新型重金属螯合剂对焚烧飞灰中Pb的稳定性能研究

Stability performance study of a new heavy metal chelating agent against Pb in domestic waste incineration fly ash

生活垃圾焚烧飞灰因富集重金属,需稳定化处理后填埋处置。采用新型重金属螯合剂(0代端二硫代羧酸基聚酰胺-胺超支化聚合物(PAMAM/4DTC-0G))、二甲基二硫代氨基甲酸钠(SDD/DTC)和乙二胺-双二硫代氨基甲酸钠(EDA/2DTC)对Pb浸出浓度较高的飞灰进行稳定化处理,考察螯合剂投加量、浸出液pH对其稳定化效果的影响,并通过Pb形态分布、红外吸收光谱和微观形貌表征探究稳定化机理。结果表明,2%(质量分数,下同)的PAMAM/4DTC-0G能使飞灰中Pb的浸出浓度低于《生活垃圾填埋场污染控制标准》(GB 16889—2008)限值;5%的PAMAM/4DTC-0G稳定化后的飞灰中Pb的浸出浓度在较宽的pH范围(2~14)内均低于标准限值;PAMAM/4DTC-0G可与Pb 2+结合形成超大三维网络状螯合物,能实现长期稳定。

Fly ash from domestic waste incineration needs to be stabilized and disposed in landfills due to enrichment of heavy metals.A new heavy metal chelating agent(0th generation terminally dithiocarboxylated polyamide-amine hyperbranched polymer(PAMAM/4DTC-0G)),sodium dimethyl dithiocarbamate(SDD/DTC)and sodium ethylenediamine-dithiocarbamate(EDA/2DTC)were used to stabilize the fly ash with high Pb leaching concentration.The dosage amount of chelating agent and pH of leachate on the stabilization effect were investigated,then the stabilization mechanism was explored by Pb morphology distribution,infrared absorption spectroscopy and transmission electron microscopy.The results showed that the leaching concentration of Pb in the fly ashafter stabilization with 2%(mass fraction,the same below)PAMAM/4DTC-0G was lower than the concentration limit of“Standard for pollution control on the landfill site of municipal solid waste”(GB 16889-2008).For the leaching concentration of Pb in the fly ash which had stabilized by 5%PAMAM/4DTC-0G,the standard was still satisfied under the condition of the leaching solution pH 2-14.PAMAM/4DTC-0G could combine with Pb 2+to form an oversized three-dimensional network chelate,which could achieve long term stability.