Concentrations Of Hexavalent Chromium Research Articles

Effect of Toxicity of Chromium (VI) Stressors Alone and Combined to High Temperature on the Histopathological, Antioxidation, Immunity, and Energy Metabolism in Fish Phoxinus lagowskii

Fish in aquatic ecosystems are often impacted by environmental stressors like temperature fluctuations and exposure to heavy metals. Chromium (Cr6+) is a known environmental pollutant that poses a threat to aquatic life. Various environmental factors, such as water temperature, have been found to affect the toxicity of dissolved chemicals in aquatic ecosystems. We investigated the toxicity of combinations of different concentrations of hexavalent chromium (Cr6+) with high temperatures in fish. Hematological indices demonstrated changes in white blood cells (WBCs), hematocrit (HCT), red blood cells (RBCs), and hemoglobin (Hb) levels during the exposure. The qualitative and semi-quantitative analyses of different tissues confirmed that higher concentrations of Cr6+ caused more significant damage than lower concentrations, with evident alterations observed in circulatory and regressive aspects. Furthermore, brain acetylcholinesterase levels decreased in both single heavy metal exposure and combined exposure at a high temperature. The activity of antioxidant oxidase and immunological parameters increased in all treatment groups compared with the control group following long-term exposure. A significant and increased effect of Cr6+ in the high-temperature groups was observed on the evaluated biomarkers, suggesting a possible synergistic effect between Cr6+ and increased temperature. The integrated biomarker response (IBR) reported the highest level of stress at 10 mg/L Cr6+ combined with high temperature. The IBR analysis revealed that the highest activity of response enzymes, such as acid phosphatase (ACP), superoxide dismutase (SOD), and glutathione S-transferases (GST), was observed in the liver, whereas the gills displayed alkaline phosphatase (ALP), GST, and SOD activity, and the kidneys demonstrated SOD, ACP, and aspartate aminotransferase (AST) to be most active. Through histopathology, antioxidant enzymes, and metabolism- and immunity-related enzymes, we determined that high temperatures enhance the potential toxicity of Cr6+ in fish. We recommend conducting a thorough assessment of the impact of climate change, particularly temperature fluctuations, when studying the toxic effects of metal pollution, like chromium, in aquatic ecosystems.

Phytoremediation of Cr(VI) from Aqueos Solution by Pistia stratiotes L.: Efficiency and Kinetic Models

Phytoremediation utilizes metal-trapping plants to recover water as the main source of contamination, Pistia Stratiotes L. is a hyperaccumulator plant that is considered capable of reducing hexavalent chromium levels in wastewater. This is evidenced by the results obtained on each of the variables investigated, namely the effect of contact time and the number of plants. Where, the effect of contact time on the most optimal reduction in hexavalent chromium concentration on day 10 is 22.55 mg/ L with an efficiency value of 54.89 %. While the effect of the number of plants on the reduction in the most optimal metal concentration was found in the first reactor with the number of plants 4, chromium concentration was 23.16 mg/ L with an efficiency value of 54.89%. This means that the longer the phytoremediation process will affect the decrease in chromium levels in waste samples but has no effect on the number of plants used if the plant mass is not calculated before treatment. The recommended kinetic models for phytoremediation systems using P. Stratiotes L plants are Richard's Pseudo First Order and Pseudo Second Order. However, when viewed from the prediction value and experimental data, Pseudo Second Order Kinetic Models are considered suitable to describe the phenomenon that occurs in this study, with an SSE value of 1.0042 and a reaction rate constant of 1.1662 day-1 to 1.5623 day-1.

Effectiveness of Pokea (Batissa violaceae celebensis Martens, 1897) shells in reducing hexavalent chromium

