Thermodynamics and density functional theory study of potassium dichromate interaction with galena

The adsorption heat and reaction rate constant of potassium dichromate on the surface of galena were studied. The results indicate that potassium dichromate tends to adsorption on the galena surface. The reaction order is only 0.08385, suggesting that the concentration of potassium dichromate has little influence on its adsorption on the galena surface. In addition, the simulation of CrO2 4- adsorption on the PbS （100） surface in the absence and presence of O2 was carried out by density functional theory （DFT）. The calculated results show that CrO2 4- species adsorb energetically at the Pb-S bond site, and the presence of O2 can enhance this adsorption.

Two Types of Potential Oscillation During the Reduction of Dichromate on Gold Electrode in H2SO4 Solution

Two different types of potential oscillations have been identified for the first time during dichromate reduction on a gold electrode in a solution of dilute sulfuric acid. One occurs before hydrogen evolution due to the formation and dissolution of passivating films of low-valence chromium oxides, and the other generates, accompanying periodic hydrogen evolution, from the coupling of electrochemical reactions with diffusive and convective mass transport. More interestingly, these two types of oscillations correspond to two crossing loops in the cyclic voltammogram （CV）. Such a relation of oscillations with crossed CVs will provide a new way to find electrochemical oscillatory systems systematically and rapidly.

Synthesis of Nicotinic Acid by Potassium Dichromate Oxidation

Nicotinic acid was synthesized from 3 methylpyridine with potassium dichromate as the oxidant. The reaction conditions, the product separation and analysis were studied. The results indicate that under the certain reaction conditions, the yield of nicotinic acid can reach 67.4%, the conversion can reach 99.7% and the selectivity can be as high as 99.8%. The final product has a high purity.

Flow Injection Determination of Oxalate Based on Its Catalytic Effect on the Oxidation of p-Chloride Aniline by Dichromate

In a sulfuric acid medium, oxalate exhibits a strong catalytic effect on the oxidation of p-chloride aniline(ClBN) by dichromate, and the red oxidation product of ClBN has a maximum absorhancy at 520 nm. Based on this founding, a new FI method for determining oxalate was developed. A calibration curve of oxalate in the range of 0.40—17.0μg/mL was obtained. The detection limit was 0.10μg/mL. Sampling rate was 103-samples/h. The possible interference by the co-existing substances or ions was examined. This new method was applied to the determination of micro amounts of oxalate in real samples with satisfactory results.

Protective effect of Citrus reticulata peel extract against potassium dichromate-induced reproductive toxicity in rats

Objective:To study the protective effect of Citrus reticulata peel extract against potassium dichromate-induced reproductive impairment in male Wistar rats.Methods:A total of 35 male Wistar rats were equally divided into 5 groups.The control group orally received an equivalent volume of saline(1 mL);group 2 was given potassium dichromate at 10 mg/kg/body weight(b.w.)orally for eight weeks;group 3 and 4 orally received Citrus reticulata peel extract at 200 and 400 mg/kg/b.w.respectively,followed by treatment with potassium dichromate.Group 5 was administered with 400 mg/kg/b.w.Citrus reticulata peel extract only.The parameters including oxidative stress(malondialdehyde,antioxidant enzymes),sex hormones(testosterone,luteinizing hormone,follicle-stimulating hormone)and inflammation indexes(tumor necrosis factor-alpha,inter leukin 6)were measured.Sperm characteristics(sperm morphology,motility and count)were also determined.Results:The decrease of male sex hormones concentration in plasma(testosterone,luteinizing hormone),testicular antioxidant parameters(reduced glutathione,catalase,superoxide dismutase,carnitine),sperm motility and sperm count induced by potassium dichromate was mitigated by Citrus reticulata peel extract.Moreover,the peel extract alleviated the increase of sperm abnormalities,follicle-stimulating hormone,testicular malondialdehyde,tumor necrosis factor-alpha and nitric oxide levels caused by potassium dichromate.The sections of rats treated with the potassium dichromate were characterized by some histopathological changes as disorganization of spermatogonial cell layers and deformation of Leydig cells.A positive immune-reaction for p53 was observed in testicular cells of the rats treated with potassium dichromate.The extract of Citrus reticulata peel improved the testicular histology and decreased p53 positive immune-reaction in potassium dichromate administered rats.Conclusions:Citrus reticulata peel extract can alleviate the reproductive toxicity triggered by potassium dichromatevia its antioxidant and anti-inflammatory properties.Citrus reticulata peel extract may act as a new natural prophylactically agent for the treatment of potassium dichromate-induced testicular damage.

