Removal of Dyes from Synthetic Waste Water by Coagulation Technique Using Natural Coagulants

Abstract

The adsorption performances of polymer coagulants were studied for color removal from the aqueous dye solution. The coagulation behavior of Naphthalene black and Alizarin red dye from synthetic waste water onto the tiger nut powder and alum was investigated using initial concentration, solution pH, contact time, coagulant dosage, and temperature and particle size. The percentage color removal for the two dye solutions were found and compared with that of alum and the result of the study showed that increase in dye initial concentration from 50mg/L to 500mg/L at room temperature with tiger nut decreased the removal efficiency from 63.74% to 34.9% for naphthalene black and alizarin red from 70.12% to 42.00%. Also, for dye concentration above 100mg/L with alum, the removal efficiency of both dyes started decreasing from 59.22 to 27.34% for naphthalene black and from 62.46 to 33.50% for alizarin red. The maximum dye removal efficiency occurred at a pH of 2 for both naphthalene and alizarin red with tiger nut but occurred at pH of 5 for both dyes with alum. Coagulant dosage from 100 to 1000mg/l with tiger nut increased the removal efficiency of naphthalene black and alizarin red from 44.08% to 94.43%; and 50.10% to 96.55 respectively while with alum it increased from 25.18% to 67.90% for naphthalene black and 35.74% to 78.89% for alizarin red. The reaction kinetics of Naphthalene black and Alizarin red was observed to obey Pseudo second-order kinetics with rate constants K2of 2.4691g/mg minutes and 2.7579g/mg min, respectively. From result, it is evident that tiger nut is a better low cost natural coagulant effective for the removal of dye from synthetic waste water. However, the removal efficiency is higher in Alizarin red than in Naphthalene black at the same concentration under the same condition.