【作者】 李波；

【导师】 刘国；

【作者基本信息】 西南科技大学 ， 环境科学与工程， 2023， 博士

【摘要】 矿山开采破坏了原生还原环境,黄铁矿被氧化产生含高浓度SO₄^2-、金属离子的强酸性矿井水,黄铁矿氧化过程中会在表面形成固膜钝化层,导致水和氧气扩散传质受阻,抑制黄铁矿氧化溶解;与黄铁矿共生或伴生的含铝矿物溶解导致Al³⁺释放,形成高铝酸性矿井水,含铝矿物是否会影响黄铁矿表面固膜钝化层的形成,抑制黄铁矿氧化溶解鲜有报道。论文通过野外调查与室内实验相结合的研究方法,以西南废弃大树硫铁矿为研究区,研究矿井水中Al³⁺主要来源及酸化成因,分析含铝矿物抑制黄铁矿氧化溶解过程,明晰黄铁矿表面微观界面变化机制,阐明含铝矿物对固膜钝化层的形成过程的影响,探讨不同Fe²⁺浓度、p H值下含铝矿物对次生矿物形成与转化的影响,揭示次生矿物形成与矿物相转变的影响因素及路径,为酸性矿井水污染防控提供理论指导。主要研究成果如下:（1）分析西南典型酸性矿井水污染特征,初步揭示含铝矿物溶解对矿井水水化学演化的影响机制。废弃大树矿区酸性矿井水污染具有“三高一低”特征,即“高铁、高铝、高SO₄^2-和低p H值”,酸性矿井水中微生物群落主要以杆状A.ferrooxidans为主;酸性矿井水中铝质粘土（简称粘土）溶解消耗H⁺,造成Al³⁺浓度和p H值升高,促进铁铝水解、沉淀生成黄钾铁矾、施氏矿物、明矾石等次生矿物,造成矿井水水化学组分发生变化,抑制矿井水酸化。（2）研究含铝矿物抑制黄铁矿氧化溶解过程及动力学影响机制。黄铁矿氧化溶解符合固膜收缩核动力学模型,少量含铝矿物(Al³⁺当量<30 mmol/L)投加可促进黄铁矿的氧化,而随投加量增加(Al³⁺当量≥30 mmol/L)则表现出明显的抑制作用,投加量越大氧化抑制效果更加明显;主要是黄铁矿表面次生矿物层的形成,阻止了水、氧与黄铁矿接触,抑制了黄铁矿的氧化溶解,使黄铁矿表面硫膜钝化层的形成和加厚,在黄铁矿表面形成由硫膜与次生矿层共同组成的固膜层钝化层,从而产生钝化现象。（3）阐明含铝矿物对固膜钝化层形成过程的影响及氧化溶解抑制机制。有无含铝矿物,黄铁矿氧化过程均符合“多聚硫酸盐-硫代硫酸盐”复合氧化途径。含铝矿物投加会促进铁铝离子水解、沉淀,一方面降低溶液中Fe³⁺浓度,使黄铁矿和硫氧化中间产物氧化受到抑制;另一方面在黄铁矿表面生成次生矿物,会阻止黄铁矿的溶解。在黄铁矿氧化过程中Fe迁移速度大于S,使S积累促进了以多硫化学物（Fe S_n）或缺铁硫化物(Fe_1-xS)为主的硫膜加厚,形成由硫膜和次生矿物层组成固膜钝化层,抑制黄铁矿氧化。（4）揭示含铝矿物对次生矿物形成和转化的影响因素及路径。酸性条件下含铝矿物溶解、Fe²⁺氧化会促进Fe³⁺/Al³⁺水解中间产物羟基硫酸盐聚合沉淀生成次生矿物。在酸性条件下（p H=2.00）Fe²⁺浓度≥30 mmol/L时,发现羟基硫酸盐聚合沉淀形成黄钾铁矾;p H值≥3.00时有利于生成施氏矿物,同时成矿过程会造成H⁺释放,促使施氏矿物转变成黄钾铁矾,这说明酸性条件下含铝矿物溶解会促进施氏矿物形成和转变。综上,酸性矿井水中含铝矿物溶解释放Al³⁺,在铁铝水解和共沉淀相互作用下促进黄铁矿表面次生矿物形成,使S在其表面积累,形成由次生矿物层和硫膜构成的固膜钝化层,抑制黄铁矿氧化溶解。同时黄铁矿氧化过程中Fe²⁺的释放和Al³⁺的溶解可调控黄铁矿表面次生矿物的形成及矿物相转变,有利于固膜钝化层形成和加厚,对酸性地下水环境污染防治和修复工作具有重要的意义。更多还原

