Absence Of Chromium Research Articles

Efficiency of oil separation and demulsification following sonication gel degradation: Influence of Cr(III) ions, NaCl concentrations, and sodium-based retarders

This study investigates the impact of chromium (III) ions, salinity, and retarders on demulsification efficiency and oil separation in oil–water emulsions stabilized by hydrolyzed polyacrylamide (HPAM) aqueous solutions. Two different concentrations of HPAM (1000 and 2000 ppm) and NaCl (0–200,000 ppm), along with two distinct retarders (sodium lactate and sodium malonate), were employed to prepare the emulsion samples. A comprehensive analysis of emulsion stability and demulsification duration was conducted under varying treatment conditions, such as the presence or absence of chromium (III) ions and resin application for chromium removal. Results demonstrate that the presence of chromium (III) ions significantly increases emulsion stability, while their removal leads to a marked reduction in demulsification duration. Notably, the impact of salinity was found to depend on the specific retarder used, with sodium lactate and sodium malonate exhibiting differing demulsification durations. As the HPAM concentration was raised from 1000 to 2000 ppm, the demulsification duration also, regardless of the presence or absence of chromium (III) ions. Additionally, the oil separation rates were higher in samples treated with a resin for chromium removal and are notably influenced by the choice of retarder. In particular, using sodium malonate as a retarder resulted in a significant improvement in the oil separation rate compared to sodium lactate under various salinity conditions. The findings of this study provide valuable insights into the optimization of oil–water separation processes, offering the potential for improved oil recovery and environmental sustainability. This study is particularly novel in its comprehensive investigation of the interplay between different factors (chromium, salinity, and retarders) in oil–water separation processes.

EDTA-enhanced Cr detoxification and its potential toxicity in rice (Oryza sativa L.)

Ethylenediamine tetraacetic acid (EDTA) is a chelating agent used worldwide for the phytoextraction of heavy metals using hyperaccumulating plants as well as in household and industrial purposes and persists in cultivated land for a long time without any known impact on nonhyperaccumulating plants. In this study, the effects of EDTA in the presence and absence of chromium on the hydroponic solution were evaluated at the cellular and molecular levels in nonhyperaccumulating rice plants (Oryza sativa L.). EDTA application enhanced phytochelatin (PC) and metallothionein (MT) synthesis, which was confirmed by the upregulation of phytochelatin and metallothionein genes in rice roots. However, a lower quantity of EDTA (25 µM) along with chromium enhanced chromium uptake (22.5%) in the root but inhibited its translocation to the shoot, indicating vacuolar sequestration of excessive chromium in the root. Conversely, in the absence of chromium, the H2O2 concentration was found to be increased, which significantly enhanced electrolyte leakage (98.5%) and lipid peroxidation (33.3%) compared with control plants. Our data indicate that excessive PCs and MTs without vacuolar sequestration enhance reactive oxygen species (ROS) generation. The findings of this investigation show that enhanced PCs and MTs owing to EDTA sequester excessive chromium in root vacuoles but, in the absence of sequestration due to a lack of chromium, enhance reactive oxygen species generation, resulting in toxicity. The outcomes of this investigation will open a new avenue of research in phytoextraction or phytoremediation activities.

Effect of Selected Electronic Waste Dump Sites on Quality of Surrounding Water Bodies in Abuja, Nigeria

Due to inappropriate management of vast amount of waste produced by various human activities, urban surface and ground water resources have been under danger of pollution. It is noted that solid waste management is a universal issue and that it is a growing source of worry in developed and developing countries due to the increase in urbanization, changes in consumer pattern, and industrialization which all directly transform to an increase in solid waste generation. The sampling points used of the research are Electronic Waste (e waste) dump sites of Guzape, Karmo and Kubuwa areas of Abuja with terrains of flowing surface water bodies/ pond water. The sample sites were chosen to investigate the impact of e-waste on the water quality of surrounding water bodies in the environment. Parameters measured from collected water samples are pH, Temperature, Conductivity, Turbidity, Dissolved Oxygen, Total Dissolved Solids, Total Suspended Solids, Calcium, Magnesium, Ammonia Nitrogen, Nitrate Nitrogen, Nitrite Nitrogen, Phosphate, Biochemical Oxygen Demand, Chemical Oxygen Demand, Bicarbonate, Manganese, Copper, Zinc, Lead, Cadmium and Chromium. Results showed heavy metal values for Cadmium and Manganese in the water samples were above the maximum permitted level as compared with standards for drinking water, it is inferred that the impact of E waste in the environment contributed to the presence of heavy metals in the water samples. Copper, Zinc, and Chromium were also detected in all water samples collect except for a sample with the absence of Chromium in the water sample.Key words: Disposal sites, Electronic waste, Water quality