Effects of Crassocephalum bauchiense (Hutch) leaf aqueous extract on toxicity indicators and reproductive characteristics in Oryctolagus cuniculus exposed to potassium dichromate

Objective:To evaluate the effects of Crassocephalum(C.)bauchiense(Hutch)leaf aqueous extract on the biochemical markers of toxicity,oxidative stress indicators and reproductive parameters in rabbit does(Oryctolagus cuniculus)exposed to potassium dichromate.Methods:A total of 36 nulliparous and sexually mature female rabbit does,aged 8 months and weighing 2.8-3.0 kg,were divided into 6 groups of 6 animals.After mating,group T0 received distilled water(1 mL/kg body weight),while groups T0-,VC100,AE100,AE200 and AE400 were treated with 40 mg/mL/kg body weight of potassium dichromate.In addition,group VC100 received 100 mg/mL/kg body weight of vitamin C,while groups AE100,AE200 and AE400 received aqueous extract of C.bauchiense leaves at 100,200 and 400 mg/mL/kg body weight,by oral gavage for 27 days,respectively.On the 28th daypost-co?tum,animals were sacrificed.Biochemical indicators such as creatinine,urea,alanine amino tranferase,aspartate amino transferase,total protein and total cholesterol were measured by using a spectrophotometer.Follicle stimulating hormone,luteinizing hormone and progesterone were measured by enzyme-linked immuno sorbent assay.Oxidative stress markers like malondialdehyde,catalase,superoxide dismutase and total peroxidase in ovary homogenates were measured by spectrophotometer.Results:Serum concentrations of urea,creatinine,alanine aminotransferase,aspartate aminotransferase and total cholesterol were significantly higher(P<0.05),and total protein level was significantly lower in T0-group(receiving potassium dichromate only)compared to other groups.Administration of ethanolic extract of C.bauchiense significantly decreased serum concentrations of urea,creatinine,alanine aminotransferase,aspartate aminotransferase and total cholesterol,and significantly increased total protein level.However,ethanolic extract of C.bauchiensehad no significant effect on the foetotoxic characteristics.The serum concentrations of follicle stimulating hormone and luteinizing hormone were significantly(P<0.05)lower in T0-group as compared to the control group while progesterone were comparable(P>0.05)among all groups;C.bauchiense leaf extracts significantly(P<0.05)increased the level of follicle stimulating hormone,but the increase in luteinizing hormone was not significant(P>0.05).Catalase and total peroxidase activities significantly decreased(P<0.05),and malondialdehyde significantly increased in T0-group compared to other groups.The administration of C.bauchiense leaf extracts significantly(P<0.05)increased the activities of catalase and peroxidase.Conclusions:Potassium dichromate-induced oxidative stress involves in hepatotoxicity,nephrotoxicity and reprotoxicity.The aqueous extract of C.bauchiense leaves could mitigate these adverse effectsvia antioxidant properties.

Potassium Dichromate Surface Modification of Polyglycolic Acid (PGA) Multifilament

For improving its hydrophilicity and biocompatibility,and preserving filament mechanical properties at the same time,polyglycolic acid( PGA) filament was modified by potassium dichromate solution with different processing time. Breaking force and water contact angle were tested. Surface changes before and after surface modifications were tested with scanning electron microscopy(SEM). Furthermore,differential scanning calorimeter(DSC) and Fourier transform infrared spectrometry(FTIR) were used to analyze the changes of molecular structure and functional group. Experimental results showed that 6 min was the most suitable time for improving hydrophilicity of PGA filament and preserving its mechanical properties.

Effects of Potassium Dichromate on Distribution of Toxocara canis Larvae within Brain of Mice

The frequency of the infective larvae of Toxocara canis, the common parasite of the dog was assessed in brain portions of male Albino mice ingested two doses： 200 mg/Kg and 400 mg/Kg of potassium dichromate-hexavalent （VI） as an indicator. Only 2,000 ova of the parasite were inoculated orally to twenty seven healthy young male mice. Frequency of the parasite was tested 13 weeks post-inoculation. Using bio-statistical analysis （one way analysis of variance） the frequency of detected larvae of both doses in the brain portions of the experimental animals showed an insignificant difference （P〉 0.05） in comparison with control. The results indicate the safety of small and mild intoxication doses of the potassium dichromate on distribution of Toxocara canis in brain portions of mice.

