Concentration Of Leaching Solution Research Articles

Optimization of Hydrochemical Leaching Process of Kaolinite Fraction of Bauxite with Response Surface Methodology

A technology for the hydrochemical processing of the kaolinite fraction of bauxite has been developed, and it involves preliminary chemical activation in a sodium bicarbonate solution and alkaline leaching in a recycled high-modulus solution with the addition of an active form of calcium oxide. Chemical activation allows for the transformation of the difficult-to-explore kaolinite phase to form easily soluble phases of dawsonite, sodium hydroaluminosilicate and bemite. An active, finely dispersed form of calcium oxide was obtained as a result of CaO quenching in Na2SO4 solution at elevated temperature and pressure. Using a central composite design (CCD) via response surface methodology (RSM), the technological leaching mode was achieved. The influence on the leaching process was studied by adjusting the CaO/SiO2 ratio, temperature, alkaline solution concentration and duration. It was found that the determining factors are the concentration of the leaching solution and the temperature. At a stable CaO/SiO2 ratio, a combination of these two factors determines the duration of the process to achieve the predicted degree of recovery. The results of experiments carried out using the developed model of the leaching process confirmed the validity of the calculated indicators, with an error of 2.01%. In an optimal technological mode at a Na2O leaching solution concentration of 260 g/L, a temperature of 260 °C, a CaO/SiO2 ratio of 1.5 and a leaching time of 5 h, the extraction of Al2O3 into the solution was 89.7%, which is close to the value of 87.9% predicted by the model.

Research on the saturated/unsaturated seepage laws of ionic rare earth ore under different leaching conditions

The seepage law of the ionic rare earth leaching process plays an important role in the efficient development and utilization. The saturation permeation test of ionic rare earth under different leaching conditions was carried out using the variable head method, and the influence of type, concentration, and leaching path on the saturation permeability coefficient was revealed. The relationship between the water content and the matric suction of ionic rare earths under different leaching conditions was measured with the Geo-Experts pressure plate apparatus, and the soil-water characteristic curves under different leaching conditions were obtained. Based on the soil-water characteristic curve model, the unsaturated permeability coefficient function of ionic rare earths under different conditions was studied. The results show that the saturated-unsaturated permeability coefficients of ionic rare earths are pure water, 3% (NH4)2SO4, and 3% MgSO4, in descending order, when the type of leaching solution is different. For different concentrations of the leaching solution, when the concentration of (NH4)2SO4 increases from 2% to 5%, the saturated permeability coefficient first increases and then decreases. The matrix suction is an important factor affecting the unsaturated permeability coefficient when the ore body is unsaturated, and the unsaturated permeability coefficient decreases with the increase of the leaching solution concentration under the same matric suction. The seepage law is related to the leaching path, and the permeability coefficient increases when leaching at high concentrations followed by low concentrations, in reverse order, the permeability coefficient decreases. The research results can provide theoretical guidance for the design of injection parameters, and improve the theory of in-situ leaching.

Effects of Fe+2 and Fe+3 in Pretreatment and Leaching on a Mixed Copper Ore in Chloride Media

A study of the pretreatment stage and subsequent leaching of a mixed copper ore with different chloride solutions containing iron was carried out. The first stage considered pretreatment tests to decide the best conditions. Two levels of each factor were analyzed, 20 and 50 kg/t of NaCl, 17 and 25 kg/t of H2SO4, 0 and 25 kg/t of Fe2(SO4)3·9.2H2O, 0 and 25 kg/t of Fe2SO4·7H2O, and a curing time of 15 and 30 days. The results showed a significant effect of NaCl and curing time on the extraction, and less effect was found with the variation of acid and iron salts. The second stage included column leaching using a solution with 0.5 g/L of Cu+2, 80 g/L of Cl−, 10 g/L of H2SO4, and variable concentrations of ferric and ferrous ions (0 and 2 g/L). The best copper extraction of 80.2% was found considering a pretreatment of 30 days, 25 kg/t of H2SO4, 50 kg/t of NaCl, and a leaching solution concentration described previously with 2 g/L of Fe+2. The results showed the leaching of all copper oxide species and 20% of the copper sulfide species. In addition, there was a reduction in the acid consumption as the resting time increases. Furthermore, to evaluate a possible decrease in time and acid in pretreatment and chloride in leaching, tests including 10 and 25 kg/t of H2SO4 and 1, 15, and 30 days of curing and a diminution of the NaCl concentration to 20 g/L (content from seawater) were executed. The results showed a significant effect on curing time below 15 days. Furthermore, the slight influence of the decrease of acid on copper extraction gives cost reduction opportunities. The diminution of chloride concentration (80 to 20 g/L) in leaching solution decreases the extraction from 79% to 66.5%. Finally, the Mellado leaching kinetic model was successfully implemented.

