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To establish a cleaner production technology of chromium salt, the pressurized leaching process of chromite ore in 60 wt.% NaOH solution, subsequent separation of a chromium salt from the leached solution and Cr2O3 preparation from the intermediate product BaCrO4 were systematically investigated, and a new highly efficient and economical process for the production of Cr2O3 from chromite ore was established. The results showed that the decomposition of chromate ore could be significantly improved by increasing the temperature, and the Cr leaching rate reached 99% at 240 ℃ for 4 h. Meanwhile, the leaching process was controlled by surface chemical reactions with activation energy (Ea) of 34.3051 kJ/mol and a pre-exponential factor (A) of 6.9560. In the leached liquor, Na2CrO4 was transformed into BaCrO4 through its reaction with Ba(OH)2, Cr separation efficiency could reach as high as 89% in the undiluted leached liquor, while the separated alkali liquor could be effectively recycled for the leaching of chromite ore. Ultimately, a new method for the preparation of Cr2O3 from the intermediate product BaCrO4 was presented by the dissolution and reduction of BaCrO4 with HCl-CH3CH2OH as the reactant. The new cleaner process for Cr2O3 preparation from chromite ore provides an attractive alternative to upgrading the current chromate salt production processes.

The recovery of rare earths elements (REEs) from NdFeB slurry by traditional hydrometallurgy has been limited becuase a large number of REEs are lost during separation together with iron. In this paper, a simple and sustainable method is proposed to efficiently separate and recover REEs and iron from NdFeB slurry. REEs were recovered by one-step selective precipitation in phosphoric acid, and the dissolved iron was recovered by oxalic acid. Phosphoric acid leaching results show that under the conditions of 4 mol/L phosphoric acid, 80 °C, L/S of 30:1 and 90 min, the leaching efficiencies of Fe and REEs reach 98.76% and 1.09%, respectively. While the rest of REEs remained in the leaching residue in the form of REEPO4·nH2O precipitation. Subsequently, the mixed rare earth oxide (rare earth oxalate roasted at 800 °C) and FeC2O4·2H2O are obtained by oxalic acid precipitation with purities of 99.49% and 97.17% from the REEPO4·nH2O dissolving solution and the phosphoric acid leaching solution. Moreover, the phosphoric acid is regenerated while recovering iron, and it can be reused in the phosphoric acid leaching step after removing the impurity C2O42−. In summary, this work provides an efficient and environmentally friendly method for recovering REEs and iron from NdFeB slurry waste.

Asymmetric hydrogenation based on heterogeneous metal nanoparticles (NPs) has attracted extensive attention for the production of chiral chemicals due to its high conversion efficiency, simple product separation, and convenient catalyst regeneration. Nevertheless, its further practical application is still impeded by the leaching of expensive chiral ligands and by the associated extra purification costs that are caused by the weak absorption of the chiral ligands on the metal NPs. In contrast, chiral metal–organic frameworks (CMOFs) have been proposed to serve as metal NP supports and chirality inducers via biomimicry of the configuration of privileged natural cinchona alkaloids on the single-chiral-site level. Among the presented engineered isoreticular valine (Val)-, serine (Ser)-, and threonine (Thr)-derived CMOFs, the Thr-MOF-supported Pt nanoparticles (NPs) exhibit impressive enantioselectivity in the asymmetric hydrogenation of ethyl pyruvate (EP) in addition to inherently robust catalytic recyclability without the need to add either fresh chiral ligands or Pt NPs.

The development of efficient and sustainable strategies that evades the utilization of petroleum reserves is highly challenging yet inevitable today. In this regard, the conversion of pine tree-derived β-pinene to highly recognized nopol is particularly attractive owing to its widespread applications. Herein, we describe an approach that enables the selective synthesis of nopol with extraordinarily activity of MIL-101(Cr). This remarkable activity of MIL-101(Cr) attributed to its high specific surface area (SSA), accessible active sites in the mesopore architecture and unsaturated Cr3+ Lewis acid sites. We have established a good correlation between the superior catalytic performance and textural properties of the materials, which can be tuned by using different mineralizing agents. To realize the unprecedented catalytic activity, the influence of reaction parameters, solvent properties, and mineralizing agents have been investigated systematically. The MIL-101(AA) (AA-Acetic acid) exemplified the highest catalytic activity, which is superior to most of the reported materials for this transformation to date. The results of catalyst recycle and hot filtration experiments have emphasized that the catalyst is resistant towards leaching of active sites and retained its original catalytic activity beyond four recycles. An Eley Rideal based model was used to study the reaction kinetics and establish a plausible reaction mechanism. The activation energy of the reaction was found to be 102 kJ mol-1 and the enthalpy of formaldehyde adsorption is -86.88 kJ mol-1.This approach opens up new avenues for the valorization of biomass-based molecules into useful chemicals.

This study is dedicated to exploring the effect of pH, leaching time, ferrous sulfate amount, temperature, as well as their interaction on the dissolution of cobalt by response surface methodology. The ferrous sulfate was used as an effective reducing agent for the dissolution of heterogenite, which constitutes the main cobalt mineral found in Congolese Copperbelt, and the experiments conducted were based on central composite design. Analysis of variance was carried out to study the effects of the individual variable as well as their combined interactive effects on the recovery of cobalt. The optimum process conditions for the cobalt recovery were determined by a desirability function. The results showed that the amount of ferrous sulfate, leaching time, and leaching temperature were statistically significant as independent linear terms. The results also revealed that the interaction of leaching time and the amount of ferrous sulfate has an important effect on cobalt dissolution. The optimal cobalt recovery was 95.79% at the leaching time of 104.48 min, pH of 1.87, amount of ferrous sulfate of 14.9 g, and temperature of 54.8 °C, while the experiment of validation at these optimum conditions gave the cobalt recovery of 93.82%. This testifies on the goodness of the model developed in this work, thus, verifying that the model is suitable and fits the experimental data with a reasonable error.

