Extraction Of Chromium Research Articles

Thermally Activated Brown and Black Coals as the Sorbents of Chromium(VI) from Aqueous Solutions

Porous materials prepared from brown and black coals were used as sorbents for the extraction of chromium(VI) from aqueous solutions. They were compared with an AG-3 commercial sorbent. The effect of the acidity of reaction medium on the adsorption of chromium(VI) was established. The extraction of Cr(VI) from aqueous solutions reached a maximum in a range of pH 1.5–2.0. A kinetic study made it possible to determine equilibration times in the porous material–chromium(VI) solution systems.

Extraction Behavior of Vanadium and Chromium by Calcification Roasting-Acid Leaching from High Chromium Vanadium Slag: Optimization Using Response Surface Methodology

ABSTRACTCalcification roasting-acid leaching were conducted to investigate the extraction behavior of vanadium and chromium from high-chromium vanadium slag (HCVS). The conditions were optimized by response surface methodology (RSM). Results showed that when HCVS and CaO were mixed in m(CaO)/m(V2O5) of 0.62, then roasted from room temperature to 840 °C and maintained for 170 min, a maximum vanadium leaching rate of 87.74% was achieved. Additionally, 0.68% chromium was co-leached, achieving the separation of vanadium and chromium. The roasting factors affecting vanadium extraction followed this order: roasting temperature>m(CaO)/m(V2O5)=holding time. For the chromium extraction, the interaction between m(CaO)/m(V2O5) and roasting temperature was significant.

Sequential extraction of chromium, molybdenum, and vanadium in basic oxygen furnace slags

Basic oxygen furnace slags (BOS) are by-products of basic oxygen steel production. Whereas the solubility of some elements from these slags has been well investigated, information about the mineralogy and related leaching, i.e., availability of the environmentally relevant elements chromium (Cr), molybdenum (Mo), and vanadium (V), is still lacking. The aim of this study was to investigate these issues with a modified, four-fraction-based, sequential extraction procedure (F1-F4), combined with X-ray diffraction, of two BOS. Extractants with increasing strength were used (F1 demineralized water, F2 CH3COOH + HCl, F3 Na2EDTA + NH2OH·HCl, and F4 HF + HNO3 + H2O2), and after each fraction, X-ray diffraction was performed. The recovery of Cr was moderate (66.5%) for one BOS, but significantly better (100.2%) for the other one. High recoveries were achieved for the other elements (Mo, 100.8-107.9% and V, 112.6-87.0%), indicating that the sequential extraction procedure was reliable when adapted to BOS. The results showed that Cr and Mo primarily occurred in F4, representing rather immobile elements under natural conditions, which were strongly bound into/onto Fe minerals (srebrodolskite, magnetite, hematite, or wustite). In contrast, V was more mobile with proportional higher findings in F2 and F3, and the X-ray diffraction results reveal that V was not solely bound into Ca minerals (larnite, hatrurite, kirschsteinite, and calcite), but also bound to Fe minerals. The results indicated that the total amount of recovery was a poor indicator of the availability of elements and did not correspond to the leaching of elements from BOS.

Roasting and leaching behaviors of vanadium and chromium in calcification roasting–acid leaching of high-chromium vanadium slag

Calcification roasting–acid leaching of high-chromium vanadium slag (HCVS) was conducted to elucidate the roasting and leaching behaviors of vanadium and chromium. The effects of the purity of CaO, molar ratio between CaO and V2O5 (n(CaO)/n(V2O5)), roasting temperature, holding time, and the heating rate used in the oxidation–calcification processes were investigated. The roasting process and mechanism were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetry–differential scanning calorimetry (TG–DSC). The results show that most of vanadium reacted with CaO to generate calcium vanadates and transferred into the leaching liquid, whereas almost all of the chromium remained in the leaching residue in the form of (Fe0.6Cr0.4)2O3. Variation trends of the vanadium and chromium leaching ratios were always opposite because of the competitive reactions of oxidation and calcification between vanadium and chromium with CaO. Moreover, CaO was more likely to combine with vanadium, as further confirmed by thermodynamic analysis. When the HCVS with CaO added in an n(CaO)/n(V2O5) ratio of 0.5 was roasted in an air atmosphere at a heating rate of 10°C/min from room temperature to 950°C and maintained at this temperature for 60 min, the leaching ratios of vanadium and chromium reached 91.14% and 0.49%, respectively; thus, efficient extraction of vanadium from HCVS was achieved and the leaching residue could be used as a new raw material for the extraction of chromium. Furthermore, the oxidation and calcification reactions of the spinel phases occurred at 592 and 630°C for n(CaO)/n(V2O5) ratios of 0.5 and 5, respectively.

