Study on removal of suspended particles and colour impurities from the paint effluent of an automotive industries by adsorption

The paper deals with the treatment of paint effluents from an automotive shop using adsorption technique. Low cost materials such as, wood charcoal (73.3% FC) and rice husk ash (4% FC) were used as adsorbents. Measurements were under isothermal condition as (a) batch wise operation, and (b) column treatment. The colour hue of the pre- and post treated effluents were determined by the dominant wave length using UV-visible spectrophotometer. Turbidity was determined using turbidity meter. The effect of variables, namely, amount of adsorbents, pH was studied on the adsorption behaviour of the effluent. The initial turbidity (85 NTU) of the effluent could be reduced to 18 NTU using wood charcoal at 2.0 g/100 ml of the effluent at neutral (8.5) pH. The turbidity could be further reduced to 8 NTU at pH 5.0 where the effluent became colourless. In case of alkaline pH, the turbidity of the supernatant after the adsorption was reduced to zero, but its colour was yellowish. The adsorption efficacy increases with increasing the quantity of adsorbent for the obvious reason of having more available surface area for the adsorption to take place. The removal of suspended materials was less effective when the rice husk ash was used as adsorbent. Comparatively poor adsorption efficiency of this material could be attributed to very low percentage of FC (4%) in it. In case of column experiments, second pass happens to be optimum as regards the removal of impurities is concerned. Probability of contaminates including fine particles of the adsorbent increases with increasing number of passes which results in increased turbidity of the supernatant.