Immobilization of some metals in contaminated sludge by zeolite prepared from local materials

In this study, zeolite was prepared from cheap local Egyptian clay (kaolin) and characterized by X-ray diffraction, X-ray fluorescence spectroscopy, SEM. The prepared zeolite was used as a binder for immobilization of the metals Cd²⁺, Cu²⁺, Ni²⁺, Pb²⁺, and Zn²⁺ in contaminated sewage sludge. Different leaching tests were conducted to determine the efficiency of the prepared zeolite for metal stabilization. The leaching of the metals from stabilized sludge decreased as the zeolite amount increased. It was found that 10% of zeolite is sufficient for the stabilization of all metal ions under investigation. It was suggested that the metal uptake mechanism by zeolite was by an ion-exchange mechanism. Examination of the solidified sample for its compressive strength after curing for 28 days yielded a value of 0.83?MPa, which indicates that the treated sludge was well solidified and safe to be used in a wide variety of applications, for instance as a raw material for pavement blocks.     

沸石作稳定化剂固化/稳定化含汞危险废弃物试验

利用沸石对汞的吸附性,将沸石作为稳定化剂掺入水泥进行含汞危险废弃物固化/稳定化试验研究.同时,探讨了沸石作为稳定化剂的水泥固化技术处理含汞废弃物的影响因素,从而明确这种方法的可行性和最佳操作条件.结果表明,沸石的掺入能够促进汞的稳定,与单独使用水泥相比固化效率显著提高.当沸石用量为0.3g·g-1以上时,固化体浸出汞浓度低于国家标准(GB5085.3-2007),固化效率从单独使用水泥固化时的47%提高到95%以上.氯离子能够影响固化效率,即使在氯离子浓度为10mmo·lL-1时,含汞1000mg·kg-1以下的固体废弃物的固化效率仍能够大于90%.这说明即使存在氯离子干扰的情况下,沸石作稳定化剂固化含汞危险废物仍然是非常经济有效的方法.实验得到沸石作稳定化剂固化含汞危险废弃物的最佳操作条件为pH=6.0～7.0之间,沸石量为0.4g·g-1,水泥量为0.7g·g-1以上.