Insoluble Cr Research Articles

Effects of distribution and growth orientation of precipitates on oxidation resistance of Cu–Cu12–[Crx/(12+x)Ni12/(12+x)]5 alloys

Abstract

Chemical stabilization of chromate in blast furnace slag mixed cementitious materials

Cement waste form (CWF) technology is among the leading approaches to disposing of metals and liquid low-level nuclear waste in the United States. One such material, saltstone, includes slag, fly ash and Portland cement to enhance the immobilization of contaminants (e.g., Cr, 99Tc) in alkaline liquid wastes. To evaluate the stability of such redox sensitive contaminants in saltstone, the effects of slag as a source of reductant on Cr immobilization was evaluated in aged (<300d) saltstone monoliths. Specifically, we investigated the effects of artificial cement pore waters on the Cr release and the spatially resolved Cr chemical state analysis using synchrotron based microfocused X-ray microprobe analysis. The microprobe analysis indicated the heterogeneous distribution of insoluble Cr(III)-species in saltstone. Although at most of 20% Crtotal was leached at the top few (2–3) millimeter depth, the release of Cr(VI) was small (<5%) at 5–30mm with slight changes, indirectly suggesting that Cr is likely present as insoluble Cr(III) species throughout the depths. The study suggests that this saltstone formulation can effectively retain/immobilize Cr under the oxic field condition after ⩽300d of aging time.

Optimizing magnetic nanoparticles for drinking water technology: The case of Cr(VI)

The potential of magnetite nanoparticles to be applied in drinking water treatment for the removal of hexavalent chromium is discussed. In this study, a method for their preparation which combines the use of low-cost iron sources (FeSO4 and Fe2(SO4)3) and a continuous flow mode, was developed. The produced magnetite nanoparticles with a size of around 20nm, appeared relatively stable to passivation providing a removal capacity of 1.8μg Cr(VI)/mg for a residual concentration of 50μg/L when tested in natural water at pH7. Such efficiency is explained by the reducing ability of magnetite which turns Cr(VI) to an insoluble Cr(OH)3 form. The successful operation of a small-scale system consisting of a contact reactor and a magnetic separator demonstrates a way for the practical introduction and recovery of magnetite nanoparticles in water treatment technology.

Mobilization of heavy metals from urban contaminated soils under water inundation conditions

A microcosm experiment was conducted to investigate heavy metal release from the urban soils heavily contaminated by past industrial activities. The aim was to assess the mobility of various heavy metals under inundation with water. The results show that reductive dissolution of iron and manganese compounds was markedly enhanced by organic matter. However, mobilization of Fe and Mn was affected by the abundance of these metals in the soils. The dissolution of Fe and Mn oxides led to the release of As and Zn that were bound to them. However, mixed temporal variation patterns were observed for As, suggesting complication of As mobility by other factors. It is likely that the added organic matter played a role in the formation of organic matter–Fe(III)–arsenic association, leading to partial re-immobilisation of the liberated As at the latter stage of the experiment. Zn showed a consistent trend where it was initially released with reductive dissolution of Fe and Mn compounds and then re-immobilised, possibly through hydrolysis to form insoluble zinc hydroxide. In spite of abundant presence, release of Pb was limited due to its low solubility under less acidic conditions. It appears that anaerobic environment stabilized the soil-borne Cr by forming insoluble Cr(OH)3.

Cr(VI) Reduction and Cr(III) Immobilization by Acinetobacter sp. HK-1 with the Assistance of a Novel Quinone/Graphene Oxide Composite

Cr(VI) biotreatment has attracted a substantial amount of interest due to its cost effectiveness and environmental friendliness. However, the slow Cr(VI) bioreduction rate and the formed organo-Cr(III) in solution are bottlenecks for biotechnology application. In this study, a novel strain, Acinetobacter sp. HK-1, capable of reducing Cr(VI) and immobilizing Cr(III) was isolated. Under optimal conditions, the Cr(VI) reduction rate could reach 3.82 mg h(-1) g cell(-1). To improve the Cr(VI) reduction rate, two quinone/graphene oxide composites (Q-GOs) were first prepared via a one-step covalent chemical reaction. The results showed that 2-amino-3-chloro-1,4-naphthoquinone-GO (NQ-GO) exhibited a better catalytic performance in Cr(VI) reduction compared to 2-aminoanthraquinone-GO. Specifically, in the presence of 50 mg L(-1) NQ-GO, a Cr(VI) removal rate of 190 mg h(-1) g cell(-1), which was the highest rate obtained, was achieved. The increased Cr(VI) reduction rate is mainly the result of NQ-GO significantly increasing the Cr(VI) reduction activity of cell membrane proteins containing dominant Cr(VI) reductases. X-ray photoelectron spectroscopy analysis found that Cr(VI) was reduced to insoluble Cr(III), which was immobilized by glycolipids secreted by strain HK-1. These findings indicate that the application of strain HK-1 and NQ-GO is a promising strategy for enhancing the treatment of Cr(VI)-containing wastewater.

