层间氧化带型砂岩铀矿床地浸过程的热力学研究：以伊犁盆地512铀矿床为例

伊梨盆地512层间氧化带型砂岩铀矿床是中国第一个工业化规模开发的地浸铀矿床,作者简要地介绍了其地质特征和地浸开发工艺,并利用较新的Gibbs自由能和平衡常数数据,对该矿床地浸处理中铀的地球化学行为进行了定量研究。首先,通过标准电动势（E^o）,氧化-还原电位（Eh）的计算和分析,阐明了H2O2、硝酸盐、大气中自由氧都能提升溶液的Eh值,从而加速矿物相U^4 的氧化溶解,为了节约地浸氧化剂成本,对于U^4 /U^6 比值不太高的矿床来说,建议充分利用大气中自由氧化氧化剂,然后,通过化学平衡计算,推导出了地下水和硫酸浸出液中铀存在形式的计算公式,计算结果表明：（1）512铀矿床矿体所赋存的含矿层地下水中,铀主要以碳酸铀酰类络合物形式存在,并且以UO2（CO3)^4-3和UO2（CO3）^2-2形式为主,并随着pH从7.31升高到8.20,UO2CO3从3.80%降低到0.06%,UO2（CO3）^2-2从21.91%降低到3.12%,而UO2（CO3）^4-3则从74.28%升高到96.82%,（2）512铀矿床硫酸浸出液中,铀主要以硫酸铀酰类络合物形式存在,其中,UO2SO4占63.28%～ 63.86%,UO2(SO4)^2-2占16.55%～21.36%,UO^2 2占15.04%～19.62%,从推导出的计算公式可以看出,硫酸浸出液中铀的存在形式随溶液pH、总SO^2-4含量的变化而变化,并呈非线性关系,为了提高离子交换树脂的吸附性能,可利用文中推导出的公式进行计算,以使调节溶浸液的pH和总SO^2-4含量,从而达到浸出液中铀存在形式的最佳比例关系,最后,因热力学数据对化学反应平衡计算的影响呈指数关系,在进行热力学数据计算时,必须采用较新、较准确的数据。     

地浸过程中铀迁移特征研究

通过室内溶质迁移试验，对地浸过程中铀迁移的规律进行了研究。结果表明：地浸过程中溶质铀主要以铀酰、硫酸铀酰为主要存在形式；铀迁移经历了溶解迁移、沉淀、再溶解迁移的多次旋回；浸出铀浓度最大值和浸出速度与浸出距离和浸出时间密切相关。     

酸性含Fe3+溶液作用下铀的溶解迁移特征

采用不同Fe~(3+)浓度的酸性溶液,对取自新疆伊犁盆地的砂岩铀矿石进行了溶浸对比试验,探讨了铀在酸性含Fe~(3+)溶液作用下的溶解迁移动力学特征及其与Fe~(3+)的关系。结果表明,在Fe~(3+)的氧化作用下,铀从矿石向溶液的迁移于10小时内快速达到平衡,溶解速度衰减迅速;铀的溶解速度与Fe~(3+)向Fe~(2+)转化速度呈正相关的指数函数关系,当Fe~(3+)向Fe~(2+)转化速度趋近零时,铀的氧化溶解基本停止,溶液中的铀达到平衡浓度;Fe~(3+)向Fe~(2+)浓度达到2g/L可使铀强烈溶解迁移,而溶液酸度增高会弱化铀溶解速度与Fe~(3+)转换速度的关系,但酸度在2g/L~4g/L(对应pH值1.65~1.33)之间变化不会对铀的浸出产生显著影响;保持Fe~(3+)浓度为2g/L、酸度为2g/L(pH值1.65)的水化学条件对铀的溶浸是经济且足够有效的。     

