Aluminum Precipitation Research Articles

Resource Recovery from Abandoned Mine Drainage Galleries via Ion Exchange: A Case Study from Freiberg Mining Area, Germany

The discharge of metal-loaded mining-influenced waters can significantly pollute downstream water bodies for many kilometers. Addressing this issue at the earliest discharge point is crucial to prevent further contamination of the natural environment. Additionally, recovering metals from these discharges and other sources of contamination can reduce the environmental impacts of mining and support the circular economy by providing secondary raw materials. This study focused on optimizing zinc recovery from mining-influenced water in the Freiberg mining region in Germany, where significant loads of zinc are released into the Elbe River. By employing pretreatment techniques, conducting 100 mL scale ion-exchange column experiments, and refining the regeneration process, we aimed to identify optimal conditions for efficient zinc removal and recovery. Initial tests showed that aminophosphonic functionalized TP 260 resin had a high affinity for aluminum, occupying 93% of the resin’s capacity, while zinc capacity was limited to 0.2 eq/L. To improve zinc recovery, selective precipitation of aluminum at pH 6.0 was introduced as a pretreatment step. This significantly increased the zinc loading capacity of the resin to 1 eq/L. Under optimal conditions, a concentrated zinc solution of 18.5 g/L was obtained with 100% recovery. Sulfuric acid proved more effective than hydrochloric acid in eluting zinc from the resin. Further analysis using SEM-EDX revealed residual acid on the resin, indicating a need for additional study on long-term resin performance and capacity variation. The research also highlighted the environmental impact of the Freiberg mining area, where three drainage galleries currently contribute nearly 85 tons of zinc annually to the Elbe River. This study underscores the feasibility of efficient zinc recovery from these point sources of pollution using advanced ion-exchange processes, contributing to circular economy efforts and environmental conservation.

Selective Precipitation of REE-Rich Aluminum Phosphate with Low Lithium Losses from Lithium Enriched Slag Leachate.

Currently, recycling of spent lithium-ion batteries is carried out using mechanical, pyrometallurgical and hydrometallurgical methods and their combination. The aim of this article is to study a part of the pyro-hydrometallurgical processing of spent lithium-ion batteries which includes lithium slag hydrometallurgical treatment and refining of the obtained leachate. Leaching was realized via dry digestion, which is an effective method capable of transferring over 99% of the present metals, such as Li, Al, Co, Cu, and others, to the leachate. In this work, the influence of three types of precipitation agents (NaOH, NH4OH, Na3PO4) on the precipitation efficiency of Al and Li losses was investigated. It was found that the precipitation of aluminum with NaOH can result in the co-precipitation of lithium, causing total lithium losses up to 40%. As a suitable precipitating agent for complete Al removal from Li leachate with a minimal loss of lithium (less than 2%), crystalline Na3PO4 was determined under the following conditions: pH = 3, 400 rpm, 10 min, room temperature. Analysis confirmed that, in addition to aluminum, the precipitate also contains the REEs La (3.4%), Ce (2.5%), Y (1.3%), Nd (1%), and Pr (0.3%). The selective recovery of these elements will be the subject of further study.

Removal of iron and aluminum from hydrometallurgical NMC-LFP recycling process through precipitation

There is a need to develop removal strategies for typical battery impurities–iron and aluminum–from actual hydrometallurgical recycling solutions. In this work, the investigated solution originated from lithium nickel manganese cobalt oxide (NMC) rich black mass, while iron phosphate (LFP) was used as an in situ reductant. It was found that the presence of phosphate ions supported selective iron precipitation already at pH = 2.0 (T = 60 °C, t = 3 h, NaOH), with nearly complete iron removal (97.8 %). The precipitate was rich in iron (21.5 wt%) and phosphorus (13.4 wt%); it also contained 0.7 wt% Ni and 0.3–0.4 wt% Mn, Co, Al, and Li. It is suggested that the presence of phosphate in minor amounts may cause this co-precipitation of battery metals. With the aim of combined precipitation of iron (100 %) and aluminum (91.0 %), the pH was increased up to 4.5. Although 90.8 % of fluoride precipitated, the remaining fluorides may have kept the aluminum partially in soluble form as Al-F complexes. The formed precipitate had lower iron (18.4 wt%) and phosphorus (11.4 wt%) content, whereas the impurity contents and thus the battery metals losses were slightly higher: Ni, Mn, Co, Al, and Cu were each between 1.1–1.9 wt% and Li and F < 1 wt%. In the precipitates investigated, iron was found predominantly as iron phosphate (FePO4), whereas a minor fraction also precipitated as iron fluoride (FeF3). The precipitated aluminum existed mainly as AlOOH. The results presented here will help to build iron and aluminum removal strategies for industrial battery recycling solutions, and also provide insights into the dominant iron and aluminum phases forming the precipitates.