Stability of Ceramic Glazes Obtained by Valorification of Anorganic Pigments Extracted from Electroplating Sludge

This paper presents the results of the research activity in order to etablish the stability and leaching potential of ceramic tiles which have been developed using glazes colored with pigments obtained by the extraction of chromium and iron metals from electroplating sludge. All these ceramic tiles contain various amounts of heavy metals in their glazes due to the pigments composition. The ceramic samples have been subjected to leaching tests in order to detect if various elements of relevance such as chromium, lead, cadmium, zinc or iron migrated to any great extent into test solutions. Leaching tests have been performed following the international standard SR ISO 10545-15 method for specific metals leaching into 4% acetic acid solutions at 220C after a 24h period and the international standard SR EN 12457/1-4 method with distilled water as leaching agent at LSR of 10 l/kg, for 24h period. Amounts of heavy metals have been negligible or non-detectable (iron) in the leaching solutions, being well below the limit values established by the legislation in force.

Efficient Separation and Extraction of Vanadium and Chromium in High Chromium Vanadium Slag by Selective Two-Stage Roasting–Leaching

Vanadium and chromium are important rare metals, leading to a focus on high chromium vanadium slag (HCVS) as a potential raw material to extract vanadium and chromium in China. In this work, a novel method based on selective two-stage roasting–leaching was proposed to separate and extract vanadium and chromium efficiently in HCVS. XRD, FT-IR, and SEM were utilized to analyze the phase evolutions and microstructure during the whole process. Calcification roasting, which can calcify vanadium selectively using thermodynamics, was carried out in the first roasting stage to transfer vanadium into acid-soluble vanadate and leave chromium in the leaching residue as (Fe0.6Cr0.4)2O3 after H2SO4 leaching. When HCVS and CaO were mixed in the molar ratio CaO/V2O3 (n(CaO)/n(V2O3)) of 0.5 to 1.25, around 90 pct vanadium and less than 1 pct chromium were extracted in the first leaching liquid, thus achieving the separation of vanadium and chromium. In the second roasting stage, sodium salt, which combines with chromium easily, was added to the first leaching residue to extract chromium and 95.16 pct chromium was extracted under the optimal conditions. The total vanadium and chromium leaching rates were above 95 pct, achieving the efficient separation and extraction of vanadium and chromium. The established method provides a new technique to separate vanadium and chromium during roasting rather than in the liquid form, which is useful for the comprehensive application of HCVS.

Isolation of Chromium(VI) from Aqueous Solution by Electromembrane Extraction

ABSTRACTElectromembrane extraction (EME) is a powerful extraction and preconcentration technique for ionizable species. However, the ionic contents in the sample can influence the extraction efficiency and system stability due to electrolysis. In this work, the electromembrane extraction of chromium(VI) was developed using various levels of ionic samples. 2-Nitrophenyl octyl ether was the most suitable supported liquid membrane that delayed the electrolytic occurrence of air bubbles at the electrodes due to its high viscosity and high dielectric constant properties. The electromembrane extraction method was optimized using 5 mM NaCl (630 µS cm−1); the applied potential was 100 V and the extraction time was 15 min. The enrichment factor of 80 was obtained over a linear working range of 10.0–80.0 µg L−1. The method performance was tested using mineral water, drinking water, tap water, and surface water. The method recoveries based on matrix-matched calibration were 95–125% with standard deviations within 15%.

