Separation Of Chromium Research Articles

Photoreduction of chromium (VI) by a composite of niobium (V) oxide impregnated with a Ti-based MOF

Herein, we report a novel composite material of Nb2O5@MIL–125 that exhibited enhanced photoreduction of hexavalent chromium. The composite material was fabricated through an impregnation approach, which comprised of a two-step hydrothermal synthesis. As-prepared Nb2O5 nanospheres exhibited very poor charge separation; MIL–125 (Ti) which is a Ti-based metal-organic framework was introduced into the lattice of the spheres to improve charge recombination rate. The synthesized material’s phase, crystallinity, textural and morphological studies were investigated utilizing XRD, Raman, TEM, SEM, and EDS, respectively. While the optical and photoelectrochemical behavior of the samples were obtained from UV–vis–DRS, PL, and EIS data. This data combined, illustrated the successful formation of a functional and effective heterointerface between Nb2O5 and MIL–125 (Ti). Ti introduced as the MOF in the lattice of Nb2O5 had an essential synergetic effect as the composite bearing the highest mole ratio of Ti showed higher effective photoreduction of hexavalent chromium. This was further complemented the PL and XPS data which highlighted the Nb–MIL–125 (2–3) composite to have excellent charge separation and rapid photoreduction of chromium.

Step-Adsorption of Vanadium (V) and Chromium (VI) in the Leaching Solution with Melamine

The vanadium (V) and chromium (VI) was hard to separate directly due to the similar nature. In this paper, separation and recovery of vanadium (V) and chromium (VI) from a leaching solution was investigated by adsorption of vanadium (V) with melamine, followed by electro-reduction of chromium (VI) and adsorption of chromium (III) with melamine, respectively. The effects of experimental parameters including dosage of melamine, reaction temperature and reaction time on the adsorption process were investigated. The results showed that melamine was a good sorbent for adsorption of vanadium (V) and chromium (III). 99.89% of vanadium (V) was adsorbed by melamine at the optimal conditions, the adsorption kinetic was followed the pseudo-second-order model and the adsorption isotherm conformed to the Langmuir model. While the adsorption of chromium (III) was followed the pseudo-first-order model and the adsorption isotherm was conformed to the Freundlich model as the adsorption efficiency was 98.63% under optimal conditions.

Direct surface functionalization of graphene oxide with ionic liquid through gamma ray irradiation induced radical polymerization with remarkable enhanced adsorption capacity

Abstract A facile one-step synthesis method based on Gamma ray irradiation induced radical polymerization was proposed for the first time for preparation of graphene oxide-ionic liquid composites (GO@IL) using 3-n-Hexadecyl-1-vinylimidazolium bromide ([C16VIm+] [Br−]) as the monomer. The GO@IL composites were utilized as adsorbents for adsorption and separation of Sunset Yellow (SY) and chromium (Cr, VI) ions from the stock solution. The maximum adsorption capacities of prepared GO@IL to adsorb SY and Cr (VI) were observed in the acidic media at room temperature, with the maximum adsorption capacities of 169.6 and 75.8 mg g−1, respectively. Various adsorption kinetics and isotherm models were employed to fit adsorption data to better understand the adsorption process and behavior of contaminants onto GO@IL surfaces. The value of ΔG0 and ΔH0 implied the adsorption were initiative and endothermic nature for SY and Cr (VI). The electrostatic and π − π stacking interactions were expected to be involved in the adsorption for SY and Cr (VI) onto the functionalized graphene oxide composite. These data illuminate that the adsorption performance of graphene oxides has enhanced remarkable after polymerization with [C16VIm+] [Br−] on their surface. Considering the regeneration ability, the easily synthetic GO@IL composites with great promise applications for wastewater treatment and purification.

Recovery and Separation of Vanadium and Chromium by Two-Step Alkaline Leaching Enhanced with an Electric Field and H2O2.