The textile industry uses synthetic dyes because they are cheaper and easier to obtain. Moreover, the color availability is guaranteed and more varied. However, these synthetic dyes have a negative impact on health and the environment. The natural dye from avocado (Persea Americana Mill) seeds can become an alternative for synthetic dyes. Polyphenol compounds, such as tannins and flavonoids, are natural color sources found in avocado seeds. The extraction of natural dyes from avocado seeds is carried out by using a non-conventional method, namely ultrasonic-assisted extraction which has great efficiency and short operating time. In this study, researchers examined the parameters that affect the yield of dye extraction from avocado seeds, namely solvent concentration and extraction time. In addition, researchers also conducted qualitative analysis on the pigment content in the yield of extraction using UV-Visible Spectrophotometry and GC-MS tests. The results indicated that the highest yield obtained from avocado seeds was 16.6742% with 90 minutes extraction time using 70% ethanol solvent. Furthermore, if the dye is applied to cellulose fibers, such as the cotton cloth, the color will change depending on the fixator added. Based on the result of the UV-Visible Spectrophotometry test, the avocado seeds contain flavonoids. Meanwhile, from the result of the GC-MS test, the compound with the largest percentage detected in avocado seeds is the 13-Tetradecynoic acid, methyl ester (C15H26O2). The compound contains a chromophore, such as a carbonyl group (C = O) which is a common feature of flavonoids.

The dissolution behaviors of various minerals in the tellurium–bismuth ore during oxidic–acidic leaching were investigated systematically in this work. The Te–Bi phase in the ore distributes in network shape, triangular shape, tree shape, strip shape, bulk shape, sparse granule, flake shape, crescent, etc., which are closely intercalated with FeS, FeS2, and CaCO3·(Mg,Fe,Mn)CO3. Under suitable conditions, 95.61% Te and 95.77% Bi can be recovered. Within 20 min of the initial leaching, most of dolomite and Te–Bi phase dissolve rapidly. With the extension of leaching time, a large amount of rod-shape CaSO4 particles form, attach on the surface of the tellurium–bismuth ore particles, and then grow and coarsen. The (Mg,Fe,Al)(Si,Al)Ox(OH)y phase dissolves mainly within 60 min. Fe–S phase can be corroded but cannot dissolve completely. SiO2 cannot dissolve at all. Besides, H2SO4 and Fe3+ play a significant role on the dissolution of various minerals in the ore. Without Fe3+ or H2SO4 in immersion liquid, Te and Bi are difficult to be leached into the lixivium from the tellurium–bismuth ore. As H2SO4 concentration and Fe3+ concentration increase, Te–Bi phase and Fe–Mg–Al–Si–O phase gradually dissolve, the Fe–S phase can be corroded obviously but cannot dissolve, and the Si–O phase has no change. The dissolution of dolomite is mainly controlled by H2SO4. The dissolution behaviors of various minerals in the tellurium–bismuth ore during oxidic–acidic leaching were investigated systematically. Most of dolomite and Te–Bi phase dissolve rapidly. A large amount of rod-shape CaSO4 particles form, attach on the surface of the tellurium–bismuth ore particles, and then grow and coarsen. H2SO4 and Fe3+ play a significant role on the dissolution of various minerals in the ore.

The structures of phosphate ore particles have great impact on their dissolution behavior. In this work, two kinds of fluorapatite structures in the phosphate ore matrix were identified. The effect of various dissolution process variables including stirring rate, reaction temperature, HCl concentration and phosphate ore particle size was investigated firstly. Then, a structure-related segmented kinetic model for phosphate ore particles dissolution in hydrochloric acid was established to discuss the influence of composition and structure of phosphate ores on the leaching rate. According to the kinetic model, the apparent activation energies were 41.99 ± 0.24 kJ·mol−1 and 46.00 ± 0.35 kJ·mol−1, respectively, for the different type of phosphate ore structures. Based on the kinetics study, the leaching process can be optimized from the point of view of the particle size of phosphoric ore in the industrial applications.

With increasing consumption of lithium-ion batteries (LIBs), recycling of spent LIBs has attracted much attention owing to their potential environmental impacts and metal values. In this work, a hy...

