Separation Of Chromium Research Articles

Separation of vanadium and chromium by selective adsorption by titanium-based microspheres

The separation and recovery of V(V) and Cr(VI) from solution can achieve the dual purpose of resource utilization and environmental protection. In this work, amorphous titanium-based microspheres with a large specific surface area of 574.86 m2/g were prepared by the simple hydrolysis of titanium alcohol. This adsorbent exhibited excellent adsorption of V(V) and Cr(VI), with maximum capacities of 153.2 and 54.21 mg/g, respectively. Most importantly, in V(V)/Cr(VI) mixed solution, selective adsorption of V(V) can be achieved by competitive adsorption. The Dubinin-Radushkevich isotherm model and Elovich kinetic model yielded the best fit for experimental data, which indicated the adsorption of V(V) and Cr(VI) onto titanium-based microspheres is a combination of chemical adsorption and physical adsorption. Selective adsorption can be achieved when sufficient V(V) was present in the V(V)/Cr(VI) mixed solution (pH 3), which is due to H3V10O283− has the more negative values of Eads (-188.12 kJ/mol) and ΔG0 (−40.72 kJ/mol). The column experiment showed promise for application in the continuous removal and separation of V(V) and Cr(VI) from wastewater to obtain qualified pure V(V) and Cr(VI) products. Through the adsorption of different concentrations of V(V)-Cr(VI) solutions, real vanadium leaching solution and real vanadium precipitation wastewater, the purification of high-concentration solutions and the treatment of low-concentration solutions could be realized.

Separation of Chromium (VI), Copper and Zinc: Chemistry of Transport of Metal Ions across Supported Liquid Membrane.

Prior to applying supported liquid membranes (SLM) with strip dispersion for separation of chromium (VI), copper and zinc, suitable chemical settings were determined through solvent extraction and stripping studies. More than 90% of copper and zinc could be simultaneously extracted with at least 3% (v/v) di-(2-ethylhexyl)phosphoric acid (D2EHPA) at a feed equilibrium pH in the range of 3.5–5.0. For stripping, theoretical model equations derived and experimental results revealed that suitable concentrations of lower acid strength reagents can strip metals that have weaker metal-extractant bond without significantly stripping metals that have a stronger metal-extractant bond. Therefore, in a setup comprising three compartments separated by two SLM, we propose to fill the three compartments in the following order: feed—strip dispersion containing low acid strength reagent—strong acid. An organic phase with 4% (v/v) D2EHPA was used. From stripping experiments, 0.2 mol/L pH 3 citrate buffer, which resulted in the highest copper recovery (88.8%) and solution purity (99.0%), was employed as the low acid strength reagent while the strong acid consisted of 1 mol/L sulfuric acid. In 26 h, 99.1% copper was recovered by citrate buffer with 99.8% purity and 95.1% zinc was recovered by sulfuric acid with 98.4% purity. Chromium (VI), copper and zinc could be separated effectively using this separation strategy.

Sol-gel matrices for the separation of uranyl and other heavy metals

The development of simple, cheap, and efficient techniques for separating and recycling heavy metal cations, including radioactive species, motivated this study of the feasibility of using sol-gel matrices as ion exchange columns. The goal of this study was to elucidate the selectivity of a sol-gel matrix for heavy and radionuclide cations to separate heavy metal cations from a solution of heavy and radioactive metals. The effect of ligand incorporation in the host matrix on adsorption capacity was determined by measuring matrix capacities to adsorb the metal cations. Analysis of the results obtained by DFT calculations showed a good fit to the relative capacity values measured by the wet experiments, and they lead to some important conclusions:The higher capacity observed for the matrices prepared at pH 13 for all of the studied cations, indicates that this method could be applicable in the durable entrapment of cations. The sol-gel matrices were found to be selective for the uranyl, and the entrapment of nitrilotris(methylene)]tris(phosphonic acid) in these matrices increases the capacity and selectivity for cerium and accelerates the cation adsorption process (the measured capacities are 25.3 μmol/g sol-gel and 28.4 μmol/g sol-gel for the TMOS-Blank and TMOS-NTPH, respectively). Since uranyl and chromium reached their maximum capacities at different times, which also differed from the times for the other cations, these matrices can be used as ion exchange columns for the separation of chromium and uranyl from other cations and for the recycling of heavy and radioactive metals.

