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The green synthesis of nanoparticles using plant extracts plays an important role in the field of nanotechnology. The potential of biomolecules present in plant extracts in reducing metal ions to nanoparticles in a single step of green synthesis process is very important. In this study we report on synthesis of Chromium oxide nanoparticles (Cr2O3) by reduction of potassium chromate solution with Manihot esculenta leaf extract. The presence of water soluble carbohydrates which have an aldehyde group may lead the formation of Cr2O3 nanoparticles. The fabricated Chromium oxide nanoparticles were confirmed by UV–Vis spectroscopy, X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM).XRD and UV–Visible absorption studies. The images showed that the size of NPs of Cr2O3 varied with average crystalline size 85–100 nm of nanosized Cr2O3.

Single and co-doped chromium and sulfur TiO2 nanotubes appropriate for photoelectrochemical water splitting application have been prepared and characterized via anodization of titanium foil. The synthesis parameters were optimized by optimization of S and Cr precursor ratio in the anodization electrolyte composition. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy-dispersive spectrometer (EDS) were used to characterize the morphology, crystallinity, and elemental composition of the nanotube samples synthesized. Chromium and sulfur doping affect the morphological and photoelectrochemical properties of samples prepared, as the results indicate. S-doped, Cr-doped, and various Cr-S-co-doped TiO2 nanotubes have enhanced photoelectrochemical activity in comparison with the reference undoped TiO2 nanotube under irradiation by xenon light. Unlike single doped S-TiO2 and Cr-TiO2, Cr-S-co-doped samples show remarkably enhanced photoelectrochemical behavior under identical conditions. The best PEC water splitting performance was shown by sample Cr25S75 prepared by anodizing titanium in in an ethylene glycol solution, which contained 9 mM potassium disulfite and 3 mM potassium chromate, as the sulfur and chromium sources, respectively. This sample showed a photocurrent density of 202 µA/cm2, which is 4.5 times that of the corresponding value for pure and undoped TiO2 nanotube. In addition, the photoelectrochemical behavior of sample Cr25S75 has been investigated using various aliphatic alcohols as sacrificial agent. The trend in the photocurrent density of Cr25S75 was as follows: methanol > ethanol > 1-propanol > 1-butanol > 1-pentanol. The photocurrent density decreased as the number of carbon atoms of the alcohols increased.

We study the currentless diffusion saturation, metal-thermal reduction, and the electrochemical behaviors of chromium- and silicon-containing melts and establish the conditions of synthesis of chromium silicides in the form of superfine powders and coatings. It is shown that the role of limiting stage of the process of diffusion saturation of chromium, molybdenum, and tungsten with silicon in chloride-fluoride melts is played by the diffusion of silicon atoms in the solid phase. In the course of currentless transfer of silicon to metals of group VIB, silicide coatings are formed on their surfaces. The combined reduction of chromium (III) chloride and sodium fluorine-silicate by metallic sodium or magnesium makes it possible to obtain silicide powders. We formulate the conditions required for getting powders of chromium silicides by electrolysis of chloride-fluoride melts containing fluorine-silicate and potassium chromate. The oxidation resistance of the obtained silicide powders is explained by the formation of silicon-oxide layers on their surfaces.

C. citratus, known as zacate de limón (lemongrass), is commonly used in Costa Rica for the treatment of "kidney diseases." Therefore, the activity as renal protector of an aqueous extract of this plant was evaluated after oral administration, in a model of acute kidney injury (AKI) in female Wistar rats. For this, an aqueous extract was characterized by thin layer chromatography and qualitative phytochemical tests. An AKI model induced by potassium chromate in female Wistar rats was carried out. The serum concentration of creatinine, sodium, potassium and glucose were determined, as well as the concentrations of creatinine, sodium, potassium, glucose and proteins in urine, together with the urinary flow determination. A histopathological analysis of the subjects' kidneys was performed, and the presence of kidney damage was identified. The characterization of the extract by thin layer chromatography, and ferric chloride, Shinoda and Wilson tests gave negative results for phenols, tannins and flavonoids. No positive changes were observed in renal function markers in urine. No histopathological evidence of nephroprotective activity of the aqueous extract of C. citratus was found. It is concluded that the aqueous extract of C. citratus obtained by infusion does not possess nephroprotective activity at a dose of 150 mg/kg evaluated by the AKI in female Wistar rats. UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Instituto de Investigaciones Farmacéuticas (INIFAR)

The genotoxic potentials of two water-based oilfield chemicals on edible aroids were investigated. Five accessions of Colocasia eculenta and three accessions of Xanthosoma maffafa were exposed to graded concentrations of sodium azide and potassium chromate; while the accessions without any chemical additive were used as controls. Results revealed that the peak periods of cell division were recorded between 12:00 noon to 4:00 pm in both the treated and control accessions. Metaphase cells increased after prophase cells and continued mostly between 10.00 am and 4.00 pm. Variations observed with the treatments included: shifts of metaphase peaks, high percentages of prophase cells, high intensity of cytoplasmic staining and induction of micronuclei among others. Sodium azide was observed to be a stronger genotoxic substance than potassium chromate. Accession NCe 001 had the highest survival rate while NCe 002 recorded the least rate of survival. Statistical evidence revealed that the difference in various mitotic stages and time of harvest between different accessions and treatments was significant at both 5% and 1%. The study provides useful information that would be used to promote cytogenetic researches as well as the exploitation and improvement of this neglected and underexploited economic plant.

