IMMOBILIZATION OF ZINC AND LEAD FROM WASTES USING SIMPLE AND FIBER-REINFORCED LIME-POZZOLANA ADMIXTURES

Immobilization techniques which include chemical fixation and physical encapsulation are used for treatment and disposal of toxic industrial wastes in order to minimise the hazards to the environment. Heavy met al ions are found in the industrial waste waters and sludges of many v ital industries. Most of these heavy metal ions, when present in appre ciable quantities may be toxic to vegetable, aquatic, animal and human life. The present paper deals with the investigations on the immobili zation of Zn and Pb present in the waste sludge in simple and fibre-re inforced lime-fly ash admixture cubes. The techniques studied include fixation, coating with sodium silicate solution and encapsulation proc edures. The fibre additives studied include glasswool, steelwool and s ugarcane-bagasse. The results indicate that excellent immobilization e fficiency can be achieved by encapsulating the heavy metal hydroxide s ludge in simple as well as fibre-reinforced lime-fly ash admixtures as per the procedure now developed. Fixation and coating techniques also yielded encouraging results for the immobilization of heavy metal ion s although they are not as efficient as the encapsulation technique. F ibre-additives help in improving the structural strength of lime-fly a sh cubes.