Separation of Chromium(VI) Metal in Wastewater Using Electrocoagulation Method with NaCl Coagulant

Waste has become an environmental problem that needs attention in its handling. Metal Cr (VI) is one of the components of a very dangerous pollutant produced by industrial activities, such as textiles. In fact, there are still many textile industry players who do not treat their waste because they feel that the processing requires expensive upfront costs. Therefore, this research was conducted to perform a sewage treatment system with a separation technique using an alternative method, namely electrocoagulation using NaCl coagulant. The research was conducted at the Laboratory of Applied Chemistry and Toxicology at the Rajawali Health Institute. The sample used is a sample of liquid waste taken directly from a textile industry in Bandung, Indonesia. The results showed a decrease in the levels of Cr (VI) after the electrocoagulation process until it reached a percentage value of 64.02%. Based on this, it can be said that the electrocoagulation method is effective enough to be used as a simple treatment technique to reduce the levels of Cr (VI) metal in wastewater.

Removing trace chromium from high concentration vanadium solution by photoreduction deposition with Ti–Zr solid solution

The preparation of ultrahigh-purity vanadium (>99.99 wt%) requires the removal of trace amounts of chromium, but economical vanadium purification is difficult to achieve using crude vanadium mother liquors (>98 wt%) because of the similar properties of V(V) and Cr(IV) ions. In this study, a Ti–Zr solid solution was used for the deep purification of high-concentration ammonium polyvanadate by removing trace chromium using photocatalytic reduction process. The results show that V(V) and Cr(VI) are competitively adsorbed and photoreduced, but V(V) adsorption is preferred and occurs more rapidly than that of Cr(VI). However, after the photoreduction product of V(V), V(IV) is desorbed, whereas after that of Cr(VI), Cr(III) is deposited on the photocatalyst, achieving the separation of vanadium and chromium. The 2 h removal efficiency of chromium exceeds 80%, and the chromium content in the obtained vanadium is less than 0.04 wt%. After precipitation, the chromium content in the obtained ammonium metavanadate is less than 0.001 wt%, and the purity of the final V2O5 product exceeds 99.99%, which meets the requirement for ultrahigh-purity vanadium products. The used photocatalyst can be regenerated and reused with stable performance. This work provides a reference method for ultrahigh-purity vanadium production and an example of the industrial application of the photoreduction process.

Extraction and separation of chromium from the solution after hydrolysis precipitation of vanadium

ABSTRACT The qualified chromium oxide product was prepared successfully using acidic chromium solution after hydrolysis precipitation of vanadium based on sodium salt roasting-water leaching process in high chromium vanadium slag. The reduction conditions of sodium thiosulfate were provided. The influences of various factors on the filtration performance of chromium hydroxide were discussed, including precipitation agents, precipitation modes and precipitation temperature. The effects of chromium hydroxide calcination conditions and washing mode on the quality of chromium oxide were investigated. The results indicated that Na2S2O3 can completely reduce the acidic chromium solution, the reduction pH was less than 4.0, and the mass ratio of Na2S2O3 to Cr(VI) in the solution was 3.1. When the temperature was higher than 60°C, chromium hydroxide obtained by parallel flow precipitation using sodium carbonate as precipitant performed much better in filtration. The washed chromium hydroxide was calcined at 1200°C for 2 h. The final product of Cr2O3 with a purity of 98.76% was obtained after grinding and washing appropriately.

Hydrothermal Separation of Titanium Vanadium and Chromium from a Pregnant Oxalic Acid Leachate.

The separation of titanium, vanadium and chromium in vanadium slag (VS) is a difficult problem restricting the comprehensive utilization of VS. This paper presents the first study on the separation of titanium, vanadium and chromium from oxalic acid leachate of VS. Firstly, the separation of titanium from the leachate by hydrothermal method was studied. The results show that more than 99% of titanium in the leachate was precipitated in the form of spherical anatase TiO2 with the purity of 95.7%. Then, the extraction separation of vanadium and chromium from the titanium-free filtrate by three-stage extraction of acidified N235 extractant and four-stage stripping of HCl solution was investigated. The extraction mechanism was identified as the anion exchange reaction between acidified N235 extractant and vanadium and chromium complex anions, which were further stripped by HCl solution in the stripping process. After obtaining the concentrated and purified stripping solution containing vanadium and chromium, the separation of vanadium and chromium from the stripping solution by hydrothermal method was studied, and the product was mainly composed of VO2 and Cr2O3. This process provides an idea for the comprehensive utilization of titanium, vanadium and chromium in oxalic acid system.

