废汽车催化剂铁捕集熔炼渣一步法制备微晶玻璃研究

One-step glass-ceramics production process using iron smelting slags of spent automotive catalysts

低温铁捕集技术是回收废汽车催化剂中铂族金属最有前途的技术之一.铁捕集熔炼渣以硅铝酸盐为主,同时含有少量有毒重金属(如Cr、Ba、Ni、Mn等),其处置与资源化利用是当前行业的难题.本文致力于铁捕集熔炼渣的重金属固化和资源化利用,充分利用硅铝酸盐为网络形成体,以重金属和酸洗污泥中CaF2为形核剂,通过一步法制备微晶玻璃.差示扫描量热分析结果表明,随着酸洗污泥用量(质量分数)从7%增至28%,样品的玻璃化转变温度与析晶温度间隙由211℃降低到150℃,基础玻璃的析晶活化能从321.8 kJ·mol^(-1)降低到303.5 kJ·mol^(-1),Avrami指数由1.7增至3.7.表明酸洗污泥可以降低成核与析晶的温差,有利于实现一步法工艺.酸洗污泥添加量(质量分数)为21%时,在900℃下热处理1.2 h制备的微晶玻璃具有较佳性能,即密度3.04 g·cm^(-3),吸水率(质量分数)0.11%,维氏硬度和抗弯强度分别为742.72 HV和119.32 MPa.浸出毒性试验表明重金属Cr、Ba、Ni等均满足美国环保局提出的毒性浸出实验(TCLP)标准.玻璃结构分析表明酸洗污泥有利于增加基础玻璃中的非桥氧含量,降低玻璃网络聚合度,增强结晶趋势.

The most important secondary resources of platinum group metals(PGMs)are spent automotive exhaust catalysts,which are called“mobile PGM mines.”Low-temperature iron-capture technology is a promising technology for recovering PGMs due to its high efficiency and low pollution.Because of the content of aluminosilicates and toxic heavy metals(Cr,Ba,Ni,and Mn),the disposal of iron-capture smelting slag is necessary.This paper is devoted to the solidification of heavy metals and the resource utilization of ironcapture smelting slag.Glass-ceramics were made by a one-step method using aluminosilicates as network formers.Heavy metals and CaF2 are employed as nucleating agents in pickling sludge.According to the analysis of differential scanning calorimetry,the glass transition temperature and crystallization temperature of samples are in the range of 650℃–700℃and 800℃–920℃,respectively.The gap between the glass transition temperature and crystallization temperature of samples decreased from 211℃to 150℃when increasing the amount of pickling sludge from 7%to 28%(mass fraction).The devitrification activation energy decreased from 321.8 to 303.5 kJ·mol^(-1),while the Avrami index increased from 1.7 to 3.7.It demonstrates that pickling sludge can reduce the temperature difference between nucleation and crystallization,which is beneficial in realizing the one-step process.The effects of pickling sludge and heat treatment systems on glass-ceramics were investigated.The diopside phase is the main crystalline phase of glass-ceramics.Nepheline and Magnetite phases were detected when the amount of pickling sludge(mass fraction)reached 28%.The physical properties of the glass-ceramics were improved with the increase in heat treatment temperature and time.When the addition amount of pickling sludge(mass fraction)was 21%,the glass-ceramics prepared by heat treatment at 900℃for 1.2 h had the best properties;namely,the density was 3.04 g·cm^(-3),the water absorption(mass fraction)was 0.11%,and the Vickers hardness and flexural strength were 742.72 HV and 119.32 MPa,respectively.The Toxicity Characteristic Leaching Procedure(TCLP)leaching standard was met by heavy metals such as Cr,Ba,and Ni in the toxicity test.Glass structure analysis revealed that the pickling sludge increased the nonbridging oxygen content in the base glass while reducing the degree of glass network polymerization,resulting in an enhanced crystallization tendency.The pickling sludge proved to have potential as an inexpensive nucleating agent in the preparation of glass-ceramics with excellent performance.The glass-ceramics with these unique properties are promising to be applied as building materials.