A simple kinetic model for sulfuric acid leaching of copper from chrysocolla

Experimental results obtained in room temperature laboratory leaching studies of lowgrade chrysocolla are interpreted by a kinetic equation of the form 1?(1?R)^1/3=(1/αKr _c) ln (αkKC ₀t+1) derived on the basis of a special form of the shrinking-core model and assuming chemical-reaction control. The experimental program encompasses a large range of particle sizes and reaction times and significantly extends previous experimental data on similar ore systems. The kinetic model, shown to be consistent with the experimental data, assumes the ore-particle structure to be characterized by pores and channelized regions which extend from the outer surface through a reacted zone into the unreacted core. Scanning electron microscope observations of unreacted particle surfaces as well as reacted particle surface structures lend support to this concept of leaching. The reaction rate is observed to vary inversely with initial mean particle radius, and diffusion in any form appears to be negligible by comparison with surface reaction phenomena.     

Kinetics of hydrochloric acid leaching of smithsonite

The dissolution kinetics of smithsonite ore in hydrochloric acid solution has been investigated. As such, the effects of particle size (−180 + 150, −250 + 180, −320 + 250, −450 + 320 μm), reaction temperature (25, 30, 35, 40, and 45°C), solid to liquid ratio (25, 50, 100, and 150 g/L) and hydrochloric acid concentration (0.25, 0.5, 1, and 1.5 M) on the dissolution rate of zinc were determined. The experimental data conformed well to the shrinking core model, and the dissolution rate was found to be controlled by surface chemical reaction. From the leaching kinetics analysis it can be demonstrated that hydrochloric acid can easily and readily dissolve zinc present in the smithsonite ore, without any filtration problems. The activation energy of the process was calculated as 59.58 kJ/mol. The order of the reaction with respect to HCl concentration, solid to liquid ratio, and particle size were found to be 0.70, −0.76 and −0.95, respectively. The optimum leaching conditions determined for the smithsonite concentrate in this work were found to be 1.5 M HCl, 45°C, −180 + 150 μm, and 25 g/L solid to liquid (S/L) ratio at 500 rpm, which correspond to more than 95% zinc extraction. The rate of the reaction based on shrinking core model can be expressed by a semi-empirical equation as:

Kinetics of leaching of zinc ferrite in aqueous hydrochloric acid solutions

The dissolution of synthetic samples of zinc ferrite in aqueous hydrochloric acid is stoichiometric. The rate appears to be controlled by a chemical reaction on the solid surface, and dependence of the dissolution rate on hydrochloric acid activity is of the first order. Activation energy of 83 kJ mol^-1 was found. Zinc ferrite leaching is a slow solubilization process in the hydrochloric acid treatment of dead-roasted Iberian pyrite ashes. The most favorable conditions are 0.5-1 M HC1 at 90 to 100 ‡C, when preferential solubilization of the spinel phases takes place on the hematitic matrix. Extensive extraction of zinc (~90 pct of total zinc) in one to two hours and low solubilization of iron (~8 pet of total iron) results under these conditions.     

氧化还原—机械活化对攀西钛铁矿浸出行为的影响

研究了"氧化还原—机械活化—盐酸浸出"的方法对钛铁矿中主要杂质离子铁离子浸出行为的影响,并采用XRD、SEM/EDS对处理前后的矿物结构进行分析。结果表明:经过氧化还原—活化处理,钛铁矿的物相明显发生改变,铁迁移至表面,形成了富铁的新表面,表面变得疏松、凹凸不平,出现了大量的微裂缝,铁浸出率有了显著的提高。     

A kinetic model for the acid-oxygen pressure leaching of Ni–Cu matte

A semi-empirical mathematical model for the acid-oxygen pressure leaching of Ni–Cu matte is presented, based on data from batch leaching experiments. The primary controlling factor in the leaching process is found to be galvanic inhibition of the more highly oxidized copper and nickel sulfide species by less oxidized species, particularly Ni alloy and Ni₃S₂. The leaching rate of many species is greatly reduced by the presence of one or both of these phases, and others will not commence leaching until neither is present. The mathematical model is based on first-order chemical reaction controlled rate expressions, as the reactions occurring are electrochemical in nature. Mass transfer effects are included only empirically. Some possibly diffusion-related phenomena are noted, although the model is not extended to incorporate these effects on a fundamental level. The model is verified and extended by the inclusion of several different factors that were tested experimentally. The effects of variations in O₂ flow rate and partial pressure, initial particle size, reaction pulp density and initial acid concentration were all studied, and included in the model. Variations in O₂ flow rate and partial pressure are found to affect the reaction rates via the dissolved oxygen concentration in the solution phase.     