Photocatalytic reduction of dichromate by titanium dioxide supported on hollow glass microbeads

The photocatalytic reduction of dichromate using TiO2/beads as a photocatalyst was studied. The results showed hat 3.8 × 104 mol/dm3 of dichromate can be completely reduced into Cr3+ after illumination far 35 min with a 375 W medium pressure mercury lamp. The effects of factors such as the amount of TiO2/beads, initial concentration of dichromate, initial pH, nitrogen and oxygen atmosphere, and concentration of Fe3+ on the photocatalytic reduction of dichromate were investigated. A possible mechanism of the photocatalytic reaction was proposed. After illumination for 200 h, no significant loss of photocatalytic activity of TiO2/beads was observed.

Preliminary Study on a Novel Process for Manufacturing Soda Ash from Sodium Sulfate

The purpose of this work is to find a new way for utilizing the rich sodium sulfate resource to produce soda ash. A novel process is proposed which uses aqueous dichromate solution as working medium through decomposition of calcium carbonate in aqueous sodium dichromate, complex decomposition of aqueous sodium sulfate and calcium chromate, regeneration of sodium dichromate and production of sodium bicarbonate from carbonation of aqueous sodium chromate solution, processing and utilization of byproduct calcium sulfate, and production of sodium carbonate from sodium bicarbonate. The process has the features of less corrosion and pollution and low energy consumption.

The Spectral VEP in Normal Subjects and Dichromats

The spectral VEP in 13 normal subjects(25 eyes),four cases(8eyes)of protanopes and 8 cases(15 eyes)of deuteranopes were tested.Innormal subjects,the shortest latencies of N1,P1,N2 were in 560 nm and thegreatest amplitudes of N1-P1 and P1-N2 were in 560-570 nm,around which thelatencies were delayed and the amplitudes were decreased as the wave-lengthes of stimulative light increased or decreased gradually.The spectralVEP pattern of deuteranopes was similar to the normal subjects.In theprotanopes,the shor...

Synthesis of Chromium(III) Oxide Nanoparticles by Electrochemical Method and Mukia Maderaspatana Plant Extract, Characterization, KMnO₄Decomposition and Antibacterial Study

Chromium oxide nanoparticles were synthesized by the reduction of potassium dichromate solution with Mukia Maderaspatana plant extract. In electrochemical methods, Cr2O3 nanoparticles were synthesized by two ways, using platinum (Pt) electrodes and K2Cr2O7 solution with H2SO4 as medium in the first case. And chromium doped platinum electrode (Pt/Cr) in presence of NaHCO3 solution in second case. The resulting Cr2O3 nanoparticles were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), UV-VIS absorption and Fourier-transform infrared (FTIR) spectroscopy. The enhancing influence of Cr2O3 nanoparticles as a catalyst for the decomposition of KMnO4 has been studied. The antibacterial effect of Cr2O3 nanoparticles against E. coli was investigated. These particles were shown to have an effective bactericide.

Migration of Cr_2O_7^(2-) and Butanone in Soil and Groundwater System After the Tianjin Port 8·12 Explosion

After the Tianjin Port 8.12 explosion, an enormous amount of potassium dichromate （K2Cr2O7） and butanone （CH3COCH2CH3） leaked into the coastal soil-groundwater system, which potentially threatened the environment and human health. Determining the transport process of hazards is necessary to establish guidelines for remediating the contaminated area. This work aims to investigate the migration of potassium dichromate and butanone in the coastal soil-groundwater system through a coupling unsaturated-saturated numerical model, incorporating the HYDRUS model into the MODFLOW/ MT3D model. In the unsaturated zone, two-dimensional HYDRUS model was applied, and its recharge flux at the bottom boundary was utilized as the input of MODFLOW/MT3D model in the saturated zone. Results showed that Cr2O^（2-）7 migrated much faster than butanone in the unsaturated zone and reached the water table in about 1 year. In comparison, butanone was unlikely to enter the aquifer even 5 years later with a migration depth of about 2.2 m. Driven by groundwater, the Cr2O^（2-）7 that entered the aquifer migrated about 161 m toward southeast 5 years later. In the saturated zone, the contamination plume covered mainly the southeast area due to the groundwater flow direction.