This paper focused on the treatment of vanadium–chromium reducing residue with a two-step alkaline leaching process: electro-oxidation leaching of vanadium and H2O2 as well as oxidation leaching of chromium in an alkaline medium. The effects of experimental parameters on the leaching performance of vanadium and chromium were investigated. The experimental data showed that in the first alkaline leaching in stage I, the leaching efficiency of vanadium reached up to 95.32% under optimal conditions, while most of the chromium could not leach out (about 4% of chromium was leached out). Chromium was easily oxidized to high valence (CrO42–) with H2O2 in the second alkaline leaching stage II. Under optimal conditions, 96.24% chromium was leached out.

Effective Separation and Beneficiation of Iron and Chromium from Laterite Sulfuric Acid Leach Residue

The utilization of laterite sulfuric acid leach residue has always been a challenge in the metallurgical industry. The current treatment involves deep-sea landfills, which leads to considerable environmental pollution and resource wastage. In this work, an effective method is proposed to recover iron and chromium from sulfuric acid leach residue. The effects of roasting temperature, reducing agent dosage, and reaction duration on the recovery of iron and chromium were investigated. The optimum conditions were as follows: roasting temperature of 1200 °C, reducing agent dosage of 30%, and reaction duration of 60 min. Results show that the concentrate contains 87% Fe and that only 0.7% S can be obtained with an iron recovery of 82%, indicating suitability for ironmaking. Meanwhile, 85% of chromium can be beneficiated in tailings at a chromium content of 3.5%. The microstructure and composition of reduction products were analyzed by XRD, SEM, and EDS to understand the phase transformation and the aggregation of the reduction products. Hematite in the leach residue is first reduced to FeS and Fe3O4 at low temperature and then reduced to metallic iron with increased temperature. Sulfur is combined with alunite to form FeS at a low temperature, and the decomposition of chromite at high temperature leads to the formation of chromium oxide. In a high temperature and reducing atmosphere, Cr2O3 reacts with FeS to transform Fe and CrS. Through the reduction roasting–magnetic separation process, most of the iron is beneficiated in the concentrate, and nonmagnetic minerals such as FeS and CrS remain in the tailings. Consequently, the separation and beneficiation of iron and chromium occur. The process is economically feasible and environmentally friendly and thus has great potential for the industrial-scale recycling of laterite sulfuric acid leach residue.

Low-cost and facile synthesis of geopolymer-zeolite composite membrane for chromium(VI) separation from aqueous solution

Inorganic membranes in wastewater treatment have captured increasing attention due to their numerous advantages. However, high cost and complicated producing process restricted their benign developments. This study proposed an novel inorganic geopolymer-zeolite composite membrane which was synthesized by using circulating fluidized bed fly ash (CFBFA) solid waste as initial material and via a low-cost and facile geopolymerization-hydrothermal treatment processes, further, the membrane was employed to separate Cr(VI) ion from aqueous solutions. X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectra results indicated that geopolymer-zeolite (Li-ABW) composite membrane was obtained successfully. Field emission scanning electron microscopy (FESEM) results demonstrated that the membrane had a compact zeolite layer with thickness about 1.5 μm. The effects of transmembrane pressures (TMP), Cr(VI) concentration, pH, ionic strength, and co-existing ions on Cr(VI) rejection were investigated, and the results revealed that the Cr(VI) rejection reached 85.45 % under 10 kPa of TMP, 1000 mg L−1 of Cr(VI), and pH 7. The separation mechanism of Cr(VI) on the geopolymer-zeolite composite membrane was considered to be size exclusion and electrostatic interaction. These results suggested that the geopolymer-zeolite composite membrane had a potential application for the effective removal of Cr(VI) contaminants from wastewater.

Separation of sodium chromate from high alkaline media based on precipitation transformation using barium hydroxide

Separation and recovery of chromium from a high-concentration NaOH solution by a Ba(OH)2 precipitation process.

