以碱渣为添加剂水泥固化/稳定化生物脱毒底泥的初步研究

以固化体强度、增容比、浸出液pH值以及重金属浸出率为指标,通过无侧限抗压强度和毒性浸出试验,考察以碱渣为添加剂辅助水泥固化/稳定化处理生物脱毒底泥的效果。结果表明,脱毒底泥经碱渣预调理后（泥渣比=10∶0.8）,在0.2—0.4kg/kg不同水泥掺入量下形成的底泥固化体的无侧限抗压强度均可达140kPa以上（龄期14d）,增容比仅为1.17—1.31,固化体浸出液pH值在11.3—11.7之间,Zn、Cu和Cr等重金属浸出得到明显控制（浸出率均≤2.2%）.与固化前相比,底泥固化体环境风险大大降低,且满足填土材料与填埋处置要求.从固化效率角度考虑,生物脱毒底泥固化/稳定化实际应用中较为合适的水泥掺入量为0.2kg/kg,即碱渣∶水泥∶底泥=6∶17∶77.

Solidification/Stabilization of Bioleached Heavy Metals-laden Sediment Using Cement and Soda Residue as Binder Materials

Acid bioleached sediment containing low content heavy metals is still an unsolved environmental problem in the bioleaching process of heavy metals-polluted sediment. Cement-based solidification/stabilization (S/S) is an option for reducing the mobility of heavy metals in the sediment and the potential hazards to human health and environment. The present work used cement as a solidified material and soda residue as an additive to solidify and stabilize bioleached heavy metals-laden sediment with an aim to search an efficient and cost-effective way for the final disposal of the sediment. The results showed that the cement/soda residue-based solidified sediment was capable of reaching all performance criteria for fill and landfill disposal at a cement dosage of 17%(wt.%) and a soda residue percent of 6% (wt.%). During 14 days of cure, the unconfined compressive strength of solidified sediment was higher than 140kpa, and the ratio of increased volume of solidified sediment was 1.17. The leaching toxicity tests (GB/T5086-1997) demonstrated that the leachate pH of solidified sediment was maintained at pH 11. 3, and that the leachability of heavy metals decreased significantly and the leaching concentrations of various metals were all below Chinese regulatory level (GB 18598-2001). Therefore, the cement/soda residue-based S/S can be considered as a feasible means for the final disposal of bioleached sediment.