GYIG OpenIR  > 研究生  > 学位论文
富镉铅锌矿床表生地球化学研究及其环境意义-以贵州都匀牛角塘矿床为例
其他题名A Study on Hypergene Geochemistry of Cadmium-rich Pb-Zn Deposits and Its Environmental Applications:An Example from the Niujiaotang Deposit in Guizhou Province, China
潘自平
2009-02-17
学位授予单位中国科学院地球化学研究所
学位授予地点地球化学研究所
学位名称博士
关键词富镉 铅锌矿床 表生地球化学 闪锌矿 反应速率 矿山环境问题
摘要丰富的铅锌矿资源为我国经济社会的发展作出了重要贡献,但也不可避免带来严重的环境污染,特别是酸性矿山废水及重金属污染已成为当今世界面临的两大环境难题。最让人们不安的是,即使在矿山关闭数十年、数百年,甚至更长时间,矿山尾矿等浸出液对矿区生态环境的影响依然存在。闪锌矿是铅锌矿中主要矿物之一,也是镉的主要载体矿物,而镉是有毒重金属元素,其毒性仅次于汞。大量含硫化物废石、尾矿暴露于地表环境,发生水-岩-气之间的反应(即氧化淋滤作用)产生酸性矿山废水和释放大量Zn、Cd等重金属元素,进入矿区水体、土壤,影响甚至破坏矿区生态环境,危害人类健康。通过表生环境条件下矿石风化淋滤实验和闪锌矿氧化动力学实验研究,认识铅锌矿石及闪锌矿氧化淋滤过程、速率及其影响因素,揭示Zn、Cd等重金属元素的释放、迁移及富集规律,并建立定量模型,为正确预测、评价和控制铅锌矿山的环境污染提供科学依据。 本文以牛角塘富镉锌矿床为研究对象,主要通过闪锌矿氧化动力学实验、矿石风化淋滤实验及矿区环境调查将闪锌矿氧化-矿石风化淋滤-环境污染有机地联系在一起,主要取得以下几点认识: 1、矿石风化淋滤实验表明,牛角塘铅锌矿石淋滤后淋滤液主要呈碱性,淋滤释放出大量Zn2+、Cd2+、Ca2+、Mg2+等阳离子及SO42-、CO32-等阴离子,淋滤过程中形成大量以石膏为主要成分的沉淀物,淋滤液中Zn、Cd主要以沉淀形式存在(可能被沉淀吸附或包裹),而水溶态Zn、Cd浓度极低。 2、牛角塘矿床中黄铁矿锌矿石中Zn和Cd淋滤率较半氧化锌矿石低得多,表明半氧化或氧化锌矿石的风化淋滤作用更强烈。 3、在Fe2(SO4)3为氧化剂时,闪锌矿氧化速率随着Fe3+浓度的增加、温度升高、pH值降低而增加,且闪锌矿氧化过程中Zn、Cd的释放速率大致相同;在有限实验时间内(本文中小于60h)黄铁矿的混入对闪锌矿氧化速率起抑制作用,可能是黄铁矿与闪锌矿与Fe3+反应过程中存在竞争关系;反应的活化能分别为Ea(Zn)41.75 kJ.mol-1、Ea(Cd)42.51 kJ.mol-1,说明闪锌矿氧化速率受矿物表面反应控制。氧气氧化闪锌矿时,随着pH值的变化闪锌矿的氧化机理发生变化,在2<pH≤6范围内,闪锌矿氧化速率随着pH值的增加而降低,而在6<pH≤7.8范围内,随着pH值增加,闪锌矿氧化速率反而增加。Fe3+和氧气均对闪锌矿的氧化起重要作用,但以Fe3+氧化为主。 4、大多数闪锌矿氧化实验中Zn、Cd的溶解曲线非常相似、活化能相近,表明Zn和Cd存在相似的地球化学行为。但在闪锌矿溶解过程中Zn、Cd的释放速率存在差异,在酸性介质条件下Cd的释放速率比Zn略快,而中碱性介质条件,Cd的释放速率比Zn慢。这与Zn、Cd同处元素周期表第ⅡB族,它们之间既存在许多相似的地球化学性质,也存在不少差异有关。 5、利用双对数图法处理实验数据,得出表生环境条件下闪锌矿氧化速率公式为: 或 该公式可用于估算一定时间内闪锌矿氧化所释放的Zn、Cd等重金属元素的总量,为正确预测、评价和控制铅锌矿山的环境影响提供科学依据。 6、牛角塘矿区环境调查结果表明,牛角塘矿山水体主要呈中碱性,水体污染较轻,大多水体中Zn、Cd含量未超过农业灌溉标准及饮用水国家标准,这主要受矿区碳酸盐岩地层的影响。但矿区土壤、河流沉积物及植物中Zn、Cd均超过相关国家标准,遭到不同程度污染。 7、本文研究表明,闪锌矿氧化及铅锌矿风化淋滤过程中,将产生矿山酸性废水和释放Zn、Cd等重金属元素,污染矿区及其下游生态环境,危害人类健康。我们可以采取以下措施进行防范和控制环境污染:第一,提高矿区水体pH值,降低闪锌矿等硫化物矿物氧化速率;第二,尽量减少废石、尾矿直接暴露于空气、Fe3+等氧化剂环境中,如可在废石(渣)、尾矿表面盖上覆土等,也可降低闪锌矿等硫化物矿物的氧化速率。
其他摘要The exploitation of abundant lead-zinc deposits have significantly contributed to the rapid development of economy and society in our country, however inevitably led to serious environmental pollution. Acid mine drainage (AMD) and heavy metal elements pollution have become two main environmental problems. What the people worried about is that, the leach solution of the mine tailings still affect the ecological environment around the mining district, even the mines were shut down in a few decades or centuries or even longer. Sphalerite is not only one of the main ores in Pb-Zn deposits, but also the main Cadmium-host ore. Cadmium is the toxic heavy metal element after Mercury. During mining, separating and smelting of Pb-Zn ores, plenty of waste rocks and tailings containing sulfide minerals were exposed to surface.The acid mine drainage and some heavy metal elements such as Zn, Cd, were released to water-body, and soils by reaction between water, rock and gas (oxidation and leaching), thus damage the environment in the mining district, and harm the human health. Based on studies of weathering and leaching on Pb-Zn ores and oxidation kinectics of sphalerite under supergene conditions, we can understand the weathering and leaching path of ores and minerals, oxidative rates and effect factors , and reveal the rule of releasing, movement and enrichment of heavy metal elements, and establish the rate law of sphalerite oxidation. It will offer scientific theories for forecasting, evaluating and controlling the mining environment pollution. In this dissertation, the weathering-leaching experiment of ores and oxidative kinetic experiment of sphalerite were carried out on a typical example of the Niujiaotang Cd-rich zinc deposit, and the environment of the mining district was investigated to study supergene geochemistry and its environmental effects. From the above studies, the following conclusions were drawn: 1. The weathering-leaching experiment shows leaching solution was neutral-alkaline. Numerous cations (Zn2+、Cd2+、Ca2+、Mg2+ etc)and anions(SO42-、CO32-) were released out, meanwhile deposits containing mainly gypsum were produced. Zn and Cd dominantly exist in these deposits, with little elements in the leaching solution. 