Optimizing the use of natural and synthetic magnetites with very small amounts of coarse Fe(0) particles for reduction of aqueous Cr(VI)

Remediation of highly toxic aqueous Cr(VI) includes its chemical reduction to the very insoluble Cr(III) species. In this work we investigated the Cr(VI) reduction performance of synthetic and natural magnetites of different particle size sat three pH values (4, 6, 8), with the purpose of cost-optimizing the procedure at the laboratory scale. Only the finest magnetite showed considerable Cr(VI) reduction yields, but rates were low and after 25 days no equilibrium was attained. Mechano chemical mixing of the finer magnetites with 5% micron-sized Fe(0) increased dramatically their reductive reactivity, especially at pH 4 and 6, and at pH 8 only for the finest sample, despite the fact that the same quantity of Fe(0) added by itself reducednegligible amounts of Cr(VI). Increasing Fe(0) concentrations in the mixtures to 10 and 15% allowed considerable improvements in the reactivity of the intermediate-sized magnetites (of ca. 7m2/g), but not that of the coarser samples for up to 20% Fe(0). This promises to be an optimal technology for remediation or treatment of Cr(VI) polluted aqueous environments and residues, that may prove beneficial for industries and pollution clean-up government agencies, because it uses readily available solid mineral samples and minimizes the use of acid reagents.

Optimization and validation of strategies for quantifying chromium species in soil based on speciated isotope dilution mass spectrometry with mass balance

Strategies were designed to quantify hexavalent (Cr(VI)), soluble trivalent (Cr(III)) and insoluble chromium (Cr) species in soil by integrating existing methods of Cr(VI) and total Cr determination with speciated isotope dilution mass spectrometry (SIDMS, EPA Method 6800). Two different extraction methods that utilize a NaOH–Na2CO3 solution (EPA Method 3060A) and alkaline solution of ethylenediaminetetraacetic acid (EDTA) were used to extract Cr(VI) (along with soluble Cr(III) in the latter case). The extracted Cr was speciated by ion chromatography-inductively coupled plasma mass spectrometry (IC-ICP-MS), and the separated species were quantified using the mathematical relationships in SIDMS with simultaneous correction for their method-induced transformations. The Cr species that fell out as insoluble solid during extraction were determined by isotope dilution mass spectrometry (IDMS) after decomposing the extraction residues in a mixture of mineral acids according to EPA Method 3052. Several certified reference materials and a soil sample were analyzed using the proposed strategies. The measured mass fractions of Cr(VI) and total Cr in the reference materials statistically agreed with the certified values at 95% CL. The insoluble fraction of Cr accounted for 64–107% of the total Cr in the samples. The validity of the strategies was proved using mass balance by comparing the sum of the mass fractions of Cr(VI), soluble Cr(III) and insoluble Cr with the total Cr measured in the corresponding samples; the latter was determined by IDMS after decomposing the soils using EPA Method 3052 with single spiking.

Bioreduction of Cr(VI) by Bacillus sp. QH-1 isolated from soil under chromium-containing slag heap in high altitude area

A chromium-reducing strain QH-1, identified as Bacillus sp., was isolated from soil under chromium-containing slag heap in Qinghai high altitude area, China. The strain was found to resist 200 mg/L Cr(VI), and Cr(VI) negatively affects the metabolic activity of the cells, as well as the cell morphology of Bacillus sp. QH-1. The reduction efficiency of Cr(VI) at concentrations of Cr(VI) 25 mg/L, 50 mg/L, 100 mg/L and 200 mg/L were 99.48 %, 65.99 %, 23.22 % and 6.99 %, respectively, decreasing with increasing initial Cr(VI) concentration. This indicates that the toxicity of Cr(VI) increased with concentration. Energy dispersive X-ray analysis revealed that there was insoluble Cr(III) generated during Cr(VI) reduction. In order to apply strain QH-1 to remove Cr(VI) from groundwater, factors of concentration of electron donors (glucose) and temperature were investigated in a synthetic medium. The results demonstrated that glucose could promote the reduction of Cr(VI) by this strain, and the general trend of Cr(VI) reduction increased with temperature within the range of 4 to 37 °C. Cr(VI) was reduced effectively at 25 °C and 37 °C, and all of Cr(VI) was reduced after 96 h at 37 °C, while the reduction was slow at 4 °C and 15 °C, and it almost ceased after about 120 h. These results could be potentially useful for the bioremediation of Cr(VI) in groundwater.