Cross-linked GO membranes assembled with GO nanosheets of differently sized lateral dimensions for organic dye and chromium separation

Membrane microstructure and separation performance largely depend on the property of building units and its subsequent patterning. In this work, three differently sized graphene oxide (GO) nanosheets were prepared by a simple centrifugation method. Supported GO membranes were then fabricated based on these separated GO nanosheets. GO nanosheets of different lateral sizes show varied degree of oxidation and distribution of oxygenated groups at both edge and in-plane areas, which leads to different membrane microstructure and separation performance. The swelling and long-term stability of GO membrane were addressed by a pre-crosslinking process with ethylenediamine (EDA). The ultimate separation performance of these GO/EDA membranes was affected by several factors such as cross-linking density, d-spacing, and microstructure like wrinkles all relating to the lateral size of GO nanosheets. Specifically, compared to smaller GO nanosheets, larger GO sheets have more surface groups and thus higher cross-linking density. In terms of microstructure, larger sheets tend to form more surface wrinkles which could sacrifice the membrane separation performance. GO membranes were tested in different pH conditions for separating methylene blue (MB), methyl orange (MO) and chromium (VI). Overall, exceptional rejection rates of higher than 99.0% were achieved at optimal separation conditions. MB separation performance has been found closely related to GO lateral size at specific pH environments.

A Novel Technology for Recovery and Separation of Vanadium and Chromium from Vanadium-Chromium Reducing Residue

This paper was to develop an efficient process for efficient recovery and separation of vanadium and chromium. The vanadium-chromium reducing residue was conducted by oxidation acidic leaching with MnO2, followed by selective adsorption of vanadium and precipitation of chromium, respectively. The results showed that 97.93% vanadium was leached out and then adsorbed by melamine at pH 1.8 at 90 °C for 60 min. Almost all chromium was leached out and efficiently recovered as Cr2O3. The leaching process was mainly controlled by surface chemical reaction, and its kinetic behaviors fitted well with the shrink core model. The apparent activation energy for vanadium and chromium leaching out wascalculated as 19.93 kJ·mol−1 and 21.26 kJ·mol−1, respectively.

Removal of Heavy Metal (Chromium) From Aqueous Solution using Acacia Arabica Wood (Black Babul)

Heavy metals become a serious problem to society in the view of water pollution. Polluted water causes many disorders in human beings, animals and plants also. The concentration of heavy metals increases mainly due to the activities like mining, agricultural activities and disposal of industrial waste products. Most of the activities releases heavy metals like Mercury (Hg), chromium(Cr), arsenic(Ar), thallium (Tl), nickel (Ni), lead (Pb), and cadmium (Cd). Separation of these heavy metals from water many treatment methods are available like chemical precipitation, ion exchange, membrane separation, electro-dialysis, ultra-filtration, nano filtration, coagulation, flocculation, floatation and adsorption. Adsorption is the best method out of all these methods. Activate carbon is normally used as adsorbent but it is expensive. Black babul wood is the cheapest and abundant available in nature. So treatment of heavy metals black babul wood used as adsorbent. In this article, effect of parameters like process time, initial concentration, adsorbent dosage, adsorbent particle and temperature on separation of Chromium from aqueous solution is studied.

Complexation separation for vanadium and chromium by dithiocarbamate and its application in treatment of chromium–vanadium-bearing slag

Abstract A novel method for the separation and reclamation of vanadium and chromium from acidic solution was proposed. The principle for the separation is based on selective complexation. In specific, V(V) can be complexated by dithiocarbamate to form VO(R1R2NCS2)3 precipitate, leaving Cr(III) remained in the acidic solution. Then the reclamation of V and Cr from VO(R1R2NCS2)3 precipitate and Cr(III)-bearing solution can be reached by decomplexation and neutralization, respectively. The kinetics of the complexation reaction was studied. In addition, the precipitation ratio of vanadium reached 97% and the loss of chromium was less than 4% after process optimization. The complexing agent could be regenerated with a high ratio of 99.5%. The method was successfully applied to treating chromium–vanadium-bearing slag produced in conventional vanadium production industry. Vanadium and chromium could be extracted from the slag in the form of calcium vanadate and Cr2O3 product with a purity of over 98%.