As an emerging pollutant, microplastics (MPs, plastic particles with size 5 mm) pollution in water has acquired extensive attention in recent years due to their small particle size and stable properties, which can act as a carrier for pollutants in water environment and have toxic hazards to aquatic organisms. After entering into water environment, MPs are readily undergone varied types of weathering processes (i.e., hydrolysis, photo oxidation, mechanical abrasion, and biodegradation), leading to shifted surface morphology (i.e., surface roughness, specific surface area, and size) and physicochemical properties (i.e., melting temperature, surface charge, molecular weight, crystallinity, and hydrophobicity). Among different weathering processes of MPs in water, sunlight induced photo aging process has been considered as primary contributor, which will further impact the MPs behaviors, such as aggregation and deposition in water column, adsorption to organic and inorganic pollutants, leaching of additives, as well as toxicity to organisms in water. From the perspective of MPs aging mechanism, photo aging process of MPs in water environment is a free radical associated chain reaction process and readily to be affected by polymer types, plastic additives, halogen ions, and natural organic matters. These components are generally photochemical activated and prone to involved in the direct or free radical associated indirect photo aging process processed. However, limited information has referred the impact of plastic additives and water constitutes on the long term weathering process for MPs in water, which will pose a great difference between laboratory-accelerated weathering and long-term natural weathering. Studying the photo aging mechanism of MPs in water environment is of great significance for evaluating their formation process and potential ecological risks. Based on the above considerations, we systematically reviewed the photo aging and fragmentation processes of MPs in water environment. The content of this work contains: (1) Photo aging mechanism and changes of MPs physicochemical properties during aging process in water. Research results revealed that photo aging process could affect the molecular arrangement and mechanical properties of MPs, and further fragment into smaller size secondary MPs even in nano-scale particles, which is important to explain the formation of MPs in current water environment. (2) Critical effect of plastic properties, such as polymer type, size, and plastic additives on the aging of MPs in water; for the impact of plastic additives on the aging process of MPs, results in this work suggested that photo aging mechanism of MPs could be modified due to the presence of plastic additive (i.e., antioxidant and colorant). (3) Role of water constitutes (i.e., Cl−, Br, and NOM) on the photo aging process of MPs in water. The results emphasized the multiple impacts of water constitutes (halogen ions and natural organic matter) in the photo aging process of MPs in the water environment, illustrating that MPs may have different aging time and mechanisms in different water matrices. Moreover, impact of microorganism induced biodegradation for MPs in water is also proposed. In further study, more concentration should be concerned on the combined effects of plastic additives and water quality conditions on the aging process of MPs, which is helpful to shorten the distance between laboratory accelerated weathering and long-term aging process of MPs in natural waters. Besides, results of this paper can also provide theoretical support for comprehensively and systematically assessing the environmental behavior, toxicological effects and ecological risks of aged MPs in natural water environment.

An eco-friendly citric acid leaching of uranium (VI) from Abu Zeneima carbonaceous shale, as well as its extraction using humic acid, has been studied. Excess of chloride anions in the leachate sol...

Leaching of toxic or reactive chemicals from polymeric materials can adversely affect the quality and safety of biopharmaceuticals. It was therefore the aim of the present study to analyze leachables from a disposable clinical administration syringe using a polysorbate-containing surrogate solution and to assess their chemical reactivity. Analytical methods did include (headspace) GC-MS, Fourier-transform-infrared spectroscopy, a ferrous oxidation-xylenol orange assay, and nuclear magnetic resonance analysis. In the syringe leachables solution, the carcinogenic 1,1,2,2-tetrachloroethane (TCE) was detected in concentrations above the ICH M7-derived analytical evaluation threshold. TCE was shown to be an oxidation product of dichloromethane used during sample preparation. Since TCE was only isolated from incubations with the contained rubber stopper, we hypothesized that a stopper-derived leachable acted as a reactive oxidant promoting this chemical reaction. Subsequently, the leachable was identified to be the polymerization initiator Luperox® 101. Combining different analytical approaches led to the structural elucidation of a chemical reactive oxidant, which has the potential to interact and alter drug products. We conclude that chemically reactive compounds, such as the newly identified rubber stopper leachable Luperox® 101, may be of concern and therefore should be routinely considered if a prolonged exposure of polymers with drug products can be anticipated.

The extraction of tungsten from scheelite was carried out using a sulfuric acid solution with oxalic acid as the chelating agent. Tungsten was obtained in the form of highly soluble hydrogen aqua oxalato tungstate (H2[WO3(C2O4)·H2O]) during the leaching process, while calcium remained in the residue as calcium sulfate dihydrate (CaSO4·2H2O). About 99.2% of the tungsten was leached at 70 °C, 1.5 mol/L sulfuric acid, 1 mol/L oxalic acid, a liquid/solid ratio of 25:1 (mL/g), an oxalic acid to sulfuric acid molar ratio of 1:1, a stirring speed of 300 r/min and a leaching time of 2 h. H2[WO3(C2O4)·H2O] was thermally decomposed into tungstic acid (H2WO4), and tungsten trioxide (WO3) was directly produced by calcining H2WO4 at 700 °C for 2 h. The surface chemical reaction was determined to be the controlling step during tungsten leaching, and the apparent activation energy was calculated to be 51.43 kJ/mol.

In order to remove phosphorus element from steelmaking slag and decrease iron loss, malic acid was selected as the leaching agent to dissolve steelmaking slag. Firstly, the influences of different factors, such as malic acid concentration, slag particle size, temperature, liquid/solid ratio and stirring speed, on the leaching ratios of phosphorus and iron were studied. Then, the kinetics for the leaching process of phosphorus was analyzed. The results showed that the leaching ratios of phosphorus and iron increase significantly with increasing the malic acid solution concentration and liquid/solid ratio. When the concentration of malic acid solution increases up to 0.01492 mol/L, about 80% phosphorus can be dissolved, and iron leaching ratio is less than 17%. In addition, decreasing slag particle size can obviously increase the leaching ratio of phosphorus. However, temperature and stirring speed have no significant effect on the dissolution of phosphorus and iron. The leaching kinetics of phosphorus follows the unreacted shrinking core model. Diffusion through product layer is the rate-limiting step of the leaching process, and the corresponding apparent activation energy is determined to be 3.32 kJ/mol. Finally, a semi-empirical kinetic equation was established.

A linear solvation energy relationship (LSER) was developed to predict the partitioning of neutral chemicals from polysorbate 80 (PS 80) micelles to water. Predicted partition coefficients were converted to a concentration dependent solubilization strength of aqueous PS 80 solutions. This solubilization strength represents a key parameter to project equilibrium levels of leaching from pharmaceutical plastic materials. To construct the LSER model equation, partition coefficients between PS 80 micelles and water were measured via a reference phase method or collected from the literature. Multiple linear regression of partition coefficients against five publicly available solute parameters was used to obtain the LSER system parameters. 112 chemically diverse compounds were incorporated for LSER model regression. The model equation shows a very good fit (R2 = 0.969, SD = 0.219) for the entire dataset. The accuracy of the multi-parameter LSER model was proven to be substantially better in comparison to a single-parameter log-linear model based on the octanol-water partition coefficient. PS 80 solubilization strength in water can expediently and accurately be calculated for neutral organic compounds with the proposed LSER model. LSER system parameters provide insightful chemical information with respect to solubilization in aqueous solutions of PS 80.