Sequential extraction of vanadium and chromium from chromium-bearing vanadium slag through two-stage soda roasting-water leaching

The sequential extraction of vanadium and chromium from the chromium-bearing vanadium slag through two-stage soda roasting-water leaching was proposed. The precipitation order and thermodynamic stability of Cr-spinel and V-spinel were thoroughly calculated with FactSage 6.3 software. The mechanism of the sequential extraction process is further determined by X-ray diffraction (XRD). Thermodynamic calculations show that the precipitation order of main phases in the chromium-bearing vanadium slag is as follows: Cr-spinel → V-spinel → Fe-olivine, while the priority of the reaction between main phases with Na2CO3 follows the order of Fe-olivine → V-spinel → Cr-spinel. XRD results reveal that the vanadium-bearing phase in roasted slag is water-soluble NaVO3, while the chromium-bearing phase in roasted slag is Cr-spinel ((Mn, Fe) Cr2O4) and solid solutions ((Fe0.6Cr0.4)2 O3) with the soda amount of 21% and temperature of 800 °C. The different evolution route of vanadium-bearing phase and chromium-bearing phase during the roasting process ensures preferential extraction of vanadium from the chromium-bearing vanadium slag. The leaching rates of vanadium and chromium reach 89.36% and 4.91% with optimized experimental conditions. The high leaching rate of vanadium and low leaching rate of chromium show good results of preferential extraction of vanadium from the chromium-bearing vanadium slag.

Manufacture of High-Carbon Ferrochrome Using Anthracite

Results are provided for industrial use of Sibantratsit anthracite in the manufacture of high-carbon ferrochrome. Qualitative characteristics are given for anthracite and operating indices for ferroalloy furnaces with the use of this reducing agent. Comparative data are provided for results of anthracite and coke nut physiochemical analysis. Low ash content, low phosphorus and sulfur content, and also high specific electrical resistance of anthracite are established. The use of anthracite in smelting high-carbon ferrochrome in furnaces with power of 21 MVA leads to a reduction in specific consumption of reducing agent and electrical energy. Chromium extraction is almost unchanged. The use of anthracite in more powerful furnaces (63 MVA) makes it possible to increase considerably the operating voltage and reduce specific electrical energy consumption. The phosphorus content in ferrochrome is reduced with an increase in proportion of anthracite in a charge.

Effect of microwave irradiation and conventional calcification roasting with calcium hydroxide on the extraction of vanadium and chromium from high‑chromium vanadium slag

A novel high-efficiency method based on microwave irradiation roasting has been proposed to extract valuable metals from minerals. In this study, we employed microwave irradiation and conventional roasting for extracting vanadium and chromium from high‑chromium vanadium slag (HCVS) with the additive calcium hydroxide. Differential thermal-thermogravimetry analysis (TG-DSC), X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy analysis (SEM-EDS), particle size distribution analysis and chemical analyses were used for the characterization and analysis to explain the mechanism of the roasting process. The results shown that roasting temperature, the m(CaO)/m(V2O5) ratio, and roasting time roasted by microwave irradiation and muffle furnace had significantly effect on extraction ratio of vanadium while the effect on the extraction ratio of chromium was relatively small. For the same roasting temperature, the degree of oxidation of HCVS roasted by microwave irradiation was higher than that roasted by muffle furnace. When the m(CaO)/m(V2O5) ratio is low, Mn4V2O9 and CaV2O6 are formed; with the m(CaO)/m(V2O5) ratio increased, Mn4V2O9 and CaV2O6 gradually converted to CaV2O7, and CaCrO3 is formed. Microwave irradiation decreased the particles size and shortened the roasting time. The optimal roasting conditions was determined to be: roasting temperature of 850°C, m(CaO)/(V2O5) ratio of 0.95, and roasting time of 1.5h. The maximum extraction ratio of vanadium and chromium roasted by microwave irradiation and muffle furnace were 98.29%, 4.32% and 85.36%, 2.48%, respectively.

