Abstract:

Aiming at the problem of excessive heavy metals in the anaerobic digestion of pig manure, this paper constructed an anaerobic digestion system using pig manure/corn straw as raw material, and compounded three kinds of passivation agents of biochar, humic acid and fly ash. Then, the organic carbon fractional extraction method was used to analyze the changes of Cu and Zn species in the optimal passivation group and to explore the interaction mechanism between heavy metals and humic substances.The results showed that humic acid and fly ash had the optimal passivation effects for Cu and Zn, respectively, and the optimal compound ratios of humic acid∶fly ash∶biochar were B1 (7.5%∶7.5%∶7.5%) and B2 (5.0%∶7.5%∶7.5%). The ratio of humic acid (HA) to fulvic acid (FA) content in the system showed an increasing trend with anaerobic digestion. Before digestion, Cu and Zn in biogas residue humus of each treatment group mainly existed in the form of FA-Cu and FA-Zn, and after digestion, heavy metals were mainly combined with HA. The proportion of HA-Zn and HA-Cu in B1 and B2 was significantly higher than that in control group (CK), and the bioavailability in B1 and B2 was significantly lower than CK. Comparing the stable states of Cu and Zn, it was found that the amplitude of the stable state of Zn conversion was small, mainly because Zn was a heavy metal of amphotericity, which was more active and easy to bind with small molecule humus FA, while Cu mainly combined with macromolecular humus HA and the binding was relatively tight. In B1 and B2, the binding form of heavy metals and humus was more stable, so the compound passivator could further reduce the biological toxicity of heavy metals Cu and Zn in the anaerobic digestion. Infrared spectroscopic analysis found that passivators increased the aromaticity of the substrate, making it easier to bind to heavy metals, and aromatic, aliphatic compounds, proteins and polysaccharide compounds were the main heavy metal binding functional group.

Key words: pig manure, anaerobic digestion, passivator, heavy metal form, humus, infrared spectral

摘要：

针对猪粪中的重金属污染问题，本文构建以猪粪/玉米秸秆为原料的厌氧消化体系，复配生物炭、腐殖酸、粉煤灰3种钝化剂，使用有机碳分级提取法反应最优钝化组中Cu、Zn形态动态变化过程，探索重金属与腐殖质的结合作用机制。结果表明：对Cu、Zn钝化效果影响最大的分别为腐殖酸、粉煤灰，钝化Cu、Zn最佳复合比分别为B1（腐殖酸∶粉煤灰∶生物炭比例为7.5%∶7.5%∶7.5%）、B2（5.0%∶7.5%∶7.5%）。对腐殖质进行提取发现，体系中的胡敏酸（HA）与富里酸（FA）含量的比值HA/FA呈增加趋势，消化前各处理组沼渣腐殖质中的Cu、Zn主要以FA-Cu、FA-Zn结合形式存在，消化后重金属主要与HA结合，B1、B2中HA-Zn、HA-Cu的占比明显高于对照组（CK），生物可利用性明显低于CK。比较Cu、Zn两种重金属稳定态发现：Zn转化稳定态的幅度偏小，主要是由于Zn是两性重金属，较活泼，易与小分子腐殖质FA结合，而Cu主要与大分子腐殖质HA结合，且结合更为紧密。B1、B2中重金属与腐殖质结合形态更为稳定，因此复合钝化剂可以有效降低厌氧消化进程中Cu、Zn的生物毒性。红外光谱分析发现钝化剂增加底物的芳香性，使得其更容易与重金属结合，芳香族、脂肪族化合物、蛋白质和多糖类化合物是主要的重金属结合点位。

关键词: 猪粪, 厌氧消化, 钝化剂, 重金属形态, 腐殖质, 红外光谱分析