Recovery of aluminum, vanadium, and nickel from waste desulfurization catalyst residue by roasting and water leaching

The improper disposal of hydrodesulfurization (HDS) catalysts poses significant environmental risks due to the presence of toxic materials and metals. This study investigates a method for recovering valuable resources, specifically aluminum, vanadium, and nickel, from industrial waste HDS catalyst residue. The process involves roasting the HDS residue at 300°C for 120 min with a 1:1 solid-to-liquid (S/L) ratio of residue to sodium hydroxide (NaOH). Subsequent water leaching resulted in the recovery of approximately 99% of Al(III) and V(V). The leaching kinetics of Al(III) and V(V) were found to follow the Shrinking-Core model, described by the equations X = kc.t and 1 − (1 − X)1/2 = kc.t, with activation energies (Ea) of 7.39 kJ/mol and 4.61 kJ/mol, respectively. The leach liquor containing Al(III) V(V) was treated with concentrated hydrochloric acid (HCl) at pH 9.5 to precipitate aluminum salt, while vanadium was extracted using ammonium chloride (NH4Cl) by adjusting the pH to 7.1 at 50°C for 30 min. The residual material was leached with 5% (v/v) sulfuric acid (H2SO4) in the presence of 15% (v/v) hydrogen peroxide (H2O2) to achieve maximum nickel dissolution, resulting in the recovery of 99% of aluminum as Al(OH)3 with 99.8% purity and 99% of nickel as NiSO4.6H2O.

Study on separation and purification of titanium alloys (TC4-6Al-4V) by molten salt electrolysis

With the widespread expansion of titanium applications and its significant increase in usage, the issue of recycling titanium resources after consumption has emerged. Focusing on titanium alloys with high usage, such as TC4 (Ti-6Al-4V), this article proposes a titanium separation and recovery method based on molten salt electrolysis. This method thoroughly analyzes the characteristics of elements in TC4 and electrochemical principles, ensuring that vanadium in the TC4 alloy does not undergo electrochemical dissolution when the electrolysis potential is below 0.3 V vs Pt. Subsequently, through electrochemical analysis, it was discovered that the precipitation of aluminum ions is influenced by concentration. Therefore, by controlling the concentration of aluminum in the eutectic molten salt, such as increasing the electrolyte concentration and shortening the electrolysis time, the precipitation of aluminum can be effectively avoided. Under the experimental conditions mentioned above, vanadium elements deposit at the bottom of the crucible in the form of anode slime, while aluminum dissolves and remains in the electrolyte. Meanwhile, titanium ions in the cathode region undergo electron reduction and deposit in the cathode area in the form of titanium, thus achieving precise separation of alloy elements. Experimental verification shows that the purity of the obtained titanium reaches 99.17 atomic percent. Therefore, this molten salt electrolysis method, which combines the physical properties of alloy elements with electrochemical principles, not only provides a new perspective for the separation and recovery of titanium and other critical metals, but also offers new research directions for the recovery technology of other alloy elements.

Exploring innovative strategies for precipitation extent enhancement in a downscaled Bayer process tank

AbstractThe Bayer process is a cornerstone of alumina production, and its precipitation stage holds the key to both efficiency and product quality. In this study, we embarked on a comprehensive exploration of strategies to enhance the precipitation extent of aluminium hydroxide, a pivotal step in the Bayer process. Utilizing a newly constructed reactor, along with experiments using reactors in series, we rigorously experimented with various factors, including the addition of hydrogen peroxide (H2O2) as an enhancer, seed activation methods, the integration of a hydrocyclone within the processing unit, the application of a magnetic field, and the injection of supersaturated liquor midway through the process. These diverse strategies were systematically assessed to decipher their individual and synergistic effects on precipitation extent. Our research aims to uncover the optimal conditions for maximizing alumina precipitation while maintaining product quality and seed particle stability. By offering new insights and practical solutions, this study contributes to the ongoing advancement of alumina production within the Bayer process.

