Low-temperature pyrolysis reduction (<500 °C) for Cr(VI) remediation in heavily polluted soil or slag has gained increasing attention. However, it is hard to realize almost 100% Cr(VI) pyrolysis reduction at a high concentration of Cr(VI) pollution (more than 10⁴ mg/kg) due to insufficient reductive pyrolysis products. In the present study, almost 100% Cr(VI) reduction was achieved by cellulose-enriched biomass assisted by an Fe mineral catalysis. Quantitative analysis of tar, reducing gases, and char on the Cr(VI) reduction efficiency suggested that the produced tar is a crucial factor to promote Cr(VI) pyrolysis reduction. Our results indicated that both the cellulose component of biomass and the Fe minerals catalyst could produce susceptible-cracking tar to help Cr(VI) reduction indirectly. FT-ICR MS and online MS results further discerned that produced tar with aromatic and lignin/CRAM-like structures or high unsaturated and oxidized structures (DBE > 15, O_x > O₆) can be cracked via a decarbonylation reaction to generate reducing gases for promoting Cr(VI) reduction. Thus, our present study provides a method to completely reduce Cr(VI) in solid wastes, perfectly avoiding the reyellowing risk of residual Cr(VI).

中文翻译：

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生物质纤维素成分和铁矿物催化帮助 Cr(VI) 实现几乎 100% 的热解还原效率

用于重污染土壤或炉渣中 Cr(VI) 修复的低温热解还原 (<500 °C) 越来越受到关注。然而，在高浓度的 Cr(VI) 污染（超过 10 ⁴毫克/公斤）由于还原热解产物不足。在本研究中，在铁矿物催化的辅助下，富含纤维素的生物质实现了几乎 100% 的 Cr(VI) 还原。焦油、还原气体和焦炭对 Cr(VI) 还原效率的定量分析表明，产生的焦油是促进 Cr(VI) 热解还原的关键因素。我们的结果表明，生物质的纤维素组分和铁矿物催化剂都可以产生易裂化焦油，间接帮助 Cr(VI) 还原。FT-ICR MS 和在线 MS 结果进一步发现，产生的具有芳香族和木质素/CRAM 类结构或高度不饱和和氧化结构（DBE > 15，O _x > O ₆）的焦油可以通过脱羰反应产生还原气体以促进 Cr(VI) 还原。因此，我们目前的研究提供了一种完全减少固体废物中六价铬的方法，完美地避免了残留六价铬的再黄化风险。