Zhao Yan, Zhang Cheng, Ma Lun, Li Junchen, Tan Peng, Fang Qingyan, Chen Gang
State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
J Hazard Mater. 2024 Jan 5;461:132663. doi: 10.1016/j.jhazmat.2023.132663. Epub 2023 Sep 29.
To reduce heavy metals (HMs) contamination from tannery sludge, this study investigated the migration behaviour of arsenic (As) and chromium (Cr) at 700-900 °C using CO gasification. The HMs enrichment results showed that As contents of ash decreased (6.42→1.87 mg/kg) while Cr contents increased (41.40→78.24 mg/kg) over 700-900 °C. More Si-O bonds and fewer Ca-O bonds with increasing temperature in ash primarily determined this migration behaviour of HMs. Meanwhile, the proportions of toxic As(III) and Cr(VI) declined from 96.02% and 64.26-76.96% and 21.24%, forming As(0) and Cr(III) with less toxicity. This reduction was conducted via two pathways: (i) carbon reduced As(III)/Cr(VI) and (ii) carbon reduced Fe(II)/Fe(III) to Fe(0), then Fe(0) reduced As(III)/Cr(VI) assisted with carbon via Fe(0)→Fe(II)→Fe(III). However, free calcium ions oxidized As(0)/Cr(III) to As(III)/Cr(VI) at 700 C. At higher temperatures, silicate glass conversion of ash immobilized free calcium ions and barely oxidized HMs. Furthermore, this study identified the positive effect of increasing temperature on enhancing the stability of HMs in ash by transforming bioavailable HMs into non-bioavailable HMs, which decreased the leaching toxicity and environmental risk. Regarding HMs emissions control and cold gas efficiency, CO gasification treatment of tannery sludge is most effective at 800 °C.
为减少制革污泥中的重金属（HMs）污染，本研究利用CO气化研究了700-900℃下砷（As）和铬（Cr）的迁移行为。HMs富集结果表明，在700-900℃范围内，灰分中的As含量降低（6.42→1.87mg/kg），而Cr含量增加（41.40→78.24mg/kg）。灰分中随着温度升高Si-O键增多、Ca-O键减少，这主要决定了HMs的这种迁移行为。同时，有毒的As(III)和Cr(VI)的比例从96.02%和64.26%下降至76.96%和21.24%，形成了毒性较小的As(0)和Cr(III)。这种还原通过两条途径进行：（i）碳还原As(III)/Cr(VI)；（ii）碳将Fe(II)/Fe(III)还原为Fe(0)，然后Fe(0)通过Fe(0)→Fe(II)→Fe(III)协助碳还原As(III)/Cr(VI)。然而，在700℃时，游离钙离子将As(0)/Cr(III)氧化为As(III)/Cr(VI)。在较高温度下，灰分的硅酸盐玻璃转化固定了游离钙离子，几乎不会氧化HMs。此外，本研究确定了温度升高通过将生物可利用的HMs转化为非生物可利用的HMs，对提高灰分中HMs稳定性的积极作用，这降低了浸出毒性和环境风险。关于HMs排放控制和冷煤气效率，制革污泥的CO气化处理在800℃时最有效。