New methodological approach for deep penetrating geochemistry and environmental studies, Part 2: field determination of Co(II)/Ni(II) and Pb(II)/Zn(II) of on-site soil extractions by electrochemical stripping techniques

In the framework of deep penetrating geochemistry for mineral exploration, we report a field electroanalytical method using disposable screen-printed working electrodes able to quantify metal pathfinders in partial extracts of soil samples at the nanomolar level on-site. Four metal pathfinders (Co, Ni, Pb and Zn) were chosen due to their geological interest and suitability of electrochemical detection. Square-wave anodic stripping voltammetry (SW-ASV) was developed for the simultaneous detection of Pb(II) and Zn(II) providing limits of detection (LOD) of 1.2 and 5.3 nM, respectively. A linear-scan cathodic stripping voltammetry (LS-CSV) methodology was developed for the joint detection of Co(II) and Ni(II) yielding LOD of 1.8 and 3.5 nM, respectively. Method validation was carried out on 14 upper B-horizon soil samples during a field survey. Two wet extraction procedures were applied for soil samples – a strong extraction using nitric acid (HNO 3 ) and a weak extraction using calcium chloride (CaCl 2 ). Excellent agreement between electroanalytical methods and inductively coupled plasma mass spectrometry (ICP-MS) was found for Pb(II), while a small underestimation was observed for Zn(II). For Co(II) and Ni(II) the LS-CSV measurements in the HNO 3 extractions were impossible due to the change from low pH to pH to 7.15 which induces precipitation of iron and aluminium. For the CaCl 2 extractions, the Co(II)/Ni(II) results obtained by LS-CSV were in excellent agreement with ICP-MS measurements.

Aluminum Removal from Rare Earth Chloride Solution through Regulated Hydrolysis via Electrochemical Method

Due to the coexistence of Al3+ and RE3+ and their similar properties, the separation of aluminum from rare earths is difficult. In this study, selective precipitation was used to separate aluminum from rare earth chloride solution via electrochemical regulated hydrolysis. By controlling the current density and electrolytic time, the rate of hydroxyl ion production was regulated, and the selective separation of rare earth and aluminum was realized according to the different precipitation sequences. By altering the temperature, current density, pH value, and other parameters, the separation performance of aluminum from rare earth in mixed rare earth chloride systems was systematically investigated. The removal rate of aluminum reached 88.35%, and the loss rate of rare earth was only 5.99% under optimized conditions. Compared with traditional neutralization hydrolysis, the new process showed higher efficiency and lower rare earth loss rate. Furthermore, a kinetic analysis of aluminum precipitation revealed that the reaction adhered to pseudo-first order kinetics. Additionally, the precipitate obtained via separation and filtration was amorphous alumina hydroxide with a small amount of rare earth attached. No reagent was consumed for the new process, which was more efficient and cleaner, providing a new idea for removing aluminum impurities from rare earth solutions.

Precipitation of amorphous iron and aluminum during the weathering of rock dust in soil columns

Precipitation of amorphous iron and aluminum during the weathering of rock dust in soil columns

Aero acoustic levitation to unveil the solidification of complex oxides: Case study of the system Al2O3–ZrO2

Binary or multi-component phase mixtures are of particular technical importance. Despite the wide field of application of Al2O3 and ZrO2 composites, the literature reveals contradictions about the liquidus region. Containerless processing avoids typical problems of conventional techniques like melt contamination or lack of suitable container materials. Composition ranging from 0–80 mol% ZrO2 were melted and solidified in an aero acoustic levitator. A high-speed camera recorded the crystallization, allowing a direct correlation with the observed microstructures. Due to homogeneous nucleation, all samples exhibited significant undercooling before crystallization. The nucleation temperature of the different compositions roughly followed the slope of the liquidus line. Undercooling, solidification kinetics, and local reheating played a considerable role in microstructure formation. A lamellae eutectic microstructure was created over a large compositional range from 36–48 mol% ZrO2. On the hypoeutectic side, the effect was attributed to solidification within the coupled zone. However, hypereutectic samples also exhibit a zirconia-rich eutectic as well. We assume impaired ZrO2 nucleation or growth favors alumina precipitation from the melt. Aero acoustic levitation proved to be an excellent technique for studying complex high melting oxide systems, enabling a better understanding of their crystallization process.