The applicability of radioactive species in high-temperature research as tracers was studied with KBr and an Nb-stabilised austenitic stainless steel. KBr-induced high-temperature corrosion was addressed by using radioactive [82Br]KBr and measuring the radioactivity of the sample surface with a high-resolution phosphor imaging device. Neutron activation by cyclotron proved to be a very cost-effective way to produce radioactive [82Br]KBr with a high radionuclidic purity and a negligible level of unwanted side products. KBr reacts rapidly with steel, forming potassium chromate and metal bromides, both of which are reducing the protective properties of the surface oxide through chromium depletion and increasing porosity.

In this work, the authors have presented a study on the variation in optical parameters that occur on doping Poly-methyl-metha crylate (PMMA) thin films with Potassium chromate (K2CrO4) by different weight percentages (1%,2%, 5% and 10%). These pure PMMA and its composite films are of thickness ∼100m and have been synthesized using the solution cast technique. The absorbance (A) and transmittance (T %) spectra of these films were recorded in the wavelength range (300-1100) nm using EI 2375 UV-VIS double beam spectrophotometer. From the obtained data, the optical parameters viz. absorption coefficient, extinction coefficient), finesse coefficient (F), refractive index (, real and imaginary parts of dielectric constant , optical conductivity and optical energy gap for indirect transition were evaluated and are found to show variation with increase of K2CrO4 concentration in the mentioned wavelength range.

Interactions of the surfaces of potassium chromate crystal nanoparticles with carbon nanotubes and graphene are computationally studied by the electronic structure calculations within the molecular cluster approach. Three types of carbon nanostructures were considered in calculations: single-walled (~ 0.7 nm in diameter) and multiwalled carbon nanotubes (~ 5 nm in diameter), fragments of graphene sheet. Potassium chromate crystal fragments of linear sizes ranging from ~0.5 to ~2 nm (chromate anion and potassium chromate clusters consisting of 1 – 32 formula units of the crystal) were modeled in calculations. The results of the calculations revealed the mechanism of bonding between oxide crystal fragments and carbon nanostructures. It was found that the graphene sheet most effectively interacts with such a surface of the potassium chromate crystal that contains the most possible number of potassium cations. It was shown that the interaction of single-layer graphene sheets with fragments of potassium chromate having linear dimensions of several nanometers leads to significant distortion (twisting) of the graphene sheet. Conclusions regarding the possibility of efficient adsorption of crystal nanoparticles by the surfaces of real carbon nanostructures were made.

A new method has been developed for determination of 210Pb and a simultaneous determination of 210Po and 210Pb was performed in solid samples. 210Po and 210Pb were sequentially leached at 250 °C with HNO3+HF, HClO4 and HCl. Twenty percent of the leaching solution was used for 210Po determination by α-spectrometry after 210Po spontaneous deposition on a silver disc from a weak HCl solution that containing hydroxylamine hydrochloride, sodium citrate and 209Po tracer. The remains of the leaching solution were used for determination of 210Pb, conducted by precipitation as PbCrO4 at about pH

Water fleas constitute major zooplankton population of fresh water aquatic ecosystem. Their population density is an indicative of well-being of aquatic bodies. Simocephalus vetulus (Crustacea - Cladocera) is a tailless water flea and is well suited lab model for environmental monitoring. Copper a Gray listed heavy metals despite being an essential micronutrient, becomes highly toxic when present in excess quantity in aquatic ecosystem thereby causing deleterious effects on aquatic flora as well as fauna. The water-flea exposed to acute 0.37 mg/l (96hr LC50), sub-acute 0.0925 mg/l (25% of 96hr LC50) value and chronic 0.037 mg/l (10% of 96hr LC50) value of copper sulphate and acute 0.16 mg/l (96 hr LC50), sub-acute 0.04 mg/l (25% of 96 hr LC50) value and chronic 0.016 mg/l (10% of 96 hr LC50) value of potassium chromate showed behavioural alterations like initial hyperactivity, fast appendage movements and in phototaxis, geotaxis and avoidance indices. At later stage erratic swimming and spinning, reduced activity, loss of balance, reduced feeding and darkening of cuticular coloration, reduced phototactic, geotaxis and avoidance indices were the major effects on its behaviour. The behavioural alterations of S. vetulus showed the most susceptible and foremost indication of potential toxic effects. Various behavioural parameters, used in present study may serve as better biomarkers about metal toxicity and monitoring of drinking water quality

Phyto-accumulation kinetics of chromium (Cr) was investigated using hydroponic experiments with excised roots or intact rice seedlings exposed to potassium chromate Cr(VI) or chromium nitrate Cr(III). Results showed that the accumulation kinetics was all described by Michaelis-Menten function, whereas very distinct half-saturation constant (KM) and maximal accumulation capacity (vmax) was obtained for the respective Cr species. The comparison of the results from intact rice seedlings to detached roots indicated that transpiration has a stronger influence on Cr(III) transport by rice seedlings. Rice seedlings exposed to Cr(III) showed significantly higher potential for Cr accumulation in plant tissues than these exposed to Cr(VI). Although roots were the major site for Cr accumulation in both Cr treatments, restriction of root-to-shoot Cr translocation was more evident in Cr(III) treatments than Cr(VI) treatments. A remarkable difference in subcellular distribution of Cr in plant materials was observed between the two Cr treatments. Cell walls of rice seedlings exposed to Cr(III) accumulated more Cr in both roots and shoots than organelles and cytosol, whereas cytosol fraction was the largest in roots from the Cr(VI) treatments. Our results suggest that significant differences in uptake, accumulation and translocation pathways for Cr(VI) and Cr(III) exist in rice seedlings.

