【作者】 屈学理；

【导师】 周秋生；

【作者基本信息】 中南大学 ， 有色金属冶金， 2011， 硕士

【摘要】 铬渣及铬污染土壤中含有的Cr(Ⅵ)具有较强的毒性,对环境和人体造成极其严重的危害。在铬渣解毒及铬污染土壤修复过程中,降低Cr(Ⅵ)含量或将Cr(Ⅵ)固定是关键。本课题研究了三种以碳酸钠溶液浸出铬渣为主体的铬渣解毒工艺及一种堆肥修复铬污染土壤的技术,并根据浸出毒性试验对解毒和修复效果进行了评价,同时对堆肥修复铬污染土壤的机理进行了探讨。主要研究内容和结论如下：通过碳酸钠溶液堆浸法解毒铬渣的试验研究,明确了浸出剂种类、碳酸钠浓度、铬渣粒度、时间对浸出率的影响规律,在最佳实验条件下,解毒后铬渣的毒性浸出液中Cr(Ⅵ)和总Cr浓度分别为4.31和4.53mg/L；通过碳酸钠溶液堆浸-硫酸亚铁还原联合解毒铬渣的实验研究,明确了循环次数对浸出液中碳酸钠浓度、Cr(VI)浓度和浸出率的影响规律。铬渣粒度显著影响其解毒效果,粒度＜0.15mm时,最终解毒渣的毒性浸出液中Cr(VI)和总Cr浓度分别为1.98和2.45mg/L,低于HJ/T301-2007规定的限值。解毒前后的铬渣物相分析结果与热力学分析基本一致；通过碳酸钠溶液搅拌浸出-硫酸亚铁还原联合解毒铬渣的实验研究,明确该实验条件下浸出和还原在处理效果中各自所占的比例大小；解毒后铬渣的毒性浸出液中Cr(VI)和总Cr浓度分别为6.38和10.14mg/L,远高于HJ/T301-2007规定的限值。通过堆肥修复铬污染土壤的实验研究,明确了修复剂、搅拌、水分含量和肥含量对土壤修复效果的影响规律,弄清了修复过程中土壤中铬形态的转化规律；在最佳实验条件下,修复后土壤的毒性浸出液中Cr(VI)和总Cr浓度分别为0.28和1.13mg/L,低于GB8978-1996规定的限值,且在120天内修复效果稳定。在堆肥修复铬污染土壤机理的研究中,确定了堆肥中有机物是堆肥修复过程中的主导因素,并初步筛选出了肥中有效基团为醇羟基、羧酸基和酰胺基,醇羟基是通过和土壤中Cr(VI)发生氧化还原反应而直接起作用的,酰胺基和羧酸基是通过增强土壤中有机组分的修复效果而间接起作用的。更多还原

【Abstract】 Hexavalent chromium (Cr(VI)) present in the chromite ore processing residue (COPR) and chromium-contaminated soil causes serious damage to the environment and human health for its high toxicity. It is critical to reduce the content of Cr(VI) or to fix Cr(VI) in the process of COPR detoxification and chromium-contaminated soil remediation. We studied three kinds of COPR detoxification techniques using Na2CO3 solution as the leaching reagent and one kind of chromium-contaminated soil remediation technique by compost, evaluated the detoxification and remediation effect using toxicity characteristic leaching procedure (TCLP), and investigated the remediation mechanism of chromium-contaminated soil by compost. Main researches and conclusions are as follows:Through the experimental study on COPR detoxification by using Na2CO3 solution as heap-leaching reagent, the influences of factors, such as leaching reagents, Na2CO3 concentration, particle size of COPR and leaching duration time, on the leaching rate were investigated. Cr(VI) and total Cr concentrations in the leachate of TCLP of the detoxified COPR are 4.31 mg/L and 4.53 mg/L respectively under the optimal expermental conditions. Based on the experimental study on COPR detoxification by the combination process of heap-leaching using Na2CO3 solution as leaching reagent and Cr(VI) reduction by FeSO4, the effects of cycle times on Na2CO3 concentration, pH, Cr(VI) concentration in the leaching solution and the leaching rate were studied. The initial particle size of COPR has a great influence on the detoxification effect. Cr(VI) and total Cr concentration in the leachate of TCLP of the final detoxified COPR (Particle size<0.15mm) is 1.98 mg/L and 2.45 mg/L, respectively, which is below the regular limit of HJ/T301-2007. XRD analyses of the untreated and detoxificated COPR approximately are agreement with the thermodynamic calculation. According to the experimental study on COPR detoxification by the combination process of stirring-leaching using Na2CO3 solution as the leaching reagent and Cr(VI) reduction by FeSO4, the proportions of leaching and reduction of the total detoxification effect were researched under the expermental conditions. The Cr(VI) and total Cr concentrations in the leachate of TCLP of the final detoxificated COPR are 6.38 mg/L and 10.14 mg/L respectively, which is beyond the regular limit of HJ/T301-2007.Effects of remediation reagents, the content of H2O and compost, and stirring on soil remediation efficiency were identified, and the transformation of forms of Cr in the soil remediation process was studied by the experimental study on chromium-contaminated soil remediation by compost. The Cr(VI) and total Cr concentrations in the leachate of TCLP of the remediated chromium-contaminated soil are 0.28 mg/L and 1.13 mg/L respectively, which is a little bit lower than the regular limit of GB8978-1996, whats more the remediation effect is stable after 120 days.In the study on remediation mechanism of chromium-contaminated soil by compost, it is determined that the organic materials present in the compost are the key factors influencing the remediation effect, and the effective groups are Hydroxyl group, acidamide group and carboxylic acid group. Chemical and FTIR spectroscopy analyses show that hydroxyl group directly acts on Cr(VI) in soil by redox reaction, and acidamide group and carboxylic acid group indirectly act on Cr(VI) in soil by strengthening remediation effect of organic materials in soil.更多还原