A review on separation and detection of copper, cadmium, and chromium in food based on cloud point extraction technology

Due to its environmental efficacy and economic effectiveness, a unique approach for extracting functional thermally sensitive bioactive components from food was recently developed. Cloud point extraction is one of the most effective alternative methods for extracting a wide range of organic and inorganic components from green surfactants. The extraction method is cloud point extraction by phase separation, which is a quick and easy approach that requires very little solvent and just a small amount of very non-flammable and non-volatile surfactant that is environmentally benign. The theoretical results of cloud point extraction's application in the food industry are summarized in this article. While presenting a series of introductions on how to extract cloud points, the benefits and applications of cloud points have been studied. The method of using cloud point extraction in food samples has been explained in this article. This method is simple, safe, cost-effective, and widely used to measure a variety of tissue samples, and it can detect analytes down to nanograms per millimeter. Spectrophotometric measurement of low levels of cadmium in some vegetables was also developed in the current study as one of the most important applications of the cloud point extraction method in the food industry.

Separation of vanadium and chromium in solution after vanadium precipitation by co-extraction with N263 and selective stripping with NaOH solution

The conventional process of extracting vanadium from vanadium slag produces a large amount of V-Cr-bearing residue (VCBR) and wastewater containing sulfate and ammonium salt. Through the research of the co-extraction and selective stripping of vanadium and chromium, this work proposes a novel process for extracting vanadium and chromium from vanadium slag to avoid the issues mentioned above. Methyl tri octyl ammonium carbonate (N263) can co-extract vanadium and chromium from solution after vanadium precipitation. Vanadium can be selectively stripped by NaOH solution from the loaded organic solution containing V and Cr. Under the most suitable conditions, including NaOH concentration of 3 mol/L, stripping temperature of 25 °C, O/A ratio of 3:1, the stripping of vanadium and chromium reached more than 99% and less than 8%, respectively, after five-stage counter current stripping. Chromium in the loaded organic solution can be stripped in the form of PbCrO4·PbO precipitate using the stripping system of PbCO3 + NaOH solution. Under the most suitable conditions, including PbCO3 addition with a Pb/Cr molar ratio of 5, NaOH concentration of 0.5 mol/L, O/A ratio of 1:1, stripping temperature of 25 °C, stripping time of 50 min, the stripping of chromium reached 99.1%.

Deep understanding of sustainable vanadium recovery from chrome vanadium slag: Promotive action of competitive chromium species for vanadium solvent extraction

The complete separation of vanadium (V) and chromium (Cr) from chrome vanadium slag is still challenging. Many studies focus on the activity of vanadium, while the effect of the other element chromium and their mutual interaction are ignored. Here, we found that proper concentration of chromium can promote the extraction efficiency of vanadium. The extraction of V and Cr with various mass ratios ranging from 8:1–4:3 at different initial pH values using primary amine N1923 were studied. The extraction efficiency of V reached nearly 100%, while none of Cr was extracted when the mass ratio of Cr and V is 0.5 under proper pH. Through the dynamic monitoring of species evolutions during extraction, the transformation of the two metals and advantage extracted species were analyzed. Cr would transfer H+ for the combination of V3O93-/V4O124-, providing a great contribution to the continuous extraction of V. The real leachate was applied and 99.9% vanadium pentoxide was produced at a scale of 50 L/h. This paper offers deep insights of the separation of similar metal elements, and guide sustainable vanadium recovery from hazardous waste.