The effect of potassium chromate (K2CrO4) compound on the inhibitive performance of type A513 mild steel was studied using linear and open circuit polarization technique with µAutolab PGstat101. The structural degradation tendency was observed with high resolution optical microscope. Data obtained from Tafel plot showed that the organic compound performed effectively in acid/chloride solution at all concentration of (K2CrO4) with average inhibitor efficiency above 60%. The outcome of the OCP showed a significant correlation with the LPR trend. The massive influence of the inhibitive compound on steel was seen as a chemisorption mechanism in which the corrosive anions and particulate were supressed significantly. The adsorption of the compound was determined and was found to obey the Langmuir isotherm model. The structural properties generally were affected with high aggressiveness of the acid/chloride ion mix with uniform corrosion propagation observed along the entire interface.

Concrete sludge is an industrial waste slurry containing hydrated cement, aggregates and water. The main components of concrete sludge are CaO, SiO2, Al2O3 and small amounts of metal oxides such as Fe2O3 and MgO. In this study, the calcium component of concrete sludge was used as a raw material for the synthesis of Ca-Al type layered double hydroxide (LDH). The chromate removal ability of the LDH was examined using a potassium chromate solution containing 180 mg/L chromate. The LDH showed a high chromate removal ability with a concentration decrease of up to 0.4 mg/L. The chromate is removed in the form of CrO42 − by anion exchange with NO3− in the Ca-Al NO3 LDH.

The interaction between two chromates [sodium chromate (Na2CrO4) and potassium chromate K2CrO4)] and bovine serum albumin (BSA) in physiological buffer (pH 7.4) was investigated by the fluorescence quenching technique. The results of fluorescence titration revealed that two chromates could strongly quench the intrinsic fluorescence of BSA through a static quenching procedure. The apparent binding constants K and number of binding sites n of chromate with BSA were obtained by the fluorescence quenching method. The thermodynamic parameters enthalpy change (ΔH), entropy change (ΔS) were negative, indicating that the interaction of two chromates with BSA was driven mainly by van der Waals forces and hydrogen bonds. The process of binding was a spontaneous process in which Gibbs free energy change was negative. The distance r between donor (BSA) and acceptor (chromate) was calculated based on Forster's non-radiative energy transfer theory. The results of UV-Vis absorption, synchronous fluorescence, three-dimensional fluorescence and circular dichroism (CD) spectra showed that two chromates induced conformational changes of BSA.

This work is directed for removal of the nondesired species (228Ra, 226Ra, 223Ra, 210Pb, Th(IV) and Fe(III)) in the rare earth chloride (RECl3) liquor before separation of Ln(III). The different factors affecting elimination of radium-isotopes, lead (210Pb), Th(IV) and Fe(III) from the RECl3 liquor, have been investigated and optimized. The results indicated that the activity concentration of radionuclides in RECl3 liquor was above the safe limits required during the separation process of Ln(III). Adjustment of pH 3±0.1 leads to eliminate 14±1% of radionuclides and Th(IV), and 40±3% of Fe(III), while 12±1% of Ln(III) was lost. The developed method shows that more than 95% of the nondesired species was selectively removed when the liquor was eliminated by potassium sulfate or sulfuric acid solutions in presence of Ba/Pb-carrier (1: 1). About 20-83% of Ln(III) was lost when the non-desired species removed by sodium or ammonium sulfate or potassium chromate solutions. Fe(III) interfered with Ln(III) when radionuclides and Th(IV) were eliminated by 2.6M H2SO4 in presence of Ba/Pb-carrier. Finally, use of 0.23M K2SO4 or 2.6M H2SO4 was efficient to reduce level of 228Ra, 226Ra, 223Ra and 210Pb to the safe limits in viewpoint of radiation protection. In addition, the interfered Th(IV) and Fe(III) were also eliminated efficiently from RECl3 liquor before the chemical processing of Ln(III).

A study was made of the effect of synthesis conditions on the properties of a magnetoactive compound obtained by the interaction of iron(II) sulfate with potassium chromate. It was found that, in the formation of the magnetoactive compound, chromium is almost completely coprecipitates with the solid phase. To produce the magnetoactive compound with high relative magnetic susceptibility, it is necessary to precipitate it from the initial solution in no less than 10 min after its preparation at a K2CrO4: FeSO4 molar ratio of 0.16–0.18.

Chemical forms of chromium (Cr) in rice seedlings ( Oryza sativa L. cv. BX139) exposed to either potassium chromate Cr(VI) or chromium nitrate Cr(III) were clarified using a hydroponic study. Seven chemical fractions of Cr in different rice tissues were extracted using a sequential extraction method. Results indicated that exposures to both Cr valents resulted in significant accumulation of Cr in rice tissues and Cr(III) was more bioavailable for rice seedlings than Cr(VI). However, Cr chemical forms were inconsistent in both plant materials (root/shoots) as well as in two different Cr variants. Although both Cr variants caused dose-dependent inhibition on relative growth rates of rice seedlings, different inhibition mechanisms most likely exited using a partial correlation analysis. Both fractions of Cr in cell wall and in intracellular location in roots significantly inhibited the relative growth rates of rice seedlings exposed to Cr(VI), while inhibition of the relative growth rate of rice seedlings exposed to Cr(III) was largely stemmed from Cr partition in intracellular fraction in shoots.