Speciation of chromium compounds from humic acid-zeolite Y to an ionic liquid during extraction

By synchrotron X-ray absorption spectroscopy, chemical structures of hexavalent chromium (Cr(VI))/trivalent chromium (Cr(III)) adsorbed on humic acid (HA)-zeolite Y and extracted in an ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim][BF4])) have been studied. By combining the competitive adsorption results and reduction of Cr(VI)-HA with the carboxyl groups of HA, Cr(III)-HA (58%) was shown to be the major compound in HA-zeolite Y using synchrotron X-ray absorption near-edge structure (XANES) spectroscopy. In an ionic liquid phase, the reduction of Cr(VI)-HA to Cr(III)-HA and the desorption of Cr(III) from HA were caused by [C4mim][BF4]. The 9F nuclear magnetic resonance (NMR) spectra show that the perturbation of the [C4mim][BF4] anion was affected by the extractable chromium species. The formation of a Cr(III) ion affected the increase in the bond distance for the 1st shell CrO of the chromium species in [C4mim][BF4] using extended X-ray absorption fine structure (EXAFS) spectroscopy. The changes in the non-extractable chromium species remaining in HA-zeolite Y were also caused by [C4mim][BF4] during extraction. The desorption of the absorbed Cr(III) on HA and zeolite Y was observed to form Cr(III) ions. As the percentage of Cr(III) ions remaining in HA-zeolite Y increased, a slightly greater bond distance for CrO was found at 2.01Å. The enhanced reduction of Cr(VI)-HA and desorption of Cr(III) adsorbed on the HA and zeolite Y to form Cr(III) ions were affected by [C4mim][BF4]. Increased mobility of Cr(III) in the simulated soil can promote the migration of Cr(III) ions into the H2O during soil washing for remediation.

Environmental Impacts Assessment of Chromium Minings in Bulqiza Area, Albania

Bulqiza District is the largest chromium source, ranked fourth in the world for chrome reserves. It lays in the north-eastern part of Albania, 330-1800 m a.s.l, with 728 km² area, between 41o30’43.1N and 20o14’56.21E. There are 136 entities with chromium extraction activity and around the city of Bulqiza (2.6 km² and 13000 inhabitants), there are 33 entities. The aim of the study was the identification of the environmental state and environmental impact assessment of chromium extraction (chromite mining) and giving recommendations to minimize the negative effects of this activity. Field observations, questionnaires, chemical analysis of soil and water, meetings and interviews with central and local institutions as well as with residents were used for the realization of the study. The obtained results showed that chromium extraction causes numerous irreversible degradation of the environment in the Bulqiza area, such as the destruction of surface land layers and erosion, destruction of flora and fauna, soil and water pollution, health problems, unsustainable use and reduction of chromium reserves, etc. The inert waste that emerges after the chromium partition is discharged to the earth surface without any regularity, covering the surface of the soil and flora, leading to irreversible degradation of the environment. Most of the mining entities do not respect the contracts and environmental permit issued by the Ministry of Energy and Industry (MEI).

Environmental Impacts Assessment of Chromium Minings in Bulqiza Area, Albania

Bulqiza District is the largest chromium source, ranked fourth in the world for chrome reserves. It lays in the north-eastern part of Albania, 330-1800 m a.s.l, with 728 km² area, between 41o30’43.1N and 20o14’56.21E. There are 136 entities with chromium extraction activity and around the city of Bulqiza (2.6 km² and 13000 inhabitants), there are 33 entities. The aim of the study was the identification of the environmental state and environmental impact assessment of chromium extraction (chromite mining) and giving recommendations to minimize the negative effects of this activity. Field observations, questionnaires, chemical analysis of soil and water, meetings and interviews with central and local institutions as well as with residents were used for the realization of the study. The obtained results showed that chromium extraction causes numerous irreversible degradation of the environment in the Bulqiza area, such as the destruction of surface land layers and erosion, destruction of flora and fauna, soil and water pollution, health problems, unsustainable use and reduction of chromium reserves, etc. The inert waste that emerges after the chromium partition is discharged to the earth surface without any regularity, covering the surface of the soil and flora, leading to irreversible degradation of the environment. Most of the mining entities do not respect the contracts and environmental permit issued by the Ministry of Energy and Industry (MEI).