大庆齐家水源地水文地球化学环境的模拟

大庆齐家水源地抽取地下水过程中，地下水中CO2和H2S气体大量逸出，造成就地实测的Eh和pH等值不能代表含水层中地下水的真实情况。本文提出用化学热力学模拟恢复水文地球化学环境的方法，在分析齐家水源地实际情况的基础上，界定了齐家水源地的水文地球化学环境指标：pH值、Eh值、游离CO2和H2S，pH值为6．56以下；Eh值为—121-—145mV之间；游离CO2为300mg/L以上；H2S(aq)大于64μg/L；HS^-大于17μg/L。指出大庆齐家水源地为偏酸性、弱还原、高游离CO2，且含H2S的水文地球化学环境；为地下除铁提供了水文地球化学环境依据。     

地浸过程中溶质(铀)迁移特征研究

本通过室内溶质迁移试验，运用化学热力学计算，对地浸过程中的溶质迁移规律进行了研究。溶质（铀）迁移研究表明：随着水地球化学条件的改变，溶质（铀）经历了溶解迁移、水解沉淀、再溶解迁移的多次旋回，章还根据铀浓度和水地球化学指标，在整个渗透途径中划分出不同特征的浸出带。     

顶山地区铀成矿水文地球化学条件研究

层间氧化带铀矿床的形成与水文地球化学条件密切相关，本文采用水文地球化学的分析方法，对顶山地区地下水的水文地球化学特征进行了研究，确定了顶山地区下水中铀主要以UO2（PO4)2^2-形式存在，并研究了铀的饱和沉淀条件，指出了铀成矿有利地区。     

砂岩型铀矿地浸过程中的溶质迁移机理

讨论了“溶质迁移、溶质迁移面和特征性溶质迁移面”的概念，以及研究溶质迁移的方法和实例。在对381砂岩型铀矿床进行地浸模拟试验的基础上，应用以上概念和方法，对地浸过程中的溶质迁移过程进行了讨论，探讨了地浸过程的机理和发生的水文地球化学作用，总结了溶浸试验过程中的溶质迁移分带。在以上溶质迁移机理研究的基础上．论证了地浸地质工艺参数。地浸过程中分带的研究清楚地显示了浸铀的发展过程及其在各个时期各个地段铀浸出作用的进展程度。     

501矿床铀矿石室内浸铀试验地质工艺研究

501矿床矿石铀品位0．052％,U^＋6／U^＋4比值1．7～4．6,对浸铀地质工艺有害的碳酸盐、硫化物和有机质含量很少,矿层水中铀和溶解氧含量较高,[HCO3]^-量低。通过静态浸出试验确定的技术参数为：用7．91g／LH2SO4,对0．007％～0．216％品位铀矿石浸泡48h,铀的浸出率为64．69％～99．17％,浸出液中铀浓度为9．51—427．6mg／L。通过渗滤浸出试验筛选出较好的溶浸剂配方为：6～8g／LH2SO4,铀的浸出率为95．71％～96．33％,浸出液中铀浓度为88．33～111．32mg/L,浸出液固比为4．46～5．66,吨矿硫酸耗量为27．58～29．83kg/t,提取1kg铀的硫酸耗量为55．17～60．06kg。说明该矿床矿石宜用酸法浸出,浸出铀的地质工艺条件较好。     

对公婆泉盆地铀成矿水文地球化学条件的认识

通过对公婆泉盆地地质、水动力、水文地球化学条件的分析和地球化学模式计算 ,确定了盆地下白垩统层间水水化学类型主要为SO4 ·Cl Na型或Cl·SO4 Na型 ;水中铀存在形式以UO2(CO3) 4- 3占优势 ;盆地内存在有利于铀还原沉淀的水文地球化学环境的可能性、及具备满足铀沉淀条件的矿化远景有利地段     