In this research, the chromium (VI) adsorption in potassium chromate (K2CrO4) and potassium dichromate (K2Cr2O7) was studied with the low-cost adsorbent derived from sweet tamarind seeds obtained from the food processing industry in Thailand. The tamarind-seed testa was prepared by decoloring the tamarind-seed husks in boiling water and 1% NaOH solution followed by bleaching in H2O2 solution. The major components found in the tamarind-seed testa were alkali hydrolysable, low molecular-weight carbohydrates. The study found that the adsorbent material derived from tamarind–seed testa could well adsorb chromium ions in both chromium compound solutions at pH 2. The adsorption took place rapidly within the first 4 hours and then gradually declined until reaching adsorption equilibrium in 12 hours. Adsorption of chromium (VI) from potassium chromate solution was superior to that from potassium dichromate. Chromium adsorption at pH 2 fitted well with Langmuir and Freundlich isotherms. The adsorption mechanism in both solutions was a monolayer chemical adsorption rather than multilayer physical adsorption. The adsorbent could almost completely remove chromium in potassium chromate (90% removal) while it could remove 57% chromium from potassium dichromate solution when the initial chromium concentration of 100 mg/l was employed.

Hydroponic experiments were conducted to investigate the influence of chromium (Cr) exposure on assimilation of 15N-labeled nitrate in rice (Oryza sativa L. cv. XZX 45) seedlings. Results showed that exposure of young seedlings to both Cr compounds led to a linear decrease in relative growth rate, nitrate reductase (NR) activity and tissue 15N accumulation though responses differed between the two Cr variants, in which potassium chromate [Cr(VI)] caused more severe effects than chromium chloride [Cr(III)]. Analysis of subcellular distribution of Cr showed that Cr deposition in cell wall was the highest in tissues of rice seedlings exposed to Cr(III), whereas the largest deposition of Cr in the roots was associated with cytosol in the Cr(VI) treatments. Analysis of a partial correlation between tissue fractions of Cr, NR activity and 15N content revealed that depression of NR activity in plant materials of rice seedlings exposed to Cr(III) was mainly associated with a decrease in 15N accumulation, whereas inhibition of NR activity from exposure of plants to Cr(VI) was most likely due to the presence of Cr in cytosol. Information collected here indicated that mechanisms of transport, subcellular distribution and phytotoxicity of the two Cr compounds were different in rice seedlings.

Different Cr–TiO2 nanocomposite photoelectrodes were fabricated by in situ anodisation of titanium in a single step process using potassium chromate as the chromium source. The morphology and structure were characterised by field emission scanning electron microscopy, X-ray diffraction and energy dispersive X-ray spectroscopy. Optical properties were investigated by UV–Vis diffuse reflectance spectra. The visible light photocatalytic activity of the Cr–TiO2 nanocomposite photoelectrodes was evaluated by measuring the degradation of rhodamine B dye under visible light irradiation. The results showed that Cr–TiO2 nanocomposite electrodes have excellent photocatalytic performance. Cr–TiO2 nanocomposite produced using 5 mM K2CrO4 exhibited better photocatalytic activity than did the pure TiO2 and Cr–TiO2 nanocomposite fabricated using other chromium concentrations. The anodisation process developed in this study is facile, reproducible and inexpensive and can be easily scaled up, thereby pioneering the fabric...

The effect of chromium doping on the photovoltaic efficiency of dye-sensitized solar cells (DSSCs) with anodized TiO2 nanotubes followed by an annealing process was investigated. Cr-doped TiO2 nanotubes (CrTNs) with different amounts of chromium were obtained by anodizing of titanium foils in a single-step process using potassium chromate as the chromium source. Film features were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and ultraviolet–visible (UV–Vis) spectroscopy. It is clearly seen that highly ordered TiO2 nanotubes are formed in an anodizing solution free of potassium chromate, and with a gradual increase in the potassium chromate concentration, these nanotube structures change to nanoporous and compact films without porosity. The photovoltaic efficiencies of fabricated DSSCs were characterized by a solar cell measurement system via the photocurrent–voltage (I–V) curves. It is found that the photovoltaic efficiency of DSSCs with CrTNs1 sample is improved by more than three times compared to that of DSSCs with undoped TNs. The energy conversion efficiency increases from 1.05 % to 3.89 % by doping of chromium.

This study examined the microbial precipitations of Cr(III)-hydroxide and Se(0) nanoparticles during anoxic bioreductions of Cr(VI) and Se(VI) using metal-reducing bacteria enriched from groundwater. Metal-reducing bacteria enriched from groundwater at the Korea Atomic Energy Research Institute (KAERI) Underground Research Tunnel (KURT), Daejeon, S. Korea were used. Metal reduction and precipitation experiments with the metal-reducing bacteria were conducted using Cr(VI)- and Se(VI)-contaminated water and glucose as a carbon source under an anaerobic environment at room temperature. XRD, SEM-EDX, and TEM-EDX analyses were used to characterize the mineralogy, crystal structure, chemistry, shape, and size distribution of the precipitates. The metal-reducing bacteria reduced Cr(VI) of potassium chromate (K₂CrO₄) to Cr(III) of chromium hydroxide [Cr(OH)3], and Se(VI) of sodium selenate (Na₂SeO₄) to selenium Se(0), with changes of color and turbidity. XRD, SEM-EDX, and TEM-EDX analyses revealed that the chromium hydroxide [Cr(OH)₃] was formed extracellularly with nanoparticles of 20–30 nm in size, and elemental selenium Se(0) nanoparticles had a sphere shape of 50–250 nm in size. These results show that metal-reducing bacteria in groundwater can aid or accelerate precipitation of heavy metals such as Cr(VI) and Se(VI) via bioreduction processes under anoxic environments. These results may also be useful for the recovery of Cr and Se nanoparticles in natural environments.

