School Civil and Environmental Engineering, Nanyang Technological University, Singapore.
School Civil and Environmental Engineering, Nanyang Technological University, Singapore.
Waste Manag. 2020 Mar 1;104:213-219. doi: 10.1016/j.wasman.2020.01.023. Epub 2020 Jan 23.
Incineration bottom ash (IBA) of municipal solid waste is a potential construction material for civil engineering. However, the possible leaching of trace heavy metals from IBA is a concern. Water washing is a simple and economic method to remove heavy metals from IBA. In order to optimize the water washing process of IBA, this study investigated the pH evolution during washing and its effect on the removal of several heavy metals, including lead (Pb), zinc (Zn), nickel (Ni), cadmium (Cd), copper (Cu), and chromium (Cr), through a small-scale laboratory experiment. The results show that the pH of washing water increases quickly in the first 1-3 h mainly due to the dissolution of quicklime and portlandite, and then decreases with the increasing of washing time might be due to consumption of OH by precipitation of metal hydroxides. The concentrations of Pb, Zn, and Ni in the washing water show a similar trend as that of the pH with time, whilst the concentrations of Cd, Cu, and Cr increase with the increase of washing time. Hence, the optimum washing time should be determined accordingly based on the most concerned metal(s), as well as the pH evaluation during washing.
城市固体废物焚烧底灰（IBA）是土木工程中一种有潜力的建筑材料。然而，IBA 中痕量重金属的潜在浸出仍然令人担忧。水洗是一种从 IBA 中去除重金属的简单经济方法。为了优化 IBA 的水洗工艺，本研究通过小型实验室实验，考察了水洗过程中的 pH 值演变及其对几种重金属（包括铅（Pb）、锌（Zn）、镍（Ni）、镉（Cd）、铜（Cu）和铬（Cr））去除的影响。结果表明，在最初的 1-3 小时内，洗水的 pH 值迅速升高，主要是由于生石灰和熟石灰的溶解，然后随着洗涤时间的增加而降低，这可能是由于金属氢氧化物沉淀消耗了 OH。洗水中 Pb、Zn 和 Ni 的浓度随时间呈相似趋势，而 Cd、Cu 和 Cr 的浓度随洗涤时间的增加而增加。因此，应根据最关注的金属以及洗涤过程中的 pH 值评估来确定最佳的洗涤时间。