Extraction of vanadium and enrichment of titanium from modified Ti-bearing blast furnace slag

An alkali leaching-acid leaching method was proposed to extract vanadium and enrich titanium from modified Ti-bearing blast furnace slag (MTBBFS). The optimal alkali leaching conditions were NaOH concentration 2.0 mol/L, leaching temperature 95 °C, and leaching time 90 min. The leaching ratio of V was 91.30%. After 4 times cyclic alkaline leaching, the vanadium concentration of leaching solution increased to 14.70 g/L and the solution could be used to recover vanadium by the precipitation of ammonium salt. The optimum acid leaching conditions were HCl concentration 2.0 mol/L, leaching temperature 65 °C, and leaching time 60 min. The TiO2 content of synthetic rutile and the total recovery ratio of Ti were 99.15% and 97.77%, respectively. Due to the TiO2 content of the rutile >99.00%, the rutile was a high-quality feedstock for titanium dioxide with the chloride process. Moreover, the mechanism of vanadium extraction and the mechanism of alkali leaching-acid leaching reaction process were discussed

In situ recovery of copper sulfide ores: Alternative process schemes for bioleaching application

There is a growing interest in exploring the application of bioleaching for treating copper sulfide ores of decreasing grade and located at larger depth by in situ recovery (ISR) for its potential savings in ore extraction, crushing, grinding and the avoidance of tailings. As copper sulfide ores are usually present in well consolidated rocks a crucial aspect for ISR to be successful is to increase the ore permeability in order to allow a good access of solution to the valuable metal values. However, in bioleaching an additional critical aspect is to guarantee an adequate supply of oxygen, the final electron acceptor in the reaction chain. Two alternative schemes to solve this issue are here characterized and compared using process simulation.One approach considers pre-treating the rock with hydrofracturing and/or confined blasting in order to create a network of cracks adequate for pumping the pressurized leaching solution into the ore bed in a saturated flow regime. In this scheme oxygen needs to be added in an external bioreactor where ferric iron is generated by bacterial oxidation of ferrous iron. A second approach considers pre-treating the ore by application of sublevel stopping techniques with partial removal of the rock to be able to irrigate the solution into the ore bed under an unsaturated flow regime. In this scheme oxygen can be directly supplied into the ore bed enabling in situ generation of ferric iron by the oxidative action of microorganisms present in the ore.The influence of irrigation rate, leaching solution concentration, bacterial population and ore bed dimensions on copper recovery and bioreactor requirements was assessed for these two process schemes. Some economic aspects of these two alternatives are discussed.

Grain Size Distribution and Clay Mineral Distinction of Rare Earth Ore through Different Methods

Although clay mineral content in ion-absorbed rare earth ores is crucial for migrating and releasing rare earth elements, the formation, distribution, and migration of clay minerals in supergene rare earth ores have not been fully understood. Therefore, this study analyzes the characteristics of clay mineral type and content, soil particle size, pH value, leaching solution concentration, and leaching rate. This analysis was performed using different methods, such as regional rare earth mine soil surveys, in situ leaching profile monitoring, and indoor simulated leaching. The results showed that the grain size and volume curve of rare earth ore have unimodal and bimodal shapes, respectively. X-ray diffraction showed the differences in clay mineral types formed by different weathered bedrocks. The principal clay minerals were kaolinite, illite, chlorite, and vermiculite, with their relative abundance varying with parent rock lithology (granite and low-grade metamorphic rocks). In the Ganxian granite weathering profile, the kaolinite content increased from top to bottom. The decomposition of feldspar minerals to kaolinite was enhanced with an increase in the SiO2 content during weathering. The in situ leaching profile analysis showed that the kaolinite content increased initially and then decreased, whereas the illite/mica content exhibited the opposite trend. Under stable leaching solution concentration and leaching rate, clay mineral formation is favored by lower pH. Low pH, low leaching rate, and highly-concentrated leaching solution (12 wt%) resulted in a slow increase in kaolinite content in the upper part of the profile (30 cm). A lower concentration of the leaching solution (4 wt%) resulted in rapid enrichment of kaolinite after 15 days. Low pH, leaching solution concentration, and leaching rate promoted the formation of distinct kaolinite horizons. We suggest that by disregarding other control factors, rare earth recovery of over 90% can be achieved through leach mining with solutions of 8 wt% and a pH of 5 at a leaching rate of 5 mL/min.

Ultrasonic-enhanced replacement of lead in lead hydrometallurgy process from lead leaching solution.