Application of MnO2Resin and Dowex 1X8 manganese dioxide impregnated resin for the separation of chromium from biological samples

MnO2Resin and Dowex 1X8 manganese dioxide impregnated resin was used for chromium separation from biological samples. We examined sorption of chromium from acid solutions: hydrochloric, nitric and sulphuric in concentration range from 0.01 to 2 mol/dm3. The sorption process was evaluated by batch and column experiments. We also examined sorption of other elements in the developed systems, to check the selectivity of the process. Determination of chromium by radiochemical neutron activation analysis after separation with MnO2Resin was described.

Effect of Ion (Ar+) Irradiation on Cluster Magnetism and Magnetic Interactions in Fe67Cr18B15 Amorphous Alloy

The comparison of the resonance magnetic absorption spectra with the data on structure and magnetic properties of Fe67Cr18B15 amorphous samples has shown that a randomly inhomogeneous medium of amorphous alloy is multiphase. Two types of samples with the same chemical composition, but with a different clusterized structure, and the use of (Ar+) ion irradiation in the experiment made it possible to separate four basic phases with different magnetic properties. The basic phase α-(Fe,Cr) contains large clusters of D < 400 A in size with a tendency to phase separation of iron (α-Fe) and chromium (α-Cr), which under irradiation, enhances the competing FM and AFM magnetic interactions and increases the intensity of the resonance magnetic absorption lines associated with α-Fe and α-Cr. The phase Fe3B (D < 100 A) is detected by independent line in the resonance absorption spectra only when its groupings are isolated from the α-(Fe,Cr) metal phase clusters. The fourth phase contains precluster groupings and disappears when the sample is irradiated.

Efficient separation of chromium and vanadium by calcification roasting–sodium carbonate leaching from high chromium vanadium slag and V2O5 preparation

Calcification roasting–sodium carbonate (Na2CO3) leaching process was carried out to separate chromium and vanadium efficiently from high chromium vanadium slag (HCVS). Then vanadium existed in the form of ammonium metavanadate (NH4VO3) after precipitation from the purified leaching liquid, and highly pure V2O5 was prepared, while chromium remained in the vanadium tailings in the form of (Fe0.6Cr0.4)2O3. The effects of separation behaviors of chromium and vanadium under different roasting and leaching conditions were studied systematically. In order to elucidate the phase evolution, XRD and SEM were used during the whole process. After calcification roasting and Na2CO3 leaching, 93.19% of vanadium and 0.04% of chromium was extracted when CaO was added to HCVS in a mole rate n(CaO)/n(V2O5) of 0.5, roasted at 900 °C and maintained for 60 min. The roasted samples were added to 160 g/L Na2CO3 solution with the mass ratio of liquid to solid (L/S) of 10, then heating at 80 °C for 60 min. CaO tended to combine with vanadium and form alkali soluble calcium vanadate, while almost all of chromium was more likely to react with iron and form (Fe0.6Cr0.4)2O3. 94.00% of vanadium was then precipitated as NH4VO3 from the vanadium–containing supernatant after CO32– removing, when NH4Cl was added with the mole rate of n(NH4+)/n(V) of 6 and precipitated for 120 min at 5 °C. The purity of V2O5 was 99.68%, which was prepared by roasting NH4VO3. This process achieved the high efficiency separation of chromium and vanadium from HCVS compared with the traditional calcification roasting–acid leaching process. And the chromium-containing vanadium tailings can be used as the raw material to extract chromium and prepare Fe-Cr alloy.