Separation and recovery vanadium (V) and chromium (Ⅵ) using amide extractants based on the steric hindrance effect

As all existed in the form of anion, the separation of vanadium (V) and chromium (Ⅵ) in weak acid solution was a difficult issue. The study developed an efficient way to achieve the separation of V(V) and Cr(Ⅵ) based on the steric hindrance effect of amide extractants. The effects of different parameters on extraction were studied to explore the optimum conditions. The recoveries of vanadium and chromium were above 97.0% and 99.8%, respectively. The extraction of vanadium with amide was an exothermic reaction. The purity of V2O5 obtained was 99.97%. The V(V) complex of amide was confirmed to be R2H6V10O28. The extraction mechanism was studied with ESI-MS and FT-IR in depth. The extraction of V(V) with amide followed ion association with hydrogen bonding. A promising way was provided to separate vanadium (V) and chromium (Ⅵ) in leaching solution with amide under weak acid condition.

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As all existed in the form of anion, the separation of vanadium (V) and chromium (Ⅵ) in weak acid solution was a difficult issue. The study developed an efficient way to achieve the separation of V(V) and Cr(Ⅵ) based on the steric hindrance effect of amide extractants. The effects of different parameters on extraction were studied to explore the optimum conditions. The recoveries of vanadium and chromium were above 97.0% and 99.8%, respectively. The extraction of vanadium with amide was an exothermic reaction. The purity of V2O5 obtained was 99.97%. The V(V) complex of amide was confirmed to be R2H6V10O28. The extraction mechanism was studied with ESI-MS and FT-IR in depth. The extraction of V(V) with amide followed ion association with hydrogen bonding. A promising way was provided to separate vanadium (V) and chromium (Ⅵ) in leaching solution with amide under weak acid condition.

On-Line Separation and Determination of Trivalent and Hexavalent Chromium with a New Liquid Membrane Annular Contactor Coupled to Inductively Coupled Plasma Optical Emission Spectrometry

We describe a new on-line sensitive and selective procedure for the determination of trivalent and hexavalent chromium in liquid samples by a tailor-made contactor (TMC), specifically a liquid membrane annular TMC, coupled with inductively coupled plasma with optical detection. The TMC was designed and developed to integrate the extraction and stripping phases of the analyte in one module to minimize the membrane solvent’s consumption and maximize the speed of transport through the liquid membrane. Moreover, the particular geometry studied, which consists of two coaxial hollow fibers, allows the TMC to be used for both separating and preconcentrating purposes. Both (−)-N-dodecyl-N-methylephedrinium bromide (30 mM) in dichloroethane and HNO3 (0.75 M) were used as the liquid membrane and receiving solution, respectively. The proposed method’s performance was evaluated in terms of the hexavalent chromium extraction efficiency and the coefficient of variation percentages; these were higher than 85% and less than 5%, respectively. In addition, the proposed procedure was applied to two real samples: a tap water sample and an eluate from solid urban waste. In both cases, the analytical performances were good and comparable to those obtained using synthetic standard solutions.

Selective separation of Chromium (VI) from aqueous solutions by adsorption onto truffle peels as novel biomass

ABSTRACT The current quest develops a simple and highly selective spectrophotometric method for trace determination of Cr(VI) in water using truffle peels powder (TPPs) as solid-phase extractor. Adsorption of Cr(VI) onto TPPs from aqueous media reached equilibrium at pH ≈1.7 in 20 min and was independent of the initial concentration of Cr(VI). The results showed that the maximum Cr(VI) adsorption capacity was found as 0.2776 mg g−1 from the Langmuir model at 25°C. The sorption of Cr(VI) followed pseudo-second-order kinetic with rate constant k2 = 0.013 g mg−1min−1 (R2 = 0.9982). Furthermore, thermodynamic parameters (ΔH, ΔS and ΔG) of Cr(VI) retention by the sorbent were calculated and assigned. The positive values of ΔH (45.61 J mol−1) proved the endothermic nature of Cr(VI) retention on TPPs and ΔS (162.45 Jmol−1K−1) reflected good absorption and/or adsorption of the chromate [(CrO3Cl)]− as an ion associate with the bulky cations and the surface area available on TPPs. The negative value of ΔG (−48.6 kJ mol−1 at 298 K) indicates the spontaneous and chemical sorption nature of Cr(VI) uptake onto TPPs.