In this paper, ultrasonic-enhanced replacement of lead by zinc in lead leaching solution was studied. The effects of reaction time, rotational speed, temperature, concentration of leaching solution and the ratio of the surface area of the zinc plate immersed in the leaching solution to the volume of leaching solution (S : V) were studied under both conventional and ultrasonic conditions. The optimum ultrasonic-assisted replacement conditions were as follows: the S : V of 0.04 (4 cm2 100 ml−1), reaction temperature of 30°C, replacement time of 30 min and the concentration of leaching solution is 5 g l−1, leading to a lead replacement rate of 94.84%. Compared with the conventional replacement process, the reaction time of ultrasonic-enhanced substitution could be reduced to one half, and the demand of reaction temperature, leaching solution concentration and other conditions were decreased accordingly. Introducing ultrasonic into the replacement reaction is promising to reduce the energy consumption in the hydrometallurgical industry also caters to the demands of environment protection.

从铜转炉烟尘中制备高纯氯氧化铋工艺研究

本文采用“稀硫酸浸出–氧化剂 + 稀硫酸浸出–固相预脱铅–氯盐浸出–浸铋液中除铅砷–沉铋”工艺处理铜转炉烟尘制备氯氧化铋。首先，前两步浸出，均在L/S = 2: 1，t = 1 h，T = 60℃的条件下水浴浸出，使大部分可溶解元素如Cu、Zn、Sn等进入溶液，Pb、Bi等留在渣中。其次，在L/S为5:1，室温下使用pH值为4.5的缓冲溶液，处理二次浸铜渣，进行固相预脱铅；再次，用改性试剂处理浸铋液，去除铅砷。结果表明，室温条件下，盐酸浓度为1 mol∙L−1，氯化钠浓度为2.5 mol∙L−1，液固比为5:1时，铋的平均浸出率达到92%，而浸出液浓度为0.20~0.30 mol∙L−1。用质量分数为1.66%的Na2CO3溶液调节酸浸液的pH值由0.5至3.0左右，沉铋。综上几步，此工艺能将有价金属元素铜、铋有效回收利用，铜的浸出率由原来的40%提高到70%以上；砷在氯氧化铋的含量从3.80%降到0.03%，去除率达到99.21%；铅在氯氧化铋的含量从3.46%降到0.189%；去除率达到96.39%；最后，沉铋后的氯盐溶液返回处理二次浸铜渣。 The process of “dilute sulphuric acid leaching-oxidant + dilute sulphuric acid leaching-initial delead from solid phase-chloride leaching-removal of lead and arsenic from dip bismuth solution- bismuth precipitation-dearsenication” was used for preparation of high-purity bismuth oxychloride from copper converter flue dusts. Firstly, dilute acid and manganese dioxide + dilute acid mixture were used as leaching agent, under the condition of 60˚C water bath, the liquid-solid ratio 2:1, leaching 1 h respectively, so that most solubility elements such as Cu, Zn, Sn could enter solution and lead, and bismuth stays in slag. Secondly, the configured solution is used with pH = 4.5 at room temperature. Under the condition of solid-liquid ratio of 5:1, treated with secondary leaching of copper residue, the purpose is to take off the lead for solid phase. Thirdly, bismuth leaching liquid was treated with modified reagents, in order to reduce metal elements of lead and arsenic content in the solution. The results showed that acid leaching under the condition of the room temperature, 1 mol∙L−1 HCl, 2.5 mol∙L−1 NaCl, and the liquid-solid ratio 5:1, was feasible, and the average extraction rate of bismuth reached 92%, while the leaching solution concentration of bismuth was 0.20 - 0.30 mol∙L−1. The pH value of leaching solution was adjusted with the sodium carbonate solution with the mass fraction of 1.66%. With the addition of sodium carbonate solution, the pH value increased from 0.5 to 3. The purpose is to deposit bismuth. In a comprehensive view, through this process, copper and bismuth as the valuable metals get an effective recycling. The leaching rate of copper was increased from 40% to 70%. This process can effectively separate the Bi from other elements. The content of arsenic in bismuth oxide decreased from 3.80% to 0.03%, and the removal rate reached 99.21%. The content of lead in bismuth oxide decreased from 3.46% to 0.189%, and the removal rate reached 96.39%. Finally, solution after Bi precipitation is treated with hydrochloric acid and sodium chloride mixed solution, and the solution is returned to leaching bismuth.