Corrosion is one of the degradation materials in Industrial problem. One of the processing to choose material is to determine how to have resistance to all the environment. This research is carried out to determine characterize the effect of various temperatures (150, 200, 250 °C) and time (4,6 and 8 hours) of exposure of Low Carbon Steel in corrosion rate and mechanical properties by using Mass Balance method and Potassium Chromate vapor as medium corrosion. The results have been shown that the increasing temperature ids increasing corrosion rate which is the maximum value is 5,1215 x 10−4 miles/years. The difference in corrosion rate increasing by 6,3 % based on increasing temperature. The microstructure has shown is intergranular corrosion mode.

In order to investigate the toxicological properties of river pollutants, potassium chromate (K2CrO4) and cadmium nitrate tetrahydrate (Cd (NO3)2·4H2O) were selected as they are commonly discharged from industry to nearby rivers. This paper studied the Median Lethal Concentration (LC50) of the pollutants to the adult red zebrafish by acute toxicity experiments within 96 hours. 120mg/L, 130mg/L, 140mg/L, 150mg/L, 160mg/L, 170mg/L potassium chromate solutions and 16mg/L, 20mg/L, 24mg/L, 28mg/L 32mg/L, 36mg/L cadmium nitrate tetrahydrate solutions were prepared with triplicates to determine the LC50. The results of the preliminary experiments and the calibration curves suggested that the LC50 of potassium chromate and cadmium nitrate tetrahydrate were 165 mg/L and 28 mg/L respectively. The toxicity of thresholds and LC100 were also evaluated. Through the observations of the tested subjects in morphological, ethological and anatomical manners, behavioural alterations, oxidative stress, and immunotoxicity were probably their major causes of death.

The common ice plant (Mesembryanthemum crystallinum L.) is a widely studied model due to its tolerance to numerous biotic and abiotic stresses. In this study, carried out in model pots, the plants were treated with variant doses of Cd(II) and Cr(VI) and proved resistant to extreme levels of these heavy metals. Initial toxicity symptoms were observed upon final concentrations of 818 mg Cd kg&minus, 1 soil d.w., and 1699 mg Cr kg&minus, 1 applied as potassium chromate. Biometric analyses revealed that none of the Cr(VI) doses affected dry weight of the plant organs thus maintaining the shoot-to-root ratio. The Cd and Cr hypertolerance strategies were divergent and resulted in different accumulation patterns. For the case of Cd(II), an excluder-like mechanism was developed to prevent the plant from toxicity. For chromate, high accumulation potential together with Cr(VI) root-to-shoot translocation at sublethal concentrations was revealed (up to 6152 mg Cr kg&minus, 1 shoot at 4248 mg Cr kg&minus, 1 soil). It is concluded that M. crystallinum reveals considerable phytoremediation capabilities due to unique growth potential in contaminated substrates and is suitable for bioreclamation of degraded soils. The plant is especially applicable for efficient phytoextraction of chromate-contamination, whereas for Cd-affected areas it may have a phytostabilizing effect.

The effect of inhibitor concentration and immersion time on the corrosion rate and inhibition efficiency of AISI 1019 steel in seawater environment were investigated by means of weight loss measurement (WLM) at an interval of 6days for a period of 60 days. AISI 1019 steel were immersed in seawater solution in the absence and presence of varying inhibitor concentrations of potassium chromate (PC), Sodium Nitrite (SN), Methyl Orange (MO), Methyl Red (MR), Terminalia Catappa Leaves (TCL) Extract, Carica papaya Leaves (CPL) Extract. The results showed that there is an increase in inhibition efficiency with increase in inhibitor concentration and decrease in inhibition efficiency with increase in immersion time. The inorganic inhibitor (potassium chromate), inorganic inhibitor (Sodium Nitrite), the organic Inhibitor (Methyl Orange), the organic inhibitor (Methyl Red), the green inhibitor (Terminalia Catappa Leaves) and green inhibitor (Carica Papaya Leaves) produced their best inhibition efficiency of 71.94%, 634%, 68.94%, 68.32%, 62.7%, 59.79% respectively at a concentration of 10g/L. From the result obtained, the potassium chromate inhibitor has better inhibitory property than other inhibitors, which revealed that it is best suited for inhibition of corrosion of mild steel in seawater environment.

Herein, we successfully prepared ternary ZnO/AgBr/Ag 2 CrO 4 nanocomposites with tandem n–n heterojunctions as novel visible-light-driven photocatalysts having excellent activity. The preparation method is a facile and low temperature and employs zinc nitrate, silver nitrate, sodium hydroxide, and potassium chromate as starting materials without using any post-preparation treatments. The resultant samples were characterized using XRD, EDX, SEM, TEM, UV–vis DRS, FT-IR, and PL techniques. The results revealed that weight percent of Ag 2 CrO 4 has substantial influence on degradation of rhodamine B under visible-light irradiation and the best activity was observed for the ZnO/AgBr/Ag 2 CrO 4 (20%) nanocomposite. Photocatalytic activity of this nanocomposite is about 16 and 7-fold higher than those of the ZnO and ZnO/AgBr samples. Increase of the photocatalytic activity was attributed to more harvesting of the visible-light irradiation and efficiently separation of the photogenerated charge carriers due to formation of tandem n–n heterojunctions between counterparts of the nanocomposite. Moreover, the preparation time and calcination temperature significantly affect the photocatalytic activity. Based on the trapping experiments, it was shown that superoxide ions and holes have major influence on the degradation reaction.