A kinetic study on nonoxidative dissolution of sphalerite in aqueous hydrochloric acid solutions

The nonoxidative leaching of sphalerite in aqueous acidic solutions was studied from a kinetic point of view. Also the selective nonoxidation leaching in a hydrochloric acid solution containing a large amount of sodium chloride was examined for a Pb-Zn sulfide bulk concentrate. The dissolution rates of sphalerites from five different mines appeared to be controlled by a chemical reaction on the surface of sphalerite. The dissolution rate of sphalerite is of the first order with respect to the hydrogen ion activity of the solutions. It is also considerably affected by the iron content of the sphalerite sample; a linear relationship was observed between iron content of the sphalerite and its dissolution rate. The addition of sodium chloride to the hydrochloric acid solutions greatly enhanced dissolution rates. Compared to the dissolution rates of galena, which were reported in a previous paper, the dissolution rates of sphalerite were found to be far slower. The difference in the dissolution rates between these two minerals becomes greater with the addition of sodium chloride to the hydrchloric acid solutions. Based on these findings, the selective leaching of Pb-Zn bulk concentrate in a hydrochloric acid solution containing a large amount of sodium chloride was examined. The experimental results clearly showed that the galena was selectively leached, leaving a residue of sphalerite. NORIO MISAKI formerly Graduate student, Kyoto University     

Simultaneous leaching of a deep-sea manganese nodule and chalcopyrite in hydrochloric acid

Hydrochloric acid leaching of chalcopyrite and a manganese nodule, in combination, was studied using powder samples. Chalcopyrite, which does not dissolve well in HCl, was effectively leached in the presence of a manganese nodule at 3 to 4 M HCl. The rates of dissolution of metal values from the nodule were also enhanced in the presence of chalcopyrite. Dissolution was found to occur through three routes: (1) the galvanic interaction between CuFeS₂ and MnO₂, (2) the action of the Fe³⁺/Fe²⁺ redox couple, and (3) the action of Cl₂ gas generated from the MnO₂-HCl reaction on CuFeS₂. The last route appeared to make the major contribution to the dissolution. The combined leaching of a nodule and chalcopyrite appears to be promising from both technical and economic points of view.     

酸性环境下黏土渗透特性的试验分析

文中以矿山蓄污土石坝黏土为原料,对其进行了在酸性环境下渗透特性的试验分析。试验表明,黏土在酸性环境下渗透系数会随着时间的推移而增加,在20%硫酸溶液条件下浸泡一周,黏土的渗透系数增加了约两倍,并且渗透系数的增加与酸性的强弱成正相关。试验还发现,黏土在酸性环境下会随着时间的推移而有失重的现象,说明酸性溶液对黏土有溶蚀作用,且浓度愈大作用愈强,致使黏土的孔隙增加,这也是渗透系数增加的原因。黏土渗透特性试验结果对进一步研究和精确预测矿山蓄污土石坝的剩余寿命具有重要意义。     

The use of coal spoils as feed materials for alumina recovery by acid leaching routes V. The effect of fluoride additions on the extraction of aluminium with hydrochloric acid

A study has been made on the effect of the addition of fluoride ions on the leaching of clay-based feed materials, and in particular the extraction of aluminium from kaolinite, illite and a number of colliery spoil and coal ash materials. In all cases, the addition of fluoride ions led to a dramatic increase in the rate of extraction of aluminium. This increase in yield was found to be independent of the source of fluoride, depending only upon the fluoride concentration in the leaching medium and on the thermal history of the feed material. Uncalcined materials and those calcined at temperatures below 1123 K gave very high yields of aluminium in relatively short leaching times at a fluoride concentration of 0.68 M. Materials calcined at temperatures in excess of 1123 K required higher concentrations of fluoride in order to obtain satisfactory recoveries of aluminium. In addition, the nature of the co-extraction of the major impurities is also described.     

盐酸法富集低品位锰矿及酸介质高值再生工艺

针对印度尼西亚某低品位锰矿,提出盐酸法富集与酸介质高值再生的工艺。借助X射线衍射分析,光学显微镜和电子显微镜等表征方法进行工艺矿物学分析。结果表明:该锰矿矿物组成简单,主要由方解石、软锰矿和少量菱锰矿、褐铁矿、高岭石等组成。筛析结果显示该锰矿粒度越小,锰含量相对越高。粗碎后以2 mm筛孔的筛子过筛可得到锰质量分数为33.32%的锰中矿。锰中矿盐酸直接浸出的最佳条件为:浸出pH 3.0、浸出时间1.5 h、搅拌转速200 r·min?1、液固比4∶1 mL·g?1,此条件下产出的锰精矿品位为54.50%,钙质量分数为0.57%。常温下盐酸再生可产出二水硫酸钙晶须,其长径比可达50以上。再生盐酸返回浸出锰中矿,产出的锰精矿品位为52.16%,钙质量分数为1.39%,验证了该工艺流程的可行性。X射线衍射分析、扫描电镜及能谱分析结果显示产出的锰精矿主要组成成分为软锰矿,杂质为少量褐铁矿、高岭石等。酸介质循环时杂质将逐渐积累,当镁离子质量浓度积累到96.74 g·L?1时,采用水解沉淀法进行除杂。      

