Recovery of Li from waste Li-containing Al electrolytes with high F and Na contents by using a CaO roasting-water leaching process.

With the increasing demand for Li, the recovery of Li from solid waste, such as Li-containing Al electrolytes, is receiving growing attention. However, Li-containing Al electrolytes often contain large amounts of F, leading to environmental pollution. Herein, a new method for preparing water-soluble Li salt from waste Li-containing Al electrolytes with high F and Na contents is proposed based on CaO roasting and water leaching. The effects of different roasting and leaching conditions on the Li leaching efficiency and reaction pathway were systematically investigated. Under the optimum processing conditions, the Li leaching efficiency reached 98%, while those of Na and F were 98.41% and 0.24%, respectively. Phase evolution analysis showed that the addition of CaO promoted the conversion of LiF and Na2LiAlF6 to Li2O, whereas F entered the slag phase as CaF2, which could be reused as a raw material for steel refinement. Overall, this study proposes an efficient and environmentally friendly method for the treatment and resource utilization of waste Al electrolytes with high F and Na contents.

Kinetics study on the low-temperature soda roasting of boron-rich blast furnace slag.

The method of preparing borax by low-temperature soda roasting and water leaching of boron-rich blast furnace slag (BRBFS) is a novel method for extracting boron from BRBFS. In order to further improve the water leaching rate of boron, this article mainly studied the low-temperature soda roasting kinetics of BRBFS. The effects of roasting temperature and Na2CO3 addition on the water leaching rate of boron were investigated. The results demonstrate that when the amount of Na2CO3 added is four times of the theoretical amount, the kinetics of NaBO2 formation can be described by the Nucleation (Avrami) model in the temperature range of 600-700 °C. The corresponding apparent activation energy is 54.45 kJ/mol, and the apparent frequency factor is 215.16 h-1. It was found that at a roasting temperature of 700 °C,when the amount of sodium carbonate added is twice, three times, and four times of the theoretical amount, the kinetics of NaBO2 formation matches with 3-D Diffusion (Jander) model, Nucleation and Growth (Avrami-Erofeev) model, and Nucleation (Avrami) model, respectively. With an increase in the amount of Na2CO3 added, the rate-controlling step for the formation of NaBO2 transitions from being diffusion-controlled to nucleation-controlled.

Cleaner separation and recovery of valuable metals from spent ternary cathode via carbon dioxide synergetic thermite reduction strategy.

The low-carbon recycling of spent lithium-ion batteries has become crucial due to the increasing need to address resource shortages and environmental concerns. Herein, a low-carbon, facile, and efficient method was developed to separate and recover Li, Al, and transition metals from spent ternary cathodes. Initially, the cathode materials post-discharge and disassembly do not require pre-sorting. Instead of using carbonaceous materials, the Al foil in the cathode serves as the reducing agent during reduction roasting. The impact of different roasting atmospheres (air, N2, CO2) on phase transitions and the extraction of valuable metals was examined. The findings revealed that after synergistic thermite reduction in a carbon dioxide atmosphere, the cathode material is completely dissociated. Li is selectively converted to Li2CO3 rather than LiAlO2, and the reduced reactivity of the Al foil encourages the formation of lower-valence oxides of Ni and Co, rather than their metallic forms. Under optimal roasting conditions at 650 °C for 1.0 h, 91.4% of Li can be preferentially and selectively extracted through carbonation water leaching, with less than 0.1% of Al and transition metals dissolving. Subsequently, ∼98% of Al and ∼99% of Ni, Co, and Mn can be leached using alkaline and acidic solutions, respectively. Compared to the traditional carbon thermal reduction process, this process offers several advantages including the elimination of pre-sorting and additional reducing agents, lower carbon emissions, and higher recovery rates of valuable metals. Thus, this process makes the recovery of metals from spent lithium-ion batteries more environmentally sustainable, simple, cost-effective, and adaptable.

An unconventional approach for the efficient recovery of iron, cobalt, copper and silicon from copper slag.

