高砷煤矿废水在Fe（Ⅲ）存在下As的自然净化机理的研究

【作者】 张雪；

【导师】 陈桐； 吴攀；

【作者基本信息】 贵州大学 ， 环境工程， 2009， 硕士

【摘要】 在自然氧化作用下,高砷煤矿中的As从含砷矿物中释放出来,经一系列复杂的物理化学过程进入矿区周围的水体和沉积物中,从而对周围环境造成污染。本研究拟通过对铁和砷在实验室酸性水环境中吸附、沉淀过程的模拟实验,观察和跟踪As、Fe元素在酸性水中的迁移转化行为,分析在酸性环境中砷元素的迁移转化机理,为高砷煤矿区酸性溪流水系环境中砷的自然净化机理提供科学的理论基础,并为酸性废水除砷工艺提供借鉴。取得以下结论:（1） H₃AsO₄和FeCl₃的反应体系中,经过三个月时间上清溶液里的残余As、Fe浓度几乎不变,说明吸附、沉淀完全。吸附率均在97%以上,说明铁离子的存在确实对砷有吸附和共沉淀的作用。（2） H₃AsO₄和Fe₂（SO₄）₃的反应体系中,上清液里的As浓度在七天的时间里急剧减少,七天到一个月时间里上清溶液里的剩余As浓度几乎不变,而后又急剧减少,可能是As在大量SO₄^2-离子存在的酸性环境下,与Fe离子的吸附、沉淀之间存在一个类似在盐效应影响过程。而后从一个月到两个月的时间里,Fe含量几乎没变,而As含量还有所降低,可能是后期沉积物对As有吸附的效果。吸附率均在99%以上,说明在大量SO₄^2-离子存在的酸性环境中,铁是砷在水体中由液相转化成固相的重要载体,对砷的自净起到了很明显的作用。（3）天然沉积物与人工模拟沉积物的红外吸收图谱显示:因采样地点相近或地质环境类似,故而天然样品TC1、TC2和TC3、TC4这两组红外图谱各自十分相似。四个现场样品（TC1、TC2、TC3、TC4）中均含有少量的臭葱石。TC1、TC2中的硫酸盐特征不很显著,TC3、TC4中的硫酸盐已发育较完善,并使水体形成了强酸介质环境。人工模拟MC1、MC2、MC3样品为H₃AsO₄和FeCl₃的反应沉积物,而MC4、MC5、MC6样品为H₃AsO₄和Fe₂（SO₄）₃的反应沉积物。两组方案沉积物的红外光谱各自十分相示,且均含有微量的臭葱石。事实上天然酸性环境中主要是铁的硫酸盐介质系统,而人工模拟的MC4、MC5、MC6样品也是在硫酸介质中进行,因此这三个红外图谱与天然沉积物典型红外吸收光谱图几乎完全一致。此外,由于野外环境中的砷含量是远小于铁的含量,MC1、MC2、MC3样品的红外图谱中显示出这种砷铁比的差距愈大,沉积物中的臭葱石的红外信号依次越弱。MC7样品已富集了MC6中的臭葱石,可以认为MC7的主要矿物之一为FeAsO₄·2H₂O。（4） MC7样品的X衍射分析结果:其矿物组成为非晶质体和隐晶质体,与前人对该研究区域沉积物所作的调查一致。组分中的大量非晶质体主要是由水体中重金属离子形成氢氧化物胶体吸附沉淀、共沉淀而成。臭葱石在X衍射的分析中并未显示出来,可能是因为沉积物中该矿物的含量太低以至于难以检出。（5）天然沉积物与人工模拟沉积物的透射电镜分析结果相似,均以氧化铁矿物为主,并吸附有微量的As,说明水体中砷的主要去除机理是铁的氧化物及氢氧化物的吸附作用。而MC7样品的透射电镜分析结果证实,在砷的迁移转化机理过程中确实有砷铁共沉淀的现象。通过人工模拟实验,进一步证实了由酸性矿山水带入水体的砷多吸附在悬浮的固体颗粒或被沉积物所吸附、络合或共沉淀,从而在水底的沉积物中富集。（6）碳酸钙对砷、铁的吸附沉淀确实有影响,其吸附砷效率也基本在60%以上。硫酸钙几乎没有吸附砷离子,说明硫酸钙对于砷离子在水溶液中几乎没有吸附影响。更多还原

