Li Jiang-Shan, Tsang Daniel C W, Wang Qi-Ming, Fang Le, Xue Qiang, Poon Chi Sun
Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong; State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China.
Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong.
Chemosphere. 2017 Nov;186:350-359. doi: 10.1016/j.chemosphere.2017.08.012. Epub 2017 Aug 5.
Chemical extraction of incinerated sewage sludge ash (ISSA) can effectively recycle P, but it may change the speciation and mobility of the remaining metals. This study investigated the changes of the leaching potential and distribution of metals in the chemically extracted ISSA. Batch extraction experiments with different extractants, including inorganic acids, organic acids, and chelating agents, were conducted on the ISSA collected from a local sewage sludge incinerator. The extraction of Zn, Cu, Pb, Ni, Cd, Ba, Cr and As from the ISSA and the corresponding changes of the mobility and speciation were examined. The results showed that the metals in ISSA were naturally stable because large portions of metals were associated with the residual fraction. The inorganic (HNO and HSO) and organic acids (citric acid and oxalic acid) significantly co-dissolved the metals through acid dissolution, but the reduction in the total concentrations did not tally the leaching potential of the residual metals. The increase in the exchangeable fraction due to destabilization by the extractants significantly enhanced the mobility and leachability of the metals in the residual ISSA. Chelating agents (EDTA and EDTMP) only extracted a small quantity of metals and had a marginal effect on the fate of the residual metals, but they significantly reduced the Fe/Mn oxide-bound fraction. In comparison, the bioaccessibility of residual metals were reduced to varying extent. Therefore, the disposal or reuse of chemically extracted ISSA should be carefully evaluated in view of possible increase in mobility of residual metals in the environment.
化学提取焚烧后的污水污泥灰（ISSA）可有效回收磷，但这可能会改变剩余金属的形态和迁移性。本研究调查了化学提取的ISSA中金属的浸出潜力变化和分布情况。使用包括无机酸、有机酸和螯合剂在内的不同萃取剂，对从当地污水污泥焚烧炉收集的ISSA进行了批量萃取实验。研究了从ISSA中提取锌、铜、铅、镍、镉、钡、铬和砷以及相应的迁移性和形态变化。结果表明，ISSA中的金属天然稳定，因为大部分金属与残渣态相关。无机酸（HNO₃和H₂SO₄）和有机酸（柠檬酸和草酸）通过酸溶作用显著共溶解了金属，但总浓度的降低与残留金属的浸出潜力不一致。萃取剂导致的不稳定作用使可交换态分数增加，显著提高了残留ISSA中金属的迁移性和可浸出性。螯合剂（EDTA和EDTMP）仅提取了少量金属，对残留金属的归宿影响较小，但它们显著降低了铁/锰氧化物结合态分数。相比之下，残留金属的生物可利用性有不同程度的降低。因此，鉴于环境中残留金属迁移性可能增加，应谨慎评估化学提取的ISSA的处置或再利用。