A new Gemini Cationic Surfactant (GCS) was synthesized to extract and separate U(VI) ions from sulfate solution. The Gemini cationic amphipathic was synthesized by refluxing N, N, N, N-tetramethyl diethylene triamine with cetyl chloride. Traditional log D-log [GCS] analysis shows that the ligand has removed uranium as a complex of 2:1 (ligand: metal) ratio. The extraction of uranium was achieved using a new GCS extractant in octanol at pH 1.5 using 0.05 M GCS extractant from sulfate solution and the process is an exothermic process (ΔH = –10.94 kJ mol–1). Finally, El-Missikat sulfate leaching liquor was treated with optimum parameters of solvent extraction for U separation.

The present study focuses on the recovery of lithium from solid phases of a lithium-containing geothermal mud through hydrochloric acid leaching. The dried mud was initially characterized using different techniques, which includes particle size analyzer, X-ray diffraction, X-ray fluorescence, and atomic absorption spectrophotometer. The leaching experiments were carried out for 24 h with different variables and at different levels of variables, which includes hydrochloric acid concentration (3 M, 4 M, 5 M, and 6 M), leaching temperature (60 °C, 70 °C, 80 °C, and 90 °C), and solid percentage (5%, 10%, 15%, and 20%). Taguchi method involving the use of orthogonal arrays was used in designing and reducing the required number of experimental conditions. A simple mathematical model was used to determine the optimum condition within the investigated conditions. Analysis of variance (ANOVA) was also used in determining the degree of significance of variables in influencing the lithium recovery. The highest lithium recovery of 98.3% was obtained at the leaching experiment with hydrochloric acid concentration of 6 M, leaching temperature of 90 °C, and solid percentage of 10%. The results of this study provide new information and insight about the possibility of the lithium extraction process from the geothermal mud which has been so far considered as waste.

Porous organic polymers hold great promise for molecular sieving membrane separation. Although the inclusion of functional ionic liquid (IL) in the pores offers a facile way to manipulate their separation properties, the IL leaching during the separation process is difficult to avoid. Herein, we report a strategy to in-situ encapsulate ILs into the micropores of the conjugated microporous polymer membrane via a 6-min electropolymerization and further seal the aperture of the pores to prevent ILs leaching by solvent-assisted micropore tightening (SAMT). Upon screening the binding energy between different ILs and gas molecules, two ILs were selected to be incorporated into the membrane for CO2/CH4 and O2/N2 gas separations. The resultant separation performances surpass the 2008 Robeson upper bound. Notably, the ILs can be locked in the micropores by a facile high surface tension solvent treatment process to improve their separation stability, as evidenced by a 7-day continuous test. This simple and controllable process not only enables efficient and steady separation performance but also provides an effective strategy for confining and sealing functional guest molecules in the porous solids for various applications.

Plasticised poly(lactic acid) (PLA)-based antimicrobial films were successfully produced via solvent-casting method. For this purpose, PLA copolymer-bearing quaternary ammonium salt in rate of 5 mol% was successfully fabricated through a two-step reaction procedure, i.e. combination of ring-opening copolymerization and copper(I)-catalysed azide–alkyne cycloaddition click reactions. The synthesized polymer was blended at three different amounts (5, 20 and 30% w/w) with commercial PLA which was plasticized with PEG-1000. After the blending process, antimicrobial activity of all the composite films was investigated against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria via contact-active method. It was determined that the films blended with polymer containing quaternary ammonium salt on its backbone had a highly effective antimicrobial activity against both bacteria, even at the lowest blending rate. Besides, the thermo-mechanical behaviours of obtained films were analysed. Thermal property of films was not changed significantly after blending process of antimicrobial polymer. As a result, it can be said that the film which contains antimicrobial polymer at the lowest amount provides the purpose of this work with the highly effective antimicrobial activity and better mechanical properties compared to other films.

A choline chloride–sulfosalicylic acid deep eutectic solvent (DES) is proposed for dissolving the oxides Co(II), Cu(II), Zn(II), Fe(III), Ni(III) and Mn(III). An experimental study of the influence of the dissolution time, solid : liquid mass ratio, temperature, and molar ratio of choline chloride and sulfosalicylic acid on the dissolution of metal oxides in the proposed DES has been carried out. The mechanism of dissolution of the investigated metal oxides has been established. It is shown that choline chloride–sulfosalicylic acid DES can potentially be used for the efficient leaching of metals from components of spent chemical power sources.

In this study, selective separation of tellurium from nitric acid leaching liquor obtained from Sarcheshmeh Copper anode slime was performed by using a bulk liquid membrane (BLM). To find the optimum operational conditions, the experiments were designed using the Taguchi method. The effect of TBP concentration in the liquid membrane phase and hydrochloric acid concentration in the donor and acceptor phases was investigated on selective extraction of tellurium. The maximum selectivity of tellurium relative to selenium and Copper was obtained equal to 10.87 and 70.05, respectively, in 4 M hydrochloric acid of the donor phase, 30% (v/v) TBP in kerosene, and the 0.5 M hydrochloric acid in acceptor phase. At these conditions, the transfer percentage (TF%) of tellurium was obtained equal to 14.04%. Moreover, to increase the selectivity and TF% of Te, the time effect and the number of separation stages (BLM) were investigated at the aforementioned optimum conditions. The results showed that TF% and the selectivity of Te to Se increase to 33.93% and 15.5, respectively, by increasing the time up to 240 min. Furthermore, using multistage BLM leads to an increase in the selectivity of tellurium than selenium and Copper up to 2549 and 4530.6, respectively, after using only four separation stages.

