垃圾焚烧飞灰H_3PO_4稳定化技术及机理研究

Immobilization Technology and Mechanism of Fly Ash Using H_3PO_4

分析了焚烧飞灰的全组分和浸出毒性，表明飞灰中含有多种重金属，其中Pb的浸出浓度为67．03mg／L，超过危险废物鉴别标准，研究了H3PO4投加量对飞灰稳定化效果及其环境长期稳定性的影响，结果表明：投加相当于飞灰质量8％～14％的H3PO4就能够有效地使焚烧飞灰无害化；8％和12％H3PO4稳定化飞灰都具有良好的环境稳定性；过多的H3PO4投加量会降低处理后飞灰对酸性环境的缓冲能力．对于12％H3PO4稳定化飞灰，XRD检测出Cr2P2O7、ZnP2、Pb3P4O13、Pb3P2O7、NaZnPO4、NaPbP3O9、Ca2ZnSi2O7等少量重金属的结晶相；SEM发现了大量独立存在的飞灰颗粒、直径约0．3～0．5μm的Pb5（PO4）3Cl棒状物；CHBr3浮选没有得到浓缩的重金属．综合分析得到：H3PO4是通过与强碱性飞灰之间的中和反应，激活飞灰中的重金属，改善稳定化进行的环境，并产生稳定化所需的PO4^3-．被激活的重金属与产生的PO4^3-在飞灰颗粒表面结合．所产生的重金属磷酸盐与SiO2、CaCO3、CaSO4、KCl和NaCl等飞灰主要构成固溶相，几乎不独立存在。

Chemical composition and toxicity leaching characteristics of fly ash was analyzed. The experiment results show that many heavy metals were contained; leaching concentration of Pb is 67.03mg/L, which exceeds the limit of identification standard for hazardous wastes. Effect of input mass of H3PO4 on immobilization of heavy metals and its long-term environmental stability was studied. The results show that when input 8 % - 14 % （H3PO4 mass/fly ash mass）of H3PO4 sound immobilization effect can be achieved; 8% and 12% of H3PO4 will bring a satisfactory environmental stability of heavy metals, while more H3PO4 led to less buffer capacity to acid conditions. In fly ash treated by 12 % H3PO4, a small quantity of crystal Cr2P2O7 ,ZnP2,Pb3P4O13, Pb3P2O7, NaZnPO4, NaPbP3O9 ,Ca2ZnSi2O7 can be detected by XRD; many independent fly ash particles and bar-shaped Pb5 （PO4）3Cl with a diameter of 0.3- 0.5μm were observed by .SEM; concentrated heavy metal materials were not obtained by CHBr3 floatation. Conclusions can be drawn that, through neutralization reaction of H3PO4 with strongly alkaline fly ash, stabilization reaction conditions were improved, entrapped heavy metals were chemically activated and PO4^3- needed in stabilization was produced. Activated heavy metals combined with PO4^3- on surface of fly ash, generated phosphates existing as forms of solid solution in SiO2, CaCO3, CaSO4, KCl, NaCl.