【作者】 马泽民；

【导师】 柴立元；

【作者基本信息】 中南大学 ， 冶金环境工程， 2009， 博士

【摘要】 铬渣是铬盐等行业在生产过程中排放的有毒废渣,我国目前年产生铬渣近60万t,历年堆存量已达400万t。铬渣中水溶性的六价铬是致癌物,对环境及人类造成严重威胁,已成为社会亟待解决的问题。2003年发生的两起铬渣严重污染事故,引起世人的高度重视,铬渣治理势在必行。铬渣治理方法概括起来,主要有干法解毒和湿法解毒,但这两类方法存在或者解毒不够彻底、易于引起二次污染,或者处理成本过高等原因,还没有实施广泛的应用,至今尚未能彻底解决铬渣污染问题。为寻求一种高效低廉的铬渣解毒方法,首先对铬渣的性质及不同条件下的浸出特性进行了详细研究。铬渣是一种物相组成较为复杂的危险固体废物,其中含有易浸出的水溶性Cr（Ⅵ）和难浸出的酸溶性Cr（Ⅵ）。摇瓶实验结果表明反应温度、颗粒细度、搅拌速度对Cr（Ⅵ）浸出率有较大的影响,在铬渣渗滤柱水浸实验中,六价铬的浸出速率与液固比成反比关系,Cr（Ⅵ）浸出速率是逐渐减小的。进行了铬渣酸浸实验,得出HCl浸出Cr（Ⅵ）的最佳实验条件为:pH 3,液固比5:1,流速180ml/min,温度40℃。铬渣HCl浸出过程的数学模型为:v=11.58t^-0.54。在铬渣盐浸实验中,NaCl浸出的动力学方程为:v=3.38×10^-7C_NaCl^0.26。铬渣NaCl浸出反应表观活化能为34.24kJ/mol,Cr（Ⅵ）浸出速率受温度影响较大,κ与温度关系式为:κ（T）=exp（13.71—4117.9/T）。研究结果对铬渣解毒工艺及其参数的选择提供理论依据。从铬渣堆放场分离到一株能还原碱性介质中高浓度Cr（Ⅵ）的细菌,经鉴定为无色细菌属杆状菌（Achromobacter sp.）,将其命名为CH-1菌。研究发现,CH-1菌适宜于碱性环境（8＜pH＜11）、好氧、中温（25-35℃）的条件下生存,可以利用有机碳和有机氮作为营养源。CH-1菌耐盐性能高,可达20 g/L;有效还原Cr（Ⅵ）达1.5g/L,耐受Cr（Ⅵ）能力可达4g/L。阳离子对还原抑制较大,阴离子影响较小;铬渣渗滤液经细菌处理后产生蓝灰色Cr（OH）₃沉淀。CH-1菌还原Cr（Ⅵ）的反应为零级反应。起到铬渣解毒细菌大规模培养。利用高效铬还原菌Achromobacter sp.CH-1进行了铬渣解毒实验,原渣摇瓶解毒Cr（Ⅵ）的浸出率达到88.69%,结果表明铬渣的微生物解毒具有可行性。提出并研究了“铬渣造粒—细菌解毒—回收铬”新工艺,铬渣柱浸解毒实验结果表明在最佳工艺条件下,Cr（Ⅵ）浸出率达到92.088%,解毒后的铬渣浸出液铬含量达到国家规定的废水排放标准（GB 8978-1996）;解毒后废渣的浸出毒性达到国家固体废物浸出毒性鉴别标准（GB 5085.3-2007）的要求。研究了细菌解毒铬渣的机制。细菌解毒铬渣主要表现为浸出还原的直接作用机制,铬渣中的物相在细菌作用下发生解离,这种溶蚀慢慢向矿物颗粒的间隙和深层延伸,并进一步促进溶蚀作用的进行;细菌还原溶液中Cr（Ⅵ）为Cr（OH）₃。解毒后铬渣中的Ca₁₂Al₁₄O₃₃和Ca₄Al₂SO₁₀·16H₂O消失,方镁石（MgO）的含量也有较大降低,包裹于这些物质中的酸溶性Cr（Ⅵ）被释放,细菌高效解毒铬渣的关键在于细菌提高了铬渣中酸溶性Cr（Ⅵ）的浸出率。采用“铬渣造粒—细菌堆浸”工艺进行了现场中试研究,运行了10t/批、20t/批规模的细菌解毒铬渣的处理工程。优化了工艺参数,经过7-10天的运行,铬渣解毒彻底,达到国家危险废物浸出毒性鉴别标准（GB 5085.3-2007）的限值,且能回收90%左右的Cr（Ⅵ）。铬渣解毒成本初步估算为200元/t渣,证明了铬渣细菌解毒工业化的可行性,为铬渣的解毒提供了一条新途径。更多还原

