Removal of coloured organic matter by adsorption onto low-cost waste materials

Twelve different adsorbents, originating from waste materials, were used to treat an effluent, of complex composition, from a chemical works. The effectiveness of each adsorbent was measured in terms of its effect on the colour (absorbance at 450 nm) and COD levels of the effluent and also in terms of its adsorption capacity towards individual constituents of the effluent. The results showed that all adsorbents would physically adsorb constituents in reversible processes. Some constituents were more readily adsorbed than others. This meant that little correlation was observed between changes to the colour and COD levels of the effluent, because individual constituents made different contributions to these properties. The problem is further complicated by adsorbents, particularly those which had not been processed, contributing new constituents to the effluent. Thermodynamic data obtained from this study were used to predict the relative distribution of three constituents on the surface of different adsorbents. These results suggest that, for this effluent, adsorption onto waste material would be most effectively applied by using it in combination with other removal techniques