Alkaline Leaching Research Articles

Influence of leaching parameters on the vanadium extraction from petroleum coke

More than 60 trace elements, including rare metals, can be found in heavy oils. The most valuable component of oils and petroleum products is vanadium. It is used as an alloying agent to create extra strong steel, as a cathode for lithium-ion batteries, and also as a catalyst in the chemical industry. Nowadays studies of various methods for extracting vanadium from heavy oils and petroleum products are actively carried out. This work presents the method of alkaline and acid leaching of vanadium from petroleum coke and also results of the examination of influence of factors such as the duration of the process (0.5, 1.5 and 2.5 h) and the ratio of solid and liquid phases (1:2, 1:3 and 1:4). The highest yield of vanadium 80% is observed using sulfuric acid with the process duration is 1.5 hours and the ratio S/L = 1:4

A new route for separation and recovery of Fe, Al and Ti from red mud

Red mud is one kind of by-products rejected from industrial production of alumina plant and characterized by high content of alkaline and containing many valuable metals such as iron, aluminum, titanium, etc. It is urgent to effectively utilize red mud for the sustainable development of aluminum metallurgy industry. In this paper, a new route was proposed to fully recover Fe, Al2O3 and TiO2 from the red mud, which includes three procedures, i.e. pre-reducing-smelting, alkaline leaching and acid leaching. The pre-reducing-smelting step was employed to recover iron from the mud, producing pig iron at an iron recovery of some 98.15% and slag containing 43.17%Al2O3 and 15.71%TiO2, respectively. Then, based on the thermal dynamic calculations, a modification of the slag-alkaline leaching and hydrochloric acid leaching process were conducted to obtain the stepwise recovery of Al2O3 and TiO2, respectively, from the smelting slag. Aluminum and titanium were recovered in the form of sodium aluminum solution and perovskite at a recovery of 85.85% and 95.53%, respectively. The innovative route is probably a potential way to achieve comprehensive and clean utilization of red mud.

Recovery of zinc and lead from Yahyali non-sulphide flotation tailing by sequential acidic and sodium hydroxide leaching in the presence of potassium sodium tartrate

The recovery of zinc and lead from Yahyali non-sulphide flotation tailing using sulfuric acid followed by sodium hydroxide leaching in the presence of potassium sodium tartrate was experimentally investigated. In the acidic leaching stage, the effects of pH, solid-to-liquid ratio and temperature on the dissolution of zinc from the tailing were explored. 82.3% Zn dissolution was achieved at a pH of 2, a temperature of 40 °C, a solid-to-liquid ratio of 20% and a leaching time of 2 h, whereas the iron and lead dissolutions were determined to be less than 0.5%. The sulfuric acid consumption was found to be 110.6 kg/t (dry tailing). The leaching temperature had no beneficial effect on the dissolution of zinc from the tailing. The acidic leach solution was subjected to an electrowinning test. The cathode product consisted of 99.8% Zn and 0.15% Fe. In the alkaline leaching stage, the Pb dissolution increased slightly in the presence of potassium sodium tartrate. More than 60% of Pb was taken into the leach solution when the leaching temperature increased from 40 to 80 °C. The final leach residue was analyzed by XRD and XRF. The XRD results indicated that the major peaks originated from the goethite and quartz while minor peaks stem from smithsonite and cerussite. The XRF analysis demonstrated that the residue contained 70.3% iron oxide. Based on the sequential leaching experiments, the zinc and lead were excellently depleted from the flotation tailing, leaving a considerable amount of iron in the final residue.

Study on the solvent extraction of thioarsenite in alkaline solutions with transformed quaternary ammonium salt

Under the advocacy of the sustainable development concept, the extraction process and reaction mechanism for arsenic in alkaline solution were studied with the aim of optimizing the alkaline leaching process of high‑arsenic copper smelting ash and promoting the recovery and harmlessness of arsenic. At 25 °C, the extractant methyltrioctylammonium underwent 6–8 conversions of Na2CO3 solution with a concentration fraction of 12%, and the extraction capacity of thioarsenite was increased to 86.91%. Furthermore, at 25 °C, at an O/A ratio of 1:1 and an phase contact time of 7 min, the thioarsenite stripping exceeded 99%, when using 4% H2O2 + saturated Na2CO3 solution as the stripping. Fourier transform infrared spectroscopy, nuclear magnetic spectroscopy, ultraviolet spectroscopy, and other analytical methods were used to determine the mechanism of the extraction process. It was evident from our experiments that the CO32−-type TOMAC and Na2CO3 solutions could be recycled and reused repeatedly. The overall process required simple materials and did not generate liquid waste. The technique involves a short process, with superior cycle performance, low cost, and high efficiency.