Structure of a Diamond–Matrix Interface and Durability of a Diamond Tool Fabricated by the Metallization of Diamond with Chromium during Sintering of the WC–Co Briquette with Copper Impregnation

The structure, as well as the elemental and phase compositions of the diamond–matrix interface of a diamond tool for abrasive wheel dressing, manufactured using a new hybrid technology, are studied. This technology combines the thermodiffusion metallization of diamond with chromium and sintering of a matrix based on a WC–6%Co carbide powder mixture with copper impregnation in a single cycle of the vacuum furnace operation. During matrix sintering, the compact arrangement of chromium powder particles around the diamond grains and the screening effect of the copper foil form favorable conditions that ensure the thermodiffusion metallization of diamond. Scanning electron microscopy, electron probe microanalysis, X-ray phase analysis, and Raman spectroscopy show that a metallized coating chemically bound with diamond is formed on the diamond surface in temperature-temporal modes and sintering conditions. The coating consists of chromium carbide and a solid solution of cobalt in chromium, which provides durable diamond retention in the copper-impregnated carbide matrix. Herewith, the matrix structure and microhardness, excluding the regions adjoining the diamond–matrix interface, remain the same as a matrix of a carbide powder mixture sintered in the absence of chromium. Comparative tests of similar diamond dressers show the high efficiency of the hybrid technology of formation of diamond-containing composites for tool application. It is shown that the specific productivity of a dresser prototype fabricated using the hybrid technology was 51.50 cm3/mg when dressing a grinding wheel made of green silicon carbide, which is 44.66% larger than a similar indicator of the same type of check dresser formed using the traditional method.

Radical chemistry of alkyl aluminum with quinoxaline ligands

The behavior of organo-aluminum species with 2,3-bis(2-pyridyl) quinoxaline (DPQ), a well-known polyazine capable of performing interesting radical transformations, was examined in the presence and absence of chromium. In spite of proving the presence of chromium as essential for reactivity, only organic radicals, coupled to aluminum-containing residues, have been isolated and characterized. The electronic structure of the organic radicals has been elucidated by a combination of crystallographic, DFT calculations and EPR studies. Experimental and computational work has highlighted the co-existence of both singlet and triplet forms in one di-radical complex.

Structural heat-resistant β-NiAl + γ′-Ni3Al alloys of the Ni–Al–Co system: II. Oxidation

The heat resistance of the β + γ′ alloys with 28–29 at % Al, 10 at % Co, and 0.25–0.4 at % Re in air at 1300°C is studied. The structures of the scale and the subscale layers that form during oxidation for 2 and 100 h due to the interdiffusion of aluminum and oxygen are investigated. Alloying with 10 at % Co is shown to increase the heat resistance in the absence of chromium and a low content of the elements tht are active to oxygen (La). The heat resistance of the β + γ′ NIAL1 and NIAL2 alloys at 1300°C, which was estimated from the surface unit mass increment in 100 h, is at level of the heat resistance of the γ′ + γ VKNA (VIN) alloys at 1200–1250°C.

