Extraction Of Chromium Research Articles

Selective extraction of chromium from chromium-bearing electroplating sludge by pressure oxidation alkaline leaching

The selective extraction of chromium (Cr) from Chromium-bearing electroplating sludge (CES) has positive significance for harmless disposal and reducing dependence on native resources. Herein, the process of pressure oxidation alkaline leaching of CES is reported. The leaching ratio of Cr was reached 89.9 % under the optimal conditions, i.e., temperature of 125℃, NaOH concentration of 1.5 mol/L, liquid-solid ratio of 10, oxygen partial pressure of 2Mpa and reaction time of 2 h, while other elements such as Cu, Ni, Fe and Zn were virtually not leached out. In addition, the concentration of NaOH required for the maximum of the leaching ratio of Cr decreased with the increase of temperature, which attributed to the synergistic effect of temperature and NaOH concentration on the solubility and diffusion coefficient of the oxidant. As the oxygen partial pressure was increased to 2 MPa, the liquid-solid ratio was raised to 10, and the reaction time was extended to 2 h, respectively, the leaching ratio of Cr reached maximum and then remained as a constant. Kinetic studies showed the leaching process of chromium was controlled by chemical reaction, and the apparent activation energy was 112.1 kJ/mol. The efficient selective recovery of Cr is of great significance to reduce the difficulty of comprehensive recovery of valuable metal elements in the CES.

Fast and efficient chromium(VI) extraction by colloidal Mg/Al layered double hydroxide nanoparticles

Due to the constraints associated with diffusion and mixing time, traditional kinetic and thermodynamic approaches were inadequate for probing the true mechanism of interaction between chromate and Layered Double Hydroxide (LDH). To circumvent these limitations, colloidal suspensions of Mg/Al-NO3 LDH, characterized by a positively charged surface (approximately +50 mV) in ultrapure water and a mean average diameter of 140 nm, allowing the formation of stable suspensions for days, were swiftly mixed with Cr(VI) suspensions at both pH = 4 and 9 using a stopped flow technique. This rapid mixing, accomplished in <5 milliseconds, enabled the examination of the initial stages of interaction between the toxic anion and the host compound. Two distinct steps in the adsorption process were identified: a very fast step (completed in <5 ms), representing up to 80% of the measured variation, and a slower step lasting up to 100 s. The fast step assumed to be driven by electrostatic interaction (ζ ∼ +50 mV) with the surface, and sites close to the surface are easily accessible to the chromate anions. The slower step corresponded to a diffusion process close or inside the particles. Chromate extraction efficiency was investigated through ultrafiltration tests, varying the LDH and chromate amounts, indicating that 2 nitrate ions are exchanged for 1 chromate, regardless of the pH considered, and a total exchange can be fulfilled with 0.1 g L−1 of LDH within the explored concentration range.

Magnetic solid-phase extraction technique based on Fe3O4@coPPy-PTH nanocomposite for extraction of cobalt, chromium, and nickel prior to determination by microsample injection system-flame atomic absorption spectrometry in alcoholic and nonalcoholic beverages.

A novel Fe3O4@coPPy-PTH nanocomposite-based sorbent was prepared via in situ oxidative polymerization using Fe3O4 nanoparticles with spherical and flower-like morphologies of thiophene and pyrrole as the feedstocks. The synthesized nanocomposite displayed sensitive extraction and determination of metal ions Co(II), Cr(III), and Ni(II) without a chelating agent, followed by microsample injection system-flame atomic absorption spectrometry. Advanced spectroscopic and imaging techniques including scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy were used to characterize the composition and morphology of the Fe3O4@coPPy-PTH nanocomposite. SEM observations showed that the size of the Fe3O4 nanoparticles changed from 30 nm to 120 nm in diameter after copolymer (PPy-PTH) coating. The Fe3O4@coPPy-PTH nanocomposite has good dispersion properties and stability in strong acid solutions. For effective extraction of the studied analytes, the influence of sample pH, volume of sample solution and eluent, amount of adsorbent, and interference of coexisting metal ions were optimized. Under the optimum conditions, preconcentration factors were obtained as 25 for all analytes. The calibration curves were linear in the range of 0.0-10.0 μg L-1 with coefficients of determination (R2) greater than 0.9957 for all three analytes. Limits of detection (S/N = 3) were calculated in the range of 0.17-0.23 μg L-1. Precision values, expressed as relative standard deviations, were lower than 3.0%, and relative recoveries were obtained in the range of 88.6%-103.6%. The proposed method (Fe3O4@coPPy-PTH/MSPE/MIS-FAAS) was successfully applied to extract and determine the studied metal ions in beer, wine, and nonalcoholic beverage samples.

