The conventional vanadium extraction process generates Cr(VI)-containing byproducts, typically treated through chemical reduction and neutralisation, which results in the formation of hazardous solid wastes and secondary pollutants. To address this environmental concern, a closed-loop recovery strategy was developed involving selective precipitation of Cr(VI) with PbSO4, followed by leaching using NaHSO4. Under optimised conditions (pH 9.5, Pb/Cr = 1.4, 30 degrees C, 240 min), chromium was effectively precipitated as PbCrO4, reducing residual Cr concentration from 0.86 g/L to 0.002 g/L. Subsequent leaching of the Cr-rich precipitate at 80 degrees C for 100 min in 0.4 mol/L NaHSO4 achieved a high Cr recovery efficiency of 97.33%. The regenerated PbSO4 and leaching solution were reused over multiple cycles. A comparative evaluation demonstrated that this method outperforms conventional Cr(VI) removal technologies in terms of efficiency, waste minimisation, and reagent recyclability. Kinetic studies confirmed pseudo-first-order leaching behaviour (k= 0.0327 min-1) and precipitation governed by a shrinking-core model (kr= 0.00921 min-1), supporting industrial applicability and process robustness. The method eliminates the need for strong reducing agents, minimises waste generation, and enables reagent recycling. This approach outperforms traditional Cr(VI) removal techniques by offering superior selectivity, operational simplicity, and environmental sustainability, establishing a robust framework for green metallurgy and circular economy principles in vanadium slag processing. Le proc & eacute;d & eacute; conventionnel d'extraction du vanadium g & eacute;n & egrave;re des sous-produits contenant du Cr(VI), trait & eacute;s typiquement par r & eacute;duction chimique et neutralisation, produisant des d & eacute;chets dangereux. Cette & eacute;tude introduit une nouvelle strat & eacute;gie de r & eacute;cup & eacute;ration en boucle ferm & eacute;e impliquant une pr & eacute;cipitation s & eacute;lective du Cr(VI) par PbSO4 suivie d'une lixiviation par NaHSO4, permettant le recyclage des r & eacute;actifs et la minimisation des d & eacute;chets. Dans les conditions optimis & eacute;es (pH de 9.5, Pb/Cr = 1.4, 30 degrees C, 240 min), on a r & eacute;duit la concentration en Cr de 0.86 g/L & agrave; 0.002 g/L (& eacute;limination de 99.7%). Une lixiviation & agrave; 80 degrees C pendant 100 mi dans 0.4 mol/L de NaHSO4 a produit une r & eacute;cup & eacute;ration de 97.33% du Cr. Le proc & eacute;d & eacute; a support & eacute; plusieurs cycles avec des performances constantes. L'analyse cin & eacute;tique a r & eacute;v & eacute;l & eacute; une lixiviation de pseudo-premier ordre (k = 0.0327 min-1) et une pr & eacute;cipitation par r & eacute;tr & eacute;cissement du noyau (kr = 0.00921 min-1). Cette m & eacute;thode surpasse les techniques traditionnelles en termes d'efficacit & eacute;, de s & eacute;lectivit & eacute; et de durabilit & eacute; pour le traitement des scories de vanadium.

Water pollution caused by heavy metals and dyes has emerged as a pressing global issue due to their adverse effects on human health and ecosystems. In this study, magnetic zeolite nanocomposite (Fe3O4–NaA) was employed as an efficient magnetic adsorbent to remove cadmium (Cd), lead (Pb), malachite green (MG), and methylene blue (MB) from aqueous solutions. The Fe3O4–NaA adsorbent was synthesized and characterized through scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) analysis. The results confirmed nanostructure, high surface area, and high adsorption capacity of this adsorbent. The point of zero charge (pHpzc) of the Fe3O4–NaA was determined to be 6.2, demonstrating its versatility for various pH ranges. Process optimization was conducted using a central composite design (CCD) matrix combined with response surface methodology (RSM) to evaluate the influence of key factors, including solution pH, Fe3O4–NaA nanocomposite amount, ultrasonic time, and initial analyte concentration. The optimal conditions (Fe3O4–NaA nanocomposite amount of 0.04 g, pH of 7, initial analyte concentration of 17 mg L-1, and ultrasound time of 16 min) resulted in removal efficiencies ranging from 91.11