Microstructure and properties of 1Cr12Ni2WMoVNb (GX-8) steel bored barrels with and without QPQ treatment

Bored barrels are one of the primary parts of small arms. In order to enhance the service life of bored barrels, specimens of 1Cr12Ni2WMoVNb (GX-8) steel bored barrels were treated by QPQ salt bath at temperatures 530°C for 1–4h, followed by the same post-oxidation process with heating temperature of 440°C for 1h. QPQ nitrided layers were formed on the surface of GX-8 steel after QPQ salt bath and the optimized treatment time was determined to be 1h. Specimens with and without QPQ-1h were studied by micro-hardness test, SEM, wear resistance test, Tafel polarization curves, salt spray corrosion and ball firing. Layers formed during QPQ-1h contains a mixture of magnetite (Fe3O4), Fe1-XO, CrN, ε phase, γ′-Fe4N and α-Fe phases. This layer leads to significant improvement in wear resistance as a result of remained Fe3O4 film, while the fine distribution of nitride precipitates introduces high hardness and large residual microstresses. The formation of thick Fe3O4 film results in an improvement in the corrosion resistance of steel. After the breakdown of Fe3O4 film, the absence of chromium in solid solute by precipitation of chromium nitrides and carbides leads to significant decreases in corrosion resistant. The QPQ-1h process results almost one times increases in the lifetime of bored barrels, as a result of wear resistance improvement after QPQ treatment.

Chromium reducing and plant growth promoting novel strain Pseudomonas aeruginosa OSG41 enhance chickpea growth in chromium amended soils

Pseudomonas aeruginosa strain OSG41, isolated from the heavy metal contaminated water irrigated to rhizospheric soil of mustard crop, tolerated chromium up to the concentration of 1800 μg ml−1 and reduced it by 100% at pH 6–8 after 120 h incubation at 30–40 °C. P. aeruginosa produced plant growth-promoting substances, both in the presence and absence of chromium; it produced 32 μg ml−1 indole acetic acid ml−1, in Luria Bertani broth with 100 mg tryptophan ml−1, solubilized tri-calcium phosphate (417 μg ml−1) and secreted 20.8 μg ml−1 exopolysaccharides (EPS) which decreased with increasing concentration of chromium added to growth medium. While investigating the impact of hexavalent chromium on chickpea, chromium application to soil had a phytotoxic effect. The application of P. aeruginosa strain OSG41 even with three times concentration of chromium increased the dry matter accumulation, symbiotic attributes (like nodule formation), grain yield and protein of chickpea compared to non-inoculated plants. The bio-inoculant decreased the uptake of chromium by 36, 38 and 40% in roots, shoots and grains, respectively. The present finding suggests that the bioinoculant effectively reduced the toxicity of hexavalent chromium to chickpea plants and concurrently enhanced the biological and chemical characteristics of chickpea, when grown in chromium treated soils.

Chromium Reducing and Plant Growth Promoting Potential of Mesorhizobium Species under Chromium Stress

ABSTRACT Chromium-reducing and plant growth–promoting potential, including production of siderophores by chromium(VI)-resistant Mesorhizobium species RC1 and RC4, isolated from chickpea nodules, was assessed both in the presence and absence of chromium(VI) under in vitro conditions. The Mesorhizobium strains displayed a high level of tolerance to chromium (400 μg ml− 1), and showed a varied sensitivity to antibacterial drugs, on yeast extract mannitol (YEM) agar plates. Mesorhizobium strains RC1 and RC4 reduced chromium(VI) by 84% and 83%, respectively at pH 7 in YEM broth after 120 h of incubation. Mesorhizobial strains RC1 and RC4 produced 27 and 35 μg ml− 1 of indole acetic acid (IAA), respectively, in Luria-Bertani broth with 100 μg ml− 1 of tryptophan. The IAA production by the mesorhizobial strains did not differ significantly (p ≤ .05) under chromium stress and showed a positive reaction for siderophore, HCN, and ammonia, both in the absence and presence of chromium(VI).The present observations suggest that the chromium reducing and plant growth promoting activities of the Mesorhizobium strains could be exploited for bioremediation of chromium(VI) and to enhance the legume productivity for chromium-contaminated soils.

Stripping of copper coatings from steel in Cr(VI)-free commercial bath

In this work the electrochemical characteristics of copper and steel in chromate, cyanide, and phosphate baths as well as in a commercial bath (ENSTRIP S-180), in the absence of chromium and cyanides were determined. Average rates of copper coatings stripping from steel in the above mentioned baths and the baths influence on the morphology of steel surfaces were described. It was found that the commercial bath ENSTRIP S-180 could be successfully used for stripping of copper coatings from steel elements.