Introduction: Preliminary data obtained showed that the Hexavalent Chromium (VI) content found in the Lasolo River had a concentration of 0.3 mg/l which exceeded the quality standard. Pokea shellfish (Batissa violaceae celebensis Martens, 1897) is an adsorbent used to reduce hexavalent chromium levels in water.
 Method: The methodology used is experimental with a quantitative approach. This study used variations in adsorbent mass and contact time, with variations in adsorbent mass of 2.5 with variations in contact time for 30 minutes, 60 minutes, and 120 minutes.
 Result: Adsorption effectiveness of Hexavalent Chromium (VI) using Pokea Shell powder (Batissa Violaceae Celebensis Martens, 1897) with a mass of 2.5 g with a variation of contact time of 30 minutes with a decrease of 16.53%. Adsorption effectiveness of Hexavalent Chromium (VI) using Pokea Shell powder (Batissa Violaceae Celebensis Martens, 1897) with a mass of 2.5 g with a variation of contact time of 60 minutes with a decrease of 21.37%. Adsorption effectiveness of Hexavalent Chromium (VI) using Pokea Shell powder (Batissa Violaceae Celebensis Martens, 1897) with a mass of 2.5 g with a variation of contact time of 120 minutes with a decrease of 33.46%.
 Conclusion: The conclusion in this journal The most effective in reducing Hexavalent Chromium (VI) was using Pokea Shell powder (Batissa Violaceae Celebensis Martens, 1897) with a mass of 2.5 g with a variation of contact time of 120 minutes with a reduction of 33.46%.

Taguchi method for optimization of Cr(VI) removal, isotherm, kinetic and thermodynamic studies

In this study, Taguchi optimization method was applied to determine the optimum operating conditions for batch adsorption of Cr(VI) from aqueous solution. Initial pH of solution, adsorbent dose, initial hexavalent chromium concentration, contact time and adsorbent type were selected as the variables, and the removal efficiency of Cr(VI) was chosen for the designated response. L18(35) orthogonal array, signal-to-noise (S/N) ratio and analysis of variance statistical procedures were applied to identify the effect of each operating parameter on the removal of Cr(VI) from aqueous solution. The signal-to-noise (S/N) ratio results showed that the optimal combination for Cr(VI) removal was at pH 1.0, adsorbent dose of 3.6 g.L−1, Cr(VI) concentration of 30 mg.L−1, contact time of 95 min and olive leaves as adsorbent type. A removal of 95.09% was obtained at these optimum conditions. The analysis of variance of the data revealed that initial pH of solution was the most dominant parameter affecting Cr(VI) removal efficiency, followed by adsorbent type, adsorbent dose, contact time and initial metal concentration. Under optimal conditions, adsorption kinetic of Cr(VI) was studied and modeled using the pseudo first-order, pseudo-second-order and intraparticle diffusion models. It was found that the pseudo-second-order model fitted the adsorption data most with the highest determination coefficient (R2 = 0.996). Freundlich isotherm model, with regression coefficient R2 of 0.953, fit well with the equilibrium isotherm data. The Langmuir maximum adsorption capacity was found to be 62.5 mg.g−1. The experimental values of ΔH°, ΔG° and ΔS° revealed that the adsorption process was spontaneous and endothermic.

The use of banana peel as a low-cost adsorption material for removing hexavalent chromium from tannery wastewater: optimization, kinetic and isotherm study, and regeneration aspects.

When the concentration of hexavalent chromium (Cr(vi)) in the environment is greater than a certain limit, it becomes a global concern. Thus, the aim of this study was to use banana peel as an adsorbent to remove heavy metals, specifically Cr(vi) ions from wastewater. Banana peel (BP) was activated in a furnace for 2 h (h) at 450 °C and 50% humidity. Subsequently, the activated BP was characterized by proximate analysis, elemental analysis, scanning-electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer Emmett Teller (BET) analysis, and thermogravimetric analysis (TGA). According to the characterization results, the activated BP possessed a porous surface and high surface area of 200 m2 g-1, which are important adsorption parameters. Additionally, the removal efficiency for Cr(vi) was evaluated in terms of pH, contact time, initial concentration, and adsorbent dose. Consequently, the optimal operating conditions for removing 94% of Cr(vi) were found to be an adsorption time of 92 min, adsorbent dose of 1.5 g L-1, pH of 3, and initial Cr(vi) concentration of 38 mg L-1. In addition, the adsorption kinetics and isotherms were examined. The pseudo-first-order model with an R2 of 0.996 and the Langmuir isotherm with an R2 of 0.997 were found to be the most effective mathematical representations of the rate and nature of Cr(vi) adsorption on the surface of the activated BP, respectively. Furthermore, it was discovered that the activated BP could be reused six times before its removal efficiency was reduced to less than 70%.

