柑桔皮与铬渣共热解毒六价铬

Detoxification of Cr(Ⅵ)from chromite ore processing residue by pyrolysis with citrus peel

铬渣是铬盐生产过程中产生的废渣,含有大量的水溶性和不溶性六价铬[Cr(Ⅵ)],对人类和生态环境均有很大危害。提出了铬渣与农业废弃物柑桔皮进行混合热解,利用柑桔皮热解产生的还原性气体及生物质炭将Cr(Ⅵ)还原为无毒的三价铬[Cr(Ⅲ)]。系统研究了热解温度、柑桔皮与铬渣质量比、热解时间和球磨时间等条件对铬渣中总Cr(Ⅵ)、水溶性Cr(Ⅵ)和难溶性Cr(Ⅵ)还原去除率的影响规律。得到较佳的实验参数:热解温度为600℃,柑桔皮与铬渣的质量比为30%,热解时间为45 min,球磨时间为1 h。在最佳条件下,铬渣中总Cr(Ⅵ)的还原去除率达到99.51%,其含量由1641.95 mg/kg降低到8.04 mg/kg,远低于25 mg/kg的国家排放标准(HJ/T 301—2007《铬渣污染治理环境保护技术规范》)。并对解毒后的铬渣进行了X射线衍射(XRD)分析,结果表明铬渣热解解毒前后物相一致。该研究结果可为无钙焙烧铬渣的无害化处理提供新的技术思路。

Chromite ore processing residue(COPR)is a by-product of the chromium salt processing and production industry,which contains a large amount of water-soluble and insoluble hexavalent chromium[Cr(Ⅵ)].The leaching of Cr(Ⅵ)exhibits great harm to human being and the ecological environment.A new process for detoxification treatment of COPR was devel oped,which included mixing and pyrolyzing COPR with the agricultural waste of citrus peel(CP)and the resulted reduction gas and biochar were used to effectively reduce Cr(Ⅵ)to trivalent chromium[Cr(Ⅲ)].Besides,the process parameters such as pyrolysis temperature,CP/COPR mass ratio,pyrolysis time,and ball milling time on the reduction efficiency(RE)and residual quantity of Cr(Ⅵ)were systematically investigated.The results showed that the pyrolysis of the COPR with CP exhibited an excellent detoxification effect on COPR,and Cr(Ⅵ)could effectively be converted into trivalent chromium[Cr(Ⅲ)].The reduction efficiency of total Cr(Ⅵ)could reach as high as 99.51%.After the detoxification treatment,the total amount of Cr(Ⅵ)in the COPR decreased from 1641.977 mg/kg to 8.04 mg/kg,which was well below the national emission standard of China of 25 mg/kg(HJ/T 301—2007“Environmental protection technical specifications for pollution treatment of the Chromium residue”).Subsequently,the XRD analysis of COPR after detoxification showed that the phase compositions before and after pyrolysis of COPR were identical.The research results could provide an alternative solution to the detoxification of the COPR from the lime-free roasting process of chromium salt industry.