Separation and preconcentration of trivalent chromium in environmental waters by using deep eutectic solvent with ultrasound-assisted based dispersive liquid-liquid microextraction method

An innovative deep eutectic solvent with ultrasound-assisted based dispersive liquid-liquid microextraction method was first time develop for separation and preconcentration of trivalent chromium in environmental water samples. The `deep eutectic solvent with ultrasound-assisted based dispersive liquid-liquid microextraction method was prepared from acetamide and zinc chloride at different molar ratio. The complexing agent calmagite was used for complex formation with trivalent chromium in the range of 8.0–10 optimum pH values. After that complex of trivalent chromium with calmagite was entrap by using deep eutectic solvent. Extraction efficiency was increase by adding tetrahydrofuran into the extraction unit. Extracted and pre-concentrated trivalent chromium contents from water determined by using graphite furnace atomic absorption spectrometry. Effected extraction efficiency parameters are pH, concentration of calmagite, volume of deep eutectic solvent, volume of tetrahydrofuran, molar ratio of the deep eutectic solvent and extraction time were optimized. The deep eutectic solvent with ultrasound-assisted based dispersive liquid-liquid microextraction method has excellent analytical figure of merits such as enrichment factor and limit of detection 85.1 and 6.0 ng L−1, respectively. Accuracy of the developed method was checked by the certified reference materials of water (TM-28.3) with percentage recovery >98%. The proposed method was successfully applied for determination of trivalent chromium in different natural water samples.

Selective separation of Cr(VI) and V(V) from solution by simple pH controlled two-step adsorption/desorption process with ZrO2

The recovery and separation of vanadium and chromium from vanadium-containing chromate solution are necessary and valuable for the comprehensive utilization and environmental protection of V-Ti-bearing magnetite ore. In this work, a tetragonal ZrO2 adsorbent was used for harmless treatment and resource reuse of a low-concentration vanadium-containing chromate solution. Results confirmed that water after treatment met the wastewater discharge standard; in addition, Cr(VI) and V(V) were efficiently separated with the V/Cr separation coefficient of 362.05 for the pH of 3.5 and the V/Cr ratio of 1:1 at the concentration of 80 mg/L. This excellent and stable separation performance of ZrO2 was ascribed to the competitive adsorption of V(V) and Cr(VI) on ZrO2, owing to the strong effect of pH on their adsorption and desorption behavior. V(V) and Cr(VI) in vanadium-containing chromate solution can be removed, recovered, separated and enriched through a two-step adsorption/desorption process. The purity of vanadium and chromium can reach more than 99.8%. The adsorption of vanadium and chromium by ZrO2 has high application value, which is beneficial to the recovery of resources and environmental protection.

Selective separation of chromium from sulphuric acid leaching solutions of mixed electroplating sludge using phosphate precipitation

The selective separation of chromium (Cr) from sulphuric acid leaching solutions is necessary for the harmless disposal and resource recycling of electroplating sludge. A method using phosphate precipitation was investigated. First, the thermodynamic analysis of a Cr3+ − Fe3+ − PO43–−H2O system and a Cr3+ − Fe2+ − PO43–−H2O system was analysed to evaluate the feasibility of Cr recovery, and the optimal operating windows were identified. The corresponding experiments were carried out based on the thermodynamic calculations, and the results showed that Cr and Fe can be selectively separated using phosphate in the presence of excess sulfite. The major factors, including the PO43−/Cr3+ ratio, solution temperature, pH and impurity concentration, were evaluated. Under the best conditions, over 97.04% of Cr can be separated and recovered as phosphate precipitation, while the precipitation efficiency of Fe was only 14.75%. Thermogravimetric and infrared analyses showed that the finial precipitation was a xCr(OH)3·yCrPO4·zH2O complex. The surface morphology of the precipitation presented in the form of an agglomeration when Fe existed in the solution. The impurities in the precipitation could be removed through a dilute sulphuric acid cleaning process. The consequence of phosphate precipitation could provide a practical and yet easy-to-adopt perspective for selectively separating Cr from sulphuric acid leaching solutions.