Immobilization of chromate in hyperalkaline waste streams by green rusts and zero-valent iron

Zero-valent iron (ZVI) and green rusts can be used as reductants to convert chromium from soluble, highly toxic Cr(VI) to insoluble Cr(III). This study compared the reduction rates of Cr(VI) by ZVI and two carbonate green rust phases in alkaline/hyperalkaline solutions. Batch experiments were carried out with synthetic chromate solutions at pH 7.7–12.3 and a chromite ore processing residue (COPR) leachate (pH ≈ 12.2). Green rust removes chromate from high pH solutions (pH 10–12.5) very rapidly (<400 s). Chromate reduction rates for both green rust phases were consistently higher than for ZVI throughout the pH range studied; the surface area normalized rate constants were two orders of magnitude higher in the COPR leachate solution at pH 12.2. The performances of both green rusts were unaffected by changes in pH. In contrast, ZVI exhibited a marked decline in reduction rate with increasing pH to become almost ineffective above pH12.

Application of high performance liquid chromatography with inductively coupled plasma mass spectrometry (HPLC–ICP-MS) for determination of chromium compounds in the air at the workplace

The toxicity and bioavailability of chromium species are highly dependable on the form or species, therefore determination of total chromium is insufficient for a complete toxicological evaluation and risk assessment. An analytical method for determination of soluble and insoluble Cr (III) and Cr (VI) compounds in welding fume at workplace air has been developed. The total chromium (Cr) was determined by using quadruple inductively coupled plasma mass spectrometry (ICP-MS) equipped with a dynamic reaction cell (DRC(®)). Soluble trivalent and hexavalent chromium compounds were determined by high performance liquid chromatography with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). A high-speed, reversed-phase CR C8 column (PerkinElmer, Inc., Shelton, CT, USA) was used for the speciation of soluble Cr (III) and soluble Cr (VI). The separation was accomplished by interaction of the chromium species with the different components of the mobile phase. Cr (III) formed a complex with EDTA, i.e. retained on the column, while Cr (VI) existed in the solutions as dichromate. Alkaline extraction (2% KOH and 3% Na2CO3) and anion exchange column (PRP-X100, PEEK, Hamilton) were used for the separation of the total Cr (VI). The results of the determination of Cr (VI) were confirmed by the analysis of the certified reference material BCR CRM 545 (Cr (VI) in welding dust). The results obtained for the certified material (40.2±0.6 g kg(-1)) and the values recorded in the examined samples (40.7±0.6 g kg(-1)) were highly consistent. This analytical method was applied for the determination of chromium in the samples in the workplace air collected onto glass (Whatman, Ø 37 mm) and membrane filters (Sartorius, 0.8 μm, Ø 37 mm). High performance liquid chromatography with inductively coupled plasma mass spectrometry is a remarkably powerful and versatile technique for determination of chromium species in welding fume at workplace air.

Micro-electrolysis of Cr (VI) in the nanoscale zero-valent iron loaded activated carbon

In this paper we prepared a novel material of activated carbon/nanoscale zero-valent iron (C–Fe0) composite. The C–Fe0 was proved to possess large specific surface area and outstanding reducibility that result in the rapid and stable reaction with Cr (VI). The prepared composite has been examined in detail in terms of the influence of solution pH, concentration and reaction time in the Cr (VI) removal experiments. The results showed that the C–Fe0 formed a micro-electrolysis which dominated the reaction rate. The Micro-electrolysis reaches equilibrium is ten minutes. Its reaction rate is ten times higher than that of traditional adsorption reaction, and the removal rate of Cr reaches up to 99.5%. By analyzing the obtained profiles from the cyclic voltammetry, PXRD and XPS, we demonstrate that the Cr (VI) is reduced to insoluble Cr (III) compound in the reaction.