【Abstract】 Chromium-containing slag is a kind of the poisonous slag generated from chromate industry.The accumulated amount of chromium-containing slag in China was more than 4 million tons and 600 thousand tons are being discharged annually.Water soluble Cr（Ⅵ） in chromium-containing slag is a carcinogenic substance,which caused a seriously environmental threat and has become a urgent problem to be solved.Since two serious accident occurred by chromium-containing slag in 2003,much more attentions were paid on the detoxification of chromium-containing slag.Generally,the detoxification of chromium-containing slag includes dry-detoxification and wet-detoxification.The above two methods was not widely applied because of high cost or incomplete detoxification that results in the secondary pollution.Therefore,the pollution problem of the chromium-containing slag is still not solved.In this dissertation,the characteristics of chromium-containing s lag and its leaching were investigated in order to seek an effective and cheap method for detoxification of chromium-containing slag. Chromium-containing slag is a kind of hazardous solid waste with complicated phase composition.Chromium-containing slag contains both water-soluble Cr（Ⅵ） that is susceptible to leached out and aci d-soluble Cr（Ⅵ） that is difficult to be leached out.It was found th at temperature,particle diameter,stirring speed obviously affected Cr（Ⅵ） leaching ratio in shaking experiment.In water leaching expe riment,the leaching velocity was inversely proportional to the ratio of solid to liquid.In acid leaching experiment,the optimum condit ion for Cr（Ⅵ） leaching by HCl were pH 3.0,5:1 of liquid to solid ratio,180mL/min of stirring speed,40℃of temperature.The kinet ics of Cr（Ⅵ） leaching by HCl can be described with the followin g model:v=11.58t^-0.54.And the kinetics model of Cr（Ⅵ） leaching by NaCl were:v=3.38×10^-7 c_Nacl^0.26 with the apparent activation energy of 34.24kJ/mol.The Cr（Ⅵ） leaching velocity was obviously influen ced by temperature and the relationship between k and temperature can be described with following equation:k（T）=exp（13.71—4117.9/ T）.The results can provide theoretic basis to select technique and i ts parameters for the detoxificationA bacterial strain that can reduce high concentrations of Cr（Ⅵ） in alkaline medium was isolated from chromium-containing slag site.It was identified as Achromobacter sp.and nominated as CH-1.Strain CH-1 grew in alkaline（8＜pH＜11） and aerobic condition,middle temperature （25-35℃） and organic carbon and organic nitrogen as nutrient source. Strain CH-1 was resistant to 20 g/L salt and 4 g/L Cr（Ⅵ）.Its ability for Cr（Ⅵ） reduction reached up tol.5g/L.Moreover,cations showed significantly inhibitory effect on Cr（Ⅵ） reduction than anions.Blue Cr（OH）₃ precipitate was observed,during Cr（Ⅵ） reduction by CH-1.The reaction of Cr（Ⅵ） reduction by CH-1 was zero reaction.The detoxification of Cr（Ⅵ） containing slag with Achromobacter sp. CH-1 was carried out.The results revealed that Cr（Ⅵ） removal reached up to 88.69%in shaking experiment,implying that detoxification of chromium-containing slag with Achromobacter sp.CH-1 was practically feasible.Moreover,a novel technique of "granulation of chromium-containing slag-microbial detoxification-chromium recovery" was put forward in this study.In column leaching experiment,Cr（Ⅴ） reaching ratio was 92.088%under the optimum condition.Cr（Ⅵ） concentration in leachate of the detoxified slag met the waste water discharge standard（GB 8978-1996）.The detoxified slag met the identification standard for hazardous waste- identification for extraction toxicity（GB 5085.3-2007）.Macroscopic mechanism of microbial-detoxification of chromium containing slag was also studied in this study.The results showed that Cr（Ⅵ） was leached from chroraium-containing slag followed by the direct reduction by bacterial stains.Consequently,the phase composition of slag was decomposed by bacterial stains and this erosion action slowly extended into interspaces between slag particles,which further promoted the proceedings of erosion.The precipitation of Cr（OH）₃ was obtained during Cr（Ⅵ） reduction processes.Ca₁₂Al₁₄O₃₃ and Ca₄Al₂SO₁₀·16H₂O in the detoxified slag disappeared.The content of periclase substantially decreased.Consequently,the enwrapped acid soluble Cr（Ⅵ） was released from the above chromium-containing substances.Thus,the key point of microbial-detoxification of chromium-containing slag was to enhance the leaching ratio of acid soluble Cr（Ⅵ）.The pilot experiment for the detoxification of chromium-containing slag was carried out using the technique of "granulation of chromium-containing slag-microbial heap leaching".The project run 10t/batch and 20t/batch,respectively.Based on the optimization of technique parameters,chromium-containing slag was completely detoxified after running 7-10 days.The detoxified slag met the identification standard for hazardous waste- identification for extraction toxicity（GB 5085.3-2007） Meanwhile,about 90%of Cr（Ⅵ）was recovered.It was approximately estimated that the expenses of microbial detoxification for chromium-containing slag was 200 yuan per ton slag. The results verified that it is practically feasible on full scale.The outcome provides a new approach for the detoxification of chromium-containing slag.更多还原