【Abstract】 Natural oxidation, the high concentration of arsenic in the As mine minerals from the arsenic released by a series of complicated physical and chemical processes to enter the mining area around water bodies and sediment, thus causing pollution of the surrounding environment. This study of iron and arsenic acid in the laboratory environment Absorption of water, sedimentation process simulation, observation and follow-up of As, Fe elements in the transfer of acid into the water behavior, analysis of arsenic in the acidic environment of the transfer element into the mechanism of coal mining area for the high-arsenic water streams acidic environment of the natural purification mechanism of arsenic in the provision of basic scientific theory and technology of acidic waste water used for reference in addition to arsenic. Made the following conclusions:（1） H₃AsO₄ and FeCl₃ in the reaction system, after three months in the supernatant solution of the residual As, Fe concentration is almost unchanged on adsorption, precipitation completely. Absorption rate of more than 97% indicating the existence of iron ions has indeed arsenic adsorption and the role of co-precipitation.（2） H₃AsO₄ and Fe₂（SO₄）₃ reaction system, the As concentration in the supernatant at the time, seven days a drastic reduction of time for seven days to a month remaining in the supernatant solution As concentration is almost unchanged, and then sharply reduction are possible As a large number of SO₄^2- ion in the acidic environment of existence, and Fe ions adsorption, precipitation between a similar effect in the process of salt. Then from one month to two months time, Fe content is almost unchanged, and also reduced As content, the sediments may be late on the Absorption As has effect. Absorption rate at 99% more than in the existence of a large number of SO₄^2- ion in the acidic environment, iron is the arsenic in water by solid-phase liquid into an important carrier of the self-purification of the arsenic has played a very significant role.（3） Natural sediments and artificial sediments map shows the infrared absorption: a result of sampling sites close to or similar to the geological environment, they are natural Samples TC1, TC2 and TC3, TC4 infrared map of these two groups is very similar to their own. Samples of four-site （TC1, TC2, TC3, TC4） are contained in a small amount of scorodite. TC1, TC2 characteristics of the sulfate is not very significant, TC3, TC4 Sulphate has been the development of a more perfect shape and the water environment has become a strong acid medium. Artificial MC1, MC2, MC3 and H₃AsO₄ Samples for the reaction of FeCl₃ sediment and the MC4, MC5, MC6 Samples for H₃AsO₄ and Fe₂（SO₄）₃ the reaction of the sediments. Two programs of their respective sediments of the infrared spectra show very similar, and contained a trace amount of scorodite . In fact the natural acidic environment of the major media are systems of iron sulfate, and the artificial simulation of MC4, MC5, MC6 sample is carried out in sulfuric acid medium, the infrared map of the three natural sediments and typical infrared absorption spectrum is almost exactly the same. In addition, the wild because of arsenic in the environment are far less than the iron content, MC1, MC2, MC3 infrared map of the sample shows that the gap between arsenic greater than iron, sediment scorodite in the infrared followed by the weaker signal. MC7 Samples have been enriched in the smell of scorodite MC6, we can think MC7 has one of the main mineral is FeAsO₄·2H₂O.（4）Samples MC7 results of X-ray diffraction analysis: The mineral composition of amorphous and cryptocrystalline body of the study area with the previous survey conducted by the same sediment. Substantial component in the amorphous mainly heavy metal ions are formed by water adsorption of colloidal hydroxide precipitation, by co-precipitation. scorodite in the X ray diffraction analysis did not show up, because the sediments are probably the mineral content is too low so that the detection difficult.（5） Natural sediments and artificial sediments is similar to the TEM analysis, are mainly of iron oxide minerals, and there is a trace amount of adsorbed As, that arsenic in water are the main removal mechanism of iron oxides and hydroxides of Adsorption. MC7 TEM samples and the results of the analysis confirmed that the mechanism of arsenic into the process of transfer has indeed arsenic co-precipitation of iron situation. Through artificial simulation experiments, further confirmed by acid mine water into the water adsorption of arsenic at many of the solid particles suspended sediments or adsorption, complexation or co-precipitation, resulting in enrichment of the bottom sediments.（6） Calcium carbonate on the arsenic, iron precipitation Absorption indeed affect the efficiency of its basic Absorption of arsenic at more than 60%. Almost no calcium sulfate ion adsorption of arsenic on arsenic ions for calcium sulfate in aqueous solution almost no impact on Absorption.更多还原