制备工艺对nZVI/污泥基生物炭中Zn、Cu、Pb形态分布及其生态风险的影响

以市政污泥为原料、纳米零价铁（nZVI）为添加剂，采用热解法制备污泥生物炭，考察了nZVI添加量、热解温度和升温速率对生物炭中Zn、Cu、Pb形态分布及其生态风险的影响。结果显示:高nZVI添加量、高热解温度及低升温速率可提高稳定态（BCR法） Zn、Cu和Pb的含量；高nZVI添加量可促使Zn、Cu和Pb向可氧化态转化，而高热解温度和低升温速率有利于残渣态Zn、Cu和Pb的生成；最优nZVI添加量、热解温度和升温速率分别为2000 mg/kg，800℃和4℃/min。此外，当nZVI添加量为800 mg/kg、热解温度为800℃和升温速率为2℃/min时有利于降低Zn、Cu和Pb的生态风险；Zn、Cu和Pb总体生态风险等级分别为低风险、低风险和无风险，与Cu和Pb相比，Zn的生态风险较高；以RI值为评价指标，nZVI/污泥基生物炭的优化制备工艺为:nZVI添加量为200 mg/kg，热解温度为800℃，升温速率为5℃/min。

EFFECT OF PREPARATION PROCESS ON SPECIATION DISTRIBUTION AND ECOLOGICAL RISK OF Zn,Cu AND Pb IN nZVI / SLUDGE BASED BIOCHARS

The biochars were prepared by pyrolysis using municipal sludge as the raw material and nano-zero-valent iron (nZVI) as the additive. The effect of nZVI addition, pyrolysis temperature and heating rate on speciation distribution and ecological risk of Zn, Cu and Pb in biochars was investigated. The results showed that the higher nZVI addition, higher pyrolysis temperature and lower heating rate could increase the contents of Zn, Cu and Pb in the steady state (BCR method). The higher nZVI addition could promote the conversion of Zn, Cu and Pb to the oxidizable state, while the higher pyrolysis temperature and lower heating rate were favorable for the formation of residual Zn, Cu and Pb. The optimized nZVI addition, pyrolysis temperature and heating rate were 2000 mg/kg, 800 ℃ and 4 ℃/min, respectively. In addition, when the addition amount of nZVI was 800 mg/kg, the pyrolysis temperature was 800 ℃ and the heating rate was 2 ℃/min, which was conducive to reduce the ecological risk of Zn, Cu and Pb. The approximate ecological risk levels of Zn, Cu and Pb were low risk, low risk and no risk, respectively. Compared with Cu and Pb, the ecological risk of Zn was higher. If the RI value was used as the evaluation index, the optimized preparation process of nZVI/sludge-based biochar was as follow: nZVI dosage of 200 mg/kg, pyrolysis temperature of 800 ℃, heating rate of 5 ℃/min.