Investigation and optimization the study of Hexavalent Chromium elimination efficiency by activated carbon prepared from modified rice husk with sorbic acid

The current work illustrates how successfully rice husk-activated carbon eliminates hexavalent chromium from aqueous solutions. The design of experiment (DOE) - response surface methodology (RSM) was utilized to build an appropriate experimental model. The experimental variables pH, contact length, and adsorbent dose were found, as well as their interactions and effects on Cr(VI) removal. The greatest result for Cr(VI) removal was obtained at pH = 2, agitation time of about 30.5 hours, and adsorbent dose = 4 g/l, with a starting hexavalent chromium content of 100 ppm. Hexavalent chromium removal is performed optimally under the parameters specified for these driving forces. ANOVA also demonstrated a strong coefficient of determination R2 > 99 %. Furthermore, Temkin isotherm and pseudosecond kinetic models with high R2 values were selected as useful for the inquiry. It illustrates that the removal of hexavalent chromium in studies is considered to follow a regular distribution of binding energies up to a given maximum binding energy. Furthermore, the rate of adsorption site occupancy is inversely proportional to the square of the number of unoccupied sites on the adsorbent.

Detection of Hexavalent Chromium Ion in Water by Optode Membrane

Chromium is a heavy metal that is often found as a water pollutant. High concentrations of hexavalent chromium (Cr(VI)) ion in nature are toxic and carcinogenic, so their presence in water needs to be monitored. Detection of heavy metals in water was carried out using an optical sensor membrane (optode). The optode was fabricated from cellulose triacetate polymer with plasticizers (oleic acid and acetophenone), aliquot 336, and the chromoionophore 1.5-diphenylcarbazide (DPC). The success synthesis of optode was evidenced by FTIR and SEM characterization. The optode performance produces a linear response in detecting Cr(VI) ion in the concentration range of 0.02-0.40 mg/L with an R2 of 0.9930, as well as the best conditioning at pH 3. The detection and quantitation limits are 0.0055 mg/L and 0.0165 mg/L. The sensitivity of the chromium optode was excellence, with a molar absorptivity value of 8.8303 × 106 M-1cm-1. The performance test results of the chromium optode were acceptable because they meet the specified requirements for minimum detection concentration value.

Improvement in the Chromium(VI)-Diphenylcarbazide Determination Using Cloud Point Microextraction; Speciation of Chromium at Low Levels in Water Samples.

A reliable, rapid, and low-cost procedure for determining very low concentrations of hexavalent chromium (Cr) in water is discussed. The procedure is based in the classical reaction of Cr6+ with diphenylcarbazide. Once this reaction has taken place, sodium dodecylsulfate is added to obtain an ion-pair, and Triton X-114 is incorporated. Next, the heating of the mixture allows two phases that can be separated by centrifugation to be obtained in a cloud point microextraction (CPE) process. The coacervate contains all the Cr6+ originally present in the water sample, so that the measurement by molecular absorption spectrophotometry allows the concentration of the metal to be calculated. No harmful organic solvents are required. The discrimination of hexavalent and trivalent forms is achieved by including an oxidation stage with Ce4+. To take full advantage of the pre-concentration effect inherent to the coacervation process, as well as to minimize reagent consumption and waste generation, a portable mini-spectrophotometer which is compatible with microvolumes of liquid samples is used. The preconcentration factor is 415 and a chromium concentration as low as 0.02 µg L-1 can be detected. The procedure shows a good reproducibility (relative standard deviation close to 3%).

Utilization of iron scrap into copperas and rambutan (Nephelium lappaceum L.) peel extract into environmentally friendly iron nanoparticles for hexavalent chromium removal and its kinetics

AbstractHexavalent chromium is a toxic pollutant that is very harmful to human health and the environment. One of the materials for hexavalent chromium removal is iron nanoparticles (INPs). In recent years, the manufacture of environmentally friendly INPs has been of great interest. In general, INPs are made using sodium tetra borane/NaBH4, which is expensive. The synthesis of INPs using NaBH4 also produces side products in the form of toxic boric acid and hydrogen gas which are explosive and flammable. In this study, INPs are made by using iron scrap waste into copperas which is then reacted with rambutan peel extract (RPE). The reaction between iron scrap and sulfuric acid until crystals are formed and then washed until blue‐green crystals are formed. The resulting crystal is made into a solution and then reacted with RPE. After forming a black solution, it was dried by spray drying. The resulting black powder was characterized by UV‐Vis Spectrophotometer, SEM‐EDX, FTIR, and XRD. The results showed that iron scrap can be synthesized into copperas with a Fe content of 19.84 ± 0.15%. RPE has a total phenol content of 877.39 ± 16.6 ppm/100 g rambutan skin or equivalent to 441.42 mg GAE/100 g rambutan skin. INPs can be made from copperas from iron scrap and RPE which have Surface Plasmon Resonance (SPR) characteristics at 214 nm absorption, particle size 20–70 nm. Hexavalent chromium removal using INPs was maximum at pH 3, hexavalent chromium concentration of 5 ppm, INPs concentration of 0.15 g/100 mL, and contact time of 10 min. The adsorption isotherm type of hexavalent chromium using iron nanoparticles can take place chemically or physically. The correlation coefficient showed that the model of Freundlich (R2 > 0.99) is more suitable than the model of Langmuir (R2 = 0.98) with an adsorption capacity of 91.74 mg iron nanoparticles/g hexavalent chromium. The use of INPs for hexavalent chromium removal is a promising and effective technology. These results can be an alternative to the production of environmentally friendly INPs by using materials from waste into useful materials for the prevention of environmental pollution.