A high-efficiency process for the separation of chromium and aluminum from waste aluminum sludge with a high chromium content using a combined oxidation and dispersion process

Waste aluminum sludge (WAS) contains an abundance of Cr(III), which restricts the potential for recycling of Al resources in WAS. The oxidation process is a potentially effective method for the separation of Cr and Al from solid waste. However, many challenges restrict the application of oxidation treatments for WAS, including their low oxidative efficiency and their inability to handle sludge with high Cr concentration. This study proposes a highly efficient combined oxidative and dispersive process for the separation of Al and Cr from high Cr(III) content WAS. The effects of varying solid–liquid mass ratios and Ca(OCl)2 concentrations in the oxidation process and Na2SO4 concentrations in the dispersion process were investigated. Using single factor experiments, the optimal conditions were found to be a solid–liquid mass ratio of 1:14 and Ca(OCl)2 dosage of 280 mg/g dry WAS in the oxidative process, allowing the Cr(III) oxidative efficiency to reach 93.83%. After treatment using the combined processes, the total Cr removal efficiency reached 95.54% and the aluminum content exhibited almost no loss. Characterization by FTIR, XRD, and SEM-EDS indicated that Ca(OCl)2 destroyed the colloidal structure of WAS, resulting in the release of Cr(III) which could subsequently be oxidized to soluble Cr(VI) by Ca(OCl)2. In the dispersion process, Na2SO4 destroyed the colloidal stability of WAS, resulting in the release of Cr(VI) and improving the Cr removal efficiency. The combined processes were found to have a significantly synergistic effect, indicating that this method is suitable for the separation and collection of Cr and Al from WAS. Furthermore, the economic analysis showed that the combined processes have cost advantage over traditional treatment.

Separation and Recovery of Chromium from Solution After Vanadium Precipitation

The separation and recovery of chromium from solution after vanadium precipitation were investigated by deep removal of vanadium, hydrolysis precipitation of chromium, and preparation of chromium oxide. Hydrous oxide of trivalent iron is an effective deep vanadium remover and can be recycled. Under the most suitable conditions including hydrous oxide of trivalent iron addition with a Fe/V molar ratio of 4, reaction temperature of 60 °C, reaction time of 10 min, as well as the solution pH value of 3.0, the removal of vanadium reached 97.4%. Cr3+ and Mn2+ in solution can be separated through precipitation method. Under the conditions including solution pH value of 6.0, reaction temperature of 35 °C, and reaction time of 2 h, the precipitation of chromium was 96.6%. After deep remove manganese using sodium thiosulfate as the reducing agent, the well-crystallized Cr2O3 product with a purity of 99.1% was prepared. The manganese in the solution after chromium recovery can be recycled as an oxidant by hydrolysis precipitation and hydrogen peroxide oxidation.

Salt-Assisted Bulk Liquid Membrane and Flame Atomic Absorption Spectrometry for the Separation and Determination of Chromium(VI)

Due to the common use of chromium in many industrial applications, as well as its potential release into water sources, the quantification of chromium in environmental samples has great importance. In this work, a novel and fast salt-assisted bulk membrane extraction (SA-BME) combination with flame atomic absorption spectrometry (FAAS) was proposed for the separation and preconcentration of Cr(VI) in water samples. The transport of Cr(VI) was performed using cetyltrimethylammonium bromide (CTAB) as the mobile carrier dissolved in kerosene/chlorofrom organic membrane at room temperature. After this process, Cr(VI) was reduced to Cr(III) in a receiving phase using an acidified iron(II) sulfate. In aqeous solutions, total chromium was determined as Cr(VI) after the oxidizing Cr(III) to Cr(VI) using potassium permanganate in acid medium and finally total chromium was measured by FAAS. The analytical parameters affecting the separation and mass transfer of Cr(VI) were optimized. With 20 µg L−1 of Cr(VI) in the feed phase, the extraction efficiency was quantitative using a 50 minute extraction time. Under the optimum conditions, the linearity (R2 = 0.9994) was from 7 to 290 µg L−1, the limit of detection 2.3 µg L−1 and the enrichment factor 35 for Cr(VI). Common cation and ions in water samples did not interfere with the separation and determination of Cr(VI). The developed SA-BME method has been successfully applied for the determination of Cr(VI) in stream, sea and waste water with good recoveries.