Preparation of synthetic rutile by hydrochloric acid leaching of mechanically activated Panzhihua ilmenite

Dissolution of mechanically activated Panzhihua ilmenite in hydrochloric acid for the preparation of synthetic rutile was investigated. Both the dissolution and its coupled titanium hydrolysis were greatly enhanced by the mechanical pretreatment. Increases in the lattice strain and surface area of ilmenite induced by energetic ball milling were responsible for the enhanced dissolution. The rapid hydrolysis led to formation of quantities of the nanosized primary particles, giving rise to a solid/liquid separation problem. The 15 min milled ilmenite, however, yielded an easy-to-filter hydrolysate due to formation of porous, micron-sized, secondary particles during the dissolution. The crystallization and aggregation behaviour of the primary particles were probably related to both the surface property of the un-reacted solid and the ferric ion concentration in solution. The technology for preparation of synthetic rutile was systematically investigated. The optimum milling and dissolution conditions were as follows: milling in air for 15 min, hydrochloric acid concentration 20%, initial reaction temperature 100 °C, ilmenite/20% acid mass ratio 1 g:5.5 g, reaction time ≥ 6 h. The synthetic rutile prepared under the optimum conditions contained 92% TiO₂ and 2.1% Fe₂O₃ as well as combined CaO and MgO of 0.28%. The results demonstrate that the mechanical pretreatment can take the place of the traditional high temperature pretreatment of ilmenite and avoid the dissolution being conducted under pressurized condition.     

Preparation of enriched cerium oxide from bastnasite with hydrochloric acid by two-step leaching

Roasted with sodium carbonate, bastnasite (Ln(Ce)CO₃F) was converted to calcine containing rare earth oxides (REO), among them cerium, which existed mainly as CeO₂. The calcine was first leached with diluted hydrochloric acid, which resulted in a sludge with the enriched cerium (IV) dioxide. The sludge was further leached with a concentrated hydrochloric acid, adding hydrogen peroxide as a reducing agent; in this manner, the enriched cerium tri-chloride (CeCl₃) was prepared. The optimal technological parameters are suggested as follows: first, the hydrochloric acid concentration, the leaching temperature, the ratio of solid to liquid, and the leaching time are 1 mol/L, 60°C, 1:20, and 90 minutes, respectively; second, the hydrochloric acid concentration, the dosage of hydrogen peroxide in every 5 g of the sludge, the ratio of solid to liquid, the leaching temperature, and the leaching time are 6 mol/L, 6 mL, 1:20, 50°C, and 90 minutes, respectively. As a result, the cerium-enriched rare earth (RE) solution, containing over 95 pct cerium oxide, is obtained, which is in turn available for use in preparing a kind of polishing powder containing high cerium. The total recovery of cerium was 91 pct (85.3 pct, in the second step).     

Kinetics of galena leaching in hydrochloric acid-chloride solutions

This article presents a series of studies on the nonoxidative leaching of galena with hydrochloric acid in the presence of a metallic chloride. A systematic study was carried out using a succession of metallic chlorides with cations of different valencies in an attempt to generalize the leaching behavior of these solutions. The reaction order for leaching galena, in terms of the mean ionic activity of HCl, is 3/2 over a wide range of concentration. The addition of soluble chlorides to a HCl solution increases the leaching rate of the galena by augmenting the mean ionic activity of the acid. A reaction order of 3/2 for the mean HCl activity in the solution is maintained for solutions in which the acid concentration is constant and the metallic chloride varies, as well as for the opposite situation. Therefore, the only activity that must figure in the kinetic equation is that of the HCl. The activation energy (58.5 kJ/mole) is independent of the chloride used to increase the activity of the hydrochloric acid. The same is true for the Arrhenius prefactor.     

Preparation of enriched cerium oxide from bastnasite with hydrochloric acid by two-step leaching

Roasted with sodium carbonate, bastnasite (Ln(Ce)CO₃F) was converted to calcine containing rare earth oxides (REO), among them cerium, which existed mainly as CeO₂. The calcine was first leached with diluted hydrochloric acid, which resulted in a sludge with the enriched cerium (IV) dioxide. The sludge was further leached with a concentrated hydrochloric acid, adding hydrogen peroxide as a reducing agent; in this manner, the enriched cerium tri-chloride (CeCl₃) was prepared. The optimal technological parameters are suggested as follows: first, the hydrochloric acid concentration, the leaching temperature, the ratio of solid to liquid, and the leaching time are 1 mol/L, 60 °C, 1:20, and 90 minutes, respectively; second, the hydrochloric acid concentration, the dosage of hydrogen peroxide in every 5 g of the sludge, the ratio of solid to liquid, the leaching temperature, and the leaching time are 6 mol/L, 6 mL, 1:20, 50 °C, and 90 minutes, respectively. As a result, the cerium-enriched rare earth (RE) solution, containing over 95 pct cerium oxide, is obtained, which is in turn available for use in preparing a kind of polishing powder containing high cerium. The total recovery of cerium was 91 pct (85.3 pct, in the second step).     

