磁性生物炭的合成及对土壤重金属污染的钝化效果

Synthesis of Magnetic Biochar and Its Application in the Remediation of Heavy-Metal-Contaminated Soils

为提高生物炭对土壤重金属的钝化能力,通过温和液相还原再氧化法制备了磁性生物炭材料.利用土壤培养实验,以0%、 0.3%、 0.6%和1.0%(质量分数)的比例向重金属污染土壤中施加磁性生物炭,考察磁性生物炭对土壤重金属污染的钝化修复效果及对土壤理化特性的影响,并对修复机制进行了探讨.结果表明,添加不同比例磁性生物炭后,土壤中Cd、Cu、Ni、Pb和Zn有效态含量均呈现不同程度的下降,且随着该材料添加比例的增加土壤中重金属有效态降幅随之增加.培养24 d后,Cd、Cu、Ni、Pb和Zn的钝化效率分别达到了27.52%、 49.55%、 55.83%、 27.33%和26.01%(添加量为1%),但土壤中重金属的形态并没有发生显著变化,可能主要与重金属和生物炭之间相对较弱的结合机制有关.同时,磁性生物炭的添加改善了土壤的理化性质,其中pH值提高0.7个单位,脱氢酶活性提高6倍,过氧化氢酶活性和有机质分别提高37.06%和22.11%.

To improve the stabilization efficiency of biochar on heavy metals in soil, the magnetic material was synthesized by a mild liquid-phase reduction and oxidation method. A soil incubation experiment [0%, 0.3%, 0.6%, and 1.0%(ω)] was carried out to verify the stabilization efficiency of magnetic biochar on heavy metals in soil and its influence on soil properties. The potential stabilization mechanism of magnetic biochar on heavy metals was also analyzed. The results showed that the application of magnetic biochar decreased the bioavailable Cd, Cu, Ni, Pb, and Zn in soil, and the decrease ratio was positively correlated with the application rate of the magnetic biochar. After 24 days incubation, the content of bioavailable Cd, Cu, Ni, Pb, and Zn in soil decreased by 27.52%, 49.55%, 55.83%, 27.33%, and 26.01%, respectively [application rate(ω)at 1%]. However, the fraction of heavy metals in the soil did not change significantly, which may mainly be attributed to the relatively weak bonding mechanisms between the metals and the biochar. The application of magnetic biochar also improved soil properties. The pH of the soil increased by 0.7 units;dehydrogenase activity increased by six times;and catalase activity and organic matter increased by 37.06% and 22.11%, respectively.