Carboxyl-functionalized hybrid monolithic column prepared by “thiol-ene” click reaction for noninvasive speciation analysis of chromium with inductively coupled plasma-mass spectrometry

A novel carboxyl-functionalized hybrid monolithic column was developed based on “thiol-ene” click reaction via “one-pot” by choosing mercaptosuccinic acid, γ-methyl methacrylate trimethoxysilane and tetramethoxysilane as reaction monomers. The design of the hybrid monolithic column was assisted by the comparison in computational simulation with existing carboxyl-functionalized materials. The characterization by scanning electron microscopy, energy dispersive X-ray spectroscopy, N2 adsorption-desorption measurement, Fourier-transform infrared spectroscopy and elemental analysis showed that the carboxyl-functionalized material has the advantages of good permeability and high mechanical strength. Then, we used the prepared carboxyl-hybrid monolith column as solid phase microextraction adsorbent for separation of trace inorganic chromium species. Under pH 4.5, the hybrid monolith column can selectively enrich Cr(III) without adsorbing Cr(VI) and afterwards, Cr(III) can be eluted by 1.0 mol L−1 HCl. The chromium speciation separation method based on carboxyl-hybrid monolith column followed by inductively coupled plasma-mass spectrometry possessed the merits of facile preparation, low cost, simple and mild extraction condition, and sensitive detection, which has been successfully applied to the separation, enrichment and detection of inorganic chromium in environmental waters.

A cost-effective solid platform based on nanosized α-Fe2O3 chemically treated polyurethane foam for separation of chromium(VI) from water: characterization, kinetic, thermodynamic study and analytical utility

ABSTRACT A low-cost and selective solid phase extractor (SPE) for complete removal of chromium (VI) sp cies from aqueous media has been developed. The proposed method was based upon formation of chlorochromate [CrClO3]− aq oxyanion in aqueous HCl (≥ 0.5 mol/L) medium followed by complete extraction onto the ion pairing 2,3,5-triphenyltetrazolium chloride (TZ+Cl−) modified α-Fe2O3 nanoparticles treated polyurethane foam (PUFs) (TZ+Cl−/α-Fe2O3 NPs/PUFs) solid phase platform. The sorption data fitted well pseudo-second-order kinetic with an overall rate constant (k2) of 0.010 g (mg. min)−1. The values of ΔH (−78.2 ± 2.1 kJ mol −1 ) and ΔG (−3.51 ± 1.1 kJ mol −1 ) revealed that, the [CrClO3]− aq sorption onto the solid sorbent are spontaneous and exothermic process, respectively. The value of ΔS (223.5 ± 2.5 J mol −1 K −1 reflects the sorption of [CrClO3]− aq onto the TZ+Cl−/α-Fe2O3 NPs/PUFs sorbent proceeded in a more random fashion. The nanocomposite sorbent packed column was successfully used for complete removal of trace levels of chromium (VI) species from environmental water samples. The retained chromium (VI) species were recovered with NaOH (0.5 M) and analysed by ICP-OES. Sorbent packed column was also used for rapid and complete retention of chromium(III) after oxidation with H2O2 in KOH. The sorbent packed column can be reused for 3–4 times without decrease (±5%) in column performance.

Separation of Chromium Cadmium Nickel and Titanium from Ilmenite Ore

This study shows the separation of chromium, cadmium, nickel and titanium from Egyptian ilmenite ore. ‎The method implicates leaching the ore in 20% hydrochloric acid. Titanium ions, after removal of the ferrous ions, were precipitated as a hydroxide. It was reduced with 1 M alcoholic ascorbic acid. Chromium, cadmium, and nickel in the leachate were estranged by a strongly basic Lewatit 600 anion exchanger. The picked-up elements were eluted using 4M hydrochloric acid. An azo resorcinol 4-(2-pyridylazo) dye helps complexing of the adsorbed elements to form negatively charged complexes. Adsorption isotherms were modelled in an ethanol/acetic acid/water media. Results show that the convenient conditions of leaching the ore were 30% HCl for 120 min at 80°C, solid: liquid ratio of 1:30 and stirring. The interaction between the metal ions and the ion-exchanger to form the complex compounds is an electrostatically controlling-adsorption step. The trivalent chromium showed a significant perception at an acid medium at a pH 3.5-4.5. Cadmium and nickel ions uptake takes place in an alkaline medium. The chelating capacity of the sorbent is proportional to the electronegativity of the metal-dye complexes. The ∆E of the leaching process amounts to 13.8 kJ per mole.