BAUXITES OF THE TATAR DEPOSIT (YENISEI RIDGE, RUSSIA): THE FIRST EVIDENCE OF CONTACT-KARST GENESIS

The Tatar bauxite deposit on the territory of the Russian Federation was formed as a result of sedimentation in contact-karst depressions of the products of denudation of lateritic weathering crusts of amphibolites. Detailed mineralogical studies of bauxites made it possible to reliably reconstruct the conditions for their formation. As it turned out parent rocks and weathered before rocks occurred due to the close location of the areas of nutrition and accumulation and denudation. At the same time, chemical processes was continuing in karst depressions. For the first time, the presence of nanoparticles of amorphous aluminum oxide was revealed into contact-karst bauxites. This characteristic feature of the form of alumina precipitation is associated with the subsequent cessation of lateritization processes and their attenuation with depth. The presence of amorphous aluminum monohydrate must be taken into account when choosing a scheme for bauxite enrichment.

Bauxites of the Tatarka Deposit (Yenisei Ridge, Russia): The First Evidence of a Contact-Karst Origin

The Tatarka bauxite deposit on the territory of the Russian Federation was formed as a result of sedimentation of the products of denudated lateritic weathering crusts of amphibolites in contact-karst depressions. Detailed mineralogical studies of bauxites made it possible to reconstruct reliably the conditions for their formation. As it turned out, the initial rocks and rocks, weathered before, have been denudated due to the close location of the areas of alimentation and accumulation. At the same time, chemical processes have been continued in karst depressions. For the first time, the presence of nanoparticles of amorphous aluminum oxide was revealed in contact-karst bauxites. This specific feature of the form of alumina precipitation is associated with the subsequent cessation of lateritization and their attenuation with depth. The presence of amorphous aluminum monohydrate must be taken into account when choosing a scheme for bauxite enrichment.

Aluminum precipitation on oxygen-deficient alumina in laser alumina reduction

Alumina reduction by thermal decomposition using CW laser ablation is being studied to obtain aluminum and oxygen on the lunar surface without the use of reducing agents such as carbon or hydrogen. When an alumina rod is heated by a laser beyond the ablation temperature, oxygen-deficient alumina (Al2O2.4-2.8) and aluminum microparticles are generated on the laser-irradiated surface. For this study, rods made of oxygen-deficient alumina were ablated to obtain more aluminum than normal alumina ablation. Results show that approximately 1.7 times as much aluminum was precipitated as that obtained from normal alumina ablation. The average particle size of the precipitated aluminum particles was found using SEM image analyses to be about 1.6 times larger than that of normal alumina.

Alumina Nucleation, Growth Kinetics, and Morphology: A Review

The reaction between aluminum and the dissolved oxygen in liquid steel yields the precipitation of alumina crystals with characteristic morphologies and size distributions. Alumina precipitation and growth involve a wide spectrum of time, length, velocity, and thermodynamic supersaturation scales throughout the refining processes. The smallest length and time scales are those quantifying the nucleation kinetics and the initial growth at the highest supersaturation. Further growth and crystal morphology depend on the concentration of surface tension elements which inhibit the crystal's faces suffering further modifications due to washing effects provided by turbulent flows. This step involves longer time, velocity, length, and moderate supersaturations. The final step involves the growth of alumina inclusions through collision–agglomeration–sintering, and capillary processes on the surfaces of argon bubbles under low supersaturations. Jumps of supersaturation, due to late aluminum additions or steel reoxidation, lead to alumina crystals changing their morphology to dendritic‐type growth. The present contribution reviews each one of these kinetic phenomena closing with the consequences that alumina precipitation has on the continuous casting process. The content of this review is useful to practitioners and theorists alike.

