生物炭负载Fe3O4对猪粪厌氧消化中重金属Cu、Zn形态的影响

Effect of Fe3O4-loaded biochar on heavy metals Cu and Zn speciation in anaerobic digestion of pig manure

为研究生物炭(BC)负载Fe3O4对猪粪厌氧消化中重金属形态的影响,采用化学共沉淀法将Fe^2+/Fe^3+和水稻秸秆BC复合制备Fe3O4/BC复合材料,将其作为钝化剂添加到以猪粪为原料的厌氧消化反应中。通过Tessier连续提取法与pH-依赖性浸出试验,探究BC和Fe3O4/BC对重金属形态的影响以及不同pH条件下沼渣中重金属浸出浓度的变化。结果表明,添加Fe3O4/BC对Cu和Zn的钝化效果更显著,与空白对照(CK)相比,添加BC和Fe3O4/BC后Cu的残渣态质量分数分别增加了-10.46%和52.40%,Zn的残渣态质量分数分别增加了16.82%和42.14%。厌氧消化后沼渣的浸出试验表现出很强的pH依赖性,Cu、Zn浸出曲线呈现出“V形”,在中性环境中(pH6~8)Cu、Zn和溶解性有机质(DOM)的浸出浓度较低,在酸性(pH<6)和碱性(pH>8)环境中较高。在弱酸弱碱条件下(pH5~9),添加Fe3O4/BC后Cu和Zn的浸出浓度均低于添加BC的试验和CK组。因此,添加Fe3O4/BC可有效降低厌氧消化后沼渣中重金属的浸出风险。

In this study,the Fe3O4-loaded biochar(BC)was prepared via chemical co-precipitation with the combination of Fe^2+/Fe^3+and rice straw BC,and mixed with pig manure to study its effect on the speciation of heavy metals during anaerobic digestion.Tessier continuous extraction method and pH-dependent leaching test were conducted to investigate the effects of BC and Fe3O4/BC on the morphology of heavy metals and the changes of the leaching concentration of heavy metals in biogas residue.The test results revealed that better passivation on Cu and Zn was found in the treatment with Fe3O4/BC.Compared with the blank group(CK),the residual mass fraction of Cu in the BC and Fe 3O 4/BC groups individually increased by-10.46% and 52.40%,while the residual mass fraction of Zn increased by 16.82% and 42.14%,respectively.The leaching test of biogas residue after anaerobic digestion showed strong pH dependence,presenting a“V-shaped”leaching curves.The leaching concentrations of Cu,Zn and dissolved organic matter(DOM)were lower in neutral environment(pH 6-8),which had the higher values in acidic(pH<6)and alkali environment(pH>8).The leaching concentrations of Cu and Zn in the Fe3O4/BC group were lower than those in the BC and CK group under weak acid and weak base conditions(pH 5-9).Thus,the addition of Fe3O4/BC could effectively reduce the leaching risk of heavy metals in the biogas residue after anaerobic digestion.