Liquid Phase Extraction and Determination of Chromium (III) Ion in Aqueous Solution Using Dithiocarbamate Derivative Reagent

تم تحضير الكاشف الجديد N-methyl-N - ((((4-bromophenyl) diazenyl) thio) carbonothioyl) aniline من تفاعل (sodium N-methyl- N-phenyl dithiocarbamate) مع (4-chlorobenzene diazonium salts). وشخص الكاشف الجديد بالطرائق الطيفية وهي، طيف الاشعة فوق البنفسجية، التحليل الدقيق للعناصر، طيف الاشعة تحت الحمراء، مطيافية الكتلة، مطيافية الرنين النووي المغناطيسي للبروتون والكاربون، التوصيلية المولارية والحساسية المغناطيسية. باستخدام البيانات التحليلية والطيفية، تم تحديد نسبة (الفلز: الكاشف)، ولوحظ أن المركب بنسبة1: 2 (فلز: كاشف). تم قياس التوصيلية المولية للمعقدات باستخدام DMF، وأظهرت النتائج أن المعقد الناتج كان أيونيا. تشير نتائج التحليل الدقيق للعناصر والدراسات الطيفية إلى أن المركب له بنية رباعية السطوح. تم تطوير الاستخلاص بنقطة الغيمة للتركيز المسبق وفصل الكروم الثلاثي في قياسات عينات الدواء باستخدام الامتصاص الذري للهب ومقياس الطيف الضوئي للأشعة فوق البنفسجية عند 536 نانومتر. تتأثر فعالية الاستخلاص بنقطة الغيمة بدرجة الحموضة، وتركيز Triton X-114 والكاشف، ونوع المادة الخافضة للتوتر السطحي، والتداخل، وتأثير الملح، والوقت، وتأثير درجة الحرارة. كان منحنى معايرة الكروم خطيًا في حدود 0.1-2 ميكروغرام مل-1 مع r2=0.9888. حد الكشف والتقدير الكمي هو (0.1246 و0.3777 ميكروغرام مل-1). تم تطبيق الطريقة الجديدة بنجاح لاستخلاص وفحص أيون المنغنيز الثنائي تحت ثلاث علامات تجارية دوائية.

EXTRACTION OF CHROME FROM FERROCHROME PRODUCTION SLAG USING THE SULFURIC ACID METHOD

Currently, the development of industrial waste recycling processes that reduce the anthropogenic load on the biosphere and ensure the rational use of natural resources is an urgent task. Technogenic waste from ferrochrome production contains chromium, which is one of the most toxic components of industrial waste. To extract chromium from them, the most acceptable method is acid leaching. The purpose of the work is to study the influence of temperature, process duration and H2SO4 concentration on the extraction of chromium from high-carbon ferrochrome slag into a sulfuric acid solution. Using mathematical planning of a 3-factor experiment, experiments were carried out to extract chromium from the slags of high-carbon ferrochrome production. The H2SO4 concentration was varied from 5 to 95% by diluting the concentrated acid. The duration of the process ranged from 10 to 180 minutes at S:L = 1:30, the temperature varied from 22 to 90 °C. Results and discussion. The maximum transition of chromium into acid occurs at a temperature of 76-90 °C and a process duration of 145-180 minutes. The degree of extraction reaches 97.9%. The smallest amount of chromium, about 20 mg/L, passes into the weakly concentrated H2SO4 solution, the degree of leaching is low and equal to 20.6%. When using 50% H2SO4, the highest degree of transition of Cr (94.8%) from ferrochrome slag to sulfuric acid occurs at a high temperature of 90 °C in 150-180 minutes. Deeper extraction of chromium cations into acid occurs at 80-90 °C. The maximum content of Cr3+ in the acid is achieved in 46-107 minutes and amounts to (0.33-0.68)%. Conclusions. It was revealed that with increasing process duration and increasing temperature, the degree of extraction increases. The maximum transition of chromium into acid from high-carbon ferrochrome slag occurs at a temperature of 76-90 °C and a process duration of 145-180 minutes. The degree of extraction reaches 97.9%. An increase in the temperature of the process of leaching chromium from VUVC with concentrated sulfuric acid initiates the extraction of chromium from the raw material.

