School of Environmental Science and Engineering, Shaanxi University of Science and Technology, Xi'an, 710021, China.
College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China.
Environ Sci Pollut Res Int. 2018 Jan;25(3):2495-2505. doi: 10.1007/s11356-017-0271-0. Epub 2017 Nov 10.
The application or disposal of char derived from tannery sludge is directly influenced by the mobility and bioavailability of Cr during pyrolysis process. This study focused on the changes of Cr speciation and organic matter in tannery sludge during low-temperature pyrolysis (100-400 °C) to evaluate the toxicity of char in terms of the leaching possibility of Cr. The results showed that (1) lower char yield and more porous structure were observed after pyrolysis. (2) Higher pyrolysis temperature increased Cr content in the char; however, Cr in this case was converted into the residual fraction which minimized its bioavailability therefore lowers its potential risk to the environment. (3) Organic matters in the acid and alkali leachates were mainly humic acid-like substance, and condensed organic matter might appear at 200 °C and then destruct. (4) Despite the comparatively high content of Cr in the char, the leaching toxicity of char was within the security range according to the national standard of China. The Cr content in the acid and alkali leachates decreased to the range of 16.5-35.3 and 0.2-6.8 mg/L, respectively. It was suggested that the potential toxicity of tannery sludge from Cr could be reduced before utilization or disposal by pyrolysis, especially under 400 °C.
制革污泥热解过程中铬的迁移性和生物可利用性直接影响其基炭的应用和处置。本研究主要关注制革污泥在低温热解（100-400℃）过程中铬形态和有机质的变化，以评估基炭浸出铬的可能性来评价其毒性。结果表明：（1）热解后，基炭产率降低，孔结构增多；（2）较高的热解温度增加了基炭中的铬含量；然而，这种情况下的铬转化为残余物，减少了其生物可利用性，从而降低了其对环境的潜在风险；（3）酸和碱浸出液中的有机质主要为类腐殖酸物质，缩合有机质可能在 200℃时出现，然后破坏；（4）尽管基炭中的铬含量相对较高，但根据中国国家标准，基炭的浸出毒性仍在安全范围内。酸和碱浸出液中的铬含量分别降低到 16.5-35.3 和 0.2-6.8mg/L。建议在利用或处置制革污泥之前，特别是在 400℃以下，通过热解降低其潜在毒性。