Chromium-reducing and plant growth-promoting Mesorhizobium improves chickpea growth in chromium-amended soil

Mesorhizobium strain RC3, isolated from chickpea nodules, tolerated chromium up to 500 mug/ml and reduced it by 90% at pH 7 after 120 h. It produced plant growth-promoting substances, both in the presence and absence of chromium. Strain RC3 produced 35 mug indole acetic acid/ml in Luria Bertani broth with 100 mg tryptophan/ml, which decreased with an increase in chromium concentration. Chromium application to soil at 136 mg/kg was toxic to chickpea plants but when RC3 at 136 mg/kg was also added, it increased the dry matter accumulation, number of nodules, seed yield and grain protein by 71, 86, 36 and 16%, respectively, compared to non-inoculated plants. Nitrogen in roots and shoots were increased by 46 and 40%, respectively, at 136 mg Cr/kg. The bio-inoculant decreased the uptake of chromium by 14, 34 and 29% in roots, shoots and grains, respectively.

Chromium Reduction, Plant Growth–Promoting Potentials, and Metal Solubilizatrion by Bacillus sp. Isolated from Alluvial Soil

The plant growth-promoting potentials, production of siderophore and solubilization of insoluble phosphorus (P) and zinc and lead by the chromium (vi) -reducing Bacillus species, PSB 1, PSB 7, and PSB 10, was assessed both in the presence and absence of chromium under in vitro conditions. The Bacillus strains tolerated chromium up to the concentration of 500 (PSB1), 400 (PSB7), and 550 microg ml(-1) (PSB10), respectively, on nutrient agar plates. Bacillus sp. PSB 10 reduced Cr (vi) by 87% at pH 7, which was followed by Bacillus sp. PSB 1 (83%) and PSB 7 (74%) in nutrient broth after 120 h of incubation. A concentration of 50 microg ml(-1) of Cr (vi) was completely reduced by Bacillus sp. PSB 1 and PSB 10 (after 100 h) and PSB 7 (after 120 h). The Bacillus strains PSB 1, PSB 7, and PSB 10 produced 19.3, 17.7, and 17.4 microg ml(-1) of indole acetic acid, respectively, in luria bertani broth at 100 microg ml(-1) of tryptophan, which consistently decreased with an increase in chromium concentration. The Bacillus strains were positive for siderophore, HCN, and ammonia both in the absence and presence of chromium. The Bacillus strains solubilized 375 (PSB 1), 340 (PSB 7), and 379 (PSB 10) microg ml(-1) P, respectively, in Pikovskaya broth devoid of chromium. In contrast, chromium at 150 microg ml(-1) reduced the amount of P solubilized by 17 (PSB 1), 15 (PSB 7), and 9% (PSB 10) compared to control. The tested bacterial strains solubilized a considerable amount of zinc and lead in nutrient broth both in the absence and presence of chromium. Generally, the chromium reduction and the plant growth-promoting potentials of chromium-reducing Bacillus were strongly correlated at the tested concentration of chromium. The present observations demonstrated that the chromium-reducing, metal-solubilizing, and plant growth-promoting potentials of the Bacillus strains PSB1, PSB 7, and PSB10 were not adversely affected by the chromium application and, hence, may be applied for raising the productivity of crops under metal-contaminated soils.

The effect of long term exposure in oxidising and corroding environments on the tensile properties of two gamma-TiAl alloys

The lightweight γ-TiAl alloys offer good mechanical properties for gas turbine applications at high temperature (up to 750 °C). In order to replace the nickel-base alloys currently in use, however, their mechanical properties must be retained after exposure in a high temperature oxidising and corroding atmosphere. A complete study of the oxidation and corrosion processes of the two alloys, γ-Ti–46.5Al–4(Cr,Nb,Ta,B) and γ-Ti–45Al–X(Nb,B,C) was performed at temperatures from 700 to 800 °C. Hot corrosion tests were carried out with salt mixtures (93.7% Na 2SO 4+2.7% NaCl (wt%) or 75% Na 2SO 4+25% NaCl (wt%)) or with pure NaCl. A strong influence of the exposure on the tensile properties of these two γ-TiAl alloys has been demonstrated. Microscopic investigation showed that the bulk microstructure was stable. The main probable causes of these property reductions included the oxidation and corrosion processes and particularly the effect of niobium in the absence of chromium that induced major internal corrosion and premature failure.