Simultaneous extraction of vanadium and chromium from vanadium slag using low-pressure liquid phase oxidation method

A low-pressure liquid oxidation method was proposed and proven to be effective to extract vanadium and chromium simultaneously from the vanadium slag in concentrated NaOH aqueous solutions. The effect of temperature, NaOH mass concentration, liquid-to-solid mass ratio, stirring speed and pressure on the extraction of vanadium and chromium in NaOH aqueous solutions were systematically investigated. Under the optimal reaction conditions (temperature of 473 K, liquid-to-solid mass ratio of 6:1, stirring speed of 700 rpm, NaOH mass concentration of 50%, pressure of 1 MPa and reaction time of 180 min), the vanadium and chromium recovery reached 95% and 90%, respectively. It was found that the reaction temperature and NaOH concentration were important factors for the extraction of vanadium and chromium. The kinetics of the decomposition of vanadium slag in concentrated NaOH aqueous under low pressure was analyzed using the shrinking core model, and the results indicated that the extraction of vanadium and chromium were both governed by the internal diffusion step, with apparent activation energies calculated to be 26.22 and 32.79 kJ/mol, respectively.

Chromium, nickel, and cobalt in cosmetic matrices: an integrated bioanalytical characterization through total content, bioaccessibility, and Cr(III)/Cr(VI) speciation.

The presence of certain metals naturally contained inside raw materials (e.g., pigments) used to produce cosmetics for make-up may represent a serious concern for the final quality and safety of the product. The knowledge of the total concentration of metals is not sufficient to predict their reactivity and their toxicological profile. For these reasons, we set up a comprehensive approach to characterize the content of Co, Cr, and Ni in two raw materials for cosmetic production, a black iron oxide and a pearly pigment, and in a finished product, pearly powder eye shadow. Namely, besides the total metal concentrations, the speciation of chromium and the bioaccessibility of the three metals were assessed. Since no standard method is so far available for hexavalent chromium extraction from cosmetic samples, three approaches were compared (EPA 3060A method, IRSA 16 method, and a Na3PO4 extraction). Results show that Na3PO4 extraction is the most selective one. Cr(VI) was undetectable in black iron oxide and present at very low concentrations (about 0.3mg/kg) in pearly pigment and in the pearly powder eye shadow samples. The extracted Cr(VI) concentrations are not related to the total Cr content in the samples. Bioaccessibility studies were performed by in vitro extractions with synthetic lacrimal fluids and sweat. Despite the wide range of metal concentrations in the samples, the amounts of bioaccessible elements were undetectable or very low (less than 0.4mg/kg), thus suggesting that metals in the three samples are present in inert forms. Graphical abstract The possible leaching of metals from cosmetics to biological fluids. Spectroscopic and chromatographic techniques provide complementary information for an integrated bioanalytical approach to risk characterization.

Citric acid assisted phytoextraction of chromium by sunflower; morpho-physiological and biochemical alterations in plants

Soil and water contamination from heavy metals and metalloids is one of the most discussed and burning global issues due to its potential to cause the scarcity of healthy food and safe water. The scientific community is proposing a range of lab and field based physical, chemical and biological solutions to remedy metals and metalloids contaminated soils and water. The present study finds out a possibility of Chromium (Cr) extraction by sunflower from spiked soil under chelating role of citric acid (CA). The sunflower plants were grown under different concentrations of Cr (0, 5, 10 & 20mgkg−1) and CA (0, 2.5 & 5mM). Growth, biomass, gas exchange, photosynthesis, electrolyte leakage (EL), reactive oxygen species (ROS; malondialdehyde (MDA), hydrogen peroxide (H2O2) and the activities of antioxidant enzymes such as, superoxide dismutase (SOD), guaiacole values peroxidase (POD), ascorbate peroxidase (APX), catalase (CAT) were measured. The results depicted a clear decline in plant height, root length, leaf area, number of leaves and flowers per plant along with fresh and dry biomass of all parts of plant with increasing concentration of Cr in soil. Similar reduction was observed in chlorophyll a and b, total chlorophyll, carotenoids, soluble protein, gas exchange attributes and SPAD. The increasing concentration of Cr also enhanced the Cr uptake and accumulation in plant roots, stem and leaves along with the production of ROS and EL. The activities of antioxidant enzymes increased with increasing Cr concentration from 0 to 10mg, but decreased at 20mgkg−1 soil. The CA application significantly alleviated Cr-induced inhibition of plant growth, biomass, photosynthesis, gas exchange, soluble proteins and SPAD value. Presence of CA also enhanced the activities of all antioxidant enzymes and reduced the production of ROS and EL. The chelating potential of CA increased the concentration and accumulation of Cr in plant roots, stem and leaves. It is concluded that the sunflower can be a potential candidate for the remediation of Cr under CA treatment, while the possibility may vary with genotype, Cr level and CA concentration.

