Ghezzi Lisa, Mugnaioli Enrico, Perchiazzi Natale, Duce Celia, Pelosi Chiara, Zamponi Erika, Pollastri Simone, Campanella Beatrice, Onor Massimo, Abdellatief Mahmoud, Franceschini Fabrizio, Petrini Riccardo
Department of Earth Science, University of Pisa, Via S. Maria 53, 56126, Pisa, Italy.
Department of Chemistry, University of Pisa, via G. Moruzzi 13, 56124, Pisa, Italy.
Sci Rep. 2023 Sep 28;13(1):16283. doi: 10.1038/s41598-023-43579-9.
Pyrolysis in an inert atmosphere is a widely applied route to convert tannery wastes into reusable materials. In the present study, the Cr(III) conversion into the toxic hexavalent form in the pyrolyzed tannery waste referred to as KEU was investigated. Ageing experiments and leaching tests demonstrated that the Cr(III)-Cr(VI) inter-conversion occurs in the presence of air at ambient temperature, enhanced by wet environmental conditions. Microstructural analysis revealed that the Cr-primary mineral assemblage formed during pyrolysis (Cr-bearing srebrodolskite and Cr-magnetite spinel) destabilized upon spray water cooling in the last stage of the process. In the evolution from the higher to the lower temperature mineralogy, Cr is incorporated into newly formed CrOOH flakes which likely react in air forming extractable Cr(VI) species. This property transforms KEU from an inert waste to a hazardous material when exposed to ordinary ambient conditions.
在惰性气氛中进行热解是一种将制革废料转化为可再利用材料的广泛应用途径。在本研究中，对热解后的制革废料KEU中Cr(III)向有毒六价形式的转化进行了研究。老化实验和浸出试验表明，在环境温度下且有空气存在时，Cr(III)-Cr(VI)会发生相互转化，潮湿的环境条件会增强这种转化。微观结构分析显示，热解过程中形成的Cr-原生矿物组合（含铬的斯列勃罗德石和铬磁铁矿尖晶石）在该过程最后阶段经喷水冷却后变得不稳定。在从高温矿物学向低温矿物学的演化过程中，Cr会结合到新形成的CrOOH薄片中，这些薄片可能在空气中反应形成可萃取的Cr(VI)物种。当暴露于普通环境条件时，这一特性会使KEU从惰性废料转变为有害物质。