High-grade heavy metal elements in copper slag (CS) are worth recovering. Unfortunately, the high viscosity of leaching solution, low leaching efficiency, difficult filtration and low separation efficiency of valuable components exist in the traditional sulfuric acid leaching process. In this study, the above problems are solved by sulfuric acid pretreatment + curing + water leaching. Moreover, iron, cobalt and copper ions in solution are separated by stepwise precipitation. The final iron, cobalt, copper and silicon recoveries are 99.01 %, 98.45 %, 93.13 % and 99.52 %, respectively. Thermodynamic calculations show that H4SiO4 can be converted to insoluble SiO2 to improve filtration properties under curing conditions of sulfur dioxide partial pressures of 10-20∼0 atm, oxygen partial pressures of 10-20∼0 atm and 400-600k. Simulation studies of the phase equilibria of the components of the leach solution by Visual MINTEQ showed that the oxidation of Fe2+ to Fe3+ is necessary for the removal of Fe2+ from the solution by precipitation. This study provides a new idea for the efficient utilization of CS.

Water Leaching Kinetics of Boron from the Alkali-Activated Ludwigite Ore.

The primary aim of this study was to investigate the boron leaching process from alkali-activated ludwigite ore. Initially, the ore underwent activation through roasting at 1050 °C for 60 min with 20% sodium carbonate. Subsequently, the study examined the influence of leaching parameters, including temperature, time, liquid-to-solid ratio, and particle size, using the activated ore as the raw material. Additionally, water leaching characteristics of the residues and boron kinetics were analyzed. The results demonstrated that boron leaching efficiency reached 93.71% from the reduced ludwigite ore under specific conditions: leaching temperature of 180 °C, leaching time of 6 h, liquid-to-solid ratio of 8:1, and feed particle size of 52.31 µm (average particle size). Leach residue characteristics indicated the dissolution of minerals during the process. The boron behavior during water leaching followed the Avrami Equation, and the kinetics equation was derived by fitting the leaching data. Moreover, the activation energy (Ea) value for boron leaching was determined to be 8.812 kJ·mol-1 using the Arrhenius Equation, indicating that the leaching process is controlled by diffusion.

Efficient Recovery of Vanadium and Titanium from Domestic Titanomagnetite Concentrate Using Molten Salt Roasting and Water Leaching.

The traditional roasting technique using sodium salts in vanadium production has been disadvantageous due to the large consumption of energy and the emission of harmful gases. A modified process using molten salt roasting and water leaching to extract vanadium and titanium from domestic titanomagnetite concentrate was investigated. The roasting process was performed under optimal conditions: the weight ratio between the sample and NaOH of 1:1, the temperature of 400 °C, and the experiment time 90 min, and the conversion of vanadium could be maximized to 90%. The optimization of water leaching (at 60 °C for 90 min with a pulp density of 0.05 g/mL) could extract 98% of the vanadium from the roasted products into the solution, leaving titanium and iron remaining in the residue. Further purification of vanadium and titanium using the precipitation/hydrolysis process followed by calcination obtained the final products V2O5 and TiO2 with high purities of 90% and 96%, respectively. A potential approach with modification of the roasting stage using NaOH was proposed, which was not only efficient to selectively extract the value metals from the titanomagnetite but also eco-friendly based on the reduction in energy consumption and emission of harmful gases.

Initial extraction of sodium silicate from sidoarjo mud by alkaline fusion and water leaching.

Sodium Silicate is a chemical compound that has properties such as water glass is a colorless, soluble in water, and is widely used in industry. Therefore, the extraction of sodium silicate by alkaline fusion is followed by water leaching. The alkaline fusion process is a technique that is often used and can further simplify the extraction process. The purpose of this research in general is to obtain the optimum conditions for the extraction of sodium silicate from the Sidoarjo mud in an alkaline fusion process followed by water leaching. The alkali used in the alkaline fusion process is Na2CO3. The effect of various experimental conditions on fusion has been studied. These variables include the amount of alkali used, the reaction temperature, and the length of the reaction time. The alkaline fusion process proved that sodium silicate could be produced and could be separated in water leaching. The highest percentage of sodium silicate extraction was 43.6% resulting from water leaching conditions with a solid-liquid ratio of 1:5, a temperature of 80 °C for 2 h.

Closed-loop recycling of spent lithium-ion batteries based on selective sulfidation: An unconventional approach.