This study investigated the performance of Amberlite IRC 748 resin in removing calcium ions from highly concentrated potassium chromate solution in a fixed bed column. The exchange capacity increased with initial calcium ion concentration and bed height but decreased as flow rate increased. Four different kinetic models, specifically the bed depth service time (BDST), mass transfer, Thomas, and Yoon-Nelson models, were applied to the experimental data to predict the breakthrough curves and determine the column parameters. The BDST model was extended to the prediction of service times of columns operated at different flow rates and influent concentrations; while the experimental and theoretical data points followed a similar trend, they deviated slightly from each other. The Thomas and Yoon-Nelson model predictions were in very good agreement with the experimental results for all the process parameters studied, indicating that they are suitable for use with these kinds of columns. (C) 2015 Elsevier B.V. All rights reserved.

In this study, Bismuth-based glasses were prepared and doped with various concentration of potassium chromate. They were melted in an electrical furnace at 1250°C for 4 hours then pressed with fire frame to plate shape and annealed at 500°C for 10 min. Optical spectra were used to analyze color shade of glasses. Homogeneity of glasses was analyzed by birefringence technique. Glasses color was changed from colorless to slightly and opaque green with an increasing amount of potassium dichromate and birefringence result showed that the glasses are non-homogenous.

Polyvinyl alcohol/potassium chromate (K2CrO4) composite films were prepared by solution casting technique using distilled water as a solvent, and were further investigated using Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, X-ray diffraction, thermogravimetric analysis, optical microscopy, scanning electron microscopy, and dielectric measurements. Microscopic studies reveal that K2CrO4 was homogenously mixed with polyvinyl alcohol matrix due to interfacial interaction between polyvinyl alcohol and K2CrO4. The composite films showed very high dielectric constant and relatively low dielectric loss. Hence, such composite materials with improved dielectric properties could be useful for fabrication of electrical charge storage device.

Cr-doped TiO 2 nanotubes (Cr–TiO 2 NTs) with different amounts of chromium were obtained directly by the electrochemical anodic oxidation of titanium foils in a single-step process using potassium chromate as the chromium source. The effects of chromium amount in anodizing solution on the morphologies, structure, photoabsorption and photoelectrochemical water splitting of the TiO 2 nanotube array film were investigated. Diffuse reflectance spectra showed an increase in the visible absorption relative to undoped TiO 2 NTs. The photoelectrochemical performance was examined under visible irradiation in 1 M NaOH electrolyte. Photo-electrochemical characterization shows that chromium doping efficiently enhances the photo-catalytic water splitting performance of Cr-doped TiO 2 nanotube samples. The sample (Cr–TiO 2 NTs-1) exhibited better photo-catalytic activity than the undoped TiO 2 NTs and Cr–TiO 2 NTs fabricated using other chromium concentrations. This can be attributed to the effective separation of photogenerated electron–hole upon the substitutional introduction of appropriate Cr amount in to the TiO 2 nanotube structure.

The degradation efficiency and kinetic degradation reaction of Ponceau 6R dye using potassium chromate have been investigated under various experimental conditions: different concentrations of H 2 SO 4 and temperatures. The immediate change of the red coloration ( λ max = 518 nm) to colorless was observed after addition of inorganic oxidizing agent (K 2 CrO 4 ) into the protonated form of Ponceau 6R dye after 48 h. This observation could be attributed to the highest oxidized form of this dye obtained (the quinoid one), which undergoes a hydrolysis reaction to produce p -hydroquinone (H 2 Q) by a mechanism similar to Schiff-base hydrolysis. The cationic form of this matrix is a crucial feature for the hydrolysis process. A kinetic model for oxidation of Ponceau 6R by the combination of chromate was developed based on experimental results. The observed kinetic reaction coefficient was determined and correlated as a function of UV spectral intensity of Ponceau 6R at 518 nm. The degradation rate follows pseudo-first order kinetics with respect to dye concentration.

Effect of chromium (both CrIII and CrVI) were studied on the oxidative damages and the induction of antioxidant defence in turnip. For this purpose turnip (Brassica rapa L.) plants were grown in refined sand under three different sources of chromium, i.e., chromium sulphate (CrIII), potassium chromate (CrVI) and potassium dichromate (CrVI) supplied at 250 µM concentrations for 4, 24 and 168 h (7 days) after 50 days of growth in normal nutrition. The extent of oxidative damage was most in dichromate as it caused a maximum increase in lipid peroxidation and H2O2 concentration in leaves of turnip plants. The growth and biomass of plants decreased, while the levels of chloroplastic pigment and iron increased in plants supplied CrVI (both potassium chromate and potassium dichromate). Exposure of plants to Cr led to increase in Cr concentration, more in the roots than in shoots. Excess supply of Cr (chromium sulphate, potassium chromate and potassium dichromate), though inhibited peroxidase activity (at 4 and 168 h exposure), stimulated catalase, ascorbate peroxidase and superoxide dismutase activities. Localization of different isoforms of APX and SOD on native gels revealed activation of certain isoform in the Cr-treated plants.