In this study, the recovery of manganese, nickel, cobalt and lithium of electroactive components from spent lithium-ion batteries is described in detail. Experiments were performed in the presence of formic acid as leachant. Temperature, time, acid concentration and solid/liquid ratio were varied. Manganese, nickel and lithium were leached in high yields (> 99 wt.%) at ~ 80 °C for 3 h using 10 mol L−1 formic acid. This acid played the dual role of leachant and reductant for nickel and manganese. However, cobalt was only half leached under these conditions. The insoluble cobalt was rapidly dissolved after adding H2O2 to the leachant. Leached manganese, cobalt and nickel, in this order, were extracted from the leachates with di-2-ethylhexylphosphoric acid (D2EHPA) (25 °C, A/O = 1 v/v) after adjusting pH of the leachate using lithium carbonate. Stripping was run using 1 mol L−1 H2SO4. Lithium (99.5 wt.%) was recovered as formate, a high-value added byproduct, by careful evaporation of the aqueous final solution, thus reducing generation of final wastes.

Datura stramonium L. (Solanaceae) possesses a rich tropane alkaloids (TAs) spectrum. The plant contains, in particular, the allelopathic compounds scopolamine and atropine, which are poorly soluble in water, thus limiting their use in agrochemical formulations as biocidal and deterrent agents against herbivore insects. The efficacy of the hydrophobic TAs extracts could be increased with the improvement of their dissolution/leaching properties. This is important for improving screening and test performance and for elucidating the activity of environmentally friendly agricultural approaches, with new perspectives for the production and use of those biodegradable insecticidal products. The present study explores the aspects of atropine and scopolamine complexation with cyclodextrin (CDs) through FT-IR and UV–Vis spectroscopies. In addition, the structures of the inclusion complex of atropine, scopolamine and β-CD have been investigated by molecular modeling techniques. The results obtained indicate that β-CDs are a promising carriers for improving the properties of TAs, therefore increasing their application potential in agrochemical formulations. Graphic abstract

In this article, the simulation of uranium mining by underground leaching using MPIparallelization technology is carried out.MPI technology is actively used in scientific calculations and allows you to speed up calculations bydividing processes into internal areas. The original calculation area was divided into internal areas for eachindividual process, and each area was divided into the same number of points for synchronous operation ofall processes. The parallel computing algorithm was tested by running different numbers of the process. Thenumber of points in the initial area was 360×180×180. As the number of processes increases, the number ofpoints allocated to it decreases, that is, the calculation time decreases.Underground leaching technology is a method of injecting leaching solution into the formationthrough wells and selectively dissolving the mineral in the rock by chemical interaction of the leachingsolution with the ore. The underground leaching method refers to a group of extractive methods based on asolution used to isolate various solids, such as salt, potassium, and sulfur.The processes of acidification of the Ore layer with a solvent, filtration of the solution of the pumpedacid in the Ore body and absorption of the productive solution are considered, the distribution of theconcentrations of the reagent, the useful component in the liquid and solid phases is determined.

Crude oil ash is the residue that is produced during oil combustion for instance fly ash, bottom ash or boiler slag which was primarily produced from the combustion of coal. With growth in oil burning power station, huge amount of fly ash considered as organic materials which are normally disposed in an on-site disposal system without any commercialization purpose. Previous researchers have studied the extraction of silica from agricultural wastes such as palm ash and rice husk ash (RHA) and FA (fly ash) by using leaching treatment method. In this study, the weaker acid, citric acid solution was used to replace the strong acid in leaching treatment to process. Result showed that the loss on ignition materials can be decrease to 12%. Meanwhile the silica can be extracted up to 54.4% from FA using citric acid leaching treatment under the optimum reaction time of 60 minutes with solution temperature of 60°C and concentration of citric acid 5% receded by gradual combustion at 900°C for 3 hours. http://dx.doi.org/10.30572/2018/kje/100306

The authors attempted to investigate the copper recovery possibilities from low-grade mixed sulfide-oxide ore in the present paper. The randomized leaching experimental results in sulfuric acid sol...

Citric acid has a very important role in the extraction process of uranium from the matrix such as hydrous oxide cake formed after alkali breakdown of Egyptian Rosetta monazite mineral concentrate....

Study of nickel leaching using sulfuric acid and phosphoric acid on the selectivity of low-grade laterite nickel ore under atmospheric conditions has been successfully carried out. In this study, the laterite nickel leaching process was carried out by varying the solution concentration and operating time. The concentrations of sulfuric acid and phosphoric acid solutions were varied at 5 M and 6 M concentrations, while the operating time was varied at 4 hours and 6 hours. For other operating conditions, it is kept constant with an operating temperature of 90 ℃, pulp density 15% w / v, particle size ≤ 200 mesh. After that, the analysis stage was carried out using an atomic absorption spectroscopy (AAS) tool to determine the nickel content in the sample. The results showed that the highest nickel recovery was obtained at the concentration of 5 M sulfuric acid solution of 2.60% and 5 M phosphoric acid of 2.59% with the optimum operating time at 4 hours of operating time.

