【作者】 李德先；

【导师】 高振敏； 朱咏煊；

【作者基本信息】 中国科学院研究生院（地球化学研究所） ， 地球化学， 2005， 博士

【摘要】 贵州省兴仁县滥木厂铊矿床是世界上唯一的铊的独立矿床。多年来,由于对铊矿产资源的开发,大量未及时提取和利用的含铊矿石堆积于地表,经过风化淋滤作用,进入当地的水源和土壤,并通过食物链进入人体。20世纪60-70年代,滥木厂地区有近1000名村民患有不同程度的铊中毒,轻者脱发、视力减退,重者失明、丧失劳动力,至今在该地区仍可见到铊中毒患者。该区成为世界上唯一爆发过大规模铊中毒的病发区。铊又是人体的非必需元素,体内任何含量的铊都会对人体造成危害。饮用水的安全标准中,铊的含量不得超过1μg╱L。因此对表生条件下,含铊矿物的氧化溶解动力学以及反应性迁移的实验研究具有重要的现实意义。 通过对滥木厂铊矿床中的主要含铊矿物(红铊矿)在酸性矿水条件下的氧化溶解过程、光照(日光照射和汞弧灯照射)对铊价态改变的影响,以及酸性矿水条件下铁对铊吸附的实验研究,得到如下几点认识: 1.红铊矿的氧化溶解动力学实验表明:红铊矿的氧化溶解速率受到温度、氧化剂中阴离子种类及氧化剂浓度的影响。随着温度的升高,红铊矿的氧化速率增高;Cl~-离子的存在更有助于红铊矿的氧化溶解,表现为氧化溶解速率的增高;随着氧化剂浓度的升高,红铊矿的氧化速率逐渐降低,这主要是由于高铁浓度下,红铊矿表面形成了一层厚约2nm的铁硫化合物的膜,减缓了红铊矿进一步溶解。 红铊矿表面形态和成分的电镜分析表明,红铊矿表面具有较多的活性点,因此含铊矿石在初露地表时对环境的污染比较强烈,经过风化淋滤作用后,红铊矿表面的活性点减少,加之硫铁化合物膜的形成,阻止了其对环境的进一步污染。但这并不排除一旦环境介质改变,红铊矿表面氧化形成的膜被破坏,红铊矿的新鲜表面暴露出来,活性点增多,溶解性加强,继续对周围环境造成强烈的污染。 从红铊矿24小时溶解的总铊量来看,酸性矿水条件下红铊矿的氧化溶解是贵州省兴仁县滥木厂地区铊污染的一个重要来源。 2.铊的光致氧化实验结果表明:无论日光还是汞弧灯照射,水溶液中的Tl(Ⅰ)均可被氧化成Tl(Ⅲ)。pH值越低、光照强度越大,铊的光氧化速率越快,UVB区的紫外光对铭的光氧化起着主要作用,微生物作用在本实验条件下,相对于光氧化作用并不明显。3.铁对佗的吸附实验表明:铁的水合氧化物对水溶液中铭的吸附除受溶液的pH值和吸附剂的阴离子种类的影响外,主要与铭的价态有直接关系。铁的水合氧化物对TI(I)具有一定的吸附能力,阴离子种类对Tl(I)吸附的作用稍有差别,C1-离子存在时,铁对Tl(工)的吸附更强一些,吸附率达到50%左右,而S叮一离子存在条件下,铁对Tl(I)的吸附率小于20%。碱性(PH=10左右)条件下,铁对Tl(1)的吸附较中性条件更明显一些。T1(m)由于自身的水解作用很强,在不同pH值和不同阴离子存在条件下,与Fe(m)均可发生共沉淀作用而被完全从水溶液中脱除。 利用光照将T1(I)氧化成T1(m),再利用T1(m)易被沉淀或共沉淀吸附的特性,将T1以Tl(OH)3的形式吸附固定下来,降低了铭的活动性,进而可以减少铭对环境的影响,为佗污染的环境治理提供了重要的理论依据。关键词:铂,铭污染,含量,分布,价态,氧化溶解,光致氧化,吸附更多还原

【Abstract】 The Lanmuchang thallium deposit in Xingren County, Guizhou Province, is the unique independent thallium deposit in the world. For many years, amounts of unpicked up and unutilized thallium minerals have been stacked on the Earth’s surface in that region. Thallium entered into local water and soil by weathering and leaching process, and were exposed in body of local people by food chain. During the period of 1960s and 1970s, a population of approximately 1000 people in Lanmuchang had been affected by Tl poisoning. They suffered poisoning and causal hair loss, reduced vision, lost labor force even blindness. The thallium poisoning case is one of the most serious health problems resulting from environmental pollution. Thallium is not necessary element to human body, trace thallium in the body will be harmful. The current China Maximum Contaminant Level (MCL) is lug/L in drinking water. It is very important to carry out the kinetic study of the oxidation and reactive transference of Tl in hypergene condition.From the oxidation-dissolution experiment of Lorandite in acidic mine water, the photochemical reaction of Tl in aqueous solution and Tl adsorption experiment by iron in acidic mine water, some conclusions can be drawn as follows:I . The results from the kinetic study of the oxidation-dissolution of Lorandite showed that the rate of oxidation of Lorandite was affected by the temperature of solution, the concentration of oxidant and kinds of anion in the oxidant. The rate of oxidation of Lorandite was increased or decreased along with the increasing of the temperature and the concentration of oxidant, respectively. This is because that the surface of Lorandite will form the film formed by sulfur and iron when concentration of iron is high, and this film will prevent from dissolution of Lorandite. Tl minerals polluted severely the environment when they were exploited early days, but the pollution will decrease after weathering-leaching. The pollution will increase againafter the oxidative film of Lorandite being destroyed.The oxidation-dissolution of Lorandite in acid mine water is one of the important sources of thallium pollution in Lanmuchang regions, Xingren County, Guizhou Province in according to the total thallium contents of soluble Lorandite in 24 hours.II. A photooxidation experiment of thallium showed that Tl( I) can be oxidized to Tl(III) under photoirradiation of the high-pressure mercury arc lamp and solar light. The photooxidation rate of thallium can be affected by the pH of the solution, intensity and wavelength of the light source. Lowering of the pH and increasing of the light intensity have the effect of increasing of the photooxidation rate. UV radiation (UVB and UVC regions) played an important role in the photooxidation of Tl( I). However, the microbial effect was not obvious in comparison with photooxidation effect in this experiment.III. The results of Tl adsorption by iron showed that the absorption of Tl by ferrous hydrate could be affected by pH of solution and the concentration of iron, especially the valence state of Tl. T1(I) can be absorbed by ferrous hydrate, especially in the Cl" solution, and the absorption rate is about 50%, but less than 20% in the SO42" solution. T1(I) absorbed by iron in alkaline (pH= 10)solution is stronger than that of the neutral solution. Tl(III) and Fe(III) coprecipitation and Tl(III) can be completely absorbed by iron in the neutral or alkaline (pH= 10) solution and different anion solution because of the hydrolysis of Tl(III).This study has provided a good method handing with thallium pollution. We combined the experiment of photooxidation. T1(I) can be oxidized to Tl(III) by light, then fixed Tl(III) by utilizing the characters of Tl absorption or coprecipitation. This can reduce thallium mobility and make effects on the aquatic environment.更多还原