The facile recycling of spent lithium-ion batteries (LIBs) has attracted considerable attention because of its great importance to environmental protection and resource utilization. A novel process is developed for cyclic utilization of spent LiNixCoyMnzO2 (NCM) batteries. The spent NCM was converted into water-soluble Li2CO3, acid-dissolved MnO, and nickel-cobalt sulfides through selective sulfidation, based on roasting condition optimization and thermodynamic calculation. More than 98 % of lithium is extracted preferentially from calcined NCM through water leaching, and over 99 % of manganese is extracted selectively from water leaching residue with H2SO4 solution of 0.4 mol/L in the absence of additional reductant. The nickel and cobalt sulfides were concentrated into the leaching residue without metal impurities. The obtained Li2CO3, MnSO4, and nickel-cobalt sulfides can be regenerated as new NCM, showing good electrochemical performance, and its discharge capacity is 169.8 mAh/g at 0.2C. After 100 cycles at 0.2C, the discharge specific capacity can still be maintained at 143.24 mAh/g, and its capacity retention ratio is as high as 92  %. An environmental assessment and economic evaluation indicate that the process is an economical and eco-friendly approach for green recycling of spent LIBs.

A process using a thermal reduction for producing the battery grade lithium hydroxide from wasted black powder generated by cathode active materials manufacturing.

Recent lithium consumption is doubled in a decade due to the Li-ion battery (LIB) demand for electric vehicles, the energy storage system, etc. The LIBs market capacity is expected to be in strong demand due to the political drive by many nations. Wasted black powders (WBP) are generated from the manufacturing of the cathode active material and spent LIBs. The recycling market capacity is also expected to expand rapidly. This study is to propose a thermal reduction technique for recovering Li selectively. The WBP, containing 7.4 % Li, 62.1 % Ni, 4.5 % Co, and 0.3 % Al, was reduced in a vertical tube furnace using a 10 % H2 gas as a reducing agent at 750 ºC for 1 h, and 94.3 % of Li was recovered from a water leaching, while other metal values, including Ni and Co remained in the residue. A leach solution was treated in a series of crystallisations, filtering, and washing. An intermediate product was produced and re-dissolved in hot water at 80 ºC for 0.5 h to minimise Li2CO3 content into a solution. A final solution was crystallised repeatedly to produce the final product. A 99.5 % of LiOH·H2O was characterised and passed the impurity specification by the manufacturer as a marketable product. The proposed process is relatively simple to utilise to scale up for bulk production, and it can also be contributed to the battery recycling industry as the spent LIBs are expected to overabundance within the near future. A brief cost evaluation confirms the process feasibility, particularly, for the company that produces cathode active material (CAM) and generates WBP in their own supply chain.

A sustainable approach for selective recovery of lithium from cathode materials of spent lithium-ion batteries by induced phase transition.

Recycling of spent lithium-ion batteries (LIBs) has attracted widespread attention because of their dual attributes to environmental protection and resource conservation. Utilization of strong corrosive acids is currently the preferred way to recover valuable metals from spent LIBs, but the extensive use of chemical reagents can pose serious environmental risks. Herein, this research proposes a green process for selective recovery of lithium using the material of spent LIBs itself without adding exogenous reagents, mechanochemistry induced phase transition. The leaching efficiency of Li can reach 94% by employing the copper foil separated from spent LIBs as the co-grinding additive during the mechanochemical reaction process. Then, the high value LiOH·H2O can be prepared through direct evaporation and crystallization without adding any precipitant. Meanwhile, cobalt is almost remained in the leaching residue which can be recovered through a step-by-step separation process. XRD, XPS, and SEM-EDS characterizations show that LiCoO2 and copper foil are transformed into the soluble Li2O, and insoluble CuO and CoO under the mechanical force. Finally, the soluble Li2O is dissolved in water to prepare the LiOH solution, and the insoluble CuO and CoO are transformed into Cu2O and Co(OH)2. On the basis of the experimental investigation, it is proven that the proposed process is suitable for selectively recovering Li from all types of cathode materials without generating salty wastewater or introducing chemical reagents. Thus, the proposed approach can ensure the efficient recovery of valuable metals from spent LIBs while avoiding the potential threat to the environment and human health.

A green process for the conversion of hazardous sintering dust into K2SO4 and NH4Cl fertilizers.

