Abstract:

In this paper, biochar (BRC) produced from biogas residue (BR) with three particle sizes (d≤0.15 mm, 0.15 mm <d≤0.25 mm, d>0.25 mm) were obtained by pyrolysis at 600℃. The effects of different particle sizes on the migration and transformation of phosphorus and heavy metals between BR and BRC were systematically studied. And toxicity characteristic leaching procedure (TCLP) leaching toxicity test and potential ecological risk assessment were used to evaluate the safety risk of BR and BRC. The results showed that the phosphorus in BR and BRC were mainly acid-soluble phosphorus (HCl-P), followed by residual phosphorus (Res-P), and the contents of other phosphorus forms were low. TP content showed a decreasing trend with increase of particle size in BR and BRC. Pyrolysis can promote the conversion of H₂O-P, NaHCO₃-P and NaOH-P to HCl-P and Res-P. As the particle size increases, the total amount of Cu and Zn in BR increases, while the amount of Cr decreases, the total amount of Cr and As in BRC increases, and the total amount of Zn and Pb decreases. Meanwhile, the F3+F4 fractions (oxidizable and residue fraction) of Cr, Zn, Pb, As in BR and that of Cr, Pb, As in BRC decreased with the increase of particle size, while Cu, Zn and Cd of BRC showed an opposite trend. The assessment results of TCLP leaching toxicity and potential ecological risk of heavy metals indicate that the heavy metals in BR and BRC are at low risk levels.

Key words: particle size, biogas residue, biochar, pyrolysis, phosphorus, heavy metals, ecological risk assessment, waste treatment

摘要：

以3种粒径餐厨沼渣为原料，在600℃下热解制备生物炭，研究粒径对沼渣（BR）及生物炭（BRC）中磷和重金属的影响，并采用TCLP浸出毒性和重金属潜在生态风险评估对其安全性进行系统研究。结果表明：BR及BRC中的磷主要以酸溶态磷（HCl-P）为主，残渣态磷（Res-P）次之，其余磷形态含量较低，总磷含量均呈现出随粒径增大而降低的趋势。热解促进H₂O-P、NaHCO₃-P和NaOH-P向HCl-P和Res-P转化。随着粒径的增大，BR中Cu、Zn总量增加，Cr减少，BRC中的Cr、As总量增加，Zn、Pb减少。并且BR中Cr、Zn、Pb和As中可氧化态和残渣态F3+F4随粒径增大而减少；BRC中Cr、Pb、As中F3+F4随粒径增大而减少，而Cu、Zn、Cd与之相反。TCLP浸出毒性和重金属潜在生态风险评估结果表明BR及BRC中重金属均属于低风险水平。

关键词: 粒径, 餐厨沼渣, 生物炭, 热解, 磷, 重金属, 生态风险评估, 废物处置