浸金体系的Eh—pH图及其热力学分析

基于"物料平衡"与"同时平衡"原理,提出绘制金-配体-水体系Eh-pH图的通用方程,又以硫氰酸盐浸金体系为例,绘制其Eh-pH图并推测了金离子浓度、络合剂浓度的变化对平衡电位的影响。在浸金体系中,由于络合剂的存在,金的氧化电位大大降低。增加溶液中络合剂的浓度,则能降低金-溶液的平衡电位,扩大溶液的稳定区,有利于金的浸出;反之,随着金的浸出,溶液中金浓度的增大,金-溶液的平衡电位随之升高,溶液的稳定区减小,不利于金的浸出。     

硫化锌加压浸出过程的电位-pH图

通过热力学计算,绘制出温度110～160℃,氧分压分别为0.7、0.9和1.1 MPa,离子浓度为1.0mol/L的ZnS-H2O系的电位-pH图.由电位-pH图可知,随着温度由110℃提高到160℃,S与Zn2+稳定区对应的pH范围逐渐变正、氧化电位值逐渐增大,提高温度有利于硫化锌的加压浸出过程在较低的酸浓度下进行,...     

液氯化法浸金过程热力学

针对氯化物体系中金的浸出反应进行热力学计算,分别绘制出Au-Cl-H2O体系电位-pH图、lg[Au(Ⅲ)]-pH图、lg[Cl-]-pH图,并分析了金氯化浸出过程的热力学影响因素。电位-pH图中存在着金氯络合物的稳定区域,在pH为中性或弱酸性并保持氧化电位高于0.9 V的条件下,金将以AuCl4-的形态浸出。AuCl4-的稳定性很差,易受氯化物浓度、AuCl4-浓度等热力学因素的影响。加大氯化物浓度或降低AuCl4-浓度,在热力学上有利于金的浸出。在保证金尽可能浸出的角度来说,热力学上最佳条件为pH 3.5～7.8、氧化电位高于0.9 V、氯化物浓度高于1 mol.L-1,AuCl4-浓度1×10-5～1×10-4mol.L-1。     

CaS升温浸出过程的电位-pH图

针对炼钢脱硫废渣的浸出去硫热力学研究,采用平均热容法通过热力学计算绘制出不同温度条件下CaS-H2O系电位-pH图;考察了温度对钙、硫稳定存在形式和体系中电极反应平衡关系的影响.结果表明,298 K时,硫化钙的浸出反应即可自发进行;降低pH,硫以H2S的形式逸出,增大pH,硫以S2-的形式进入浸出液.随着温度升高,有利于HS-向S2-和H2S转化和微溶物质CaSO4的浸出,提高硫的浸出率。与常温相比,高温条件下,pH>7时,更有利于钙形成Ca(OH)2和硫以S2-,HS-,SO4-2离子进入浸出液或以H2S的形式逸出.     

液氯化法浸出硫化金精矿压热氧化渣的电位变化研究

根据氯化物体系中金的浸出热力学,预测合理的电位和pH值范围。通过对硫化金精矿压热预处理后的氧化渣进行液氯化浸出试验,考察了浸出过程中电位变化与浸金率之间的关系。氯化浸出金适宜的热力学条件为pH值8以下、电位0.9 V以上。从次氯酸钠溶液的氧化能力角度考虑,pH值在4～5.5时其氧化能力较强,此时溶液中氧化剂以HClO为主。对金精矿压热氧化渣的次氯酸钠浸出,为得到较高的浸金率,必须控制至少2 h电位在1.0 V以上。若在浸出过程中电位低于1.0 V,已溶解生成的金氯络合物会再沉淀,使浸金率下降。在初始有效氯质量分数为0.5%、初始pH值为4.0时,可保证2 h内电位在1.0 V以上,此时浸金率可达到96%以上。     

难浸金精矿生物浸出体系的电位-pH图分析

电位-pH图是一种重要的热力学分析方法,能够直观地反映出浸出体系中的各种热力学平衡,有助于推断出物质发生化学反应的趋势,在难处理金精矿生物浸出体系中有重要指导作用。通过热力学计算,针对生物浸出环境绘制并分析了313 K温度下,pH=0~7.0,E=-1.2~1.2 V范围内适宜生物氧化黄铁矿-水系、毒砂-水系的电位-pH图。结果表明：在酸性体系下黄铁矿的稳定区域存在于0.336 V以下,毒砂则为0.133 V以下,毒砂的稳定性比黄铁矿的稳定性低,在较低的电位条件下便会被氧化溶解。     

Study on potential change of chlorination gold leaching from pressure oxidation residue of gold sulfide concentrate

根据氯化物体系中金的浸出热力学,预测合理的电位和pH值范围.通过对硫化金精矿压热预处理后的氧化渣进行液氯化浸出试验,考察了浸出过程中电位变化与浸金率之间的关系.氯化浸出金适宜的热力学条件为pH值8以下、电位0.9V以上.从次氯酸钠溶液的氧化能力角度考虑,pH值在4～5.5时其氧化能力较强,此时溶液中氧化剂以HClO为主.对金精矿压热氧化渣的次氯酸钠浸出,为得到较高的浸金率,必须控制至少2h电位在1.0V以上.若在浸出过程中电位低于1.0V,已溶解生成的金氯络合物会再沉淀,使浸金率下降.在初始有效氯质量分数为0.5％、初始pH值为4.0时,可保证2h内电位在1.0V以上,此时浸金率可达到96％以上.     