Non-Dispersive Extraction of Chromium(VI) by Cyphos IL102/Solvesso 100 Using the Pseudo-Emulsion-Based Strip Dispersion Membrane Operation.

The removal of chromium(VI) from an acidic (HCl) medium through non-dispersive extraction with strip dispersion (NDXSD) was investigated using a microporous PVDF membrane support in a permeation cell. The ionic liquid Cyphos IL102 (phosphonium salt) in Solvesso 100 was used as an organic phase. In NDXSD, the stripping phase (NaOH) is dispersed in the organic phase on the cell side with an impeller stirrer adequate to form a strip dispersion. This pseudo-emulsion phase (organic + strip solutions) provides a constant supply of the Cyphos IL102/Solvesso 100 to the membrane phase. Various hydrodynamic and chemical parameters, such as variation in the feed and pseudo-emulsion stirring speeds, HCl and Cr(VI) concentrations in the feed phase, and carrier concentration, were investigated. Results indicated that the best chromium(VI) transport was obtained under the following conditions: feed and pseudo-emulsion stirring speeds of 1000 min-1 and 600 min-1, respectively; an HCl concentration in the feed phase of 0.1 M; a chromium concentration of 0.01 g/L in the same phase; and carrier concentration in the organic phase in the 2-5-10% v/v range. From the experimental data, several mass transfer coefficients were estimated: a bulk diffusion coefficient of 3.1·10-7 cm2/s and a diffusion coefficient of 6.1·10-8 cm2/s in the membrane phase and mass transfer coefficients in the feed (5.7·10-3 cm/s) and membrane phases (2.9·10-6 cm/s). The performance of the present system against other ionic liquids and the presence of base metals in the feed phase were investigated.

Depollution of Polymeric Leather Waste by Applying the Most Current Methods of Chromium Extraction.

The leather industry is one of the most polluting industries in the world due to the large amounts of waste following raw hide processing but also due to the high content of chemical substances present in leather waste. The main problem with chromium-tanned leather solid waste is related to the storage, due to the ability of chromium to leach into soil or water, and also owing to the high ability of trivalent chromium to oxidize to its toxic form, hexavalent chromium. The purpose of this article is to present the most current methods of chromium extraction from solid tanned leather waste in order to obtain non-polluting leather, which can constitute secondary raw material in new industrial processes. The extraction methods identified in the present study are based on acid/basic/enzymatic hydrolysis and substitution with the help of organic chelators (organic acids and organic acid salts). In addition, this study includes a comparative analysis of the advantages and disadvantages of each identified extraction method. At the same time, this study also presents alternative chromium extraction methods based on the combination of conventional extraction methods and ultrasound-assisted extraction.

Selective removal of chromium from laterite residue with high content of iron by the co-operation of phosphoric acid and oxalic acid

With the rising demand for nickel and cobalt, laterite residue containing chromium is extensively generated through the laterite hydrometallurgical process, posing a significant burden on environmental protection and the sustainable development of the nickel industry. This study presents a novel and environmentally friendly method for selectively extracting chromium from laterite residue and yielding iron phosphate concentrate. In this method, iron, as the major component, is simultaneously transformed into iron phosphate as solid state, while chromium is extracted into solution by a minimal amount of phosphoric acid. The effects of phosphoric acid and oxalic acid usage, temperature, liquid-to-solid ratio, and leaching time on the transformation and removal were investigated. Thermodynamic analysis and experimental results indicated that the addition of oxalic acid promoted chromium extraction with minimal impact on the transformation of hematite and iron phosphate. The results of SEM, XPS, and XRD revealed the conversion of laterite residue to iron phosphate. At an oxalic acid dosage of 10 %, almost 90 % of the iron remained in the residue as iron phosphate, while over 60 % of the chromium was extracted into the solution, resulting in a chromium concentration of 1.1 g/L. The solution underwent a two-step treatment process, primarily to recycle the soluble iron species. The extracted chromium was captured by adding calcium hydroxide at pH ∼ 3.0 in the form of phosphate.