Amino-modified hemp stem for high-capacity adsorption of Cr(VI) from aqueous solution

Two novel adsorbents, triethylenetetramine-grafted hemp stems (HS-TETA) and choline chloride-grafted hemp stems (HS-CL), were prepared by using epichlorohydrin as etherifying agent. The obtained adsorbents were comprehensively characterized, and the adsorption capacity for hexavalent chromium (Cr(VI)) was evaluated under various single-factor conditions, including adsorbent dosage, contact time, solution pH, initial hexavalent chromium concentration, and temperature. HS-TETA and HS-CL exhibit excellent adsorption performance, with maximum adsorption capacities of 396.88 and 335.04 mg/g, respectively, outperforming previous relevant studies. The adsorption behavior of Cr(VI) by HS-TETA and HS-CL was investigated using adsorption kinetics, adsorption isotherms, and adsorption thermodynamics. The adsorption process follows the pseudo-second-order kinetic model and the Langmuir isotherm model, suggesting a monolayer adsorption process with chemical adsorption. Thermodynamic analysis reveals that the adsorption of Cr(VI) on two adsorbents is spontaneous and exothermic. Combined with the characterization, it can be speculated that the adsorption of Cr(VI) on two adsorbents involves electrostatic effects, reduction, and complexation processes. HS-TETA and HS-CL exhibit good recyclability. After 5 cycles, HS-TETA and HS-CL maintain over 50% and 85% of their initial adsorption capacity, respectively. The cycling performance of HS-CL containing quaternary ammonium and amine groups is significantly superior to that of HS-TETA containing only an amine group, indicating that the introduction of the quaternary ammonium group enhances the cycling performance of the adsorbent. HS-TETA and HS-CL, as cost-effective and efficient adsorbents, offer a promising solution for the treatment of Cr(VI)-contaminated wastewater and facilitate the recycling of agricultural waste.

A comparative study on the removal and recovery of hexavalent chromium from tannery wastewater using an isolated strain Aspergillus proliferans LA and a known strain Aspergillus terreus

Isolation of a potent microorganism from the soil near tanneries and a comparative analysis of the removal and recovery of different concentrations of hexavalent chromium using known strain Aspergillus terreus and isolated strain Aspergillis proliferansLA are done. The isolated fungal species from the chromium contaminated soil sites located in the industrial area of Kanpur, U.P. were tested for its potential for the removal of hexavalent chromium from wastewater streams. The experiments were conducted comparing the biosorption efficiency of the isolated species Aspergillus proliferansLA and Aspergillus terreus by varying the initial Cr (VI) concentration and media constituents. The highest removal efficiency of 99.19% was shown by the isolated species Aspergillus proliferansLA for an initial Cr (VI) concentration of 10ppm followed by increasing the concentration to 50ppm whereas Aspergillus terreus showed 78.43% removal of hexavalent chromium. This was then followed by desorption using 0.8M NaOH and 75.12% hexavalent chromium was desorbed from the cells. The isolated strain Aspergillus proliferansLA was seen to show better removal and recovery results than the known strain Aspergillus terreus.

