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生物炭与微生物联合修复金尾矿的汞砷污染
魏永洋
学位类型硕士
导师潘响亮
2017-05-01
学位授予单位中国科学院大学
学位授予地点新疆乌鲁木齐
学位专业理学硕士
关键词生物炭 金矿尾矿 尿素分解菌 MICP Biochar Gold mine tailing Staphylococcus succinus MICP Hg2+ As3+
摘要Xinjiang is rich in mineral resources and large in number of gold mines. The productof gold mining tailings has a huge amount, in which has high concentration of Hg2+ andAs3+. The open-air stacking lead to the migration of Hg2+ and As3+ with rain and snow, thatcaused serious environmental pollution and posed a threat to the ecosystem and humanhealth.However, there are few methods for handling tailings at present. Generally, it isopen-air stacking and has not been dealt with, which has a serious impact on the ecologicalenvironment. There are also few tailings dealt with cement, but which is expensive and isnot conducive to the reuse of tailings. In order to solve this situation, the research teamdeveloped new MICP technology to solidification tailings and was applied it to thesolidification experiments under laboratory conditions. But the effect of tailingssolidification is not ideal, mainly as follows: the unconfined compressive strength is nothigh, and the control effect of some heavy metals needs to be improved. Therefore, thisstudy is expected to enhance the effect of tailings solidification by biochar. Biochar is aneco-friendly material which has a good adsorption effect on heavy metals. We expect theaddition of biochar to enhance the strength of the curing and the effective control of theleaching of heavy metals. In this paper, cotton straw biochar as the material, the biological and physicalproperties of biochar were studied. The adsorption properties of biochar on mercury andarsenic under different conditions also were studied. The thermodynamic process ofmercury adsorption by biochar was investigated by isothermal titration calorimetry (ITC). In combination with the special saline-alkali environment in Xinjiang and the high contentof heavy metals in tailings, bacteria with the ability of urea decomposition and tolerance toheavy metals were isolated. The ability of this bacterium to induce calcium carbonate andthe removal of mercury and arsenic by calcification were investigated. Finally, under theoptimum solidification conditions, biochar was added into the tailings to study the effect of biochar on the control of heavy metal pollution by MICP tailings. The main conclusions ofthis study are as follows:(1)Biochar has abundant pore structure, large surface area and negative charge. Salinity has some effects on biochar adsorption of mercury and arsenic. Biochar has highadsorption capacity of Hg2+ at pH 5 and the maximum adsorption capacity was 5.81 mg/g. The adsorption capacity of biochar of 10 mg/L Hg2+ was up to 4.26 mg/g at 5 ‰ saltconcentration. Solution pH influenced the morphology of As solution, adsorption capacityof biochar on As3+ was up to a maximum of 2.76 mg/g at pH 7. The effect of salinity on theremoval of arsenic by biochar was not obvious, maximum adsorption capacity was 2.60mg/g at 5 mg/L As3+. (2) A thermodynamic study on the adsorption of mercury by biochar using a newSIITC method. At the initial stage it was surface adsorption process, that can be simulatedwith linear model. After that was surface adsorption and particle diffusion process and thenwas particle diffusion process which can be simulated with linear model. Proton adsorptionexperiment proved the particle diffusion process. The whole adsorption process of Hg2+ was available of index equation fitting. (3) A strain Staphylococcus succinus with high urea decomposition ability and acertain tolerance to heavy metals was isolated. Using SIITC technology to study thetolerance of S. succinus to heavy metals, and SIITC is a microbial detection method whichcan be applied to other heavy metals contaminated by other factors. (4) S. succinus bacteria had the ability of calcification and could produce CalciumCarbonate Granules. In the process of MICP had good removal effect of Hg2+, As3+ andremoval rate were more than 90%. The addition of humic acid had no obvious effect on thecalcification process. (5)Through different screening conditions, final optimum solidification conditionswere OD600=0.7, 4% urea and 40 mM calcium chloride. 2.5% biochar was the optimaldosage. The irregular calcium carbonate crystals were formed after solidification of thetailings. The calcium carbonate crystals connected the tailings particles and biochar particles together, thereby enhancing the curing effect. The content of heavy metals in theleachate of the samples decreased with the increase of the amount of biochar, theexchangeable state of the heavy metals decreased, and the binding state of the carbonatebound and Fe-Mn oxides bound were increased. The process of freezing and thawingreduced the curing effect of tailings, and the compressive strength decreased with theincrease of freeze-thaw cycles.