Anion Transport in Columns of Variable Charge Subsoils: Nitrate and Chloride

AbstractAcid variable charge subsoils exhibit a positive charge, which retards the passage of anions through the soil profile. The objective was to study the NO−3 adsorption isotherms and the effect of changing the subsoil positive charge on NO−3 and Cl− retention, estimate NO−3 and Cl− retardation in different subsoils, and quantify relationships between transport and adsorption parameters. Subsoils from different subtropical and tropical areas were used in column experiments. Four lime treatments and four leaching solutions were used to create different anion exchange capacities (AECs) in subsoils. In the Cecil subsoil (Fine, kaolinitic, thermic Typic Kanhapludult), NO−3 isotherms were linear between 5 and 30 mmol NO−3 L−1. When forced through the origin, an L‐curve NO−3 isotherm was observed at native and low soil pH. The NO−3 adsorption was largely affected by the changes in both pH and concentration of the leaching solution. Other variable charge subsoils have varying capacities to retard anions, which is reduced when either soil pH or leaching solution concentration is increased. Both parameters equally reduce the distribution coefficient Kd and the retardation coefficient R. The AEC correlates closely with R and Kd. As a result, AEC can be successfully used in the solute transport models to estimate Kd or R without measuring it to correct for the NO−3 retardation.

Nutrient Retention and Release Characteristics From Municipal Solid Waste Compost

A bench-scale laboratory study was conducted to examine municipal solid waste (MSW) compost nutrient dynamics. Two MSW compost batches varying in stability were compared for their ability to retain or leach total Ca, Mg, K, P, and N. Composts were leached with 150 ml of deionized water or one of two concentrations of nutrient solution 12 times over a six-week period. Increasing the concentration of nutrient leaching solutions generally resulted in no significant differences in leachate nutrient mass. Water soluble Ca, Mg, and K leached from both composts during the first four leachings and accounted for most of the total elemental mass lost from composts. Both composts had low C:N ratios (below 20:1) and substantial mineral N was added as soluble NO3−, but little mineral N appeared in leachates, or in an organic form in the composts after leaching ceased. Both composts C:P ratios were below 200:1, but the total P mass in leachates was generally low and declined steadily despite repeated addition of mineral P to composts. The least stable MSW compost (Compost B) released a significantly greater mass of Ca and Mg and retained more P than the more stable compost (Compost A). In general, outputs of Ca, Mg, and K were greater than inputs for all compost treatments, while inputs of P were greater than outputs. Total N outputs nearly equaled inputs, but total N accumulations were not noticed in the final compost analysis, suggesting denitrification occurred. In all but one case, increasing the nutrient leaching solution concentration did not induce development of statistically different concentration gradients in compost leaching tubes. This suggests nutrient leaching solutions depleted the compost of nutrients uniformly before an equilibrium was reached between the compost and compost solution.

ROLE OF IN-SITU PRODUCED METHANOL ON THE CATALYST DEACTIVATION IN THE LIQUID PHASE METHANOL SYNTHESIS PROCESS

ABSTRACT The role of methanol produced in-situ in the liquid phase methanol synthesis process has been experimentally examined. The catalyst crystallite size is found to be more stable when the produced water and methanol are consistently removed from the catalyst active sites. The experimental evidence shows that in-situ produced water is not the only culprit for the catalyst crystallite size growth, rather, methanol is also responsible for contributing to crystallite growth and therefore catalyst deactivation Hydrothermal leaching of the catalyst was also determined to be an active participant in catalyst deactivation. Two experimental designs were run to assess the influence of temperature, leaching solution concentration and pretreatment conditions on the extent of leaching of the methanol synthesis catalyst. Water and methanol were found to be active participants in the reduction of catalyst activity. Hence, the methanol/water solutions serve as potentially harmful agents in the leaching of aluminum ...

Leaching Kinetics of Platinum and Palladium from Spent Automotive Catalysts

Abstract Empirical rate expressions for both platinum and palladium were obtained from mass balances and concentration-time data in a packed bed reactor using different (HCl):(HNO3) leaching solution concentration ratios. The spent catalysts used in this study (-60+70 mesh to -120+140 mesh) were analyzed to be 3791 ppm platinum and 1306 ppm palladium. High initial rates for both platinum and palladium were obtained for the early stages of leaching and were followed by rapid decay up to about 110 minutes and 50 minutes respectively. Typical concentrations in the leached solution were about 40 ppm Pt and 20 ppm Pd after about 5 hours for the experimental conditions used. The extent of reaction for platinum was in the 90 percent range while that of the palladium was in the 70 percent range.

Leaching of Container Media

Abstract Leaching of salt from container media was investigated by means of the miscible displacement theory for 6 peat-perlite-glass bead combinations plus 4 other mixes. Columns were salinized with 15 meq 1−1 each CaCl2 and NaCl, then allowed to equilibrate. Electrical conductivity of the effluent was recorded as columns were leached, using 1 cm constant water head, with solutions of 1, 4, or 7 meq 1−1 each of CaCl2 and NaCl. The replacement efficiency of the soil solution by the leaching solution increased as glass bead content increased. Replacement efficiency of the soil solution had high correlation with mixture physical properties. No relationship to particle size distribution could be ascertained. Leaching solution concentration did not influence replacement efficiency and, generally, after 1 to 1.5 container capacities of effluent, removal of the original soil solution decreased substantially.