基于铀矿中本源硫杆菌对黄铁矿和铀矿浸出的协同作用

研究砂岩型铀矿床中本源嗜酸性氧化亚铁硫杆菌（Acidithiobacillus ferrooxidans, At.f）、嗜酸性氧化硫硫杆菌（Acidithiobacillus thiooxidans,At.t）对黄铁矿及铀矿浸出的协同作用。采用富集培养法、无机盐硅酸钠平板法对砂岩型铀矿中的硫杆菌分离纯化,通过分析菌株的形态学特征、生理生化结果及16S rDNA序列确定菌株的系统发育地位,并利用摇瓶培养法设计浸矿试验,向黄铁矿浸出体系中分别加入分离纯化的At.f、At.t及混合的At.f和At.t,检测pH值、氧化还原电位值（Eh值)的变化,浸矿40 d,测定浸矿体系的总铁离子浓度和硫酸根离子浓度,并分析黄铁矿矿渣表面形态及成分。根据黄铁矿的浸出结果,设计铀矿浸出试验,浸矿40 d,测定浸出体系中的pH值、Eh值、总铁离子浓度、硫酸根离子浓度等参数并计算四价铀的浸出率。结果表明,分离的两株优势菌中SW-2鉴定为嗜酸性氧化亚铁硫杆菌(At.f),SW-3鉴定为嗜酸性氧化硫硫杆菌(At.t)。At.f、At.t浸出黄铁矿和铀矿时存在协同作用,At.f为浸矿体系的强氧化剂,主要将Fe2+氧化成Fe3+,Fe3+将UO2氧化成可溶性的UO22+;At.t可为浸矿体系提供酸性环境;At.f: At.t = 5:1试验组对黄铁矿和铀矿的浸矿效果最好,四价铀的浸出率为55.60%,黄铁矿矿渣表面形态显示细菌对黄铁矿存在直接的氧化作用;At.f、At.t高效浸出黄铁矿的菌量比例对以黄铁矿为伴生矿的铀矿的细菌浸出也具有明显的促进作用,研究结果可以为工业微生物浸铀时提供一定的支持并为以黄铁矿为伴生矿的其他矿物的微生物浸出提供参考。     

西秦岭铀矿床铀迁移形式的热力学研究

利用热力学方法计算了西秦岭铀矿床含矿热液中铀的迁移形式。结果表明，从含矿热液早阶段到主成矿作用发生之前，热液中的铀主要以「ＵＯ２（ＣＯ３）＾０」形式迁移；在晚阶段残余热液中，铀的迁移形式改变为「ＵＯ２（ＳＯ４）＾０」为主。铀迁移形式改变的原因与大气降水中ＳＯ＾２－４离子的大量带入有关，表明含矿热液来自深部而非大气降水。     

浅析碎裂蚀变花岗岩型铀矿床的特点和形成条件

碎裂蚀变花岗岩型铀矿床是当前我国找矿的主攻方向之一，它具有大碎裂带、以交代作用为特征的大蚀变带。低品位大矿量易浸出的特点。该类型矿床形成的主要地质条件是：地台边缘活动带或褶皱带的花岗岩隆起区；受非造山的大复式花岗岩基内自变质作用发育的小岩体和双断裂夹持区或断裂构造结的双重控制；酸交代或碱交代蚀变发育区；红层不整合覆盖、负地形、表生叠加富集区。同时，强调了在找矿过程中要加强地浸试验和经济技术评价。     

Factors influencing in-situ leaching of uranium mining in a sandstone deposit in Shihongtan,Northwest China

The Shihongtan uranium deposit in northwest China is a sandstone-type deposit suitable for alkaline in-situ leaching exploitation of uranium. Alkaline leaching tends to result in CaCO3 precipitation there by affecting the porosity of the ore-bearing aquifer. CaCO3 deposits can also block pumping and injection holes if the formulation parameters of the leaching solution are not well controlled. However, controlling these parameters to operate the in-situ leaching process is challenging. Our study demonstrates that the dissolved uranium concentration in the leaching solution increases as HCO3－ concentration increases. Therefore, the most suitable HCO3－ concentration to use as leaching solution is defined by the boundary value of the HCO3－ concentration that controls CaCO3 dissolution-precipitation. That is, the dissolution and precipitation of calcite is closely related to pH, Ca2+ and HCO3－ concentration. The pH and Ca2+ concentration are the main factors limiting HCO3－ concentration in the leaching solution. The higher the pH and Ca2+ concentration, the lower the boundary value of HCO3－ concentration, and therefore the more unfavorable to in-situ leaching of uranium.     