Long-term stability and toxicity effects of three-dimensional electrokinetic remediation on chromium-contaminated soils

The three-dimensional electrokinetic remediation (3D EKR) achieved efficient removal of chromium (Cr) from the soil through mechanisms including electromigration, electroosmosis, and redox reactions. In this study, the long-term stability, leaching toxicity, bioavailability, and phytotoxicity of Cr in remediated soils were systematically analyzed to comprehensively evaluate the effectiveness of the 3D EKR method. The results showed that the concentration of hexavalent chromium (Cr (VI)) in the leachate of the 3D EKR system with sulfidated nano-scale zerovalent iron (S-nZVI) was more than 40% lower than those of the other 3D electrode groups, and the time required to reach the level III standard of groundwater quality criterion in China (0.05 mg/L, GB/T 14848-2017) was significantly shortened. The stabilization of Cr(VI) in contaminated soil after 3D EKR was maintained for 300 pore volumes (PVs), indicating that the treated Cr(VI) had good long-term stability. The leaching toxicity and bioaccessibility of Cr were assessed by the synthetic precipitation leaching procedure (SPLP), the toxicity characteristic leaching procedure (TCLP), and the physiologically based extraction test (PBET). The concentration of Cr(VI) in the SPLP, TCLP, and PBET leachates of the S-nZVI group decreased by more than 25% compared to the other 3D electrode groups, corresponding to the decrease in leaching toxicity and bioavailability of the treated Cr during the 15-day remediation period. In addition, the germination rate of wheat seeds and the average biomass of wheat seedlings in the S-nZVI group under alkaline conditions (EE) were higher than those in the non-polluting group (Blank-OH), indicating that the remediated soil had no obvious toxicity to wheat. In summary, 3D EKR achieved a satisfactory and stable remediation effect on Cr-contaminated soil, especially when using S-nZVI as the 3D electrode.

Pseudocapacitive deionization of high concentrations of hexavalent chromium using NiFe-layered double hydroxide/polypyrrole asymmetric electrode

The wastewater polluted by high concentrations of aqueous hexavalent chromium (Cr(VI)) has serious adverse effects on ecological environment and human health. As a burgeoning, environmental-friendly, and promising wastewater treatment technology, capacitive deionization (CDI) process for efficient removal of aqueous Cr(VI) needs to be investigated. In this work, pseudocapacitive NiFe-layered double hydroxide/ polypyrrole (NiFe-LDH/PPy, denoted as NiFe/PPy) electrode was synthesized by the in-situ polymerization of PPy on the NiFe-LDH surface. Results of characterizations manifested that NiFe/PPy had the chain spherical structure of PPy. In particular, excellent PPy provides effective reversible capacitance and ion diffusion and improves the conductivity and pseudocapacitance performance of NiFe-LDH. Then, the NiFe/PPy anode and activated carbon (AC) cathode were assembled into the CDI cell for capacitive removal of high concentrations of aqueous Cr(VI). In 20 mL/min of flow velocity, 1.2 V, and 100 mL 100 mg/L of Cr(VI) solution, the Cr(VI) electrosorption capacity and removal ratio attained to 47.95 mg/g and 95.89%, respectively. The electrosorption of Cr(VI) slightly decreased under the common competing anions of Cl−, NO3−, SO42−, HCO3−, and CO32−. Based on Langmuir isotherm model, the maximum theoretical removal capacity of NiFe/PPy for Cr(VI) was 111 mg/g. The electrostatic attraction, reduction, and surface complexation played primary roles in the CDI system of NiFe/PPy//AC asymmetric electrodes. The outstanding electrosorption performance makes this CDI system have a favorable application prospect in the actual wastewater treatment containing high concentrations of Cr(VI).

Study on the performance of vertical flow constructed wetland microcosm with Canna sps. for treatment of high chromium-containing wastewater

Chromium (Cr (VI)) pollution has plagued the environment due to chromite mining and various industrial actions. Constructed wetlands (CW) have emerged as a potential wastewater management technique that utilizes physical, chemical, and biological processes. The present study investigates the use of vertical flow-constructed wetlands (CW) using manure-rich garden soil and sand as substrates in planted CW (CW–P) and unplanted CW (CW-UP) to remove Cr (VI) from simulated wastewater. The experiment was performed in two phases, i.e., Phase I and II, in the same system. In Phase I, initial Cr (VI) concentrations were varied between 5 and 200 mg/l at a fixed hydraulic retention time (HRT) of 48 h, while in Phase II, the effect of HRT (24 h, 48 h, and 96 h) was studied at a fixed Cr (VI) concentration of 200 mg/L in the influent. At 24 h, HRT removal efficiencies were 90.20% for CW-P and 86.41% for CW-UP. However, at 96 h of HRT, the system showed nearly the same removal efficiency. Scanning electron microscopy with energy dispersion X-Ray spectroscopy analysis suggested the conversion of Cr (VI) to Cr (III) in soil precipitate and the translocation of Cr (VI) in plant tissues (Canna sps.). Moreover, microbial diversity profiling indicated that microbial diversity involved in pollutant removal differed in both systems. The phytotoxicity test clearly showed the decrease in toxicity level in the treated effluent, concluding the reusability of treated water. This exploratory study suggested that the CW can potentially remove a higher concentration of hexavalent chromium at longer HRT.