A kinetic study on the pressure leaching of sphalerite

The dissolution of sphalerite (ZnS) in sulfuric acid solution under oxygen pressure was investigated. Effects of temperature, percent solids, agitation, sample size, oxygen partial pressure and foreign ions were evaluated. The effect of hydrogen pretreatment on sphalerite leaching rate was also examined. Leaching of sphalerite at 90°C and 150 psi oxygen pressure was found to occur at a constant rate. This rate was determined from the experimental data observed under the different leaching conditions mentioned above. The constant leaching rate was attributed to the chemical reaction occurring on the surface of the flat-plate type sphalerite sample. The rate-controlling step of the reaction was determined to be the oxidation of hydrogen sulfide to elemental sulfur. Oxidation of hydrogen sulfide was studied through the addition of iron and through the observation of the change in iron concentration during leaching. The oxidation was concluded to be by reaction with ferric ion rather than by direct oxygen oxidation. Leaching tests run with samples pretreated with hydrogen do not show any increase in the rate of zinc extraction. M. T. HEPWORTH, formerly with University of Denver.     

Kinetics of nonoxidative leaching of galena in perchloric, hydrobromic, and hydrochloric acid solutions

Several kinetic studies are presented on the nonoxidative leaching of galena with solutions of hydrocloric, hydrobromic, and perchloric acid. The kinetic parameters were set up in terms of the mean ionic activities of the electrolytes. The apparent order of reaction for the mean ionic activity of perchloric acid is one. For hydrochloric acid the order of reaction over a wide range of concentrations is 3/2 with respect to its mean activity. For hydrobromic acid, whose anion has greater complex-forming power for lead than HC1, the order of reaction is 2. Activation energies are 64.4 kJ/mole for HC1, 71.5 kJ/mole for HC10₄, and 66.5 kJ mole for HBr. The complete kinetic equations are given for the three reactions.     

Kinetics of nonoxidative leaching of galena in perchloric,hydrobromic, and hydrochloric acid solutions

Several kinetic studies are presented on the nonoxidative leaching of galena with solutions of hydrocloric, hydrobromic, and perchloric acid. The kinetic parameters were set up in terms of the mean ionic activities of the electrolytes. The apparent order of reaction for the mean ionic activity of perchloric acid is one. For hydrochloric acid the order of reaction over a wide range of concentrations is 3/2 with respect to its mean activity. For hydrobromic acid, whose anion has greater complex-forming power for lead than HC1, the order of reaction is 2. Activation energies are 64.4 kJ/mole for HC1, 71.5 kJ/mole for HC10₄, and 66.5 kJ mole for HBr. The complete kinetic equations are given for the three reactions.     

Effects of mechanical activation on the kinetics of terbium leaching from waste phosphors using hydrochloric acid

The effect of mechanical activation(MA) on the kinetics of terbium(Tb) leaching from waste phosphors using hydrochloric acid was investigated. Leaching kinetics, such as apparent reaction rate, activation energy and reaction order, were determined using the shrinking-core model and the Arrhenius equation. Results obtained from experiments with different concentrations of HCl and under different leaching temperatures were used for the determinations. The impacts of factors such as rotational speed, HCl concentration and leaching temperature on the leaching rate of Tb were also discussed. The results showed that MA could dramatically increase the leaching rate of Tb from waste phosphors, and the apparent reaction rate(k_(ap)) of leaching was accelerated as well. For inactivated waste phosphors, the apparent activation energy(E_(ap)) was 52.82±3.95 kJ/mol, indicating that the rate-controlling step of the leaching process was the chemical reaction. The E_(ap) dropped to 25.96 ±3.90 kJ/mol and 10.96±2.79 kJ/mol when the waste phosphors were mechanically activated at rotational speeds of 400 and 600 r/min, respectively; the leaching process transformed to a hybrid(chemical-reaction and diffusion) control process, and even a reagent-diffusion(through the product layer) control process. The apparent reaction order for Tb leaching from 400 r/min-activated waste phosphors was 2.49±0.11, and it decreased to 1.16±0.17 when the rotational speed of 600 r/min was used. Kinetics results indicated that MA could make Tb leaching occur spontaneously, and the activation intensity of waste phosphors was strengthened with higher rotational speed.