Sintering dust from the steelmaking industry is a hazardous waste that is rich in valuable metals. The purpose with the present study has been to design an efficient process for the preparation of K2SO4 and NH4Cl fertilizers by using sintering dust as raw material. The K, S, and Cl in the sintering dust were selectively and efficiently leached using water. The leaching of Ca impurities was then greatly reduced and the appearance of Zn and Mg was avoided. The Cl- ions in the leachate were, thereafter, adsorbed by a 201 × 7 resin to form a K2SO4 solution. Finally, the loaded Cl- on the resin was desorbed to form a NH4Cl solution, and the resin was regenerated and recycled. The purified solutions were crystallized to prepare K2SO4(s) and NH4Cl(s) products, which met the national standard of China for superior potassium sulfate and ammonium chloride, to be used for agricultural use. The recoveries of K, Cl, and S from the sintering dust were 80.78%, 92.63%, and 93.92%, respectively. Notably, the Mn content in the leaching residue increased from 9.08% to 14.19%. This could be used for the conversion of Mn impurities into recyclable manganese-rich raw materials. This green process enables an effective extraction of important impurities in hazardous sintering dust, thereby providing a new potassium source for potash fertilizer manufacturing with notable economic and environmental benefits.

A clean and efficient process for simultaneous extraction of Li, Co, Ni and Mn from spent Lithium-ion batteries by low-temperature NH4Cl roasting and water leaching.

The recycling of valuable metals from spent lithium-ion batteries (LIBs) has great significance for environmental protection and resource conservation. In this paper, a low-temperature clean chlorination roasting-water leaching process was proposed to simultaneously extract Li, Ni, Co and Mn from cathode material (NCM) of spent LIBs. The temperature range of chlorination roasting was determined by thermodynamic analysis to be 250-600 °C. The effect of some factors on the conversion of valuable metals in the process of chlorination roasting and water leaching was systematically studied. The results showed that more than 98 % of Li, Co, Ni and Mn could be extracted under optimized chlorination roasting and water leaching conditions. The chlorination roasting mechanism and phase transformation evolution was determined by means of thermodynamic analysis, TG-DTA, XRD, SEM and EDS. The extraction of valuable metals was realized by the reaction of the metal oxides produced by the decomposition of NCM with NH4Cl or its evolved HCl to form water-soluble metal chlorides or chlorinated metal-ammonium complexes. The chlorination technique using NH4Cl provided an effective and clean approach for the simultaneous extraction of Li, Co, Ni and Mn from spent LIBs.

An integrated and sustainable hydrometallurgical process for enrichment of precious metals and selective separation of copper, zinc, and lead from a roasted sand.

This study developed an efficient and sustainable hydrometallurgical process for the enrichment of gold and silver and the stepwise separation of copper, zinc, and lead from sulfated roasted sand of waste printed circuit board smelting ash. Selective separation of copper and zinc was achieved by water leaching, and silver dispersion was reduced by controlling the amount of NaCl added during the leaching process. The results of the water leaching showed that the copper and zinc leaching rates were 99.85% and 99.47%, respectively, whereas the loss rate of silver was 2.1% with optimal leaching parameters. The high-chloride-complex method was used to study the efficient conversion and separation of lead from the leached residue, and the leaching kinetics and conversion mechanism of lead were discussed. The results showed that under the optimal conditions, the leaching rate of lead was 99.79%. Leaching kinetics analysis showed that lead leaching in the high - chlorine system was controlled by a chemical reaction; the apparent activation energy was 53.63 kJ/mol. After the leaching of copper, zinc, and lead, 1.66% Ag and 213 g/t Au were enriched in the leached residue; and the precious metal enrichment goal was reached. The chlorinated leachate showed good recycling performance, and a lead leaching rate of 97.93% was obtained after three circulations. After cooling, crystallization, and purification, lead chloride with a purity of 99.89% and high economic and industrial value was obtained from the lead-rich leachate. This process has favorable and sustainable industrial application prospects.

Hydrometallurgical enhanced liberation and recovery of anode material from spent lithium-ion batteries.

