【作者】 肖凯；

【导师】 方秦汉； 李国成；

【作者基本信息】 华中科技大学 ， 岩土工程， 2012， 博士

【摘要】 铬的化合物在钢铁制造业、纺织业、皮革制造业及其他行业有着广泛的应用。铬盐制作过程中会产生大量的铬渣,铬渣中的六价铬能导致人体多种器官产生病变、甚至癌症。由于我国工业的快速发展,每年产生的铬渣量已达近百万吨,加上历年产生的铬渣,已严重威胁到了我国多个地区的自然环境和人的健康。因此,系统地研究我国的铬渣的特点及相应的处理方法有着重要的理论和工程应用价值。本文的研究内容包括三个方面：1)利用先进的矿物分析技术,如X射线荧光试验(XRF)、X射线衍射试验(XRD)和环境扫描电子显微镜试验(ESEM)等,对铬渣进行系统的分析,构建铬渣的矿物属性框架；2)考虑铬渣与酸溶液的反应时间、铬渣的粒径等因素,通过批次试验,系统地研究酸溶液(H2SO4和HNO3)对铬渣中六价铬溶出的影响,为研究铬渣的化学处理方法奠定基础；3)采用化学还原法,用硫酸亚铁(FeSO4)和多阳离子聚硫化物试剂混合(CaSx)作还原剂的柱式试验,研究有效的铬渣处理方法。本文的研究主要取得了以下成果：(一)系统地建立了铬渣的矿物属性框架。研究了铬渣的元素组成、矿物成分、颗粒形貌及元素分布特点等,结果表明,铬渣的主要元素组成按含量从大到小依次为钙、铁、镁、铝、硅和铬,其中铬的含量约为6%。组成铬渣的主要矿物为钙铁石、方镁石、方解石、白云石、水钙铁榴石、铬铁矿、石英,可能还有含量很少的水铝钙石和斜硅钙石。包含六价铬的矿物为水钙铁榴石,且存在于颗粒内部,而被认为含三价铬的钙铁石存在于铬渣颗粒的外围。从整体上看,铬较均匀的分布于铬渣中,但在颗粒内部的浓度稍高。(二)通过两组批次试验系统地研究了铬渣中六价铬的滤出特性。试验结果表明,滤出液中铬浓度的大部分为六价铬。与酸的种类相比,铬渣的颗粒粒径六价铬释放的影响更大,粗颗粒很难与酸完全反应。与硝酸相比,硫酸更容易降低pH值并释放铬渣中的六价铬。铬渣中铬的溶出有很强的持续性。铬渣的酸中和能力很强,这意味着用酸处理铬渣可能成本偏高。(三)采用化学还原法对铬渣的处理效果进行了系统的研究。结果表明,当渗透液为FeSO4和H2SO4混合溶液时,在短期内能有效地控制滤出液中六价铬的含量,但随后铬渣容易结块,会阻碍后续的反应。被CaSx处理过的铬渣,再用去离子水渗透的过程中,滤出l液中始终没有检测出六价铬,结合XRD和ESEM的试验结果,表明用CaSx处理铬渣的效果比用FeSO4和H2SO4混合溶液处理更好。本文系统地建立了铬渣的矿物属性框架、分析了铬渣中六价铬的溶出特性、对采用化学还原法处理铬渣的效果进行了系统的研究,为今后大规模地处理铬渣奠定了坚实的理论基础。更多还原

【Abstract】 Chromate is widely applied in steel, textile, leather and other manufacturing industries. In chromate making process, chromite ore processing residue (COPR) would be made as by-product. Hexavalent chromium (Cr(VI)) in COPR could cause disease, so much as cancer in human organs. As the rapid development of industry in our country, nearly one million tons of COPR are produced every year. Considering the COPR produced over the years, natural environment and human health at various locations in China are seriously threatened. Therefore, it is very important in theory research field and engineering practice to systematically study the characteristics and appropriate treatment methods of the COPR produced in our country.Three aspects of the research contents of this thesis are:1) applying advanced techniques such as X-ray fluorescence (XRF), X-ray diffraction technology (XRD) and environmental scanning electron microscopy (ESEM) to systematically analyse COPR, and consequently developing the mineralogical framework for China-based COPR; 2) studying the effects of acid solutions (HNO3 or H2SO4) on the leach of Cr(VI) from COPR by batch tests respect to reaction time and COPR particle size, and laying the foundation of the subsequent research for chemical treatment methods; 3) using chemical reduction methods to study the effectiveness of treatment methods with ferrous sulfate (FeSO4) or a cationic polysulfide reagent (CaSx) as reducing agents.The main achievements of this thesis are as follows:(1) The mineralogical framework for China-based COPR was developed. Elemental composition, mineral composition and surface feature of COPR were identified, respectively. The result shows that the dominant elements of COPR are Ca, Fe, Mg, Al, Si and Cr by descending order of the content, which are evenly distributed throughout of COPR particles. The weight percentage of chromium is around 6%. COPR particle consists of brownmillerite, periclase, calcite, dolomite, hydroandradite, chromite and quartz. Hydrocalumite and larnite are possibly contained in COPR. Cr(Ⅵ) possibly exists in hydroandradite which presents inside COPR particle. Cr(Ⅲ)-bearing brownmillerite occurs in the rim of COPR particles. As a whole, a low content of Cr evenly distributes in COPR particles, while slightly high concentration of Cr occurs inside particles.(2) The leaching behavior of Cr(Ⅵ) from COPR was investigated by batch leaching tests. According to the test results, aqueous Cr(Ⅵ) accounted for most of the content of total Cr in leachate. It was difficult for coarse-sized particles in this study completely reacting with acid. Comparing with acid type used, the particle size may have a more significant impact on the release of Cr(Ⅵ) from COPR. It was easier to lower the pH value in leachate and release Cr(Ⅵ) from COPR with H2SO4 relative to HNO3. In addition, the leach of Cr(Ⅵ) from COPR was persistent. The acid neutralization capacity of COPR was relatively large, which suggests that the application of acid treatment method for COPR disposal may be costly.(3) Chemical reduction treatment methods of COPR were studied systematically. When COPR was permeated with FeSO4-H2SO4 solution, Cr(Ⅵ) concentration in leachate could be controlled to a low value in a relatively short time. However, the subsequently blocking remanent COPR prevented further reaction with FeSO4. In the whole column experiment process, Cr(Ⅵ) concentrations could not be detected in leachates from COPR treated with CaSx and permeated with DI water. Complemented with the results of XRD and ESEM, the treatment with CaSx and permeated with DI water is more effective compared with the treatment using FeSO4-H2SO4 solution.This thesis systematically developed a mineralogical framework for China-based COPR, investigated leaching characteristics of Cr(Ⅵ) and evaluated the effectiveness of chemical reduction treatments of COPR. They lay the foundation for future large-scale treatment of COPR.更多还原