In this study, an efficient membrane composed of polysulfone and graphene oxide was developed and evaluated for its efficacy in chromium adsorption. Characterization of the synthesized membrane involved comprehensive analyses including scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR) to assess its structural properties. Subsequently, the membrane’s performance in removing chromium from aqueous solutions was scrutinized, considering key operational parameters. Response surface methodology (RSM) based on central composite design (CCD) was employed to optimize parameters. Additionally, the pH parameter revealed the most significant (F-value = 184.25) on the amount of chromium removal by the membrane process. The interaction between pH and contact time is the most significant among all interactions, with an F-value of 40.99. Moreover, the high R2 (97.58

In this study, we utilized a comprehensive dataset comprising over 19,000 data points with inputs represented by coordinates (x, y) and the corresponding output denoted as concentration (C). The case study was analysis of mesoporous material for adsorption separation of target solute from aqueous solution. Mass transfer and machine learning evaluations were carried out to obtain separation efficiency. Our objective was to develop predictive models for C using three distinct base models: decision tree (DT), support vector regression (SVR), and Gaussian process regression (GPR). To enhance the predictive performance of these base models, we employed the ensemble method AdaBoost, which combines their outputs to yield more accurate predictions. Hyper-parameter optimization was achieved through particle swarm optimization, allowing us to fine-tune the models for optimal results. The results of our experiments demonstrate promising performance across the ensemble models. Specifically, AdaBoost combined with decision tree (ADA-DT) yielded an impressive R2 of 0.96984 and a mean squared error (MSE) of 7.9407E+00. AdaBoost combined with SVR (ADA-SVR) achieved an even higher R2 score of 0.97148 with an MSE of 7.6362E+00, while AdaBoost combined with GPR (ADA-GPR) produced a commendable R2 score of 0.95963 with an MSE of 8.16352E+00.

An efficient, simple, cheap and environmental friendly microextraction procedure was developed by hydrophobic deep eutectic solvents based vortex-assissted liquid-phase microextraction (HDES-ALPME) followed by ETAAS detection. A family of DESs were synthesised using l-menthol and different carboxylic acids including hexanoic acid, octanoic acid, decanoic acid and dodecanoic acid and their efficiency in extracting complexed Cr(III) ions was evaluated. The results showed that the DES made of l-menthol and decanoic acid creates a stronger interaction with the analytes and has a better extraction efficiency. After optimising all effective parameters, the proposed procedure showed good linear range of 0.7-70 mu g kg-1 with coefficient of determination (r2) 0.9950. The limit of detection was 0.2 mu g kg-1 (S/N = 3) for Cr(III) ions, and the high enrichment factor was 277. For measuring the precision, the inter-day and intra-day relative standard deviations (RSDs) were determined to be between 3.6 - 7.2% in three selected concentrations. The potential of the synthesised DES in the separation of Cr(III) from vegetable samples was then examined under optimum conditions. Total chromium (t-Cr) was extracted similarly after reduction of Cr(VI) to Cr(III) with hydroxylamine hydrochloride solution and Cr(VI) concentration was calculated by difference.

This study investigated the removal of tetracycline and ciprofloxacin antibiotics from an aqueous solution in a batch system using magnetic copper ferrite (CuFe2O4) nanoparticles as adsorbents. Next, the effects of important parameters such as concentration, adsorbent dosage, ultrasonication time, and pH were examined on the efficiency of the tetracycline and ciprofloxacin removal process. The optimum conditions of the parameters were determined through the Box-Behnken design (BBD) based on the design of the experiment (DOE). The second-order regression coefficients were estimated following the statistical analysis of the results by analysis of variance (ANOVA). The optimal points were determined accurately by combining the results and drawing a second-order multivariate equation. The optimum conditions were obtained at a concentration of 30 mg L-1, a dosage of 0.021 g, a pH of 7, and an ultrasonication time of 11 min. Under the optimum conditions, the maximum removal efficiency was 96.89% and 99.03% for tetracycline and ciprofloxacin, respectively. The performance of CuFe2O4 adsorbent in five consecutive experiments did not show much decline, indicating the reusability and stability of the adsorbent. The study results showed that CuFe2O4 adsorbent could remove tetracycline and ciprofloxacin from real water samples by more than 98%.