2. The leaching rate of Zn and Cd from pyrite-bearing zinc ore was lower than the half oxidative ore, indicating that the half oxidative or oxidative zinc ore weathers and leaches more easily. 3. Taking Fe2(SO4)3 as oxidant, oxidative rates increase with increasing ferric concentration and temperature, deceasing pH value, and the releasing rates of Zn and Cd were generally similar. The apparent activation energy is 41.75kJ.mol-1 and 42.51 kJ.mol-1 for Zn and Cd, respectively, indicating that the rate is chemically controlled. In limited time(less than 60 h),the oxidative rate of sphalerite decreases with increasing content of pyrite because of competition relationship between sphalerite and pyrite with Fe3+. Taking oxygen (O2 ) as oxidant, oxidative mechanism change with variation in pH value. In the pH range of 2.0-6.0, the rates decrease with increasing pH value, while the rates increase with increasing pH value in a range of 6.0-7.8. Both Fe3+ and oxygen play an important role during oxidation of sphalerite, but the latter is more important . 4. Most of the dissolution curves of Zn and Cd are very similar, and their apparent activation energy are close, suggesting that Zn and Cd are similar in geochemistry. Nevertheless, the released rates of Zn and Cd exhibit difference during dissolution of sphalerite: the rate of Cd is faster than Zn under the acidic condition, but the rate of Cd is slower than Zn under the neutral-alkalic condition. It was mainly because that Zn and Cd belong to ⅡB system, showing geochemical similarity and difference. 5. On the basis of data regression, a rate expression of sphalerite oxidation was produced as follows: or The rate law of sphaerite would be applied for calculating Zn and Cd during sphalerite oxidation. This may provide theories for forecasting, evaluating and controlling mining environment pollution. 6. The investigating results of the mining district environment indicate that water body was neutral-alkaline, and water pollution was not serious. Neither Zn or Cd concentration exceeds the Chinese National standard. However, the soils, river deposits and plants were polluted in a certain extent. 7. This study indicates that oxidation of sphalerite and weathering of Pb-Zn ores result in discharge with low pH and high-metal concentration, and pollute environment of the mining district , finally harm the human heath. In order to prevent and control environment pollution, some measures can be made as below. Firstly, increasing pH value, can decrease the oxidative rate of sulfides such as sphalerite. Secondly, avoiding expose of waste rocks and tailing ores to oxidative conditions containing air and ferric, can decrease the oxidative rate of sulfides (e.g., sphalerite) .
页数113
语种中文
文献类型学位论文
条目标识符http://ir.gyig.ac.cn/handle/352002/3478
专题研究生_研究生_学位论文
推荐引用方式
GB/T 7714
潘自平. 富镉铅锌矿床表生地球化学研究及其环境意义-以贵州都匀牛角塘矿床为例[D]. 地球化学研究所. 中国科学院地球化学研究所,2009.
条目包含的文件
文件名称/大小 文献类型 版本类型 开放类型 使用许可
10001_20061800651402(2330KB) 暂不开放--请求全文
个性服务
推荐该条目
保存到收藏夹
查看访问统计
导出为Endnote文件
谷歌学术
谷歌学术中相似的文章
[潘自平]的文章
百度学术
百度学术中相似的文章
[潘自平]的文章
必应学术
必应学术中相似的文章
[潘自平]的文章
相关权益政策
暂无数据
收藏/分享
所有评论 (0)
暂无评论
 

除非特别说明,本系统中所有内容都受版权保护,并保留所有权利。