Recovery of chromium by calcium-roasting, sodium-roasting, acidic leaching, alkaline leaching and sub-molten technology: a review

Chromium is a major strategic mineral widely used in industrial processes, yet mineral resources are decreasing, calling for advanced recycling techniques to recover chromium from ores, waste and contaminated media. Here, we review chromium resources and methods to leach out Cr, such as calcium-roasting, sodium-roasting, acidic leaching, alkaline leaching and sub-molten technology.

Isolation of Zinc, Copper, and Nickel from Glutamate Media by Solvent Extraction

Solvent extraction scheme to isolate Zn, Cu, and Ni from glutamate media as hypothetical product of electric arc furnace dust alkaline leaching was developed, with concentrations being 17.6, 0.35, and 0.14 g/L, respectively. Three extractants were investigated: Cyanex 272, DEHPA, and Acorga M5640 selectively separated Zn, Ni, and Cu from each other. Aside from pH, parameters investigated included O/A ratio, extractant concentration in kerosene as diluent, and sulfuric acid concentration as stripping agent. pH was the most critical factor in determining the separation factor among three metals since pH controlled metal speciation in pregnant leach solution and regulated the interaction between metal ions and extractant. Based on previous studies, a flowsheet for Zn, Cu, and Ni isolation is proposed, which obeys the following sequence: Zn separated from Cu and Ni by Cyanex 272 (in pregnant leach solution at pH 8, log separation factor Zn–Cu 4.78, Zn–Ni 2.51), followed by Ni separation from Cu by DEHPA (in raffinate at pH 7, log separation factor Ni–Cu 3.92), and finally Cu extraction (in raffinate at pH 4, log distribution coefficient 3.19). Sulfuric acid was proved to be a suitable stripping agent with optimum concentrations of Zn, Ni, and Cu being 0.5, 0.25, and 2 M, respectively.

Constructed wetlands for the treatment of bauxite residue leachate: Long term field evidence and implications for management

Alkaline leachate from bauxite residue disposal areas is likely to require treatment for post-closure. Traditional treatment methods are not attractive in the long-term due to management requirement, energy input and operational logistics and passive approaches offer an alternative approach. Constructed wetlands are widely cited as a potential treatment option but there is limited data on long term field-scale applications.Treatment of alkaline residue leachate was assessed over a 52 month period and showed effective pH reductions from ca. pH 11.2 (inflow) to 7.2 (outflow). Trace element content measured during the 4th year of operation demonstrated effective reduction in trace element (Al 17,256 μg/l to 330 μg/l; V 140 μg/l to 13 μg/l) with no evidence of toxicity in test species Vibrio fischeri, Skeletonema costatum, Tisbe battagliai and Oncorhynchus mykiss in the wetland outflow. Sediment analysis found some increases in trace element content but no evidence of accumulation in Phragmites was found in vegetation sampling.Longevity and management requirements for constructed wetland treating alkaline bauxite residue leachate are more likely to be impacted from increases in soil Na and pH. Increases are more evident in front sections of wetland but it is proposed that loading to wetlands can be decreased by incorporation of other passive technologies within the overall treatment approach and by feeding different sections of the wetlands on a cyclical basis.

Comparison of dried sludge and sludge ash for phosphorus recovery with acidic and alkaline leaching

AbstractNowadays, the recovery of phosphorus has been in the spotlight due to its importance for food security and depleting sources. In this study, phosphorus recovery from dried sewage sludge and sludge ash by acid and alkaline leaching was evaluated. Optimum extraction time and temperature were determined as two hours and ambient temperature. Results showed the superiority of strong acidic conditions for leaching; 75 ml/g with 0.4N HCl and 25 ml/g with 0.6N HCl were determined as optimum conditions to achieve efficient phosphorus dissolution from sludge ash (94.6%) and dried sludge (91.1%), respectively, with the lower heavy metal concentrations. Lower L/S ratio put forward the dried sludge as a more advantageous resource for phosphorus extraction. Besides, by alkaline leaching of sludge ash and dried sludge, 60.3 and 70.3% phosphorus dissolutions were achieved with 75 ml/g and 1N NaOH; and the leachate was a suitable product for phosphorus precipitation due to its high pH.