【Abstract】 When the primary reduction environment is destroyed by mining,pyrite is oxidized to produce acid mine water with high concentration of SO₄^2-,H⁺and metal ions.In the process of pyrite oxidation,solid film passivation layer will be formed on the surface,leading to the diffusion of water and oxygen mass transfer is blocked,and the oxidation dissolution of pyrite is inhibited.Pyrite is often co-occurring or associated with aluminum-bearing minerals,which will lead to dissolution and release of Al³⁺and form highly aluminum-acidic mine water.There are few reports on whether it will affect the oxidation dissolution of pyrite and the formation of solid film passivation layer on the surface.In this paper,the main sources of Al³⁺and the causes of acidification in typical acidic mine water in southwest China were clarified through a combination of field and indoor studies.On this basis,the formation process of the solid film passivation layer on the surface of pyrite was characterized,the microscopic interface change mechanism during the oxidation of pyrite was revealed,the influence of Al-containing minerals on the formation of secondary minerals under different Fe²⁺concentrations and p H was explored,and the regulatory mechanism of the formation and transformation of secondary minerals on the formation of solid film passivation layer on the surface of pyrite was elucidated,which has important theoretical significance for the remediation and source prevention and control of acid mine water pollution.The main research results are as follows:Typical acid mine water pollution characteristics were analyzed to clarify the influence of dissolved aluminum-containing minerals on the hydrochemical evolution of mine water.The acid mine water pollution in abandoned Dashu mining area has the characteristics of"three high and one low",namely"high iron,high aluminum,high SO₄^2-and low p H value".The acid mine water microbial community is mainly composed of A.ferrooxidans;the dissolution of aluminous clay（clay for short）in acid mine water consumes H⁺,resulting in the increase of Al³⁺concentration and p H,which promotes the hydrolysis and precipitation of iron and aluminum to produce iron and aluminum secondary minerals such as jarosite,schwertmannite and alunite,causes the change of chemical components of mine water and inhibits the acidification of mine water.The influence mechanism of Al₂O₃ and clay on the oxidation and dissolution kinetics of pyrite was revealed.The oxidation dissolution of pyrite accords with the nuclear dynamic model of solid film contraction.The addition of a small amount of Al₂O₃ and clay(Al³⁺equivalent<30 mmol/L)can promote the oxidation of pyrite,while the addition of Al³⁺equivalent≥30 mmol/L can significantly inhibit the oxidation of pyrite.The oxidation inhibition effect of clay with the same dosage is more obvious than that of Al₂O₃ on pyrite.It is mainly the formation of the secondary mineral layer on the surface of pyrite,which prevents the contact between water and oxygen and pyrite,inhibits the oxidation and dissolution of pyrite,and makes the formation and thickening of the sulfur film passivation layer on the surface of pyrite.The solid film passivation layer formed by the sulfur film and secondary mineral layer is formed on the surface of pyrite,resulting in the passivation phenomenon.The forming process of solid film passivation layer and the mechanism of inhibiting the oxidation and dissolution of pyrite were.The oxidation process of pyrite conforms to the"polysulfate-thiosulfate"pathway with or without aluminum-bearing minerals.On the one hand,the Fe³⁺concentration of the reaction system is reduced,so that the oxidation of pyrite and sulfur oxidation intermediates is inhibited.On the other hand,secondary minerals such as jarosite,schwertmannite and alunite are generated on the surface of pyrite,which prevents the surface material transmission of pyrite.In the process of pyrite oxidation,the migration rate of iron element is higher than that of sulfur element,which causes the accumulation of sulfur element on the surface of pyrite,promotes the thickening of sulfur film dominated by polysulfide chemical（Fe S_n）or iron-deficiency sulfide(Fe_1-xS),and forms a solid film passivation layer composed of sulfur film and secondary mineral layer,which inhibits the oxidation of pyrite.The regulation mechanism of aluminum-bearing minerals on the formation and transformation of secondary minerals under different Fe²⁺concentration and p H value was revealed.The dissolution of Al₂O₃ and aluminum-bearing minerals in clay and the oxidation of Fe²⁺can promote the polymerization and precipitation of hydroxyl sulfate,the intermediate product of Fe³⁺/Al³⁺hydrolysis,to produce secondary minerals under acidic conditions.Under acidic conditions（p H=2.00）with Fe²⁺concentration≥30 mmol/L,jarosite was formed by polymerization of hydroxyl sulfate.The p H value≥3.00 is conducive to the formation of schwertmannite minerals,and the mineralization process will cause the release of H⁺and promote the transformation of schwertmannite minerals into jarosite,which indicates that the dissolution of aluminum-bearing minerals under acidic conditions will promote the formation and transformation of schwertmannite minerals.To sum up,Al³⁺is released by the dissolution of aluminum-bearing minerals（Al₂O₃ and clay）in acid mine water,which promotes the formation of secondary minerals on the surface of pyrite under the interaction of iron and aluminum hydrolysis and co-precipitation,so that sulfur elements accumulate on the surface,forming a solid film passivation layer composed of secondary mineral layer and sulfur film,which inhibits the oxidation and dissolution of pyrite.At the same time,the release of Fe²⁺and dissolution of Al³⁺during the pyrite oxidation process can regulate the formation of secondary minerals and mineral phase transformation on the surface of pyrite,which is conducive to the formation and thickening of solid film passivation layer,and has important reference significance for the prevention and remediation of acid groundwater environmental pollution.更多还原