飞灰典型重金属的多组分螯合剂的效果优化及机理分析

Effect Optimization and Mechanism Analysis of Multi-component Chelating Agent for Typical Heavy Metals in Fly Ash

针对深圳市某生活垃圾焚烧发电厂产生的高浓度重金属飞灰,该文在对多种螯合剂组分进行筛选的基础上,使用响应曲面法进行试验设计,通过模型拟合与方差分析评价了复合螯合剂对Zn、Pb、Cd的螯合影响,并通过SEM、FTIR、XPS对螯合机理进行了分析。结果表明,以2.5%(w)过磷酸钙+3%(w)福美钠水剂辅以0.074%(w)十二烷基苯磺酸钠的复合螯合剂可实现多批次高浓度飞灰的最优螯合效果与适应性;过磷酸钙与福美钠水剂分别对Zn和Cd的螯合起显著性作用,而Pb受两种组分的拮抗影响。在螯合-陈化的过程中,飞灰内部夹带重金属的组分发生了溶解、结晶、固定的转变:Zn与磷酸根结合固定,但在高温下陈化会降低其螯合稳定性,Pb形成高价态的稳定的化合物,而Cd主要被有机螯合剂的交联基团包覆。

In view of the high concentration of heavy metal in fly ash produced by a municipal solid waste incineration plant in Shenzhen,this paper based on the screening of various chelating agent components,and the response surface methodology was used to design the experiment.The effects of complex chelator on the chelation of Zn,Pb and Cd were evaluated by model fitting and variance analysis,and the chelating mechanism was analyzed by SEM,FTIR and XPS.The results showed that the combination of 2.5%(w)calcium superphosphate+3%(w)sodium dimethyldithiocarbamate water agent,supplemented by 0.074%(w)sodium dodecyl benzene sulfonate,could achieve the best chelating effect and applicability for multiple batches of high concentration fly ash.Calcium superphosphate and sodium dimethyldithiocarbamate water agent had significant effects on the chelation of Zn and Cd,respectively,while Pb was affected by the antagonism of the two components.During the chelation and aging process,the components of heavy metals in the original ash were dissolved,crystallized and fixed:Zn was combined with phosphate,but aging at high temperature would reduce its chelating stability,Pb formed a stable compound with high valence,while Cd was mainly coated by the cross-linking group of organic chelating agent.