A zirconium metal–organic framework functionalized with a S/N containing carboxylic acid (MOF-808(Zr)-Tz) as an efficient sorbent for the ultrafast and selective dispersive solid phase micro extraction of chromium, silver, and rhodium in water samples

Metal-organic frameworks (MOFs) are good adsorbents for targeted chemicals with their adjustable properties. Herein, we prepared a zirconium based MOF (MOF-808(Zr)) and functionalized it employing 2-mercapto-4-methyl-5-thiazolacetic acid (MOF-808(Zr)-Tz). The prepared MOFs were characterized by XRD, FTIR, SEM-EDX, TGA, N2 sorption, zeta potential measurements, and elemental analysis. The surface area of MOF-808(Zr)-Tz was 1348 m2/g. Dispersive solid-phase micro-extraction (D-SPµE) method based on MOF-808(Zr)-Tz was firstly developed and applied to the extraction of chromium, silver, and rhodium in waters. The determination of the analytes was done by FAAS. The optimal pH and eluent for analytes were 7.0 and 3 mL of 2 mol L−1 HCl, respectively. The contact times were 1 min for adsorption and 3 min for elution. The LOD and PFs of the D-SPμE for analytes were 2.3 μg L−1 and 13.3 for chromium, 2.1 μg L−1 and 13.3 for silver, and 3.1 μg L−1 and 13.3 rhodium, respectively. The D-SPμE method was verified with analyses of NW-TMDA-54.6 Lake water and SPS-WW1 Batch 114 Wastewater and with spiked dam water, river water, well water, sea water, and wastewater. The recoveries of the analytes changed from 89 to 108 %. The results indicated that the method is selective, simple, effective, and rapid for extracting chromium(III), silver(I) and rhodium(III) in waters.

Green redox separation and efficient extraction of vanadium and chromium from leaching solution of chrome-vanadium slag

Green separation and efficient extraction of vanadium and chromium from vanadium-chromium leaching solution are serious challenges for the utilization of chrome-vanadium slag. A green sucrose reduction-H2O2 selective oxidation route is proposed for deep separation of vanadium and chromium from vanadium-chromium leaching solution based on different redox properties. Eh-pH diagram of V-Cr-H2O system and existence forms of vanadium and chromium ions are calculated. Obvious difference of redox properties between V(V) and Cr(VI) exists in acidic environment. The dependences of selective separation on pH for reduction, temperature, m(sucrose)/m(Cr(VI)) and n(H2O2)/n(V(V)) are studied. The concentration ratio of vanadium to chromium in solution after selective separation of chromium decreases from 1.6 to 0.06. The extraction ratios of Cr2O3 and V2O5 are 96.3% and 93.8%, respectively. The redox behavior of V(V) and Cr(VI) is revealed. Cr(VI) and V(V) are reduced to Cr(Ⅲ) and V(IV) by 5-hydroxymethylfurfural, a hydrolysate of sucrose, and then V(IV) is selectively oxidized to V(V) by H2O2. Cr2O3·n(H2O) and ammonium polyvanadate obtained by hydrolysis and ammonium precipitation are calcined to Cr2O3 and V2O5, respectively. Cr2O3 with the purity of 99.4% can be used as high-quality pigment. The purity of V2O5 meets the requirements of YB/T 5304–2011 for 98 V2O5.

