热解温度对畜禽粪便生物炭重金属特征变化的影响

Effect of pyrolysis temperature on the characteristics change of heavy metals in biochar derived from animal manure

为了揭示畜禽粪便生物炭中重金属的特征变化,以鸡粪、猪粪渣和牛粪为原料,采用低氧控温法制备生物炭,研究了不同热解温度(350、450、550、650和750℃)的畜禽粪便生物炭产率、重金属(Cu、Zn、Cd、Pb、Cr和Ni)含量和相应富集系数的变化,以及原料来源、热解温度和重金属特征的相关性.结果表明,随着热解温度的升高,畜禽粪便生物炭产率逐渐下降,各重金属元素含量(Cd除外)逐渐增加,多数重金属富集系数呈降低的趋势,总体上高温热解虽增加了畜禽粪便生物炭的重金属含量,但也利于炭化过程中重金属的挥发迁移.畜禽粪便生物炭中重金属含量与热解温度、原料来源密切相关,其中与热解温度的相关性均显著,各生物炭的重金属富集能力表现为鸡粪>猪粪渣>牛粪.综合分析发现,热解温度对畜禽粪便生物炭的重金属特征变化有显著影响,选择低重金属含量和低富集系数的畜禽粪便可避免高温制备的生物炭在实际应用中由自身重金属可能带来的二次污染.

This study aims to investigate the characteristics of heavy metals in biochar derived from animal manure. In this work three types of biochars derived from chicken manure（ CM）,solid-liquid separated pig manure（ PR） and dairy manure（ DM）,were prepared by pyrolyzing at different temperatures（ 350,450,550,650 and 750 ℃）,under an oxygen-limited condition. The effects of temperature on the yield,heavy metal contents and their relative enrichment factors of biochars were analyzed. Meanwhile,the relationship between material source,pyrolysis temperature and heavy metal characteristics was discussed. The results showed,as pyrolysis temperature increased,the biochar yields decreased,while the contents of heavy metals in biochars gradually increased except for Cd,and the enrichment factors of most of the heavy metal had a downward trend. In general,with increased temperature,the heavy metal contents in biochars were enhanced,and also contributed to the volatilization of heavy metals in the process of manure carbonization. The heavy metal contents in biochars were closely related to material source and pyrolysis temperature,and the correlation between heavy metal content and pyrolysis temperature was significant. The heavy metal enrichment capacity of biochars was in order of DM 〉PR 〉CM. Comprehensive analysis showed that the pyrolysis temperature had a significant effect on the characteristics of heavy metals in manure derived-biochars. The selection of low-heavy metal content and low enrichment factor of animal manure could avoid the secondary pollution of heavy metal in biochar while pyrolysis at high temperature in the practical application.