Chromate and the Environment： Removal and Utilization of Industrial Waste

Chromate and dichromate sodium as a function of oxidizer characteristics are used in several industrial areas; for example, in surface protection of coated parts of cadmium, zinc and aluminum （chromate coated treated）, corrosion inhibitors, the treatment of leather, the manufacture of pigments, etc. However, the use of such products has been questioned due to the problems of toxicity and pollution that can be caused in the environmental. The Brazilian environmental agency has established that the concentrations of chromate in water courses are less than 0.5 ppm. In order to reuse chromate （CrO42） from industrial effluent, laboratory experiments have been proposed based on chemical reduction or electrolytic processes, in order to transform these chromate ions in a final mix of oxides （in solid form）, which can then be packed and sent to the production process of sodium chromate. The results of these experiments have become useful industrially （without regard to costs） considering the environmental reuse and the life cycle of the chemical compound.

Application of H-Point Standard Addition Method and Multivariate Calibration Methods to the Simultaneous Kinetic-Potentiometric Determination of Cerium(IV) and Dichoromate

A kinetic-potentiometric method for simultaneous determination of Cerium(IV) and dichoromate (Cr2O72-) by H-point standard addition method (HPSAM), partial least squares (PLS) and principal component regression (PCR) using fluoride ion-selective electrode (FISE) is described. In this work, the difference between the rate of the oxidation reaction of Fe(II) to Fe(III) in the presence of Ce4+ and Cr2O72- is based of the method. The rate of consume fluoride ion for making complex is detected with a FISE. The results show that simultaneous determination of Ce4+ and Cr2O72- can be done in their concentration ranges of 1.0-30.0 and 0.1-20.0 μg/mL, respectively. The total relative standard error for applying the PLS and PCR methods on 8 synthetic samples was 2.97 and 3.19, respectively in the concentration ranges of 1.0-30.0 μg/mL of Ce4+ and 0.1-20.0 μg/mL of Cr2O72-. In order for the selectivity of the method to be assessed, we evaluated the effects of certain foreign ions upon the reaction rate and assessed the selectivity of the method. The proposed methods (HPSAM, PLS and PCR) were evaluated using a set of synthetic sample mixtures and then applied for simultaneous determination of Ce4+ and Cr2O72- in different water samples.

Spectrophotometric Assay for the Quantification of Plasma Ethanol Levels in Mice through Chromium-Ethanol Oxidation-Reduction Reaction

The quantification of blood/plasma ethanol concentration (BEC/PEC) is of great importance in experiments involving basic research, clinical studies, and bioethanol production. Traditional methods commonly used to measure BEC can be expensive and require high-cost equipment and qualified labor. The aim of this study was to develop a low-cost method that can be performed with simple infrastructure commonly available in research laboratories. For this, we developed a protocol to quantify PEC in mice, using the method of reduction of potassium dichromate by ethanol. However, this oxidation-reduction (redox) reaction is not specific to ethanol. Thus, the PEC was measured following a sequence of chemical reactions to eliminate the reductive interfering substances presented in the samples. Firstly, we evaluated the sensitivity of the dichromate reactive to ethanol and to different reducing substances found in the plasma, in order to determine which the main interfering substances are. Next, once the main interfering substances were determined in the dichromate reduction, plasma was assayed for PEC. First, mice received intraperitoneally (i.p.) saline (basal reading, 0% ethanol) or ethanol injections (0.5, 1, 2, 3, and 4 g/kg) and had their plasma collected. After plasma deproteinization and plasma glucose oxidation, it was mixed with the dichromate/acetic acid reactive, and then the products of the redox reaction were determined by the spectrophotometric method. Then, we determined the PEC with the same plasma samples using a commercial ethanol assay kit as a positive control. We found an excellent correlation between the administered ethanol doses and PECs in both the methods analyzed. The values of PEC found in the dichromate reaction method were similar to those obtained in the literature with the same ethanol doses, and to the commercial enzyme activity assay. Therefore, despite the need for a background reading, this method can be successfully applied to determine PEC using low-cost chemical reagents.

Real Time Diffraction Efficiency and the Anti-humidity Mechanism of NGD Holograms

<正> Jn this paper,a new holographic recording material,nongelatin dichromated holographic film (NGU).is reported.The NGD holograms exhibit stronger real time effect,higher diffraction efficiency,better humidity,stability,stronger surface relief modulation,etc.An experimental study of the influence of electron donors on real time diffraction efficiency (RTDE) of NGD holograms has been earned out,and the anti-humidity mechanism of holograms analysed based on the rracrochemical structure of chelate.The concept that the symmetry of chelate structure is essential for good humidity stability of holograms is suggested.Remarkable is the contrast between NGD and DCG.The latter is another member of dichromated light sensitive systems and used to be considered the best phase holographic recording material However,the holograms of DCG,if not sealed,would decay quickly after several hours at relatively high temperature and humidity