Determination of chromium in foodstuffs by using novel adsorbent in vortex assisted-dispersive solid phase micro-extraction method: An application of multivariate techniques

A new graft copolymer composed of polystyrene and polylinoleic acid (PLinas) with the sodium salt of iminodiacetate (Ida) was synthesized and used as an adsorbent. The vortex-assisted dispersive solid-phase micro-extraction (VA-dSPµE) method was used for the extraction and pre-concentration of chromium. Multivariate methodologies, such as factorial design and 3D surface plots, were applied for screening and optimizing effective extraction parameters. The influence of diverse analytical parameters, such as pH, sample volume, and interfering ions, on the extraction of chromium was studied. The calibration standard curve exhibited a linear range from 0.01 to 0.50 μg L−1. The relative standard deviation and limit of detection were found to be 1.65 % and 0.003 μg L−1, respectively. Extraction recoveries were found in the range of 96 to 99 % by using certified reference materials (CRMs). The adsorbent capacity of PLinas-Ida was found to be 112 mg g−1. The VA-dSPµE method demonstrated its effectiveness in the pre-concentration and determination of chromium within samples of foodstuffs by graphite furnace-atomic absorption spectrometry (GF-AAS).

Adsorption and Kinetics Modelling for Chromium (Cr6+) Uptake from Contaminated Water by Quaternized Date Palm Waste

The pervasive challenge of heavy metal pollution in water necessitates urgent interventions to mitigate chromium contamination. It poses significant threats to human health, aquatic ecosystems, and the environment. This research delves into the potential of date palm waste as a precursor of adsorbent for extraction of chromium from contaminated water, underscoring its potential in heavy metal remediation. Date palm waste, traditionally regarded as agricultural waste, underwent modification employing N-(3-chloro-2-hydroxypropyl) trimethylammonium chloride resulting in quaternized date palm waste (QDPW) as a prospective adsorbent for chromium extraction. The characterization techniques, including FTIR, SEM/EDX, BET, XRD, TGA/DTA, and element analysis, were employed to examine the structural and surface properties of both DPW and QDPW fibers. Optimal chromium uptake was achieved at a solution pH 6.5 over two hours, with a peak removal efficiency of 88% and an adsorption capacity of 22.26 mg/g. The equilibrium isotherms studies are consistent with Langmuir, Redlich-Peterson, and Sips isotherms, presenting a coefficient of determination (R2) of 0.989, 0.981, and 0.983, respectively. Moreover, the pseudo-second-order model was mostly aligned with the kinetics data with R2 value of 0.999. These findings showed that the quaternized date palm waste can be considered a good option to recycle the date palm waste and reduce the environmental threats in aqueous solution.

Green and efficient separation of vanadium and chromium from high-chromium vanadium slag: a review of recent developments

Strategies for efficient extraction and separation of vanadium and chromium from high-chromium vanadium slag with green chemistry principles are summarized.

An Effective Sol-Gel-Functionalized Polyurethane Foams Solid Platform Packed Minicolumns for Complete Extraction of Chromium (VI) from Water: Kinetic, Sorption Isotherms, Thermodynamic Study, and Analytical Utility.

In the modern era, sol-gel plays a key role in the progress of a new generation of dispersive solid-phase microextractors (d-µ SPMEs) for the removal of organic and inorganic pollutants in complex matrices. Thus, the current study reports the use of sol-gel-functionalized polyurethane foams (PUFs) as a novel solid platform for complete extraction of chromium (VI) species from aqueous media. The planned protocol was based upon the complete extraction of the formed binary complex ion associates between the protonated ether and/or urethane groups of PUFs and chlorochromate anion [CrO3Cl]- aq in aqueous HCl (≥1M) medium in addition to H-bonding and the electrostatic π-π interaction that resulted between the CrO3Cl- and the silanol group (Si/ZrO2, Si-O-Zr) and siloxane (Si-O-Si) groups of the sol-gel. The impact of the analytical parameters (solution pH, natural mineral acids, shaking time, temperature, and chromium (VI) concentrations) was critically studied. At the optimal conditions, the uptake capacity of the established extractor (9.9 mg·g-1) was in agreement with the Langmuir adsorption capacity (12.08 mg·g-1) of the monolayer. The sorption data fitted well with the pseudo first-order kinetic model (R 2 = 0.9961) with an overall rate constant (k 1) of 0.081 min-1 and an equilibrium capacity (q e ) of 8.6 mg·g-1, which is in a good agreement with the experimental value (9.9 mg·g-1). The sorption of the oxyion [CrO3Cl]- aq onto the solid sorbent is an endothermic and spontaneous process as reflected from the values of ΔH (6.99 kJ·mol-1) and ΔG (-8.14 kJ·mol-1 at 293 K), respectively. The ΔS value (15.13 kJ·mol-1·K-1) reflects that the [CrO3Cl]- aq retention onto the sol-gel-treated PUFs sorbent proceeded in a more unplanned fashion. Sol-gel-treated PUFs sorbent-packed minicolumns were successfully used for the complete removal of trace levels of chromium (VI) species from water samples. Sorbed chromium (VI) species were recovered with NaOH (0.5 M) and analysed by spectrophotometry, which supports the utility of the sol-gel-treated PUFs as a low-cost solid extractor for water treatment.