Coal gangue (CG) is one of the main solid wastes emitted by coal mining. It causes severe damage to the environment. CG contains high levels of valuable elements (Al, Si) and has the potential for utilization and clean disposal. Here, an environment-friendly process for separating valuable components from CG was proposed: the closed-loop system of activation-leach-separation. The results show that the decarbonization rate was close to 100% under the optimum conditions of CG particle size of 0.075 mm to 0.15 mm and activated at 800 degrees C for 120 min. Subsequently, it was transformed into a mixed-acid system with a hydrochloric acid (HCl) concentration of 4.5 mol/L, hydrofluoric acid (HF) volume fraction of 15%, and the liquid-solid ratio of 10:1, which achieved excellent separation efficiency. The residual rate of Al in the solution was only 0.7%, and the extraction rate of Si can reach 71.6%. Further, industrial-grade AlF3 products were also recovered. By adding saturated KCl solution and reacting at 33 degrees C for 15 min, Si was further recovered in K2SiF6, and the yield was 85.83%. Particularly, the leaching solution maintained good extraction efficiency in the subsequent three cycles, the yield of K2SiF6 was 88.29%, confirming the feasibility of the closed-loop system. This treatment embodied the environmental-friendly properties of low acid consumption and low effluent discharge, providing a feasible method for clean treatment and resource utilization of CG.

Copper slagCopper slag is a major waste produced in pyrometallurgical plants during the smelting and converting operations and has caused heavy environmental contamination. A pyro-hydrometallurgical process for the treatment of copper slagCopper slag has been developed to accomplish recovery of nickelNickel, cobaltCobalt, and copperCopper and reuse of iron source. It was proved that the slag phase was reconstructed by sulfation-sulfate decomposition roastingRoasting followed by water leachingLeaching, over 95

The effect of mechanical activation on extraction of vanadium from chromium-containing vanadate solution by precipitation with calcium salt and leaching with sodium carbonate salt was investigated. The whole process including selective precipitation of vanadium, alkali leaching of vanadium and cyclic utilization of calcium. Compared with stirring, ball milling is more effective for vanadium precipitation under the same experiment conditions. This is because the calcium vanadate formed on the surface of Ca(OH)(2) can be peeled off by mechanical activation, which can also be confirmed by SEM image, EDS spectra and XRD patterns of the precipitation. The effect of temperature ranging from 20 degrees C to 50 degrees C on vanadium leaching efficiency was studied with the other reaction conditions fixed as stirring speed of 400 r/min, NaHCO3/V molar ratio of 2.80, L/S ratio of 4:1 ml/g. It is observed that vanadium leaching efficiency exceeding 99% was obtained after only 6 min of reaction as well as leaching temperature had little influence on vanadium leaching efficiency. After filtration, the leach solution was used to prepare crystals of NH4VO3 and the leach residue was calcined to obtain CaO. The precipitation efficiency of V was 99.34% by adding CaO into chromium-containing vanadate solution according to Ca/V molar ratio 1.80 and ball milling for 90 min with 140 rpm at room temperature. Mechanical activation can not only increase the vanadium precipitation efficiency and improve the leaching performance of the precipitate, but also to realize the cyclic utilization of calcium salt and crystallization solution.

The conventional process of sodium carbonate roasting-water leaching for vanadium extraction cannot be applied to high chromium bearing vanadium slag, and the production process will produce a large amount of V-Cr-bearing reducing slag and wastewater containing sulfate and ammonium salt. To avoid these questions, this work proposes a novel process for the extraction of vanadium and chromium from vanadium slag. In the current research, the vanadium precipitation part of the novel process was studied in detail. The experiment results show that weak basic ammonium bicarbonate precipitation method can realize the selective precipitation of vanadium from chromium-containing vanadate solution. The presence of Cr(VI) in the solution has a great influence on precipitation, crystallization as well as product purity of NH4VO3. Chromium can increase the solubility of NH4VO3 and reduce the supersaturation degree of NH4VO3. Furthermore, it can change the crystal morphology of NH4VO3 and affect the precipitation of NH4VO3. The precipitation of NH4VO3 increased with the increase of N/V molar ratio, but decreased with the increase of chromium concentration in the solution. The content of chromium in V2O5 increased with the increase of N/V molar ratio as well as the chromium concentration in solution. For vanadate solutions containing 2.0, 5.0, 10, 20 and 25 g/L Cr, under the most suitable vanadium precipitation conditions, the precipitation of vanadium is 83.5%, 80.1%,73.8%, 61.2% and 60.3%, respectively.

