State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, School of Resource and Environmental Engineering, East China University of Science and Technology, Shanghai, 200237, China.
State Environmental Protection Engineering Center for Urban Soil Contamination Control and Remediation, Shanghai Academy of Environmental Sciences, Shanghai, 200233, China.
J Environ Manage. 2022 May 15;310:114792. doi: 10.1016/j.jenvman.2022.114792. Epub 2022 Feb 24.
Owing to the human activities such as smelting and mining, arsenic (As), lead (Pb) and cadmium (Cd) seriously polluted the soil of non-ferrous metal mining areas, thus efficient methods for the simultaneous immobilization of the three heavy metals are urgently needed. In the present study, Mg-Al modified biochars (MABs) were synthesized through a simple one-pot pyrolysis method to immobilize the three heavy metals. According to the BET (Brunauer-Emmett-Teller) test method, MABs had larger specific surface areas than biochar. Compared to the materials obtained at 300 °C and 700 °C, MAB with a pyrolysis temperature of 500 °C (MAB 500) had a significant immobilization effect on As, Pb and Cd in the Gansu mining area. Compared with BC, the removal efficiencies of As, Pb and Cd increased from -62%, 17% and 5% to 52%, 100% and 66%, respectively. And the toxicity characteristic leaching procedure (TCLP) test showed that the leaching concentrations of the three heavy metals in the treated soil were all lower than the standard value. X-ray photoelectron spectroscopy and kinetic experiments showed that there were various mechanisms in the immobilization process of the three heavy metals, and the large specific surface area and the multi-Mg/Al-OH of MABs play an important role in this process. More charges were provided by larger specific surface for ion exchange with heavy metals. In addition, larger specific surface area also provided more adsorption sites. More complex sites were provided by Mg/Al-OH to form Mg/Al-O-M then immobilize the heavy metals. In summary, the immobilization mechanism may involve electrostatic attraction, precipitation/co-precipitation, and surface complexation.
由于人类活动如冶炼和采矿，砷（As）、铅（Pb）和镉（Cd）严重污染了有色金属矿区的土壤，因此迫切需要有效的方法来同时固定这三种重金属。本研究通过简单的一步热解法合成了 Mg-Al 改性生物炭（MAB），以固定这三种重金属。根据 BET（Brunauer-Emmett-Teller）测试方法，MAB 具有比生物炭更大的比表面积。与在 300°C 和 700°C 下获得的材料相比，在 500°C 热解温度下获得的 MAB（MAB 500）对甘肃矿区的 As、Pb 和 Cd 具有显著的固定效果。与 BC 相比，As、Pb 和 Cd 的去除效率分别从-62%、17%和 5%提高到 52%、100%和 66%。毒性特征浸出程序（TCLP）测试表明，处理土壤中三种重金属的浸出浓度均低于标准值。X 射线光电子能谱和动力学实验表明，三种重金属的固定过程中存在多种机制，MAB 的大比表面积和多 Mg/Al-OH 在此过程中起着重要作用。较大的比表面积为重金属的离子交换提供了更多的电荷。此外，较大的比表面积还提供了更多的吸附位点。Mg/Al-OH 提供了更复杂的位点，形成 Mg/Al-O-M 然后固定重金属。综上所述，固定机制可能涉及静电吸引、沉淀/共沉淀和表面络合。