The efficient recycling of spent anode material (SAM) from spent lithium-ion batteries (LIBs) is generally critical in terms of electronic waste recyclingas well as increasing resource shortage and environmental problems. This research reported a novel and green method to recycle lithium, copper foil, and graphite from SAM by water leaching treatment. The results indicated that 100% of graphite was exfoliated from the anode material and 92.82% leaching efficiency of lithium was obtained under the optimal conditions of 80 °C, 60 g/L, 300 rpm, and 60 min, respectively. This finding revealed that the SAM got a full liberation characteristic due to the removal of binder, which produced an ideal leaching lithium efficiency rivaling the acids' performance. The mechanism of the liberation of SAM and lithium leaching is presented based on the analysis of results. The graphite was purified and recovered after water leaching treatment. Besides, lithium was recovered in the form of lithium carbonate (Li2CO3), and the copper foil was recovered in a sheet. This study endeavors to develop an economical and environmentally feasible plan to recycle graphite, copper, and lithium from SAM.

Efficient process for recovery of waste LiMn2O4 cathode material: Low-temperature (NH4)2SO4 calcination mechanisms and water-leaching characteristics.

An efficient process for recycling waste LiMn2O4 cathode material is proposed in this research. This report constitutes low-temperature (NH4)2SO4 calcination mechanisms and water-leaching characteristics of the calcined samples. A calcination temperature range of 420.65-634.12 °C is determined by analysis of the TG-DSC curve under the conditions of heating from 25 to 1000 °C, with a molar ratio of n(2Li + Mn):n(NH4)2SO4 = 1:1 in air atmosphere. The sample calcined at 600 °C for 45 min when the excess coefficient of the (NH4)2SO4 was 1.1 exhibits optimal water-leaching efficiencies of the Li and Mn elements, which are approximately 100% and 96.73%, respectively. The macro-reaction mechanism of the waste LiMn2O4 cathode material calcined with (NH4)2SO4 is determined as the liquid-solid reaction by analysing the apparent morphologies of the calcined samples and their water-leaching residues under different calcination conditions. Moreover, the micro-reaction mechanism is investigated by analysing the phases of the calcined samples and their water-leaching residues under different calcination conditions. The free high-energy H+ released by the decomposition of the NH4+ generated by the molten (NH4)2SO4 play a key role in the entire calcination process. The spinel structure of the LiMn2O4 is broken and Li+ is released owing to the H+ bombarding the MnO bonds. Finally, the LiMn2O4 is converted into soluble sulphate salts, such as Li2Mn2(SO4)3 and MnSO4.

Water-leaching characteristic of valuable trace metals (U, V, and Ga) from (NH4)2SO4-treated coal ash: A coprecipitation behavior at high temperature.

Coal ash (CA) becomes the most significant industrial solid waste and attracts much attention due to its potential environmental risk and reuse as the supplementary material. In this study, experiments were conducted to investigate the mode of occurrence and the leaching behavior of valuable trace metals (U, V, and Ga) from CA and (NH4)2SO4-treated CA (NCA), based on the recovery of aluminum. Integrations of Fe- and K-oxide with Si-Al glass increased the ash strength and obstructed the activation of NH4+ on amorphous Al-bearing phases, resulting in a limited improvement in the leaching efficiency of trace metals. On the other side, a higher liquidus temperature, contributing to the dissolutions of Al3+ and Ca2+, could promote the leaching of U from NCA as well, whereas the water-leaching behaviors of V and Ga involved a sophisticated trend with temperature > 40℃. Water-leached V/Ga tended to transfer into Fe-Mn oxide-bound and residual V/Ga owing to the noticeable hydrolysis of Fe and Ti ions that facilitated the formation of coprecipitation. However, 0.1 M H2SO4 could re-dissolve that coprecipitation, and thus leaching efficiencies of U, V, and Ga were 1.9, 1.3, and 5.0 times higher than those by directly leaching CA, respectively.

Calcined Post-Production Waste as Materials Suitable for the Hydrothermal Synthesis of Zeolites.

