow after 2 h and was 25% for direct fast scarlet after 1 h. The optimum mucilage dose was 10 mg/l and 15 mg/l for golden yellow and direct fast scarlet, respectively. The pH values also seem to affect the percent removal of both the dyes significantly. In case of vat dye, the pH value of the test samples affected the percent removal significantly. The change was highly significant between neutral and alkaline pH. In case of direct dye, there was no significant change in percent removal at pH 7 and pH 4 whereas a significant change in percent removal was observed between pH 7 and pH 9.2. The plausible mucilage-dye interaction and flocculation mechanism has been discussed. This new flocculant works better in the case of vat dye removal compared with the direct dye. (c) 2005 Elsevier Ltd. All rights reserved.