有机酸-硫化零价铁处理高浓度含铬废液及铬铁资源化的研究

Study on treatment of high concentration chromium⁃containing waste liquid with modified iron preparation and recycling of chromium⁃containing iron

针对含铬废液净化污泥杂质含量高、铬含量低导致铬回收难的问题,以有机酸-硫化零价铁为铬废液净化剂,在高效去除废液中铬的同时,可净化污泥并直接制备铬铁合金。通过考察零价铁硫化程度、初始废液pH值、不同有机酸摩尔比、硫化零价铁用量等影响因素对废液铬净化与污泥铬富集的影响,探索铬污泥直接制备铬铁合金工艺。研究显示,采用有机酸-硫化零价铁协同处理后,废液总铬质量浓度可由5 324.1 mg/L降低至4.30 mg/L,与未改性零价铁技术相比,铬净化去除率由65.45%提高至99.92%。净化污泥铬铁元素平均质量分数大于46%,在1 500℃,氩气保护气氛下,添加质量分数为30%碳粉即可成功制备铬铁合金。铬铁合金产物中铬铁元素分布均匀,杂质含量较少。XRD分析显示,硫化零价铁的掺入质量增大可降低合金产品中杂相的生成。研究方法为冶金、化工等行业含铬废液的高效净化及资源化处理提供了一条新路径。

The recycling of chromium faces many problems in waste liquid treatment,such as low chromium contents and high impurity amounts in treatment sludge.Sulfide⁃modified Zero⁃Valent Iron(S ZVI)and organic acid were employed as the purification agent for chromium waste liquid.With the efficient removal of chromium in the waste liquid,the ferrochrome alloy can be directly prepared by purifying the sludge.The effects of key factors such as the sulfidation degree of zero⁃valent iron,pH value of initial waste liquid,proportion of organic acid,and dosage of S ZVI on the purification of waste liquid chromium and the enrichment of chromium in sludge were investigated.The direct preparation of chromium alloy from chromium sludge was explored.The results show that the optimal reaction conditions are as follows:the molar ratio of n(S)/n(Fe)was 0.116,the total concentration of organic acid was 12 mmol/L,n(C4H6O6):n(C6 H8 O7·H_(2) O)=3:1,adding iron mineralizer w(Cr)/w(Fe)=0.11.The total chromium of waste liquid can be reduced from 5324.1 mg/L to 4.30 mg/L.Compared with the unmodified zero⁃valent iron,the removal rate of chromium can be increased from 65.45%to 99.92%.The contents of Na,O,and other impurity elements in the sludge are about 50%,much lower than that in conventional sodium bisulfite reduction sludge(about 69%).The average content of chromium element in the sludge is>46%,which is easy to be recycled.The result shows that ferrochrome alloy was successfully prepared by adding carbon powder with a mass fraction of 30%under 1500℃and an argon protective atmosphere.XRD analysis shows that the impurity in the alloy products can be reduced with the increase of the addition of S ZVI SEM EDS analysis shows that the ferrochrome products are evenly distributed with fewer impurities.The carbon consumption amount is only 66.7%of the previous technology,which provides a new path for the green and low⁃carbon recovery of chromium in hazardous waste.