Pro-oxidative vs antioxidative properties of ascorbic acid in chromium(VI)-induced damage: anin vivo andin vitro approach

The effect of antioxidant ascorbic acid (vitamin C) pretreatment on chromium(VI)-induced damage was investigated using the yeast Saccharomyces cerevisiae as a model organism. The objective of this study was to pretreat yeast cells with the antioxidant ascorbic acid in an effort to increase cell tolerance against reactive chromium intermediates and reactive oxygen species formed during chromium(VI) reduction. Intracellular oxidation was estimated using the fluorescence indicators dihidro-2,7-dichlorofluorescein, dihydroethidium and dihydrorhodamine 123. The role of ascorbic acid pretreatment on chromium(VI) toxicity was determined by measuring mitotic gene conversion, reverse mutations, 8-OHdG, hydroxyl radical, superoxide anion and chromium(V) formation. The chromium content in the biomass was determined by flame atomic absorption spectrometry. In the absence of chromium, ascorbic acid effectively protected the cells against endogenous reactive oxygen species formed during normal cellular metabolism. In vitro measurements employing EPR and the results of supercoiled DNA cleavage revealed that the pro-oxidative action of ascorbic acid during Cr(VI) reduction was concentration-dependent and that harmful hydroxyl radical and Cr(V) had formed following Cr(VI) reduction. However, the in vivo results highlighted the important role of increased cytosol reduction capacity related to modification of Cr(V) formation, increased chromium accumulation, better scavenging ability of superoxide anions and hydrogen peroxide, and consequently decreased cytotoxicity and genotoxicity in ascorbic acid pretreated cells. Ascorbic acid influenced Cr(VI) toxicity both as a reducing agent, by decreasing Cr(V) persistence, and as an antioxidant, by decreasing intracellular superoxide anion and hydrogen peroxide formation and by quenching free radicals formed during Cr(VI) to Cr(III) reduction. Increased 8-OHdG and decreased reduced glutathione in ascorbic acid-treated cells might induce an endogenous antioxidant defense system and thus increase cell tolerance against subsequent Cr-induced stress.

Investigation of Steel Surfaces Treated by a Hybrid Ion Implantation Technique

Implantation of nitrogen ions into stainless steel in combination with oxidation often results in a decrease or even complete removal of the chromium in the nitrogen containing outermost surface layer. While iron nitrides can be formed easily by this method, due to the absence of chromium, the formation of chromium nitrides is impossible and the beneficial influence of chromium in the steel for corrosion resistance cannot be used. To overcome this problem we use the following hybrid technique. A thin chromium layer is deposited on steel and subsequently implanted with nitrogen ions. Chromium can be implanted by recoil into the steel surface and thus the formation of iron/chromium nitrides should be possible. Both beam line ion implantation and plasma immersion ion implantation are used. Due to the variation of the process parameters, different implantation profiles and different compounds are produced. The produced layers are characterized by Auger electron spectroscopy, conversion electron Mossbauer spectroscopy and X-ray diffraction. The obtained results show that due to the variation of the implantation parameters, the formation of iron/chromium nitrides can be achieved and that plasma immersion ion implantation is the most suitable technique for the enrichment of chromium in the outermost surface layer of the steel when compared to the beam line implantation.

Phenol degradation by a bacterium Pseudomonas putida in the presence of chromium

Phenol and Phenolic compounds are well known components in aqueous waste of many different pollution generating industries. These compounds must be regarded as hazardous to the environment and are resistant to biological degradation. Degradation of Phenol in the presence of hexavalent chromium was studied using phenol degrading bacteria, Pseudomonas putida. The bacteria was able to degrade phenol up to 80% in the absence of chromium but the degradation was increased up to 81.67% in the presence of 25mg/l initial concentration of chromium (VI). The degradation was declined further up to 21.67%, when concentration of Chromium (VI) was applied 50mg/l.