Current industrial methods of biodiesel production lead to an excess of crude glycerin which requires costly purification before commercialization. Production of oxygenated fuel additives is a potential route for glycerin valorization. Glycerin acetylation was carried out over heterogeneous acid catalysts (15%, glycerol weight basis) using glacial acetic acid (molar ratio = 9). The catalysts, containing different amounts of phosphate species (P/Si from 10 to 20 atomic ratio), were prepared by wet impregnation of commercial silica with aqueous solutions of diammonium phosphate and ortho-phosphoric acid. X-ray diffraction patterns of calcined solids presented amorphous patterns like raw silica. The prepared catalysts presented, at 120 °C, glycerol conversion higher than 89.5% after 1 h of reaction, been diacetin the major product, with triacetin selectivities lower than 26.1%. Diacetin selectivity was found to be almost invariant with catalyst acidity thus underlining the relevance of catalyst porosity due to the large acetins molecules sizes. The slow rate of triacetin diffusion in narrow pores of catalyst might be responsible for the relatively low yield obtained. Surface phosphate species showed a slow rate of leaching in the reaction medium showing high catalyst stability.

The conversion of biomass-derived products to fine chemicals and fuels is extremely important for the utilization of renewable energy sources. Water is not only a by-product formed during the hydrogenation of biomass-derived oxygenated chemicals, but also an inexpensive and nontoxic solvent. The instability of solid catalysts for aqueous-phase reactions caused by metal leaching and the collapse of a catalyst support represents a significant challenge. In this work, various catalyst stabilization strategies including the nanospace and interfacial confinements that prevent sintering and leaching of metal nanoparticles as well as modification methods for increasing the support stability are summarized and systemically discussed. In addition, feasible approaches to designing stable and efficient heterogeneous catalysts for aqueous-phase reactions are proposed.

The permeability of the weathered crust elution-deposited rare earth ores directly affects the efficiency of in-situ leaching. The soil-water characteristic curve (SWCC) is an important constitutive relation for calculating the permeability of ore body, which is related to many factors. Soil-water characteristic tests of rare earth ore samples considering different factors were carried out by using the pressure plate instrument. Effects of dry density, particle size and solution leaching on water holding behavior and the mechanism were investigated. The experimental observations indicate that with the decrease of dry density, the pore ratio increases gradually, and the saturated water content increases. Under the same matric suction, the water content decreases gradually with the increase of particle size, thus decreasing water holding capacity of ore accordingly. In the same water content, matric suction is inversely proportional to particle size. Under the same matric suction, the water content of ore samples after leaching is less than that of the ore samples before leaching, indicating that solution leaching can decrease water holding capacity of ore.

The use of natural stuff in textile dyeing is gaining popularity all over the world. Therefore, there is a need for developing better solid-liquid extraction techniques for leaching natural dyes from plant materials for applications in food and cosmetic fields as well as textile industries. The influence of supercritical CO2 on natural stuff extraction from different potential dye yielding plant materials has been studied in comparison with aqueous and Soxhlet process. The color yielding plant materials used in the present study include Acacia cyanophylla flowers, Tamarix aphylla leaves, tomato processing residues and Pepper (Capsicum annuum L.) by-products. UV-VIS spectrophotometry and gravimetric analysis were performed on each extract. The results indicated a significant improvement in the extraction efficiency of the dyeing stuffs obtained from different plant materials due to the use of supercritical CO2. Afterwards, preliminary tests were carried out to investigate the dyeing potential of the extracts obtained by different techniques using multifiber fabrics.

Lithium ion batteries have been undergoing rapid development in the global market due to their superior performance. However, the soaring number of lithium ion batteries in the market presents serious disposal challenges at the end of life. Moreover, continuous mining processes are harmful to the environment. From the viewpoint of cleaner production and green chemistry, the efficient recovery and reutilization of spent lithium ion batteries are necessary. In this perspective, the overall process of lithium ion battery recycling, especially the recent advances of hydrometallurgical methods, are summarized, focusing on the leaching, separation, and purification processes. The proper disposal of the waste discharged during the recycling process is proposed, highlighting the mitigation of secondary pollution. In addition, the environmental impact of recycling processes is summarized and thoroughly evaluated by recent life cycle assessment studies, revealing the key role of recycling strategic metal elements toward sustainability in an anthropogenic cycle. Finally, the current challenges in this area are pointed out and perspectives on sustainable approaches, cleaner production, and life cycle assessment are proposed.

Nowadays, oils and organics pollutions have become more serious, which causes great threats both to the ecological environment and human life. To solve this problem, development of absorbent materials with high absorption capacity and good recyclability for large-scale oils and organics separation from water still remains large challenge. In this work, we propose a facile and low-cost method to prepare 3-D PVDF/TPU composite foam with superoleophilicity (0°) and hydrophobicity (143°) by combining vacuum-assisted solution casting and particle leaching techniques. The proposed PVDF/TPU composite foam shows high absorption capacity toward different of oils and organics, and its maximum absorption capacity can achieve 55 g/g for dichloromethane, which is attributed to its high porosity (95%) and excellent interconnectivity. The absorbed oils and organics can be readily removed by simply squeezing the PVDF/TPU composite foam due to its outstanding elasticity, suggesting that it has prominent recyclability. More importantly, the composite foam can quickly and continuously separate oils and organics from water through a peristaltic pump and has a high separation efficiency of 98.5% even after 10 cycles, which indicating a promising prospect for cleaning the large-scale oils and organics pollutions. Furthermore, the composite foam also can be applied to separate surfactant-stabilized oils and organics in-water emulsion. These results showed that the PVDF/TPU composite foam has the potential to be widely applied in practice for oils and organics separation.