Modeling hydration of mine tailings: Production of hydraulic binders from alkali-activated materials

The production of alkali-activated materials and geopolymers from the finer fraction of tailings is being increasingly investigated, as they could be used for building and public works, or to retain heavy metals in a consolidated solid matrix. The present study proposes a Pitzer-based geochemical model to reproduce the alkaline leaching for two mine tailing samples and the polymerization reactions. The model fits the results of the leaching tests quite well over the reaction duration and up to NaOH 10 M and 60 °C. Discrepancy for the dissolved Mg concentration indicates that the database can handle ionic strength up to 5 mol.kg−1. A geopolymer solid solution was developed for setting reactions modeling. The results compare favorably with compressive strength tests results, with C-S-H, M-S-H and geopolymers as the main hydration products. The study proposes an innovative application of Pitzer database developments with application to the mining industry.

Reducing Environmental Pollution of Fuel Fly Ash by Extraction and Removal Vanadium Pentoxide

In the current project, V2O5 extraction from fuel fly ash was carried out, and the advanced extraction method was investigated. This reduced the percentage of industrial fuel fly ash residue pollution in the environment. The project was done with two materials: V2O5 and fuel fly ash. The extraction method includes alkaline leaching, pH regulation, ammonium compounds addition, and calcination. The experiment was identified using V2O5 as the primary material. Under the optimum amounts, the extraction efficiencies of V2O5 reached 92.9%, 92.9%, 99.6%. moreover, V2O5 eliminated over 90% of fuel fly ash. The obtained products were characterized using X-ray powder diffraction (XRD), Alkaline fusion-ICPMMS, Ultraviolet-visible (UV-Vis), and Fourier Transform infrared (FT-IR).

High-efficiency core-shell magnetic heavy-metal absorbents derived from spent-LiFePO4 Battery

Search for simple and efficient recycling methods to utilize spent lithium-ion batteries is crucial for achieving sustainable resource development and reducing the hazardous materials released from the spent batteries. Herein, we have developed a new strategy to utilize the spent LiFePO4 batteries by utilizing the cathode plate as raw material to synthesize mesoporous core-shell adsorbent Mm@SiO2 (Mm denoted as the magnetic material) through a simple alkaline leaching process. The as-converted material exhibits excellent adsorption capacity when it has been used to remove heavy metal ions in heavy metal polluted water. The adsorption capacities for Cu2+, Cd2+, and Mn2+ have been achieved up to 71.23, 80.31 and 68.73 mg g−1, respectively. The detailed adsorption mechanism has been elucidated with comprehensive characterization techniques, including TEM, XPS, NEXAS, and EXAFS, the edge shared [Cu2O8] bipyramids can be fit against the EXAFS data to represent the atomic-scale local structure after Mm@SiO2 adsorbs Cu2+. The present work demonstrates a novel routine to reutilize the spent lithium batteries, which is of great importance to achieve sustainable development based on the “waste-to-treasure” and “waste-to-control-waste” strategy for simultaneously reducing the hazardous release from industrial solid waste and heavy metal polluted water.

Recycling of copper telluride from copper anode slime processing: Toward efficient recovery of tellurium and copper

Copper telluride is a sort of solid waste generated from copper anode slime processing, from which the recovery of copper and particularly the high-value element of tellurium always encounter technical difficulties due to the complex physicochemical properties of tellurium. In this study, an efficient and compact process for copper telluride recycling has been developed. Efficient separation of tellurium and copper from copper telluride was achieved through a pressure oxidizing alkaline leaching process under the optimal conditions of 5 mol/L for NaOH concentration, 5:1 for liquid to solid ratio, 150 °C for temperature, 0.7 Mpa for system pressure, and 2 h for reaction time, by which over 95% of tellurium was selectively dissolved in the solution and copper was enriched in the solid phase mainly in the form of copper oxides. Tellurium was subsequently recovered as TeO2 by neutralization of the alkaline leaching solution with sulfuric acid to pH 4.5, delivering a TeO2 precipitation efficiency of over 95%. In general, the masses of tellurium and copper balanced well in both the liquid and solid phases for each step, and the overall recovery efficiencies of Te and Cu reached as high as approximately 91% and 98%, respectively.