Textile-dye polluted waters as a source for selecting chromate-reducing yeasts through Cr(VI)-enriched microcosms

Chromate-resistant microorganisms able to reduce toxic Cr(VI) into insoluble Cr(III) are seen as promising candidates for alleviating Cr(VI)-contamination. In this study, chromate-reducing yeasts could be isolated from a textile-dye effluent and associated biofilm by using microcosm methodology with periodical 1 mM Cr(VI)-pulses. Viable cell count seemed to reveal a progressive tolerance increase to Cr(VI). However, fungal colony numbers decreased after 108 h of cultivation most likely as a consequence of the accumulated toxic effects of metal during enrichment. From 49 different Cr(VI)-tolerant fungal morphotypes isolated under selective conditions, 12 yeasts showed resistance up to 50 mM and 6 filamentous fungi up to 2 mM. These highly tolerant yeasts could be subsequently grouped into 8 OTUs (Operational Taxonomic Units) according to the ITS1-NL4 RFLP (Restriction Fragment Length Polymorphism) analysis. From them, microsatellite amplification, sequencing and Cr(VI)-removal ability allowed to select two representative isolates. A polyphasic approach including morphological, physiological/biochemical characterization and molecular taxonomy analysis allowed to identify these isolates as Cyberlindnera jadinii M9 (previously Pichia jadinii) and Wickerhamomyces anomalus M10 (previously Pichia anomala). Cy. jadinii M9 and W. anomalus M10 were grown in YNB' medium plus 1 mM Cr(VI) at 25 °C and pH 5.0, causing complete chromium removal before reaching 48 h of cultivation. Flame Atomic Absorption Spectroscopy (FAAS) assays suggested that Cr(VI) withdrawal was coupled to Cr(III) appearance. Electron microscopy studies indicated absence of precipitates on the cell wall region or microprecipitates into the cellular cytoplasm. These complementary results revealed that biospeciation to Cr(III) would the main detoxification mechanism in selected chromate-resistant yeasts, which could be thus envisaged as promising tools for future biological treatment of Cr(VI) pollution.

Optimization and characterization of chromium(VI) reduction in saline condition by moderately halophilic Vigribacillus sp. isolated from mangrove soil of Bhitarkanika, India

A Gram-positive moderately halophilic Cr(VI) tolerant bacterial strain H4, isolated from saline mangrove soil, was identified as Vigribacillus sp. by biochemical characterization and 16S rRNA analysis. In LB medium, the strain could tolerate up to 1000mgL−1 Cr(VI) concentration and reduced 90.2 and 99.2% of 100mgL−1 Cr(VI) under optimized set of condition within 70h in absence and presence of 6wt.% NaCl, respectively. The fitting of time course reduction data to an exponential rate equation yielded the Cr(VI) reduction rate constants in the range (0.69–5.56)×10−2h−1. Analyses of total chromium and bacterial cell associated with reduced product by AAS, SEM/EDS, TEM/SAED, FT-IR and UV–vis–DRS indicated the formation of about 35% of insoluble Cr(III) either as Cr(OH)3 precipitate in nanometric size or immobilized on the bacterial cell surface while the remaining 65% of reduced chromium was present as soluble Cr(III) in the growth medium. Powder XRD analysis revealed the amorphous nature of the precipitated Cr(OH)3. The high Cr(VI) reducing ability of the strain under saline condition suggests the Vigribacillus sp. as a new and efficient strain capable of remediating highly saline Cr(VI) polluted industrial effluents.

Mechanism insights into enhanced Cr(VI) removal using nanoscale zerovalent iron supported on the pillared bentonite by macroscopic and spectroscopic studies

NZVI was supported on a pillared bentonite (Al-bent) to enhance the reactivity of NZVI and prevent its aggregation. The performance and mechanisms of the combined NZVI/Al-bent on removing hexavalent chromium (Cr(VI)) was investigated by batch and XAFS experiments. The batch investigations indicated that Cr(VI) could be almost completely removed by NZVI/Al-bent after 120min. The efficiency was not only much higher than that by NZVI (63.0%), but also superior to the sum of NZVI reduction and Al-bent adsorption (12.4%). Besides, NZVI/Al-bent exhibited good stability and reusability, and Al-bent could reduce the amount of iron ions released into the solution. XANES results provided evidence that NZVI/Al-bent could reduce Cr(VI) entirely into Cr(III), while NZVI reduced Cr(VI) partly into Cr(III) with a trace of Cr(VI) adsorbed on the corrosion products. The structure of Cr(VI)-treated NZVI/Al-bent determined with EXAFS revealed the formation of Cr–Al/Si bond, suggesting that some insoluble Cr(III) species might be transferred to the surface of Al-bent, therefore the precipitates on iron surface could be greatly reduced. The results demonstrated that Al-bent plays a significant role in enhanced reactivity and stability of NZVI, and may shed new light on design and fabrication of supported NZVI for environmental remediation.