Exploring a unique water ecosystem under long-term exposure to hexavalent chromium – An in situ study of natural diatom (Bacillariophyceae) communities

This paper reports the third in a series of three studies of a unique aquatic phytobial consortium that developed in a polluted ditch situated near an old chromium waste landfill. The ditch is a specific ecological niche having increased loads of several chemical compounds, including extreme hexavalent chromium concentrations up to two thousand times the allowed limit (0.02 mg dm−3 in Poland) in the more polluted section B; the moderate concentrations in section A are twice the limit. We focus on the microscopic algae group of diatoms, one of the most important components of the phytobial consortium, and continue our novel attempt to analyze the bioremediation potential of the entire consortium under those environmental conditions. We used numerical methods to analyze differences in diatom biodiversity between sections A and B, and assessed the relations between diatoms and selected water chemistry properties, including hexavalent chromium, chlorides and sulphates, the latter two known to positively influence the resistance of algae to the impact of hexavalent chromium. We noted 37 diatom taxa in section A of the ditch and 30 in section B. The most frequently observed diatoms were cosmopolitan taxa and/or characteristic taxa of saline waters. Sulphates were the most important factor influencing the diatom composition in the ditch, explaining 52% of the total variability, followed by chlorides (30%) and hexavalent chromium (9%). Gomphonema acuminatum, Melosira varians and Nitzschia frustulum var. frustulum were found to be most resistant to hexavalent chromium and were selected for further experimental studies on their biotechnological usefulness.

Tissue Accumulation, Cytotoxicity, Oxidative Stress, and Immunotoxicity in African Catfish, Clarias gariepinus Exposed to Sublethal Concentrations of Hexavalent Chromium.

Hexavalent chromium (Cr6+) is one of the stable oxidation states of chromium that has been reported to elicit various toxic effects in aquatic organisms. However, the mechanisms of Cr6+ toxicity are still poorly understood. Thus, the present study investigated the tissue accumulation, cytotoxic, oxidative stress, and immunotoxic effects of Cr6+ in juvenile Clarias gariepinus. The fish were exposed to waterborne Cr6+ concentrations (0, 0.42, 0.84, and 1.68 mg/L) for 28 days, after which they were sacrificed and various organs were harvested for the determination of Cr6+ levels. Other parameters that were indicators of oxidative stress, cytotoxicity, and immunotoxicity were measured. Cr6+ accumulated more in the kidney and liver of the exposed fish, especially at the highest concentration. The levels of lipid peroxidation and DNA fragmentation increased significantly in the exposed fish. The activities of superoxide dismutase and lactate dehydrogenase increased significantly in exposed fish compared to the control. The total white blood cells, lymphocytes, and neutrophils counts were significantly higher in the exposed fish compared to the control fish. The respiratory burst activity decreased significantly in the exposed fish while the myeloperoxidase content did not differ significantly. There were upregulations of TNF-α and HSP 70 while CYP II and MHC 2 were downregulated in the exposed fish. Also, exposure to Cr6+ resulted in various histopathological alterations in the architecture of the head kidney. The results indicate concentration-dependent toxic effects of Cr6+ in C. gariepinus. The study reveals the potentials of Cr6+ to accumulate in the different tissues of fish and caused cytotoxic, oxidative stress, and immunotoxic effects in the exposed fish.