The results of experimental investigation on the study of leaching kinetics of copper oxide ore in sulphuric acid solution were discussed. The effect of time, pH, stirring speed and temperature on the extend of dissolution was investigated. The XRD analysis indicated that copper is mainly in the form of malachite mineral CuCO3(OH)2. The elemental analysis by XRF showed that the copper oxide ore is composed mainly of 10.07% Cu, 0.71% Co, 4.12% Fe, 24.29% Si, 5.20% Mg, 2.50% Al, 1.00% Ca and 0.48% Mn. Results of dissolution studies showed that the copper oxide ore leaching in H2SO4 solution increase with increasing time, pH, stirring speed and temperature at fixed H2SO4 concentration of 0.77 M. The study showed that 97.02%, 85.41% and 39.64% of copper, cobalt and iron were, respectively, leached by H2SO4 at 70 °C, pH value 1 within 60 min. The important part of this study was to analyse the mechanism and to develop fitting models for leaching process of copper oxide ore by sulphuric acid solution. In understanding the mechanism of dissolution, the reaction rate controlling factor and the order of reaction are of interest. The experimental data were best fitted by mixed controlled mechanism (diffusion and chemical reaction). The corresponding activation energies were calculated to be 24.0 kJ/mol for copper, 28.1 kJ/mol for cobalt and 19.5 kJ/mol for iron. The reaction order was determined to be Gompertz kinetic model. In developing fitting models for the prediction of leaching of copper, cobalt and iron, Eureqa Newtonian software was used. Results confirmed that the suggested models can be effective tools to predict the behaviour and outputs of the dissolution process.

The continuous change in solution concentration in ore pores during in situ mineral leaching influences the stability of ore aggregate. In this study, influences of the concentration of ammonium sulfate ((NH4)2SO4) solution on the interaction forces between ore particles were calculated. On this basis, the mechanism by which (NH4)2SO4 solution concentration influences the stability of ore aggregate was analyzed. Furthermore, an empirical formula for estimating the critical (NH4)2SO4 solution concentration for aggregation and dispersion of ore body aggregates with different grain composition was proposed. Some major conclusions were drawn. First, for ore bodies with an initial particle size of less than 0.075 mm, the interaction force between particles was net attraction, with the distance range of this force increasing as the concentration of (NH4)2SO4 solution increased from ≤0.001 to 0.16 mol·L−1, aggregation of ore particles occurring within this distance range. Secondly, for ore bodies with initial particle size of less than 0.075 mm, the interaction force between particles was net attraction, but with the distance range of this force decreasing when the (NH4)2SO4 solution concentration increased from 0.16 to 0.28 mol·L−1, dispersion of ore particles occurring beyond this distance range. Thirdly, for ore bodies with particle sizes of less than 0.038, 0.075 and 0.1 mm, the cation exchange capacity (CEC) was 9.13, 8.96, and 8.8 cmol·kg−1, respectively, and the critical (NH4)2SO4 solution concentration affecting the aggregation and dispersion of ore bodies was 0.12, 0.16, and 0.20 mol·L−1, respectively.

Recycling end-of-life lithium-ion batteries has attracted widespread attention due to their potential environmental hazards and the importance of key metal supplies. However, the previously reported research methods are intended only for spent Ni–Co–Mn (NCM)-based lithium-ion batteries or spent lithium iron phosphate batteries. In this letter, a new method is proposed for recovering the mixed cathode materials of LiFePO₄ and LiNi₀.₅Co₀.₂Mn₀.₃O₂ from spent lithium-ion batteries by sole Fe₂(SO₄)₃. According to our design, ferric iron itself acts as a Lewis acid and facilitates LiFePO₄ to release the reducing agent of ferrous iron to reduce LiNi₀.₅Co₀.₂Mn₀.₃O₂. Additionally, the environmentally friendly and efficient leaching process has been achieved for Ni, Co, Mn, and Li by reasonably adjusting the ratio of trivalent iron, LiFePO₄, and LiNi₀.₅Co₀.₂Mn₀.₃O₂. This method of processing mixed spent lithium-ion battery cathode materials significantly reduces the amount of reducing agent or oxidant usage. Also,it is effective at reducing time, energy consumption, and water consumption. It provides a new solution to recycling used lithium-ion batteries.

The present study evaluates the reductive leaching of indium from indium-bearing zinc ferrite using oxalic acid as a reducer in sulfuric acid solution. The effect of main factors affecting the process rate, including the oxalic-acid-to-sulfuric-acid ratio, stirring rate, grain size, temperature, and the initial concentration of synergic acid, was precisely evaluated. The results confirmed the acceptable efficiency of dissolving indium in the presence of oxalic acid. The shrinking-core model with a chemical-reaction-controlled step can correctly describe the kinetics of indium dissolution. On the basis of an apparent activation energy of 44.55 kJ/mol and a reaction order with respect to the acid concentration of 1.14, the presence of oxalic acid was found to reduce the sensitivity to temperature changes and to increase the effect of changes in acid concentration. Finally, the equation of the kinetic model based on the factors under study is presented.

The United Nations’ Sustainable Development Goals have sparked growing interest in biosurfactants from many surfactant-loaded industries including those utilizing froth flotation for mineral separation. However, the interaction of biosurfactants with mineral surfaces is currently poorly understood. We bridge this gap by studying adsorption of a yeast-derived bola acidic sophorolipid (ASL) biosurfactant on djurleite (Cu1.94S). The methods used include Hallimond flotation, contact angle, adsorption isotherm, zeta potential, leaching measurements, and X-ray photoelectron spectroscopy (XPS). To facilitate the interpretation of the adsorption results, we characterize the activity of ASL at the air-water interface and measure its critical micelle concentration (CMC) at different pH using static surface tension. We find ASL to be a multifunctional surfactant with an unusual, pH-sensitive interfacial behavior. At the air-water interface, ASL is most active at pH 8, while its CMC goes through minimum as low as 40 μM at pH 7. The surfactant adsorption at the djurleite-water interface makes the sulfide surface hydrophilic at acidic pH and hydrophobic at neutral and basic pH. In addition, ASL has strong affinity to copper sulfide and demonstrates metal leaching properties. Finally, ASL demonstrates detergency properties. We offer a mechanistic interpretation of these findings. Our results provide a basis for the application of acidic glycolipids in froth flotation and have implications for their application in ion separation using hydrometallurgical routes, as well as for the chemical stability of metal sulfides in environmental systems. © 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Wet process phosphoric acid (WPA) represents the main route for phosphate fertilizers world’s production using sulfuric acid as leaching agent. The produced acid is contaminated with various metal ions as iron, aluminum, cadmium, arsenic, uranium, etc. that limits its uses in metal finishing, food, cosmetics and electronic industries. Hence, purification of the wet phosphoric acid is a challenge task. The presence of high concentration of iron in phosphoric acid leads to many problems that affect the production process as increasing the viscosity, decreasing the filtration ration rate, formation of precipitates during concentration, clarification and storage, P2O5 loss in addition to decreasing the solubility of fertilizers, The present review gives an overview on the removal of iron from crude phosphoric acid by some commonly used techniques including precipitation, sorption and solvent extraction to evaluate the efficiency and drawbacks of each process. The pre- treatments of phosphoric acid are also discussed.

