砷(As)和镉(Cd)的二元污染已成为中国主要的土壤环境问题。作为吸附剂或固定剂,改性生物炭在砷和镉污染土壤的修复中发挥着越来越重要的作用。这里,本研究强调了原始生物炭作为修复As和Cd污染土壤的固定剂的局限性。同时,综述了生物炭改性修复As和Cd污染土壤的方法,并分析了主要的相互作用机制。最后,提出了改性生物炭修复As和Cd污染土壤的前景和存在的问题。结果表明,金属改性生物炭对As和Cd污染土壤的修复具有较好的协同作用,具有较好的应用前景。利用生物炭材料修复As和Cd的固定化机理受到其改性方法的影响。例如,(非)金属改性生物炭的机理涉及官能团诱导的键合络合,共沉淀,和氧阴离子作为氧化还原;对于微生物改性的生物炭,机理是沉淀和As氧化还原,物理和酸改性的生物炭只包括物理吸附和弱静电吸引。鉴于目前应用改性生物炭修复As和Cd污染土壤的研究存在的局限性,未来的研究建议进行以下研究:①生物质原料类型的影响,热解温度,准备条件,成本,和土壤老化;②评价不同环境因子下改性生物炭修复重金属的稳定性和耐久性;③了解材料修复As和Cd污染土壤的关键机制。
Binary pollution of arsenic (As) and cadmium (Cd) has become the main soil environmental problem in China. As an adsorbent or immobilizer, modified biochar is playing an increasing role in the remediation of As and Cd-contaminated soil. Here, the limitations regarding the primitive biochar as an immobilizer for the remediation of As and Cd-contaminated soil were highlighted by this study. Meanwhile, the biochar modification methods for the remediation of As and Cd-contaminated soil were reviewed, and the main interaction mechanisms were analyzed. Finally, the prospects and questions for the future remediation of soil contaminated with As and Cd using modified biochar were proposed. The results showed that metal-modified biochar had a better synergistic effect on the remediation of As and Cd-contaminated soil and thus had better application prospects. The immobilization mechanisms of As and Cd using biochar material remediation were affected by its modification methods. For example, the mechanisms for (non)metal-modified biochar involved the functional group-induced bonding complexation, co-precipitation, and oxyanion As redox; for microorganism-modified biochar, the mechanisms were precipitation and As redox, and those for physical- and acid-modified biochar only included the physical adsorption and weak electrostatic attraction. In view of the limitations of present research on the application of modified biochar for the remediation of As and Cd-contaminated soil, future research is suggested to study the following:① the effect of biomass feedstock type, pyrolysis temperature, preparation conditions, cost, and soil aging; ② evaluation for stability and durability of heavy metal immobilization by modified biochar remediation under different environmental factors; and ③ insight to key remediation mechanisms of As and Cd-contaminated soil by material.