A new method in estimation of total hexavalent chromium in Portland pozzolan cement

Variamine blue was used first time for the detection of hexavalent chromium from cement samples. In present method, cement was treated sequentially with water, sulphate and carbonate buffer to extract soluble, sparingly soluble and insoluble hexavalent chromium respectively. Extracted Cr (VI) was determined using variamine blue as chromogenic reagent. The determination is based on the reaction of hexavalent chromium with potassium iodide in an acid medium to liberate iodine. This oxidizes variamine blue to form a violet coloured species having an absorption to maximum at 556 nm. Energy-dispersive X-ray spectroscopy (EDX) and Infrared Spectroscopy (IR) confirmed the complete extraction of hexavalent chromium by sequential extraction process. SRM 2701 (Reference material from NIST, USA) was used for revalidating the results. The percentage of recovery for proposed and reference method (diphelycarbazide method) varied from 98.5 to 101 and 97.5 to 100.5. Whereas, their relative error percentage varied from -1.5 to 0.33 and -2.5 to 0.5.

Green and Efficient Process for Extracting Chromium from Vanadium Slag by an Innovative Three-Phase Roasting Reaction

The traditional industrial practice for extracting vanadium from vanadium slag involves a Na2CO3–Na2SO4–NaCl-added pellet roasting at 800 °C followed by water leaching. About 5% of chromium and 85% of vanadium can be extracted in this case. The disposal of this leaching residue containing high contents of chromium and vanadium is still an unsolved problem and has seriously impeded the sustainable production of vanadium in China. A complete extraction of chromium and vanadium from vanadium slag might be a solution. To extract efficiently chromium from vanadium slag, some NaOH-added pellets were used to replace traditional pellets here. It was found that the volume of a NaOH-added pellet increased by 144% and many cavities were formed spontaneously throughout the pellet during roasting and a three-phase reaction of solid (slag)-liquid (NaOH)-gas (O2) occurred in the porous pellet. The Cr extraction was thus increased by 43% when a NaOH-added pellet sample was used to replace the corresponding powder sample....

Chemical Speciation and Health Risk Assessment of Fine Particulate Bound Trace Metals Emitted from Ota Industrial Estate, Nigeria

In this study carcinogenic and non-carcinogenic health risk due to exposure to PM2.5-bound trace metals from an industrial area in Southwestern Nigeria was estimated. A four-step chemical sequential extraction procedure was employed for the chemical extraction of arsenic (As), cadmium (Cd), chromium (Cr) copper (Cu), manganese (Mn), nickel (Ni), and zinc (Zn). Samples were analyzed using inductively coupled plasma mass spectrometry (ICP-MS). Results reveal Cr and Cu as the most dominant exchangeable fraction metals, indicating possibility of their being readily soluble once PM2.5 is inhaled. Cd and Cr record the highest bioavailability index of 0.7. The cumulative lifetime cancer risks due to inhalation exposure for adults (4.25×10-2), children 1-6 years old (4.87×10-3), and children 6-18 years old (1.46×10-2) were found above Environmental Protection Agency’s acceptable range of 1×10-6 to 1×10-4. The hazard index values for all studied trace metals suggest significant potential for non-carcinogenic health risks to adults and children. The choice of chemical speciation as an essential tool in facilitating a better predictive insight on metal bioavailability and toxicity for immediate remediation action has been highlighted.

Improvement of Chromium(VI) Extraction from Acidic Solutions Using a Poly(vinyl chloride)-based Polymer Inclusion Membrane with Aliquat 336 as the Carrier.

An important reason for the inefficient extraction of Cr(VI) from its acidic solutions into polymer inclusion membranes (PIMs), consisting of poly(vinyl chloride) as the base-polymer and Aliquat 336 as the carrier, was found to be associated with the leaching of Aliquat 336 from the PIMs into the solutions, where it subsequently reduced the anionic Cr(VI) species to cationic Cr(III) species. The PIM extraction efficiency for Cr(VI) was significantly improved by the addition of NaNO3 to the solutions, which suppressed the leaching of Aliquat 336 and the reduction of Cr(VI) to Cr(III).