Speciation of the binary Cr(III)-citrate system in the leachate samples of phosphate ore

This report focuses on the determination of chromium chemical forms in the lixiviates of phosphate ore using speciation modelling with the MATLAB 7.7 Language. Citric acid has been used as aleaching agent for the extraction of chromium (III) from phosphate ore. A computational approach was used to determine the concentration of differentionic species present in the Cr(III)-citric acid system. The results show that the main aqueous species identified in the systemwere both free and complex ions. In addition, it was found that the concentration of total chromium in the leachate was dependent on the concentration of citric acid.On the other hand, the formation of different species and the evolution of their concentration led to an increase in the ionic strength of the solution. The ionic complex CrHCit+ showed the highest activity coefficientamong the different Cr (III) species. It was also observed that free ionic species (H3O+, H2Cit-, Cr3+) have a higher activity than chromium ionic complexes (CrH3Cit3+, CrH2Cit2+, CrHCit+).

Removal of chromium from electroplating sludge by roasting-acid leaching and catalytic degradation of antibiotics by its residue

The recycling of electroplating sludge is of great significance to alleviate environmental pollution and resource depletion. However, due to the complex composition of electroplating sludge, especially chromium-containing electroplating sludge is difficult to treat, and the methods for detoxification and resource utilization of chromium-containing electroplating sludge are still lacking. Herein, we extracted chromium from electroplating sludge by a facile and economical roasting and acid leaching method to achieve detoxification, and the remaining detoxification residue was converted into a Fenton-like catalyst, which was used for the degradation of tetracycline to achieve resource utilization. The results showed that the extraction of chromium by this method could reach 93.35%, the resulting catalyst had excellent degradation performance over a wide pH range (3−11), and the removal of tetracycline could reach 98.8% under optimal conditions. Furthermore, cost calculations have shown that this method has cost advantages over traditional processing methods. In this work, an excellent performance catalyst was obtained that can be used for tetracycline degradation along with the detoxification of electroplating sludge, which provides a new route for the harmless treatment and resource utilization of electroplating sludge, with important theoretical fundamental value and potential application prospect.

Selective recovery of vanadium from high-chromium vanadium slag by a mechanically activated low-sodium salt roasting-water leaching process

Stabilizing the toxic element chromium and improving vanadium recovery are crucial for the economic and efficient treatment of high chromium-bearing vanadium slag. This study employed mechanical activation to enhance vanadium extraction from high chromium-bearing vanadium slag through a low-sodium salt roasting-water leaching process. The effects of Na2CO3 addition, roasting temperature, and roasting time were investigated to determine the optimal roasting parameters. Subsequently, the effects of mechanical activation on the morphological and microstructural changes were characterized using a laser diffraction particle size analyzer, a micropore physisorption analyzer, scanning electron microscopy, energy dispersive spectrometry, and X-ray diffraction. The effects of mechanical activation on the extraction of vanadium and chromium were determined by leaching the roasted samples after varying activation times. The results indicated that mechanical activation decreased particle size, increased surface area, and enhanced the activity of the samples. The leaching results demonstrated that mechanical activation enhanced the leaching efficiency of vanadium by 5 %, reduced the optimum roasting temperature by 50 ℃, and slightly increased the leaching efficiency of chromium by 0.5–1 %.