Trivalent Chromium: A Neglected Latent Contaminant

As the 21st most abundant element in earth’s crust, chromium has been extensively used in industrial activities such as paint pigments and leather tanning. As a consequence, there is a continual influx of chromium contaminants into the environment, thereby posing a serious environmental problem. Chromium exhibits a wide range of possible oxidation states, where trivalent chromium [Cr (III)] is most stable energetically, but Cr (III) and Cr (VI) are most commonly observed in aquatic environment. Cr (VI) species are of great environment concern due to their well-known toxicity, carcinogentic properties and high mobility in environmentally relevant media. Cr (III) is generally regarded as benign and even essential for human and animal, since trace amounts of Cr (III) is required for sugar and lipid metabolism.In this context, it is a common strategy in environmental remediation to reduce toxic Cr (VI) to Cr (III) by various redox reactions. Cr (III) is thought to be immobilized by precipitating into insoluble Cr (III) hydroxides

A chromate-contaminated site in southern Switzerland – Part 1: Site characterization and the use of Cr isotopes to delineate fate and transport

Abstract The risk of groundwater contamination by chromate at a former chromite ore processing industrial site in Rivera (Switzerland) was assessed by determining subsoil Cr(VI) concentrations and tracking naturally occurring Cr(VI) reduction with Cr isotopes. Using a hot alkaline extraction procedure, a total Cr(VI) contamination of several 1000 kg was estimated. Jarosite, KFe 3 ((SO 4 ) x (CrO 4 ) 1− x ) 2 (OH) 6 , and chromatite (CaCrO 4 ) were identified as Cr(VI) bearing mineral phases using XRD, both limiting groundwater Cr(VI) concentrations. To track assumed Cr(VI) reduction at field scale δ 53 Cr values of contaminated subsoil samples in addition to groundwater δ 53 Cr data are used for the first time. The measurements showed a fractionation of groundwater δ 53 Cr values towards positive values and subsoil δ 53 Cr towards negative values confirming reduction of soluble Cr(VI) to insoluble Cr(III). Using a Rayleigh fractionation model, a current Cr(VI) reduction efficiency of approximately 31% along a 120 m long flow path was estimated at an average linear groundwater velocity of 3.3 m/d. Groundwater and subsoil δ 53 Cr values were compared with a site specific Rayleigh fractionation model proposing that subsoil δ 53 Cr values can possibly be used to track previous higher Cr(VI) reduction efficiency during the period of industrial activity. The findings strongly favor monitored natural attenuation to be part of the required site remediation measures.

Cr Stable Isotopes in Snake River Plain Aquifer Groundwater: Evidence for Natural Reduction of Dissolved Cr(VI)

At Idaho National Laboratory, Cr(VI) concentrations in a groundwater plume once exceeded regulatory limits in some monitoring wells but have generally decreased over time. This study used Cr stable isotope measurements to determine if part of this decrease resulted from removal of Cr(VI) via reduction to insoluble Cr(III). Although waters in the study area contain dissolved oxygen, the basalt host rock contains abundant Fe(II) and may contain reducing microenvironments or aerobic microbes that reduce Cr(VI). In some contaminated locations, (53)Cr/(52)Cr ratios are close to that of the contaminant source, indicating a lack of Cr(VI) reduction. In other locations, ratios are elevated. Part of this shift may be caused by mixing with natural background Cr(VI), which is present at low concentrations but in some locations has elevated (53)Cr/(52)Cr. Some contaminated wells have (53)Cr/(52)Cr ratios greater than the maximum attainable by mixing between the inferred contaminant and the range of natural background observed in several uncontaminated wells, suggesting that Cr(VI) reduction has occurred. Definitive proof of reduction would require additional evidence. Depth profiles of (53)Cr/(52)Cr suggest that reduction occurs immediately below the water table, where basalts are likely least weathered and most reactive, and is weak or nonexistent at greater depth.

