低温热裂解处理对猪粪中重金属的钝化效应

Influence of Low-temperature Pyrolysis Treatment on Bioavailability of Heavy Metals in Pig Manure

随机采集全国11个大型猪场猪粪样品,进行重金属(As、Cu、Zn、Cd、Pb、Ni)含量的分析,并分别设置350、400、450℃三个热裂解温度,将猪粪进行限氧热裂解炭化,分析热裂解后猪粪中重金属的含量变化。结果表明:猪粪样品中重金属Zn、Cu、Ni、As、Pb、Cd含量的变化范围分别为261.6~2 564.5、87.98~700.6、2.19~7.17、0.45~19.57、1.69~4.02、0.10~0.17 mg·kg-1,平均含量分别为928.2、294.7、4.80、3.60、2.39、0.12 mg·kg-1,其中以Zn、Cu含量最高,Cd含量最低,不同猪场间重金属残留量的变异性以As为最大,变异系数达到155.7%;经不同温度热裂解处理后的猪粪生物质炭中重金属Ni、Cu、Zn、Pb、Cd和As含量较猪粪原样分别提高了57.7%~104.4%、59.7%~99.4%、50.7%~94.0%、47.1%~73.5%、30.8%~61.5%和17.1%~30.5%,而猪粪生物质炭中Cu、Ni、Zn、Pb、As的重金属有效态含量较猪粪原样分别显著下降94.4%~95.4%、91.9%~95.1%、91.3%~92.5%、80.4%~81.0%、76.6%~84.0%。由此可见,猪粪限氧低温热裂解炭化可对重金属起到良好的钝化效果。

Animal wastes often contain heavy metals, thus posing environmental risks. Carbonization by pyrolysis is an important approach to reusing waste biomass. In this study, an experiment was designed to investigate the influence of low-temperature pyrolysis treatment on bioavailability of heavy metals in pig manure. Pig manure samples, collected from commercial pig farms across the China, were analyzed for heavy metal contents(arsenic, copper, zinc, cadmium, lead and nickel)and also subjected to pyrolysis at 350 ℃, 400 ℃ or 450 ℃. The ranges and averages of heavy metal content(mg·kg-1)in pig manure were 261.6~2 564.5 and 928.2 for Zn, 87.98~700.6 and 294.7 for Cu, 2.19~7.17 and 4.80 for Ni, 0.45~19.57 and 3.60 for As, 1.69~4.02 and 2.39 for Pb, and 0.10~0.17 and 0.12 for Cd. The greatest varia-tion was 155.7% for As. Metal content in the pig manure-derived biochar was increased by 57.7% ~104.4%(Ni), 59.7% ~99.4%(Cu),50.7% ~94.0%(Zn), 47.1% ~73.5%(Pb), 30.8% ~61.5%(Cd) and 17.1% ~30.5%(As). However, the bioavailability of metals in the biochars decreased greatly. DTPA-extractable metals in the biochars were decreased by 94.4%~95.4% for Cu, 91.9%~95.1% for Ni, 91.3%~92.5% for Zn, 80.4%~81.0% for Pb and 76.6%~84.0% for As, as compared with the pig manures. It suggests that low-temperature pyrolysis could reduce the environmental risks of heavy metals in pig manures.