PROSPECTS FOR THE EXTRACTION OF CHROMIUM FROM SLAG FERROCHROME PRODUCTION BY ACID METHOD

In the Republic of Kazakhstan, there is a noticeable upward trend in the volume of industrial waste, including from the production of ferrochrome. The problems of man-made pollution of the natural environment are becoming more acute every year, and are beginning to take on a global dimension. Technogenic ferrochrome production waste contains chromium, which is highly toxic and carcinogenic, which poisons water, soil, negatively affects the activity of all living organisms. Slags contain a significant number of valuable components used in various industries, and above all, chromium, which is irrevocably lost during storage. The main task still remains the development of industrial waste disposal processes that reduce the anthropogenic load on the biosphere and ensure the rational use of natural resources. The purpose of the work is to justify the choice of the method of processing the slags of the ferrochrome production. Conclusions: The analysis of the modern scientific and patent literature on acid processing and utilization of chromium-containing slags from the production of refined and high-carbon ferrochrome has been conducted. It should be noted that the described methods of various methods of processing ferrochrome production slags, despite their availability, are characterized by a multi-stage nature and do not allow complete processing of ferrochrome production slags in Kazakhstan. Currently, there is an excess of sulfuric acid production in Kazakhstan, so it becomes advisable to use sulfuric acid as a reagent for leaching chromium from slag from the production of ferrochromium. It can be expected that in sulfuric acid under certain conditions, such as heating, a sufficiently high degree of extraction of chromium (III) will be achieved in slags from the production of high-carbon chromium and in refined ferrochem slags.

Hydrophobicity Tuned Polymeric Redox Materials with Solution-Specific Electroactive Properties for Selective Electrochemical Metal Ion Recovery in Aqueous Environments.

Adaptable redox-active materials hold great potential for electrochemically mediated separation processes via targeted molecular recognition and reduced energy requirements. This work presents molecularly tunable vinylferrocene metallopolymers (P(VFc-co-X)) with modifiable operating potentials, charge storage capacities, capacity retentions, and analyte affinities in various electrolyte environments based on the hydrophobicity of X. The styrene (St) co-monomer impedes hydrophobic anions from ferrocene access, providing P(VFc-co-St) with specific response capabilities for and greatly improved cyclabilities in hydrophilic anions. This adjustable electrochemical stability enables preferential chromium and rhenium oxyanion separation from both hydrophobic and hydrophilic electrolytes that significantly surpasses capacitive removal by an order of magnitude, with a robust perrhenate uptake capacity of 329 mg/g VFc competitive with established metal-organic framework physisorbents and 17-fold selectivity over 20-fold excess nitrate. Pairing P(VFc-co-X) with other solution-specific electroactive macromolecules such as the pH-dependent poly(hydroquinone) (PHQ) and the cesium-selective nickel hexacyanoferrate (NiHCF) generates dual-functionalized electrosorption cells. P(VFc-co-X)//PHQ offers optimizable energetics based on X and pH for a substantial 4.6-fold reduction from 0.21 to 0.04 kWh/mol rhenium in acidic versus near-neutral media, and P(VFc-co-St)//NiHCF facilitates simultaneous extraction of rhenium, chromium, and cesium ions. Proof-of-concept reversible perrhenate separation in flow further highlights such frameworks as promising approaches for next-generation water purification technologies.

The effect of diluent on the extraction: Amide extracting chromium (VI) as an example

As an essential separation and purification method, solvent extraction was widely used in many fields. In previous studies, extractants had received much attention, while the role of diluents had often been ignored. However, the diluent had a very complex effect on the extraction process. In the study, the influence of diluent on the extraction of chromium with amide as an extractant was discussed in detail. In order to increase the universality of the study, the common organic solvents, including alkanes, aromatic hydrocarbons, and halohydrocarbons, were selected as diluents. The extraction performance, formation of extracted complex, and thermodynamics under different diluents were determined. In addition, FT-IR and UV–Vis spectral analyses have been carried out to investigate the influence of diluent on the spectrum. The results showed that the diluent had an obvious influence on the spectrum of the amide group before extraction, and the influence was weakened after extraction. Based on the analysis of molecular electrostatic potential, the effect of diluent on the reaction site of amide extractant was investigated. Further, the molecular polarity index was used to calculate polarity parameters and deepen the understanding of the effect of diluent on the extraction process. The study provided a theoretical basis for other extraction systems to select appropriate diluents.