响应曲面法优化碳热还原重铬酸钠制备超细氧化铬  

Optimization of preparation of ultrafine chromium oxide by carbothermal reduction of sodium dichromate by response surface methodology

作　　者：张志强 崔康平[1] 陈星 李海洋 ZHANG Zhiqiang;CUI Kangping;CHEN Xing;LI Haiyang(School of Resources and Environmental Engineering,Hefei University of Technology,Hefei 230009,China;Zhongxin Lianke Environmental Technology(Anhui)Co.,Ltd.,Hefei 230009,China)

机构地区：[1]合肥工业大学资源与环境工程学院,安徽合肥230009 [2]中新联科环境科技安徽有限公司,安徽合肥230009

出　　处：《无机盐工业》2023年第10期136-144,共9页Inorganic Chemicals Industry

摘　　要：以含铬电镀污泥中分离提取的重铬酸钠为前驱体,采用响应曲面法优化碳热还原法制备了高纯度超细氧化铬,有效避免了传统工艺生产过程中产生大量含铬废弃物而引起环境污染等弊端,实现了铬资源综合利用与零污染物排放目标。考察了n(C)/n(Na_(2)Cr_(2)O_(7))、反应时间、反应温度对RECr(Ⅵ)[Cr(Ⅵ)还原转化率]的影响,在此基础上运用响应曲面法进行优化选择,并通过热重分析仪、X射线衍射仪等分析手段对反应物及还原产物进行表征分析,探讨了碳热还原机理。实验结果表明:最佳还原条件为n(C)/n(Na_(2)Cr_(2)O_(7))=4、反应时间为2 h、反应温度为550℃,此时RECr(Ⅵ)达到99.947%;各因素对RECr(Ⅵ)影响的显著性由大到小的顺序依次为n(C)/n(Na_(2)Cr_(2)O_(7))、反应温度、反应时间。碳热还原机理为还原过程中Na_(2)Cr_(2)O_(7)率先被炭黑还原为Cr_(2)O_(3)与Na_(2)CO_(3),之后熔融状Na_(2)Cr_(2)O_(7)中和Na_(2)CO_(3)生成Na_(2)CrO_(4),最后Na_(2)CrO_(4)进一步被炭黑还原为Cr_(2)O_(3)。碳热还原反应温度不宜过高,过高的反应温度会促使Cr_(2)O_(3)向NaCrO_(2)转变。在最佳条件下制备的Cr_(2)O_(3)产品纯度达到99%以上、平均粒径为214.246 nm,符合工业三氧化二铬一类优等品指标要求,满足等离子喷涂、铬绿颜料等材料高值化利用需求。The high purity ultrafine chromium oxide was prepared by carbothermal reduction method optimized by response surface method using sodium dichromate separated and extracted from chromium⁃containing electroplating sludge as precursor.It effectively avoided the disadvantages of environmental pollution caused by a large amount of chromium⁃containing waste produced in the production process of traditional processes,and achieved the goal of comprehensive utilization of chromium resources and zero pollution emission.The effects of n(C)/n(Na_(2)Cr_(2)O_(7)),reaction time and reaction temperature on RECr(Ⅵ)were investigated.On this basis,the response surface method was used to optimize the selection,and the reactants and reduction products were characterized by thermogravimetric analyzer and X-ray diffractometer.The mechanism of carbothermal reduction was discussed.The results showed that the optimum reduction conditions were n(C)/n(Na_(2)Cr_(2)O_(7))=4,reaction time of 2 h,reaction temperature of 550℃,and the RECr(Ⅵ)reached 99.947%.The significant order from big to small of the influence of various factors on RECr(Ⅵ)was:n(C)/n(Na_(2)Cr_(2)O_(7)),reaction temperature,reaction time.The mecha⁃nism of carbothermal reduction was that Na_(2)Cr_(2)O_(7)was first reduced to Cr_(2)O_(3) and Na_(2)CO_(3) by carbon black during the reduction process,then molten Na_(2)Cr_(2)O_(7)neutralized Na_(2)CO_(3) to form Na_(2)CrO_(4),and finally Na_(2)CrO_(4) was further reduced to Cr_(2)O_(3) by carbon black.At the same time,the reaction temperature should not be too high,too high reaction temperature would promote the transformation of Cr_(2)O_(3) to NaCrO_(2).The purity of the prepared Cr_(2)O_(3) product was more than 99%,and the average particle size was 214.246 nm,which met the first⁃class quality index of industrial chromium trioxide and met the high⁃value utilization requirements of materials such as plasma spraying and chrome green pigments.

关 键 词：碳热还原 三氧化二铬 重铬酸钠 响应曲面法 

分 类 号：TQ136.11[化学工程—无机化工]