Dissolution characteristics of copper in hydrochloric acid medium and the effect of potassium chromate and sodium molybdate on the corrosion process have been studied using potentiodynamic technique, and Electro impedance spectroscopy (EIS). corrosion current density ( I corr) were obtained by Tafel extrapolation technique. Charge transfer resistance (R ct) was obtained from the electrochemical impedance spectroscopy (EIS). The corrosion rate was retarded in presence of sodium molybdate mainly because of the adsorption of the inhibitor on the electrode surface and it was found that the optimum concentration of this inhibitor in 1 M HCl was 0.008 M with an protection efficiency 79.17%, while the corrosion rate was accelerated in presence of potassium chromate.

The oxidizing roasting of carbon ferrochrome in the presence of potassium carbonate and air was investigated. The effects of reaction temperature, reaction time, ratio of alkali-to-ore were studied, together with a discussion of the thermodynamics and macro kinetics. It is observed that the reaction temperature and reaction time have significant influence on the roasting reaction. The reaction mechanism changes greatly as the temperature varies. A two-stage roasting process is favorable for the roasting reaction, and a recovery ratio of 96.51% is obtained through this two-stage roasting method. The chromium residue yielded from this method is quite little, only one third of the product. Moreover, the component of Fe in the residue is as high as 54.28%. Therefore, it can be easily recovered to produce sponge iron, realizing zero-emission of chromium residue.

The corrosion behaviour of a FeCrAl alloy was investigated at 600 °C in O2 + H2O with solid KCl applied. A kinetics and microstructural investigation showed that KCl accelerates corrosion and that potassium chromate formation depletes the protective scale in Cr, thus triggering the formation of a fast-growing iron-rich scale. Iron oxide was found to grow both inward and outward, on either side of the initial oxide. A chromia layer is formed with time underneath the iron oxide. It was found that although the alloy does not form a continuous pure alumina scale at the investigated temperature, aluminium is, however, always enriched at the oxide/alloy interface.

The oxidizing roasting process of carbon ferrochrome to prepare potassium chromate in the presence of potassium carbonate and air was investigated. The effects of reaction temperature, reaction time, mole ratio of potassium carbonate to carbon ferrochrome were studied, and thermodynamics and kinetics were also discussed. It was observed that the reaction temperature and reaction time had a significant influence on the roasting reaction of carbon ferrochrome. The reaction mechanism changed greatly as the temperature varied. A two-stage roasting process was favorable for the roasting reaction, and a chromium recovery rate of 97.06% was obtained through this two-stage roasting method. The chromium residue yielded from this method was only 1/3 of the product. Moreover, the component of Fe in the residue was as high as 55.04%. Therefore, it can be easily recovered to produce sponge iron, realizing complete detoxication and zero-emission of chromium residue.

Al-Mg alloys can precipitate β phase, Mg2Al3, along grain boundaries during long-term exposure to moderate temperatures, resulting in susceptibility to intergranular corrosion. It is of interest to investigate the corrosion inhibition of this alloy in this sensitized condition. Furthermore, recent work has shown that the presence of an altered surface layer (ASL) affects the corrosion behavior of polished AA5083, making it difficult to determine the effectiveness of corrosion inhibitors. The combined effects of the presence of the ASL and inhibitors are not well understood. In this work, the effects of adding potassium chromate (K2CrO4), sodium silicate (Na2SiO3), and sodium vanadate (NaVO3) to NaCl solution were examined using electrochemical methods on sensitized and solutionized AA5083 with and without the ASL present on the surface. The ASL alone may protect the alloy depending on whether or not the alloy was sensitized. All of the tested inhibitors exhibited a suppression of the cathodic reaction, with chromate causing mixed inhibition on sensitized AA5083 without the ASL present. The composition and surface morphology of samples exposed to inhibitors were also investigated. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. [DOI: 10.1149/2.0501509jes] All rights reserved.

The very early stages of KCl-induced corrosion of a FeCrAl and a FeNiCrAl alloy in an 0211420 environment were studied using in-situ Environmental Scanning Electron Microscopy (ESEM). The samples were KCl contaminated and then exposed to lab air at a total pressure of 4.8 Ton at 450 degrees C. After exposure, the samples were analyzed using SEM-EDX, FIB and STEM-EDX. For both alloys, fast oxide growth occurred at the KCl particles. Far away from the KCl particles, a thin base oxide formed with potassium chromate nodules on top. The base oxide was layered, consisting of iron-chromium oxide on top and alumina in the bottom part. The FeCrAl alloy suffered internal oxidation while the FeNiCrAl did not. Both alloys formed sub-scale chlorides. A mechanism is proposed for the reaction of KCl on the surface and for the formation of different surface features at the KCl particles.