其他摘要新疆矿产资源丰富,金矿数量多。金矿开采的产物-尾矿堆存量巨大,金矿尾矿中汞、砷含量高;尾矿露天堆放使得其中的汞、砷易随降雨、雪水迁移扩散,造成严重的环境污染,对生态系统和人类健康构成威胁。而目前对尾矿的处理方式很少,一般露天堆放未作处理,对生态环境产生严重影响;也有很少的尾矿使用水泥等方式固定,但这种方式成本高昂,不利于尾矿的二次利用。为解决此现状,研究团队研发MICP 固化尾矿新技术,并应用到实验室条件下的固化实验。但尾矿固化后效果不是很理想,主要表现在为:无侧限抗压强度较低,对部分重金属控制效果有待于提高。为此,本研究期望应用生物炭强化尾矿固化效果。生物炭是一种生态友好型材料,对重金属具有良好的吸附效果。我们期望生物炭的添加能够增强固化强度以及有效的控制重金属的淋出。本文以棉花秸秆生物炭为材料,研究了生物炭的基本理化性质,不同条件下生物炭对汞、砷的吸附性能。利用等温滴定量热仪(ITC)探索了生物炭吸附汞的热动力学过程。结合新疆特殊的盐碱环境以及尾矿重金属含量高的特征,分离出具有尿素分解能力并对重金属有一定耐受性的细菌。研究此细菌是否具有诱导产生碳酸钙的能力及钙化过程对汞和砷的去除效果。最后在最佳固化条件下添加生物炭固化尾矿,研究生物炭对 MICP 固化尾矿控制重金属污染的效果。本研究的主要结论如下:(1)生物炭具有丰富的空隙结构,比表面积较大,表面带有负电荷。盐碱度对生物炭吸附汞和砷有一定的影响。pH 5 时生物炭对 Hg2+的最大吸附量为 5.81 mg/g;5 ‰盐浓度下生物炭对 10 mg/L Hg2+的吸附容量达到 4.26 mg/g。溶液 pH 为 7 时生物炭对 As3+的吸附容量最大为 2.76 mg/g;盐度随生物炭去除砷的影响较小,5 mg/L As3+ 浓度下最大吸附容量可达 2.60 mg/g。(2)利用 SIITC 新方法研究生物炭吸附汞的热动力学过程。生物炭吸附汞的初始阶段为表面吸附过程;利用 t 和 t1/2证明汞在生物炭颗粒内扩散为线性过程;质子吸附实验验证了质子在生物炭颗粒内扩散过程属于线性吸附。生物炭吸附汞的整个吸附过程属于指数变化过程。(3)分离筛选出具有较高尿素分解能力并对重金属有一定的耐受性的菌株Staphylococcus succinus。运用 SIITC 新技术研究 S. succinus 对重金属耐受性,SIITC是一种可应用于其他影响因素下的不同重金属污染的微生物检测手段。(4)S. succinus 菌具有钙化能力,能够诱导产生碳酸钙颗粒;在诱导产生碳酸钙过程中对 Hg2+ 、As3+具有良好的去除效果,去除率达到 90%以上。腐植酸的添加对细菌的钙化过程没有显著的影响。(5)金尾矿最优固化条件为 OD600=0.7,尿素添加量 4%,氯化钙添加量 40 mM。2.5%添加生物炭添加量为最优添加量。尾矿固化后样品出现了不规则的碳酸钙晶体。碳酸钙晶体将尾矿颗粒和生物炭颗粒连接在一起,增强了固化效果。生物炭的添加降低了固化后样品淋滤液中重金属的含量;固化后重金属的可交换态减少,碳酸盐结合态和铁锰氧化物结合态升高。无侧限抗压能力随冻融循环次数增加而降低。
学科领域环境科学
语种中文
文献类型学位论文
条目标识符http://ir.xjlas.org/handle/365004/14906
专题研究系统_荒漠环境研究室
作者单位中国科学院新疆生态与地理研究所
第一作者单位中国科学院新疆生态与地理研究所
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魏永洋. 生物炭与微生物联合修复金尾矿的汞砷污染[D]. 新疆乌鲁木齐. 中国科学院大学,2017.
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