High- and low-temperature mineral phases from the pyrometamorphic rocks, Jordan

The present review of high- and low-temperature minerals demonstrates the value of the pyrometamorphic rocks, altered varicolored marble (cement zones), travertine, and regolith in Jordan as analogues of cementitious repositories. The alkaline leachate contains hazardous elements such as Zn, Cd, Fe, Ni, Cu, V, Cr, Fe, Mo, As, Co, U, etc. The sites offer a good chance to investigate the interaction of the circulating high alkaline water with the rocks. The unusual high- and low-temperature minerals proved to be durable elements immobilizers which act as sinks for hazardous trace elements. The identified minerals and the solid solution series are indicators of the long-term behavior of natural analogues of cement-dominated repositories.

Investigation of Alkaline Leaching Parameters on Stibnite Concentrate

According to critical statistical studies, antimony is one of the rarest elements in the world, and global resources could be exhausted by 2050. In light of these observations, its extraction will be costly due to poor-quality ore, deep mining, remote locations, and high energy consumption. In the present study, an alkaline leaching process was carried out on stibnite concentrate to evaluate the effect of reaction parameters on the percentage of antimony extraction. The leaching efficiencies of different sulfur and hydroxide sources were studied and compared to one another to create a better understanding of the reaction process. Kinetic models were investigated to identify the reaction pathway and calculate the activation energy. The activation energy of the stibnite dissolution was assessed as 19.13 kJ/mol using a two-dimensional diffusion-reaction model. The value of activation energy indicates the quantity of energy necessary for a reaction to proceed. As expected, potassium hydroxide leaching was significantly more successful than was sodium hydroxide; however, in terms of economics, the use of sodium hydroxide was found to be more cost-efficient. Interestingly, this finding indicated that caustic leaching is still the most effective method for stibnite extraction.

An environmental-friendly process for recovery of tellurium and copper from copper telluride

In the present study, a novel process for effective recoveries of Te and Cu from copper telluride from anode slime processing in copper smelters was proposed. The process consists of two hydrometallurgical steps of atmospheric alkaline leaching for Cu and Te separation, and TeO2 precipitation with H2SO4 for Te recovery. The effects of NaOH concentration, liquid to solid ratio, temperature, H2O2 to Cu2Te mole ratio, and reaction time on the dissolution behavior of tellurium were investigated. A Te leaching efficiency of about 91% was obtained under the optimal experimental conditions. The results of thermodynamic and kinetic analysis indicate that a lower temperature is favorable for the dissolution of Te, and mass transfer inside the solid particle is the rate-determining step. In addition, a mechanochemical-assisted leaching was conducted, by which Te leaching efficiency was enhanced to approximately 93% with ball milling at 180 rpm for 5 h. After Te leaching, H2SO4 was utilized to adjust the pH value of the Te-containing alkaline leach solution to 4.5 for TeO2 precipitation. The crystallization of TeO2 can be completed by reacting for 1 h and the overall tellurium recovery has reached nearly 90%.

Recovery of vanadium(V) from synthetic and real leach solutions of spent catalyst by solvent extraction using Cyphos IL 104

This study addresses the extraction and recovery of vanadium(V) from synthetic and real leach solution of spent V2O5 catalyst using Cyphos IL 104. Vanadium(V) is extracted as [(R3R′P+)4H2V10O284−]org in Cyphos IL 104 and stripped from the loaded organic phase as VO2+ using HNO3 as a stripping agent. The extractant is recyclable up to several cycles and shows high loading capacity. Vanadium(V) was separated from aluminium(III), titanium(IV), chromium(III), manganese(II), iron(II)/(III), molybdenum(VI) and tungsten(VI) with good separation factors. Metals were leached from spent catalyst using alkaline leaching. McCabe-Thiele plots indicated two stages for both extraction and stripping at A/O and O/A = 3/1. Vanadium is finally recovered as V2O5 from the strip liquor and characterized by XRD, FE-SEM and EDX techniques.