Chromium transport in an acidic waste contaminated subsurface medium: The role of reduction

A series of wet chemical extractions and column experiments, combined with electron microprobe analysis (EMPA) and X-ray photoelectron spectroscopy (XPS) measurements, were conducted to estimate the extent of Cr(VI) desorption and determine the mechanism(s) of Cr(VI) attenuation in contaminated and naturally aged (decades) Hanford sediments which were exposed to dichromate and acidic waste solutions. Results from wet extractions demonstrated that contaminated sediments contained a relatively large fraction of tightly-bound Cr. Results from column experiments showed that effluent Cr concentrations were low and only a small percentage of the total Cr inventory was removed from the sediments. EMPA inspections indicated that Cr contamination was spread throughout sediment matrix and high-concentrated Cr spots were absent. XPS analyses confirmed that most surface Cr occurred as reduced Cr(III), which was spatially associated with Fe(III). Collectively, the results from macroscopic experiments and microprobe and spectroscopic measurements demonstrated that reduction of Cr(VI) have occurred in these sediments, limiting dramatically the mass flux from this contaminated source. The most likely mechanism of Cr(VI) reduction is the acid promoted dissolution of Fe(II)-bearing soil minerals and/or their surface coatings, release of Fe(II) in the aqueous phase, abiotic homogeneous and/or heterogeneous Cr(VI) reduction by aqueous, sorbed and/or structural Fe(II), and subsequently, formation of insoluble Cr(III) phases or [Cr(III) Fe(III)] solid solutions. The results from this study will improve our fundamental understanding of Cr(VI) behavior in natural heterogeneous subsurface media and may be used as a basis for developing or selecting potential remedial measures.

Concomitant Microbial Generation of Palladium Nanoparticles and Hydrogen To Immobilize Chromate

The catalytic properties of various metal nanoparticles have led to their use in environmental remediation. Our aim is to develop and apply an efficient bioremediation method based on in situ biosynthesis of bio-Pd nanoparticles and hydrogen. C. pasteurianum BC1 was used to reduce Pd(II) ions to form Pd nanoparticles (bio-Pd) that primarily precipitated on the cell wall and in the cytoplasm. C. pasteurianum BC1 cells, loaded with bio-Pd nanoparticle in the presence of glucose, were subsequently used to fermentatively produce hydrogen and to effectively catalyze the removal of soluble Cr(VI) via reductive transformation to insoluble Cr(III) species. Batch and aquifer microcosm experiments using C. pasteurianum BC1 cells loaded with bio-Pd showed efficient reductive Cr(VI) removal, while in control experiments with killed or viable but Pd-free bacterial cultures no reductive Cr(VI) removal was observed. Our results suggest a novel process where the in situ microbial production of hydrogen is directly coupled to the catalytic bio-Pd mediated reduction of chromate. This process offers significant advantages over the current groundwater treatment technologies that rely on introducing preformed catalytic nanoparticles into groundwater treatment zones and the costly addition of molecular hydrogen to above ground pump and treat systems.

Effects of Cr(III) organic compounds on Lactobacillus plantarum

Biotransformation of Cr(VI) to less toxic Cr(III) has been known to produce insoluble Cr(III) compounds and soluble Cr(III) organic complexes. However, recent research reports have indicated that Cr(III) organic complexes are relatively stable in the environment. Little has been reported on the fate and toxic effects of Cr(III) organic compounds on organisms. In this study, the toxic effects of the soluble Cr(III) organic complexes [Cr(III) citrate, Cr(III) histidine, Cr(III) lactate and Cr(III) glutamate] to a local strain of Lactobacillus plantarum isolated from sauerkraut was investigated. Growth inhibition, viable cell count and lactic acid inhibition were measured to determine the toxicity potential of the test compounds. The EC50 values of Cr(III) citrate, Cr(III) histidine, Cr(III) lactate, and Cr(III) glutamate, calculated from the percent growth inhibition were found to be 56 mg L−1, 70 mg L−1, 81 mg L−1, and 85 mg L−1, respectively. Similar trend was observed in the viable cell counts and lactic acid production. Cr(VI) was observed to be more toxic than the Cr(III) organic compounds, while inorganic Cr(III) was the least toxic. The severity seemed to increase with increase in chromium compounds’ concentration. The results showed that Cr(III) citrate was the most toxic Cr(III) organic compound, while Cr(III) glutamate was the least.