Cyclic metallurgical process for separation and recovery of Cr from vanadium precipitated solution by precipitation with PbCO3 and leaching with Na2CO3 was investigated. The concentration of Cr residue in the solution decreases from 2.360 to 0.001 g/L by adding PbCO3 into vanadium precipitated solution according to Pb/Cr molar ratio of 2.5, adjusting the pH to 3.0 and stirring for 180 min at 30 °C. Then, the precipitates were leached with hot Na2CO3 solution to obtain leaching solution containing Na2CrO4 and leaching residue containing PbCO3. The leaching efficiency of Cr reaches 96.43% by adding the precipitates into 0.5 mol/L Na2CO3 solution with the mass ratio of liquid to solid (L/S) of 10:1 mL/g and stirring for 60 min under pH 9.5 at 70 °C. After filtration, leaching residue is reused in Cr precipitation and leaching solution is used to circularly leach the Cr precipitates until Na2CrO4 approaches the saturation. Finally, the product of Na2CrO4·4H2O is obtained by evaporation and crystallization of leaching solution.

The recovery of chromium from vanadium precipitated solution obtained by adding Ca(OH)(2) into the chromiumcontaining vanadate solution and ball milling was investigated by precipitation with lead salt and leaching with sodium carbonate. It has been found that chromium can be effectively enriched by adding PbCO3. The precipitate is the mixture of PbCO3 and PbCrO4 center dot PbO. The concentration of Cr residue in the solution can be decreased to 16.0 mg/L by adding PbCO3 into vanadium precipitated solution according to Pb/Cr molar ratio 4.0 and adjusting the pH to 12.5 with NaOH stirring for 180 min at 20 degrees C. Then the precipitates were leached with hot Na2CO3 solution under pH 10.0 at 50 degrees C to obtain the leach solution containing Na2CrO4 and the leach residue containing PbCO3. After filtration, the leach residue was reused in Cr precipitation and the leach solution was used to circularly leach the Cr precipitate until Na2CrO4 near saturation. Finally, the product of Na2CrO4 center dot 4H(2)O with purity 99.3% was obtained by evaporation and crystallization of the leach solution.

In this paper, the production of crystal Cr2O3 with V-Cr-bearing reducing slag was studied. After the V-Cr-bearing reducing slag was roasted with H2SO4 and CrO3 at about 140 degrees C, can not only Cr in the roasted materials be selectively leached with water, but V be enriched in the leaching residue. Then the leaching residue was used to produce V2O5 , and the leaching solution was used to produce Cr2O3 . After impurities V, Fe and Si were removed by adding Fe-2 (SO4)(3) and Na2CO3 into the leaching solution under pH 3.2-3.8, the precipitate of Cr2O3 center dot xH(2)O was formed by adjusting the pH to about 8 with NaOH. The crystal of Cr(2)O3 with purity > 98 % was produced by treating the Cr2O3 center dot xH(2)O under vacuum 10-15 pa at 650 degrees C for 4 h. Under vacuum, the transformation temperature of Cr(2)O(3 center dot)xH(2)O to crystal Cr2O3 can be significantly reduced. Therefore, using this process, not only V and Cr can be separated and recovered from V-Cr-bearing reducing slag, but also the production cost of crystal Cr2O3 can be reduced.

The recovery of Cr(VI) from vanadium precipitated solution obtained by adding Ca(OH)2 into chromium-containing vanadate solution and ball milling was investigated by precipitation with PbSO4. It was found that Cr can be effectively precipitated from the solution by PbSO4. The precipitate is mixture of PbSO4 and PbCrO4.PbO. The concentration of Cr remained in the solution decreases from 2.360 g/L to 0.002 g/L by adding PbSO4 into vanadium precipitated solution according to PbSO4/Cr molar ratio 3.0 under pH 11.5 and stirring for 120 min at 30 °C. After filtration, the precipitates were leached in H2SO4-Na2SO4 system solution to obtain Na2Cr2O7 solution and the filtrate can be reused to leach the precipitate contain PbSO4 and PbCrO4.PbO.

循环冶金工艺是指,既可经济高效提取有价金属,又能实现工艺过程所用的化工原料及水的循环利用的冶金工艺,是从源头上减少或避免“三废”产生的冶金工艺.随着国家经济转型发展,生态文明建设及环境保护工作的深入进行,冶炼行业面临严峻的挑战,许多传统冶金工艺不得不转型升级.以钒渣提钒液分离回收钒铬及碳酸钠,硝酸退镀液分离回收铜和硝酸,及铜电解液自净化分离回收砷、锑、铋为例,介绍循环冶金工艺的开发与应用.