Response of Saccharomyces cerevisiae to chromium stress

Chromium (Cr) is widely used in different industries, such as steel production, wood preservation, and leather tanning. It poses a severe threat to the ecological system due to its toxic effect on most life forms. In this paper, the response of Saccharomyces cerevisiae to different chromium concentrations was investigated. The results demonstrated that the growth of S. cerevisiae in the presence of chromium showed a lag phase much longer than in the absence of chromium. Inhibition was dependent upon the chromium concentrations. Chromium, at concentration of 15 μM, inhibited microbial growth by approximately 30% with regard to control, whereas chromium, at a concentration of 5 μM, did not have a significant effect on microbial growth. The existence of chromium did not perturb cell–protein synthesis and there was a good correlation between dry cell weights and total protein content ( R=0.98). The RNA/DNA ratio in the microbial cells varied with the chromium concentration and there was a significant positive correlation between chromium concentration and the RNA/DNA ratio. Assimilation of ammonium ion was inhibited by chromium in the medium.

Biochemical responses of Cr-tolerant and Cr-sensitive mung bean cultivars grown on varying levels of chromium

Biochemical investigations were carried out in Cr-tolerant and Cr-sensitive cultivars of mung bean ( Vigna radiata L.) with different concentrations of hexavalent chromium (as K 2Cr 2O 7) in hydroponics culture. Seeds were germinated and grown in the presence or absence of chromium under controlled environmental conditions. Protein, pigment and enzyme analysis were conducted in both Cr-tolerant and Cr-sensitive cultivars of mung bean after 72 h of treatments. Chlorophyll and protein contents were reduced in Cr-sensitive cultivars more than those of the tolerant ones. The enzyme activity varied among the Cr-tolerant and Cr-sensitive ones. Activities of catalase, peroxidase, glucose-6-phosphate dehydrogenase and superoxide dismutase were greater in Cr-sensitive than tolerant cultivars.

Chromium(III) picolinate produces chromosome damage in Chinese hamster ovary cells.

Chromium(III) complexes currently being sold as dietary supplements were tested for their ability to cause chromosomal aberrations in Chinese hamster ovary cells. Complexes were tested in soluble and particulate forms. Chromium picolinate was found to produce chromosome damage 3-fold to 18-fold above control levels for soluble doses of 0.050, 0.10, 0.50, and 1.0 mM after 24 h treatment. Particulate chromium picolinate doses of 8.0 micrograms/cm2 (corresponding to a 0.10 mM solublized dose) and 40 micrograms/cm2 (0.50 mM) produced aberrations 4-fold and 16-fold above control levels, respectively. Toxicity was measured as a decrease in plating efficiency relative to controls. The above treatments produced > or = 86% survival for all doses except 1.0 mM chromium picolinate, which produced 69 +/- 10% survival. Chromium nicotinate, nicotinic acid, and chromium(III) chloride hexahydrate did not produce chromosome damage at equivalent nontoxic doses. Damage was inferred to be caused by the picolinate ligand because picolinic acid in the absence of chromium was clastogenic. Data are evaluated in terms of their relevance to human exposure based on pharmacokinetic modeling of tissue accumulation and are discussed in terms of literature reporting toxic effects of picolinic acid.

The effect of molybdenum on the corrosion behaviour of steel alloy in sea water

The present paper is part of a research program aimed at determining the role played by the molybdenum in steel alloys. Seven different iron-base alloys were used containing molybdenum in the range of 0% to 25% wt. Various corrosion techniques were employed, including: weight loss measurements in static conditions for 3.5% NaCl and seawater and Gulf seawater and quiescent flow conditions with Atlantic seawater, electrochemical measurements (LPR and Tafel Plot) under static and dynamic conditions using 3.5% NaCl and Gulf seawater. The tested samples in all cases were investigated by metallography. The preliminary results indicated that an increase in molybdenum level does not affect the corrosion rate, and that molybdenum alone, in the absence of chromium, is not as effective as originally believed, whilst in the presence of chromium it acts as a triggering agent to enhance the action of the chromium.