The zeolite production process is currently being very intensively researched. Due to environmental protection, as well as issues related to the guidelines of a zero-waste economy, all activities aimed at obtaining such materials from post-processed waste are extremely important. This article presents an innovative method of utilising calcined carboniferous shale in order to produce synthetic zeolites. The raw material for testing came from two Polish hard coal mines. Both the chemical and phase composition of the coal shale were characterised. Based on the recorded thermal analysis results coupled with the mass spectrometer, the processes occurring during the heating of raw materials were interpreted and the calcination temperatures were determined. The changes in the phase composition of raw materials resulting from the calcination process used were also analysed. The heat-treated raw materials were subjected to the synthesis of zeolites in an aqueous solution of sodium hydroxide by means of the hydrothermal method at a concentration of 2.75 M. The results of water leaching and structural parameters are presented for both raw materials, as well as the produced synthesis. The conducted research confirmed that after the application of the synthetic process on coal shale, a zeolite with a surface area of SBET equal to 172 m2/g can be obtained.

Recovery of scandium from Canadian bauxite residue utilizing acid baking followed by water leaching.

The current study put the emphasis on developing a novel and environmentally friendly waste valorization process, called "acid-baking water-leaching", to recover scandium from bauxite residue produced by the aluminum industry. In this process, bauxite residue is mixed with concentrated sulfuric acid, baked in a furnace at 200-400 °C, and leached in water at ambient conditions. Compared with direct acid leaching processes, the developed process offers the advantages of less acid consumption, less wastewater generation, and fast kinetics. With fundamental investigation into the reaction mechanism, acid baking temperature was shown to be the controlling factor that dictates the final phases of the process. Baking at 200 °C results in the formation of (H3O)Fe(SO4)2 that leaches in water rapidly (<5 min), but extraction efficiency is low (58% scandium). In contrast, baking at 400 °C results in the formation of Fe2(SO4)3 that leaches at slower kinetics (>45 min), but results in higher extraction efficiency (80% scandium). The acid baking water leaching process proves to be a promising technique as the first step of a potential near-zero-waste integrated process for the sustainable valorization of bauxite residue to help build the circular economy.

A novel roasting process to extract vanadium and chromium from high chromium vanadium slag using a NaOH-NaNO3 binary system.

This paper proposed a novel roasting process of extracting vanadium from high chromium vanadium slag. In this process, the high chromium vanadium slag was treated by NaOH-NaNO3 binary sodium salts, roasted in microwave heating furnace, and leached by water. During the roasting process, the temperature and time took a significant role in the conversion of vanadium and chromium. This novel microwave roasting was able to improve heating speed, accelerate the oxidization and decomposition of slag, and shorten the roasting time, compared with conventional muffle roasting. Under the optimum microwave roasting conditions (1 NaOH/NaNO3 mass ratio, 450 ℃ roasting temperature, and 10 min roasting time), the leaching rates of vanadium and chromium were 94.11% and 90.81%, respectively. In the leaching process, the reaction mechanism for the water leaching process was proposed. The process showed that leaching time and sample size played a significant role, while leaching temperature and liquid-to-solid ratio showed no obvious effect. The leaching residue analysis showed the major mineralogical phases were Fe2O3, Na2TiO3, NaFeSiO4, and a small amount of polymeric substance ((Mn,Ca)x(Fe0.6,Cr0.4)yOz·nSiO2).

An efficient utilization of chromium-containing vanadium tailings: Extraction of chromium by soda roasting-water leaching and preparation of chromium oxide.

Chromium-containing vanadium tailings (CCVT), an industrial waste, were utilized to extract chromium efficiently by soda roasting-water leaching process and for the preparation of highly pure chromium oxide. The effect of extraction of chromium under different roasting and leaching conditions were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The maximum chromium extraction rate of 91.51% was obtained when soda (Na2CO3) and CCVT were mixed in a molar ratio (n (Na2CO3)/n (Cr2O3)) of 8, roasted at 900 °C and maintained for 120 min. Then, the roasted product was leached in water at 60 °C for 60 min with a liquid-solid mass ratio (L/S) of 10. During soda roasting, the chromium-containing phase (Fe0.6Cr0.4)2O3 combines with Na2CO3 to form Na2CrO4, which was then transferred into the leaching liquid, post water leaching. The by-products such as NaFeTiO4, Na2CaSiO4, and Na0.68Fe0.68Si0.32O2 were left in the leaching residue which was called chromium tailings (CT). 87.40% chromium oxide was recovered from the unpurified leaching liquid after reduction and precipitation by adding Na2S, followed by roasting the deposit. This process not only relieved the potential threat of the industrial waste CCVT to the environment but also realized the recovery of the valuable element chromium.