Highly efficient catalytic ozonation degradation of levofloxacin by facile hydrogenation-modified red mud wastes

Iron-rich red mud (RM) is a potential catalyst. However, as industrial waste, is strongly alkaline, low effectiveness, and safety concerns are problems that cannot be ignored, it is urgent to mine out a reasonable disposal and utilization technology for the waste. In this study, an effective catalyst (H-RM) was obtained by facile hydrogenation heating modification of red mud. Then above-prepared H-RM was applied in the catalytic ozonation degradation of levofloxacin (LEV). The H-RM exhibited more remarkable catalytic activities than the RM in terms of LEV degradation, and the optimal efficiency can reach over 90% within 50 min. The mechanism experiment proved that the concentration of dissolved ozone and hydroxyl radical (•OH) significantly increased, which enhanced the oxidation effect. Hydroxyl radical played a dominant role in the degradation of LEV. In the safety test, it is concluded that the concentration of total hexavalent chromium (total Cr(Ⅵ)) in the H-RM catalyst decreases and the leaching concentration of water-soluble Cr(Ⅵ) in aqueous solution is low. The results indicated that the hydrogenation technique is an available Cr (Ⅵ) detoxification method for RM. Moreover, the H-RM has excellent catalytic stability, which is beneficial to recycling and maintains high activity. This research provides an effective means to fulfill the reuse of industrial waste as an alternative to standard raw materials, and comprehensive utilization of the waste to attain the purpose of treating pollution with wastes.

Tin Oxide Nanoparticles via Solar Vapor Deposition for Hexavalent Chromium Remediation.

Tin oxide nanoparticles optimized to capture low concentrations of hexavalent chromium from water were developed through a facile, scalable, and low-cost one-step solar vapor deposition methodology. Considering the preservation of high electron donation capacity as the key to support the reduction of mobile Cr(VI) into insoluble forms, the growth of SnO nanoparticles was favored by the co-evaporation of SnO2 with Fe powders at various mass ratios. Characterization techniques indicated that the percentage and the stability of SnO is proportional to the Fe content in the target with a requirement of at least 50% wt to inhibit the formation of a passive SnO2 surface layer. The produced particles were evaluated regarding their efficiency to capture Cr(VI) under conditions similar to water treatment for drinking purposes (pH 7). It was revealed that passivation-free SnO nanoparticles deliver significant improvement in the adsorption capacity corresponding to the residual concentration of 25 μg/L, reaching a value of 1.74 mg/g for the sample prepared with 50% wt Fe in the target. The increase of water acidity was found responsible for the activation of more reduction sites on the particle surface, as reflected through the elevation of efficiency by more than 20% at pH 6.

Hexavalent chromium induced oxidative, histopathological and hematological changes in snakehead fish, Channa punctatus

Aim: To evaluate the effect of hexavalent chromium on biochemical, hematological and histopathological responses and to assess its concentration in fish Channa punctatus. Methodology: Fishes were randomly distributed into Cr6+ treated groups, T1 (2 mg l-1), T2 (4 mg l-1), T3 (6 mg l-1), and one control (0 mg l-1) for 30 days exposure period. Potassium dichromate (K2Cr2O7) was used as source of Cr6+. The liver, kidney and blood were sampled after 10, 20 and 30 days intervals. Results: The significant (p < 0.05) increments in the concentration of hexavalent chromium and in the activities of enzymes (superoxide dismutase, catalase and glutathione reductase) as well as lipid peroxidation were recorded in the liver and kidney tissues of fish.However, the significant (p < 0.05) decline of reduced glutathione and total protein were noticed in both the tissues of fish. The red blood corpuscles count, hemoglobin and hematocrit significantly (p <0.05) decreased, while the white blood corpuscles count increased in blood of fish. Remarkably, the histopathological anomalies, pyknosis, hypertrophy and inflammation in liver and cavity reduction in renal tubules and glomerulus degenerative changes in kidney were prominently observed in fish. Conversely, the necrosis and vacuolization were observed in liver and kidney tissues of fish. Interpretation: The findings of the present study can be a useful tool as biomarkers for monitoring environmental pollution in aquatic ecosystem caused by hexavalent chromium. Key words: Biochemical, Biomarkers, Channa punctatus, Hematological, Hexavalent chromium, Histopathological

89 Improvements to a Method for the Determination of Hexavalent Chromium in Workplace Air

Abstract ISO 16740:2005 specifies an ion chromatographic method for the determination of the time-weighted average mass concentration of hexavalent chromium in workplace air and is applicable to the determination of masses of 0,01 micrograms to 10 micrograms of hexavalent chromium per sample, without dilution. For a nominal 1 cubic metre air sample, this equates to a measurement range of between approximately 0,01 micrograms per cubic metre to 10 micrograms per cubic metre, suitable for assessing exposures in plating or weld shops. However alkaline extractants, required to liberate insoluble chromates from air samples collected in paint shops, can be contaminated with trace levels of chromium thereby negating the inherent sensitivity of this method. Work to address this issue, by sourcing and testing cleaner reagents, will be presented.