Desilication and recycling of alkali-silicate solution seeded with red mud for low-grade bauxite utilization

When low-grade high-silica bauxite undergoes desilication by alkaline leaching, a large amount of alkali-silicate solution will be produced. To realize its recycling, the alkali-silicate solution needs to be desiliconized. In this study, the effectiveness of red mud and a mixture of red mud and CaO as desilication reagents of the alkali-silicate solution are compared and the desilication mechanisms were analyzed. Results show that when adding 30–50g/L of red mud, the desilication rate is only 36–38% while adding 30g/L of red mud and CaO mixture with a calcium-silicon ratio of 1 reaches a desilication rate of ∼89%. Analyses by SEM-EDS and other mean show that this is mainly due to the growth of sodalite seed crystals in red mud and its synergistic desilication with CaO. Bauxite underwent cyclic desilication and the alumina/silica ratio was increased from ∼4.1 to >7.5. Effective utilization of red mud and alkali-silicate solution greatly reduces the cost of the desilication process, thereby making it applicable to low-grade bauxite in the Bayer process.

Selective leaching of arsenic from copper converter flue dust by Na2S and its stabilization with Fe2(SO4)3

Abstract The alkaline leaching of arsenic (As2O3) by Na2S, together with its precipitation by Fe2(SO4)3 was studied. Response surface methodology based on central composite design was employed to quantify and qualify the effect of pertinent factors and to develop statistical models for optimization purposes. Based on the obtained results, 89% of arsenic is removed from the dust under following optimum predicted conditions: Na2S concentration of 100 g/L and solid to liquid ratio of 0.163 g/mL at 80 °C. It is found that solid to liquid ratio and Na2S concentration are the significant factors influencing the leaching process. In the precipitation process, more than 99.93% of arsenic from the leaching solution is removed in the form of amorphous ferric arsenate, at pH 4.8 when Fe3+ to arsenic and H2O2 to arsenic molar ratios are set at 5:1 and 4:1, respectively. Also, Fe3+ to arsenic ratio and pH are the most significant factors, and the interaction between these terms is significant.

Concentration of Rare Earth Elements (Sc, Y, La, Ce, Nd, Sm) in Bauxite Residue (Red Mud) Obtained by Water and Alkali Leaching of Bauxite Sintering Dust

One of the potential sources of rare-earth elements (REE) is the industrial waste known as red mud (bauxite residue), in which the majority of REE from the initial bauxite are concentrated via the Bayer process. Therefore, the studies of the subject, both in Russia and outside, focus almost exclusively on red mud processing. This article looks into the possibility of REE concentration into red mud by leaching an intermediate product of the bauxite sintering process at Russian alumina refineries, namely electrostatic precipitator (ESP) dust. The experimental works were performed by X-ray diffraction (XRD)and electron probe microanalysis (EPMA) of the sinter and sinter dust. The determination of major and rare-earth elements in the sinter from the rotary kilns and in the ESP dust before and after leaching was carried out by X-ray fluorescence (XRF) and plasma mass spectrometry (ICP-MS). The study showed that it is possible to obtain red mud that contains three times more REE than traditional waste red mud after two-stage leaching ESP dust in the water at 95 °C followed by leaching in an alkaline-aluminate liquor at 240 °C. The shrinking core model was used to study the kinetics of leaching of the original ESP dust and water-treated dust in alkaline-aluminate liquor. The study showed the change in the limiting stage of the alkaline leaching process after water treatment, with the activation energy growing from 24.98 to 33.19 kJ/mol.

Monosodium Glutamate as Selective Lixiviant for Alkaline Leaching of Zinc and Copper from Electric Arc Furnace Dust

The efficacy of monosodium glutamate (MSG) as a lixiviant for the selective and sustainable leaching of zinc and copper from electric arc furnace dust was tested. Batch leaching studies and XRD, XRF and SEM-EDS characterization confirmed the high leaching efficiency of zinc (reaching 99%) and copper (reaching 86%) leaving behind Fe, Al, Ca and Mg in the leaching residue. The separation factor (concentration ratio in pregnant leach solution) between zinc vs. other elements, and copper vs. other elements in the optimum condition could reach 11,700 and 250 times, respectively. The optimum conditions for the leaching scheme were pH 9, MSG concentration 1 M and pulp density 50 g/L. Kinetic studies (leaching time and temperature) revealed that the saturation value of leaching efficiency was attained within 2 h for zinc and 4 h for copper. Modeling of the kinetic experimental data indicated that the role of temperature on the leaching process was minor. The study also demonstrated the possibility of MSG recycling from pregnant leach solutions by precipitation as glutamic acid (>90% recovery).