改性生物炭修复砷镉复合污染土壤研究进展

Modified Biochar for Remediation of Soil Contaminated with Arsenic and Cadmium:A Review

砷镉复合污染(As/Cd污染)已成为我国主要的土壤环境问题,改性生物炭作为一种吸附固定剂在修复土壤As/Cd污染中正发挥日益重要的作用.在明确原始生物炭作为钝化剂修复As/Cd污染土壤局限性的基础上,综述了针对As/Cd污染土壤修复的生物炭改性方法研究进展,分析了相关作用机制,并对未来利用改性生物炭修复As/Cd污染土壤的前景和存在问题进行展望.结果表明,金属改性生物炭具有较好的协同修复As/Cd污染土壤的效应,从而具有良好的应用前景.通过不同改性方法制备的生物炭材料修复As/Cd污染的固定机制各异,其中,金属改性和无机非金属改性生物炭对As/Cd的固定作用主要涉及官能团配位、共沉淀和As氧化还原;微生物改性生物炭涉及沉淀作用和As氧化还原;物理和酸改性方法则局限于物理吸附和弱静电引力.针对当前研究现状,建议未来应加强生物质原料类型、热解温度、制备工艺、经济成本和土壤老化等因素对改性生物炭修复As/Cd污染土壤的影响研究,实施不同因素影响下材料对重金属固定的稳定性和长效性评估,揭示材料修复As/Cd污染土壤的关键作用机制.

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:①the effect of biomass feedstock type,pyrolysis temperature,preparation conditions,cost,and soil aging;②evaluation for stability and durability of heavy metal immobilization by modified biochar remediation under different environmental factors;and③insight to key remediation mechanisms of As and Cd-contaminated soil by material.