3110矿床成矿流体地球化学特征

通过对３１１０矿床不同成矿阶段石英流体包裹体成分的研究,阐述了该矿床成矿的物理化学环境。该矿床成矿流体来源于改造围岩的构造热液和大气降水混合。成矿流体中铀的迁移形式,矿前期为ＵＯ２（ＣＯ３）３＾４－（７７．４％）和ＵＯ２（ＣＯ３）２＾２－（２２．５％）;成矿期为ＵＯ２（ＣＯ３）２＾２－（９９．９％）;矿后期ＵＯ２（ＣＯ３）３＾４－（５４．４％）和ＵＯ２（ＣＯ３）２＾２－（４２．０％）。矿化是在混合     

The behaviour of uranium, thorium and tin during leaching from a coarse-grained porphyritic granite in an arid environment

During the routine analysis of chip samples from water boreholes it was noted that the DeBakken granite south of Kenhardt has high uranium and tin contents. Rock samples collected on surface, however, revealed low concentrations of both these elements indicating that they have been leached from the surface samples. The distribution of thorium in the borehole profiles showed that while both tin and uranium have been removed above the water table, other “immobile” elements and thorium remained unaffected.The geological data showed that the leaching took place since the start of the Tertiary. Initially, the movement of uranium was vertical and accumulated in pedogenic calcrete above the granite. This vertical leaching was controlled by fluctuations in the water table and took place from the Pliocene to Pleistocene. Later, in the Holocene, the pedogenic calcrete was removed and deposited as non-pedogenic calcrete along the rivers. These nodular calcrete deposits, which are abundant in Namaqualand, are mineralized only along those rivers which drain the DeBakken granite, indicating that this granite was the source of the uranium.When the water table reached depths of ten metres or more the vertical migration of uranium ceased and horizontal leaching caused by the movement of ground water became active. Where the water table cuts the surface, such as in the pans, uranium deposition due to evaporation of groundwater is still active.Leaching of uranium from this granite, together with the formation of the secondary deposits is mineralogically controlled, and is ascribed to the fact that uranium is not hosted in zircon. Granites such as the DeBakken granite, in which the uranium is hosted in biotite, monazite and apatite, cannot be recognized by surface sampling and hence a lithogeochemical approach, using sub-surface samples has to be adopted. Calculations showed that approximately 1400 tons of uranium metal has been leached from this granite since the start of the Tertiary and that the maximum reserve of the province as a whole is relatively small.The distribution of tin is erratic, and although it has been leached from the surface samples, it has not been transported for any significant distance. Thus the tin distribution in the profiles does not show the same degree of leaching as does uranium. This is ascribed to the fact that samples from a percussion drill would include both the rock fragments from which tin has been leached and the clay-rich alteration products in which it has been trapped. Tin is generally immobile when present as cassiterite, but when enclosed in biotite, and when the groundwater is enriched in chlorine and fluorine, it leaches readily from the biotite.     

Leaching of metals from copper smelter flue dust (Mufulira,Zambian Copperbelt)

The leaching behaviour of electrostatic precipitator dust from the Mufulira Cu smelter (Copperbelt, Zambia) was studied using a 48-h pH-static leaching experiment (CEN/TS 14997). The release of metals (Cd, Co, Cu, Ni, Pb and Zn) and changes in mineralogical composition using X-ray diffraction and PHREEQC-2 modelling were investigated in the pH range of 3–7. The highest concentrations of metals were released at pH 3–4.5, which encompasses the natural pH of the dust suspension (～4.3). About 40% of the total Cu was leached at pH 3, yielding 107 g/kg. Chalcanthite (CuSO₄·5H₂O), magnetite (Fe₃O₄) and delafossite (CuFeO₂) represented the principal phases of the studied dust. In contact with water, chalcanthite was dissolved and hydrated Cu sulphates precipitated at pH 4–7. Gypsum (CaSO₄·2H₂O) and secondary Fe or Al phases were observed in the leached residues. Serious environmental impact due to leaching may occur in dust-contaminated soil systems in the vicinity of the smelting plants.