Cu-Cl~--H_2O系的热力学分析及电位-pH图

<正> Cu-Cl~--H_2O 体系及其在不同温度的电位-pH 图,以往都是确定简单离子和络合离子各自的热力学稳定区,而且也只考虑个别络离子的存在。我们认为,这样处理不符合实际情况,不便于解决实际问题,因为真实的溶液既含有简单离子,又含有络离子;而且在一定条件下,各种金属离子平衡     

用溴盐氧化法从矿石中浸出金试验研究

研究了用溴盐(NaBr)、氧化剂(YA)和配合剂(NaCl)从矿石中氧化浸出金,考察了溴盐、氧化剂、配合剂用量、体系pH、浸出时间对金浸出率的影响。结果表明:对于100 g矿石,在固液质量体积比1/3、NaBr浓度0.146 mol/L、YA浓度0.071 mol/L、NaCl浓度0.342 mol/L、浸出时间8 h、溶液pH=6、反应温度17～25℃条件下,金浸出率超过92.4%,浸出效果较好。     

大洋多金属结核氨浸工艺影响因素研究

在低温水溶液条件下,以亚铜离子为催化剂,一氧化碳为还原剂,在氨性体系中,对日处理10 kg大洋多金属结核扩大试验的浸出行为影响因素进行研究。试验考察了浸出体系电位、金属离子浓度、温度、液固比等因素对有价金属浸出率的影响。结果表明,控制浸出体系的电位对维持较快的反应速度和较高的金属浸出率十分重要;溶液中的钴离子浓度对钴浸出率影响较大,随着溶液中钴离子浓度的增加,钴浸出率下降,镍离子浓度对镍浸出率的影响很小;液固比对镍、钴、铜浸出率的影响不显著;温度对有价金属浸出率有一定影响,最好控制在40~50℃。     

Adsorption of gold on activated carbon in bromide solutions

Adsorption of gold on activated carbon from gold bromide solutions was examined as a function of pH, particle size, amount of carbon, initial gold bromide concentration, bromine concentration, temperature, and various cations and anions. The pH did not have any effect on gold adsorption below pH = 6. Above pH = 6, pH had a dramatically negative effect. The adsorption occurred according to a first-order reaction-rate model. The reaction-rate constant was proportional to the inverse of carbon particle radius, the amount of carbon, and independent of the initial gold concentration. Temperature had very little effect on the rate of gold adsorption. Cations (Cu²⁺, Fe³⁺, Ca²⁺, Mg²⁺, and Na⁺) and anions (SO ₄ ² , Cl^-, Br^-) did not have any effect on gold adsorption. Free bromine had a very negative effect on gold uptake. Gold bromide is very stable and stays in this form on the carbon surface. Contrary to this, gold chloride is unstable, and elemental gold precipitates on the carbon surface. Loading capacity of carbon depended on the presence of free bromine. In the presence of free bromine, it was further dependent on temperature (increased with increasing temperature). AtT = 25 °C, gold loading was 27 to 64 kg Au/t carbon. In bromine-free solutions, gold loading was 174 to 315 kg Au/t carbon.     

Reaction mechanism of gold dissolution with bromine

The dissolution of gold with elemental bromine was studied by using a rotating disc technique. The main parameters studied were bromine and bromide concentrations, stirring speed, pH, and temperature. The effect of various salts, manganese, and hydrogen peroxide was also examined. The dissolution kinetics of gold with Br₂ and NaBr mixture is complex. The reaction mechanism is a function of solution composition, which determines the kind of adsorbing species. For an excess concentration of bromide ions, the rate expression is Rate = (2k _cl7 k _al6)^1/2 K ₁₅ [Br ₃ ⁻ ] and for an excess concentration of bromine, the rate expression is Rate = (2k _c27 k _a29)^1/2 [Br⁻]^1/2 {K₂₅ [Br₂]³/(1 +K ₂₅ [Br₂]³)}^1/2 Gold in bromine solutions dissolves according to electrochemical/chemical (EC) mechanisms. The electrochemical component of the mechanism is responsible for the formation of AuBr₂. In the chemical component of the mechanism, this monovalent gold bromide disproportionates into gold and stable AuBr ₄ ⁻ , which reports into solution. With respect to pH, there are two characteristic dissolution regions. In the pH range of 1 to 7, gold dissolution rates were insensitive to pH. Above pH 7, gold dissolution rates decreased with increase of pH.     