Pilot Scale Testing of Lignite Adsorption Capability and the Benefits for the Recovery of Rare Earth Elements from Dilute Leach Solutions

Naturally occurring organic materials containing humic acids show a strong affinity towards rare earth elements (REE) and other critical elements. Leaching experiments on lignite coal waste produced from construction sand production revealed that the contained REEs were associated with the organic matter. Furthermore, adsorption studies revealed that the lignite waste was capable of extracting REEs from a model solution and increased the REE content of the lignite waste by more than 100%. As such, this study aimed to utilize the lignite waste to adsorb REEs from pregnant leach solutions and acid mine drainage sources having low REE concentrations and subsequently leach the lignite material to produce pregnant leach solutions containing relatively high amounts of REEs, which benefits the performance and economic viability of downstream separation and purification processes. An integrated flowsheet was developed based on this concept and tested at a pilot scale. The pregnant leachate solution (PLS) was generated from a heap leach pad containing 2000 tons of Baker seam coarse refuse. The pilot scale circuit was comprised of aluminum precipitation, adsorption using the waste lignite, and rare earth-critical metal (RE-CM) precipitation stages in succession. The results indicated that the aluminum precipitation stage removed over 88% and 99% of the Al and Fe, respectively. The adsorption stage increased the REE content associated with the waste lignite from 457 ppm to 1065 ppm on a whole mass basis. Furthermore, the heavy REE (HREE) content in the feedstock increased by approximately 250%, which raised the percentage of HREE in the REE distribution by 19 absolute percentage points. In addition to the REEs, concentrations of other critical elements such as Mn, Ni, and Zn also improved by 75%, 37%, and 250%, respectively. Bench-scale tests revealed that increasing the solids concentration in the waste lignite and PLS mix from 1% to 20% by weight enhanced the adsorption efficiency from 32.0% to 99.5%, respectively. As such, a new flowsheet was proposed which provides significantly higher REE concentrations in the PLS that can be fed directly to solvent extraction and/or oxalic acid precipitation and, thereby, enhancing process efficiency and economics.

Efficient extraction and recovery of lithium from waste aluminum cryolite electrolyte

The accumulation of alkali metals in cryolite electrolyte has negative impacts on the operation of aluminum electrolysis, and part of electrolytes need to be periodically replaced and discharged. A cleaner and efficient process was proposed to recover LiF and Al2(SO4)3 from the waste cryolite electrolyte. Under the optimum sulfated roasting conditions, 87.55% of Li and 30.30% of Al were leached. The obtained cryolite residue with a low molecular ratio could be returned to the aluminum electrolysis system. The addition of sodium benzoate achieved the efficient separation of Al3+ from Li-containing leachate, and the Al precipitation ratio was 99.78%. Acid leaching of the aluminum precipitate regenerated benzoic acid and recovered 99.62% of Al2(SO4)3. Finally high-purity cubic LiF was prepared from Li2SO4 solution, and the recovery of LiF was 98.78%.

Experimental study on the degree and damage-control mechanisms of fuzzy-ball-induced damage in single and multi-layer commingled tight reservoirs

Fuzzy-ball working fluids (FBWFs) have been successfully applied in different development phases of tight reservoirs. Field reports revealed that FBWFs satisfactorily met all the operational and reservoir damage control requirements during their application. However, the damage-control mechanisms and degree of formation damage caused by fuzzy-ball fluids have not been investigated in lab-scale studies so far. In this study, the degree of fuzzy-ball-induced damage in single-and double-layer reservoirs was evaluated through core flooding experiments that were based on permeability and flow rate indexes. Additionally, its damage mechanisms were observed via scanning electron microscope and energy-dispersive spectroscopy tests. The results show that: (1) For single-layer reservoirs, the FBWF induced weak damage on coals and medium-to-weak damage on sandstones, and the difference of the damage in permeability or flow rate index on coals and sandstones is below 1%. Moreover, the minimum permeability recovery rate was above 66%. (2) For double-layer commingled reservoirs, the flow rate index revealed weak damage and the overall damage in double-layer was lower than the single-layer reservoirs. (3) There is no significant alteration in the microscopic structure of fuzzy-ball saturated cores with no evidence of fines migration. The dissolution of lead and sulfur occurred in coal samples, while tellurium in sandstone, aluminum, and magnesium in carbonate. However, the precipitation of aluminum, magnesium, and sodium occurred in sandstone but no precipitates found in coal and carbonate. The temporal plugging and dispersion characteristics of the FBWFs enable the generation of reservoir protection layers that will minimize formation damage due to solid and fluid invasion.