A cleaner and efficient process for extraction of vanadium from high chromium vanadium slag: Leaching in (NH4)2SO4-H2SO4 synergistic system and NH4+ recycle

A cleaner and novelty leaching medium, (NH4)2SO4-H2SO4 synergistic system was introduced into the leaching process for extracting vanadium efficiently after calcification roasting with high chromium vanadium slag (HCVS), and then V2O5 was prepared after precipitation and roasting. The effects of leaching and precipitation conditions were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). 93.45% vanadium and 0.24% chromium were leached when the calcification roasted sample was leached in the (NH4)2SO4-H2SO4 synergistic system at 20 °C for 60 min with a liquid–solid ratio (L/S) of 10, achieving the efficient separation of vanadium and chromium in HCVS. The optimal (NH4)2SO4-H2SO4 synergistic system was composed with 250 g/L (NH4)2SO4 and 3.75 mol/L H2SO4, the amount of H2SO4 was 1 mL in every 30 mL leaching system. The introduction of (NH4)2SO4 provided much NH4+, which could promote the acid leaching reaction. 99.75% vanadium was precipitated further from vanadium-containing leaching liquid when heating the liquid at 60 °C for 60 min after adjusting the system pH at 8.0, and the deposit was ammonium polyvanadate (NH4)2V6O16. Then, V2O5 with a purity of 95.71% was prepared after roasting, and recovery rate of vanadium from HCVS was higher than 93%. After precipitation, the supernatant containing a large amount of NH4+ could be recycled as the new leaching medium with some (NH4)2SO4 adding according to NH4+ loss after vanadium precipitation. This process achieved the efficient extraction of vanadium from HCVS and provided a new thinking for the leaching process based on the (NH4)2SO4-H2SO4 synergistic system.

Влияние ионного (Ar-=SUP=-+-=/SUP=-) облучения на кластерный магнетизм и магнитные взаимодействия в аморфном сплаве Fe-=SUB=-67-=/SUB=-Cr-=SUB=-18-=/SUB=-B-=SUB=-15-=/SUB=-

Comparing the magnetic resonance absorption spectra with the data on structure and magnetic properties of amorphous Fe67Cr18B15 samples, we have shown that a randomly inhomogeneous medium of amorphous alloy is multiphase. The presence of two types of samples with a different clusterized structure and the use of ion (Ar+) irradiation in the experiment contributed the observation of four main phases with different magnetic properties. The main α-(Fe,Cr) phase contains large clusters D&lt;400 Å in size with a tendency to phase separation of iron (α-Fe) and chromium (α-Cr) under irradiation, which enhances the competitive FM and AFM magnetic interactions and increases the intensity of absorption lines related to α-Fe and α-Cr. In the samples with a developed cluster system, the phase of Fe3B (D&lt;100 Å) interacting with the α-(Fe,Cr) phase is detected in the resonance absorption spectra only when these groupings are isolated. The fourth phase represented by precluster groupings disappears under irradiation.

Efficient extraction and separation of vanadium and chromium in high chromium vanadium slag by sodium salt roasting-(NH4)2SO4 leaching

A novelty process based on sodium salt roasting-(NH4)2SO4 leaching was proposed to extract vanadium and chromium in high chromium vanadium slag (HCVS). V2O5 and Cr2O3 was then prepared. The effects of roasting and leaching conditions on vanadium and chromium extraction behavior were studied systematically and completely. Vanadium precipitation conditions and chromium reduction conditions were optimized further. 94.6% vanadium and 96.5% chromium were extracted when HCVS and Na2CO3 were mixed in the molar ratio of n(Na2CO3)/n(V2O3+Cr2O3) of 2.5, then leached in 30g/L (NH4)2SO4 solution. 94.8% vanadium was precipitated as ammonium polyvanadate (APV) just by adjusting the leaching liquid pH at 4.5, almost all chromium was remained in liquid, achieving the efficient separation of vanadium and chromium. Chromium was then recovered by reduction and precipitation. More than 99% chromium was reduced when Na2S2O5 was added in m(Na2S2O5)/m[Cr(VI)] above 3. By roasting the deposits of vanadium and chromium respectively, 91.49% V2O5 and 89.89% Cr2O3 were obtained. The supernatant after vanadium and chromium extraction containing NH4+ could be recycled as the new leaching medium with some new (NH4)2SO4 added, which greatly reduced the discharge of ammonia-nitrogen wastewater and made the whole process more environmentally friendly.