金矿的溴氧化浸出工艺试验

在实验室条件下,详细考察了溴氧化浸出金的各项条件。结果表明,对含金量为55 5g/t的广东某硫化矿,经破碎至-0 147mm,600℃焙烧后,在常温、试剂浓度2%NaCl-0 1%Br2,液固比1∶1,浸出时间1h的条件下,金的平均浸出率达97 2%。     

Heterogeneous phase equilibria as a basis for crevice corrosion modelling

The presented crevice corrosion model is intended to provide basic understanding of formation and dissolution of passivating layers during time dependent metal dissolution in an already deoxygenated crevice. It operates along a constant cathodic polarization curve in subsequent time steps with time dependent anodic polarization curves and corrosion currents. The anodic polarization curves are determined by dissoluted ionic chromium and respective Nernst potentials as well as by the mass of precipitated passivating chromiumhydroxide layers. All chemical reactions including diffusion of chloride into the model crevice configuration are assumed to be at equilibrium during the respective time steps. The amounts of passivating chromiumhydroxide masses are determined by lever-rule application at increasing chromium and chloride contents in aquaeous solution of the quaternary water-chromium-hydrogen-chloride phase diagram at various Nernst potentials. For this purpose, the established water–chromium Pourbaix diagram had to be redrawn in terms of ternary water-chromium-hydrogen phase diagrams for constant potentials. It was tentatively extended to the quaternary chloride including diagram based on literature results. This included solubility of chromiumchloride in hydrochloric acid and most probable effects of chloride ions on chromiumhydroxide solubility at saturation with chromium metal. The results of the interactive corrosion process are based on a crevice geometry drawn from previous publications and given initial solution concentrations as well as assumed polarization curves for time steps of one second. It is shown, how the process starts with concentration changes of chromium, chloride and hydrogen in the crevice, the subsequent formation of the passive layer and the corresponding decrease in the corrosion current and increase in the mixed potentials. In the presence of the chromiumhydroxide phase, however, chromium and hydrogen remain at low levels in the equilibrium aqaeous solution while chloride is increasing. The saturated solution reaches the four phase equilibrium concentration including saturation by chromium, chromiumhydroxide and chromiumchloride at corresponding Nernst potentials. The further increase in total chromium and chloride concentrations of the crevice then leads to initiation and propagation of crevice corrosion by formation of non-passivating chromiumchloride at the expence and finally, the total dissolution of passivating chromiumhydroxide, at decreasing mixed potentials and increasing currents. Due to the low solubility of chromiumchloride in hydrochloric acid, the latter is finally formed with the result of the well-known increase in crevice acidity. Thus, it is demonstrated that the acidification itself is not a requirement for crevice corrosion but rather a consequence of it.     

Use of Phosphate Rock for the Removal of Ni2+ from Aqueous Solutions: Kinetic and Thermodynamics Studies

A study was carried out in batch conditions to examine the removal of nickel ions from an aqueous solution by phosphate rock. The effect of different sorption parameters, such as initial metal concentration, equilibration time, solution pH, and temperature on the amount of Ni2+ sorbed was studied and discussed. The sorption process followed pseudo-second-order kinetics with necessary time of 2?h to reach equilibrium. The maximum removal obtained is at initial pH around 8. Nickel uptake was quantitatively evaluated using the Langmuir and Dubinin–Kaganer–Radushkevich model. The Langmuir adsorption isotherm constant corresponding to adsorption capacity, Q0, was found to be 7.63?mg/g. The possibility of metal recovery was investigated using several eluting agents. The desorbed amount of nickel decreased continuously with increasing pH, and increased with increasing Ca2+ concentration in leaching solution.     

A Review of Ammoniacal Thiosulfate Leaching of Gold: An Update Useful for Further Research in Non-cyanide Gold Lixiviants

This literature review provides an update of ammoniacal thiosulfate as a potential lixiviant of gold, the history of thiosulfate leaching and recent progress on thiosulfate leaching of gold, as well as the production, oxidation, and stabilization of thiosulfate. The leaching results of different types of gold ores including oxide, sulfide, carbonaceous, and refractory ores/concentrates and the fundamentals relevant to the oxidation of pure gold are summarized. The factors affecting gold leaching such as pH, temperature, and oxidants in leaching solutions, reagent concentrations, and foreign ions are presented to update the current understanding on gold dissolution in a Cu(II)-NH₃-S₂O₃^2-system.     

镁离子对锰电解液理化性能影响的实验研究

对纯硫酸锰溶液和含铵硫酸锰溶液在不同镁离子浓度及温度下的溶液密度、粘度、电导率进行了测定。结果表明：在同一温度下，2类溶液的密度和粘度都随镁离子浓度的增加而增大，而溶液电导率随镁离子浓度的增加而降低。在同一镁离子尝试下，2类溶液的密度和粘度都随温度的升高而降低，而电导率随温度的升高而增大。在相同温度和镁离子浓度下，含铵硫酸锰溶液的密度、粘度和电导率都比纯硫酸锰溶液大。