Overlooked effect of ordinary inorganic ions on polyaluminum-chloride coagulation treatment

Application of poly-aluminum chloride (PACl) coagulant is a popular mode of water treatment worldwide because of the high capacity of PACl to neutralize charge. The manufacture and use of PACls with various basicities in different regions around the world suggest that the characteristics of the raw water are important determinants of the efficacy of PACl application. However, attention has not been fully paid to the effects of water quality other than the substances to be removed. In this study, two typical PACls with different basicities were used to investigate why the performance of PACls depends on the characteristics of the raw water. We focused on the concentrations of inorganic ions in the raw water. Use of high-basicity PACl (HB-PACl) with a high content of polymeric-colloidal species (Alb+Alc) resulted in very slow floc formation and little turbidity removal in raw water with low concentrations of sulfate ions. The performance of the HB-PACl was inferior to that of normal-basicity PACl (NB-PACl), although the charge-neutralization capacity of the HB-PACl was higher. Rates of floc formation were strongly correlated with the rate of aluminum precipitation by hydrolysis reaction, which was identified as an indicator for evaluating the compatibility of raw water with PACl treatment. Among the common ions in natural water, the sulfate ion had the greatest ability to hydrolyze and precipitate PACl because of its divalency and tetrahedral structure. This conclusion followed from experimental results showing similar effects for selenate and chromate ions as for sulfate ions and somewhat smaller effects for thiosulfate ions. Bicarbonate ions and natural organic matter affected PACl hydrolysis-precipitation, but chloride ions, nitrate ions, and cations had little effect on PACl hydrolysis-precipitation. Interestingly, the abilities of sulfate ions to hydrolyze HB-PACl and NB-PACl were very similar, but bicarbonate ions were less effective in hydrolyzing HB-PACl than NB-PACl, and bicarbonate ions contributed little to the hydrolysis-precipitation of HB-PACl in raw water with normal alkalinity. Therefore, sufficient coagulation with HB-PACl therefore usually requires a certain concentration of sulfate ions in water to be treated. The implication is that which anions are most influential to the hydrolysis-precipitation of PACl, and thus to PACl's coagulation ability depends on the constituents of the PACl.

Recovery of vanadium and nickel from spent-residue oil hydrotreating catalyst by direct acid leaching-solvent extraction

A process for the selective extraction and separation of vanadium and nickel from spent-residue oil hydrotreating catalysts by a direct acid leaching−solvent extraction method was studied. The extraction and separation of vanadium(IV) and nickel(II) are divided into two stages: acid coleaching of vanadium and nickel and solvent extraction. In the acid coleaching stage, the leaching ratios of vanadium and nickel reach 88.07% and 75.58%, respectively, which can realize highly effective coleaching. In the solvent extraction stage, countercurrent experiments show that the extraction ratio of vanadium can reach 99.21% after a three-stage extraction with P204 as the high-efficiency extractant of vanadium in the acidic environment, while nickel and iron are not extracted. After the anti-extraction solution is pretreated by aluminum precipitation, the extraction ratio of nickel reaches 99.79% after a three-stage extraction with LIX84-I as a high-efficiency extractant of nickel in ammonia medium. A process flow for the recovery of vanadium and nickel is proposed, which not only can realize the separation and recovery of vanadium and nickel but also can realize the recycling of reagents.

A closed-loop process for high-value regeneration of spent LiFePO4 cathodes after selective aluminium precipitation

A recycling process is proposed in which spent cathode materials and Al foil are leached by low-concentration acids, then Al is selectively precipitated, finally the lithium iron phosphate material is synthesized by a one-step hydrothermal synthesis.