Research into radionuclide leaching behavior in the treatment of low-level radioactive waste solidification has been a widespread concern. Bioleaching of uranium was carried out using Aspergillus s...

This work aims to develop a green method for the recovery of vanadium from spent contact process catalyst (SVC) with 6–7% V2O5. The efficiency of leaching was evaluated using oxalic acid by varying...

Cost-effective, efficient and green solid acid catalysts have been synthesized by incipient wetness impregnation of various weight fractions of phosphomolybdic acid (5, 10, 15 and 25 wt. %) on mechanically and thermally activated coal fly ash. N2 adsorption–desorption, XRD, FT-IR, SEM, SEM–EDX, TEM, TGA, UV–Vis DRS, solid state 31P MAS NMR were used for characterization of as synthesized catalysts. Catalytic active sites were developed on inert surface of coal fly ash by using various activation techniques whose performance was assessed over a series of acylation of various aliphatic alcohols. For rapid and higher catalytic activity, reactions were conducted in microwave heating mode. Impregnation of phosphomolybdic acid generates Lewis acidic sites on coal fly ash surface as inferred by pyridine adsorbed FT-IR studies which were then utilized in acylation reactions. Various reaction parameters like weight fraction of catalysts, molar ratio of reactants, time, temperature, etc. were optimized for attaining highest conversion %. The catalyst with 15 wt. % of phosphomolybdic acid was found to be more efficient and could be recycled up to five reaction cycles with analogous conversion %. Negligible leaching of catalyst was confirmed by hot filtration test. This work suggests an alternative approach for valorisation of industrial solid waste, coal fly ash in development of innovative, economical solid catalysts.

In anaerobic digestion processes, pH has a vital role due to the direct impacts on the microbial community. An eco-friendly approach has been applied to control pH in anaerobic bioreactors, using waste-containing fly ash geopolymer spheres (GS) instead of powdered chemical compounds, to promote continuous alkalis leaching. The influence of GS porosity and concentration on the behavior of anaerobic sequential batch reactor treating cheese whey was evaluated. Results showed that the use of GS with the highest concentration and porosity promoted an increase in methane yield up to 30%, compared to the assay with powdered chemical compounds addition. In addition, GS boosted butyric acid production to the detriment of propionic acid, which favored methane production by a factor up to 1.2. This innovative approach indicates that GS addition can regulate pH in anaerobic digesters treating challenging wastewaters and, simultaneously, improve not only its efficiency but also the sustainability of the entire process.

A new eco-friendly process to comprehensively utilize boron-concentrate is proposed in this paper. In this process, Iron-concentrate, silicon dioxide, magnesium oxide, and boric acid could be produced from boron-concentrate. The highlight of this process was minimal waste discharge during the whole process. Iron removal was a key step to ensure the quality of boric acid and magnesium oxide. The introduced goethite precipitation method could remove iron to a very low level. With the addition of 3 cm3 H2O2 (5 vol. %) as an oxidizing agent, more than 99% of iron was removed from the leaching liquor. After the removal of iron, the resulting liquor was used to prepare magnesium precipitate. And the optimal preparation conditions were: the temperature of 30 °C and precipitation time of 60 min, ammonium- magnesium ratio of 1.5, the magnesium ion concentration of 34.8 g·L−1. Under those conditions, the magnesium precipitation efficiency was up to 98.5%. Magnesium oxide was obtained by roasting magnesium precipitate at 550 °C for 2 h. Then the mixed crystals of ammonium sulfate and boric acid were obtained by evaporating the liquor after iron removing and magnesium precipitating. Boric acid was separated from ammonium sulfate by dissolving the mixed crystals in ethanol solution.

The leaching behavior of Tunceli smithsonite ore in nitric acid was evaluated in two study steps including optimization of leaching process and kinetics modeling. The individual and synergistic effects of effective parameters such as nitric acid concentration, solid-to-liquid ratio, stirring speed, and temperature on the dissolution rate of zinc were investigated using central composite design. Four factors including temperature (30–50 °C), nitric acid concentration (0.2–0.5 mol/L), stirring speed (350–600 rpm), and solid-to-liquid ratio (0.004–0.01 g/L) were investigated. The dissolution percent of zinc (97%) was obtained in 120 min of leaching time: acid concentration 0.5 mol/L, temperature 50 °C, stirring speed 500 rpm, and solid–liquid ratio 2/500 g/mL at the optimum conditions obtained using the central composite design. The dissolution kinetics of smithsonite was examined according to heterogenous models and it was found that the dissolution rate was controlled by ash layer diffusion process. It was found that the leaching rate increased with increasing temperature, stirring speed, and acid concentration as well as decrescent particle size and solid/liquid ratio. The trial data were analyzed by statistical and graphical methods and the activation energy of this leaching process was determined to be 28.63 kJ·mol−1.