We systematically compared the impacts of four Cr salts (chromic chloride, chromic nitrate, potassium chromate and potassium bichromate) on physiological parameters and chlorophyll fluorescence in indigenous moss Taxiphyllum taxirameum. Among the four Cr salts, K2Cr2O7 treatment resulted in the most significant decrease in photosynthetic efficiency and antioxidant enzymes, increase in reactive oxygen species (ROS), and obvious cell death. Different form the higher plants, although hexavalent Cr(VI) salt treatments resulted in higher accumulation levels of Cr and were more toxic than Cr(III) salts, Cr(III) also induced significant changes in moss physiological parameters and chlorophyll fluorescence. Our results showed that Cr(III) and Cr(VI) could be monitored distinguishably according to the non-photochemical quenching (NPQ) fluorescence of sporadic purple and sporadic lavender images respectively. Then, the valence states and concentrations of Cr contaminations could be evaluated according to the image of maximum efficiency of PSII photochemistry (Fv/Fm) and the quantum yield of PSII electron transport (ΦPSII). Therefore, this study provides new ideas of moss's sensibility to Cr(III) and a new method to monitor Chromium contaminations rapidly and non-invasively in water.

Sodium content of foods can be determined by various methods, including an ion-selective electrode (ISE), the Mohr or Volhard titration procedure, or indicator test strips. Some of these methods are official methods of analysis for specific products, and all these methods are faster and less expensive procedures than analysis by atomic absorption spectroscopy or inductively coupled plasma-optical emission spectroscopy. This laboratory exercise allows one to compare sodium analysis of several food products by ISE, Mohr titration, and Quantab® Chloride Titrators.

The main industrial application s of heavy metals in leather and textile manufacturing, electro painting, corrosion inhibitio n, plating, glassware - cleaning solutions and the production of pigments has increase d concentration of hexavalent chromium in the environment that lead to a serious problem to the ecosystem. Since, h exavalent chromium is found to be toxic in human beings. The present study has been designed to determine hexavalent chromium induced bio molecular changes in Spirulina platensis . Spirulina platensis, a filamentous cyanobacterium known as blue green algae of aquatic ecosystem has high economic importance due to i ts therapeutic potential. Blue green algae , Spirulina platensis was exposed to different concentration (0.01, 0.1, 1, 5, and 10 mg/l) of hexavalent chromium as potassium chromate and observed for different growth parameters for 9 days of incubation period. The concentration variation of carbohydrate, protein and chlorophyll - a pigment in Spirulina platensis was observed in the presence of chromium. T he growth of Spirulina platensis was inhibited upon exposure of different concentrations of chromium. Maximum growth inhibition was observed in 10 mg/l of chromium treated cells as compared to control. The extent of toxicity increased wi th increasing concentration of c hromium along with exposure time.

The effect of several important parameters on the removal of hexavalent chromium by humic acid was evaluated using an optimal experimental design based on Box-Behnken Response Surface method. The factors included temperature、pH、initial potassium chromate concentration and adsorbent dosage. A quadratic model for predicting the optimum removal conditions was derived, and the obtained optimal parameters were temperature 51°C, pH=2.34, initial potassium chromate concentration 14.30mg/L and adsorbent 0.58g. At the optimal conditions, the maximal removal rate of hexavalent chromium reached 73.17 %( forecast value was 73.26%).

Phase equilibria of the system KOH–K2CrO4–K2CO3–Al2O3–H2O and its subsystems were investigated at 150 °C in the high alkali concentrated region. In the concentrated alkali region of the system and its subsystems KOH–K2CrO4–Al2O3–H2O and KOH–K2CO3–H2O, the equilibrium solid-phase K2CO3·1.5H2O was found. In the concentrated alkali region of the complex system, potassium aluminate and K2CO3 play an evident salting-out role to potassium chromate, respectively, and their combined operation lowers the solubility of K2CrO4. The solubilizing effect of K2CrO4 on Al2O3 in the system KOH–K2CrO4–Al2O3–H2O is similar to that of Na2CrO4 on Al2O3 in the system NaOH–Na2CrO4–Al2O3–H2O. These findings can provide a significant and precious database for the production of K2CrO4 and K2CO3 and the recovery of alumina from a concentrated alkali solution.

In this paper, effect of potassium-chromate (K 2 CrO 4 ) and sodium-nitrite (NaNO 2 ) on concrete steel-rebar degradation in sulphuric-acid and in sodium-chloride media were studied. Electrochemical monitoring of open circuit potential and compressive strength effect of the different concentrations of these admixtures in steel-reinforced concretes immersed in the acidic/marine-simulating environments were analysed for detailing admixture performance. Results subjected to ASTM C876 interpretations showed that concrete admixed with 0.145 M potassium-chromate exhibited optimum inhibition effectiveness with good compressive strength improvement in the acidic medium. In the saline medium, the concrete admixed with 0.679 M sodium-nitrite exhibited optimal inhibition performance, but with reduction in concrete compressive strength.

A series of CuFe2O4 nanoparticles was synthesized with the assistance of organic amines or inorganic bases via a hydrothermal method. The prepared samples were confirmed as a spinel-type structure by x-ray diffraction. The shapes of the samples were detected by transmission electron microscope (TEM), which confirmed that all the synthesized samples were nanoparticles. The electrocatalytic properties of the samples modified on a glassy carbon electrode were investigated for the reduction of p-nitrophenol, potassium chromate (K2CrO4), and sodium nitrite (NaNO2) in basic solution using the cyclic voltammetry method. The results showed that all the samples showed enhanced catalytic activity for the reduction of p-nitrophenol, K2CrO4, and NaNO2. Among the samples, CuFe2O4 prepared with cyclohexylamine (S-2) showed the highest catalytic activity for p-nitrophenol reduction, whereas CuFe2O4 prepared with NaOH and PVP (S-4) showed the highest activity for both K2CrO4 and NaNO2 reduction in basic solution.