Showing papers on "Potassium dichromate published in 2011"

In situ Carica papaya stem matrix and Fusarium oxysporum (NCBT-156) mediated bioremediation of chromium.

Abstract: Removal of heavy metal chromium was carried out using the fungus Fusarium oxysporum NCBT-156 strain isolated from soil of leather tanning effluent in in situ condition using potassium dichromate solution with 10 per cent Czapek-dox liquid medium. Biosorbent matrix was developed using Carica papaya plant dry stem to colonize the fungal strain to facilitate bioabsorption process. Bioabsorption of chromium was by metabolically mediated intracellular accumulation process. Maximum efficiency of chromium removal by biosorption upto 90 per cent was achieved at the end of 5th day of incubation (120 h of contact time) for 100 and 200 ppm concentration, upto 80 per cent for 300 and 400 ppm, and upto 65 per cent for 500 ppm to 1000 ppm concentrations with pH ranging from 5.8, 5.6, 5.5, 5.4 and 5.2, respectively for 100, 200, 300, 400, 500-1000 ppm concentration. SDS-PAGE protein profile showed significant difference in 34 kDa protein band after chromium absorption by the fungus. FTIR spectroscopic analysis revealed that the main functional groups involved in the uptake of chromium by F. oxysporium strain were carbonyl, carboxyl, amino and hydroxyl groups.

Transcriptomics Evaluation of Hexavalent Chromium Toxicity in Human Dermal Fibroblasts

Abstract: Significant exposure to hexavalent chromium, a metal with broad toxicity potential in humans, has been reported. In order to understand the mechanisms of dermal toxicity induced by hexavalent chromium, global gene expression profiling of human dermal fibroblasts exposed to potassium dichromate was performed. Microarray analysis of the gene expression profile in the fibroblasts treated with potassium dichromate identified significant differential expression of approximately 1,200 transcripts compared with the control cells. Functional categorization of the differentially expressed genes identified the enrichment of genes involved in several cellular processes, including apoptosis and oxidative stress, in the fibroblasts exposed to hexavalent chromium. Induction of apoptosis and oxidative stress in the dermal fibroblasts in response to their exposure to chromium was independently confirmed by additional experiments. The potassium dichromate-induced cytotoxicity, apoptosis, and oxidative stress were significantly blocked by the addition of ferrous sulfate, an agent known for its ability to reduce chromium to the insoluble and therefore impermeable trivalent form, to the cell culture medium. Taken together, our data provide insights into the potential mechanisms underlying the dermal toxicity of hexavalent chromium and provide experimental support for the proposed protective role of ferrous sulfate in hexavalent chromium-induced toxicity.

A synthesis of pseudo-mauveine and a homologue

Abstract: Treatment of N-phenyl-p-phenylenediamine and two equivalents of aniline with potassium dichromate in hot water acidified with a small amount of sulfuric acid gives 3-phenylamino-5-phenyl-7-aminophe...

Comparative tests on different methods for content of soil organic matter

Abstract: Four kinds of methods,TOC analyzer,550℃ loss-on-ignition(LOI),950℃ LOI and hydrated heat potassium dichromate oxidation-colorimetry,were employed to determine the content of organic matter(OM) of the sediments in Changjiang RiverThe accuracy and precision of the above methods as well as their influences on the measurements of content of soil OM were discussedStandard OM reference materials and five sediment samples from Qinhuai River in Nanjing were analyzedThe results of the four methods were comparedA conclusion is drawn that the test accuracy of the four methods has the sequence of TOC analyzer,550°C LOI method,hydrated heat potassium dichromate oxidation-colorimetry and 950°C LOI methodThe precision has the sequence of TOC analyzer,hydrated heat potassium dichromate oxidation-colorimetry,550°C LOI method and 950°C LOI methodThe TOC analyzer method and the 550°C LOI method are superior,and the other two should not be employedThe results of the hydrated heat potassium dichromate oxidation-colorimetry are too small and the 950°C LOI method leads to large errors in the results

Sonochemical Degradation of Pharmaceutical Wastewater

Abstract: This study presents the influence of the addition of additives such as activated carbon, carbon tetra chloride, hydrogen peroxide, and potassium dichromate on ultrasonic reduction of pharmaceutical wastewater chemical oxygen demand (COD) under laboratory conditions. The addition of activated carbon increased the % COD reduction whereas the combined addition of activated carbon and H 2 O 2 /CCl 4 /K 2 Cr 2 O 7 was found to show higher reduction. Among the various combinations investigated, the combined addition of activated carbon and CCl 4 was found to be the best combination. However, the environmental and health problems associated with these chemicals limit the applicability of the process in an industrial level. Further investigation with this system showed that the initial pH and initial COD have significant influence on the removal rate. The data obtained were fitted with first order and Langmuir-Hinshelwood kinetic models. The values of the rate constants obtained indicated that the pharmaceutical wastewater can be treated efficiently by the proposed methods.

Inhibition effect of potassium dichromate on the corrosion protection of mild steel reinforcement in concrete

Abstract: The inhibition of potassium dichromate on the corrosion protection of mild steel embedded in concrete and partially immersed in sulphuric acid and sodium chloride environments was evaluated at ambient temperatures. The experiments were performed using electrochemical potential monitoring method. Varying quantities of the inhibitor was used. In the NaCl test medium, the effectiveness of the inhibitor improved as higher concentration was used. The best inhibition was achieved in the reinforced concrete sample admixed with 9 g potassium dichromate. Steel-reinforced concrete sample admixed with 3 and 9 g potassium dichromate inhibitor had the highest improvement in compressive strength. The potassium dichromate inhibitor was most effective amongst other inhibitor concentrations used when 7.5 g was admixed with the sample in the H2SO4 medium. The sulphuric acid medium had a deleterious effect on the strength of concrete test specimens.

Method for analyzing all iron in molten steel ingot

Abstract: The invention provides a method for analyzing all iron in a molten steel ingot, which comprises the following operating steps: preparing standard solution of potassium dichromate; pretreating a test sample; titrating; and computing. In a test sample pretreatment process, smoke of perchloric acid is used to completely dispel low-boiling-point acid before the Fe is reduced by the SnCl2, the chromium is completely removed from the solution according to the property that hydrochloric acid and chromium ions form a volatile gas easily, the Fe is reduced by SnCl2, the interference of the chromium with a detection process is eliminated, the chromogenic reaction in a titrating process is more obvious, and the accuracy of the detection result is ensured.

Kinetic and mechanistic study of oxidation of ester by K2Cr2O7

Abstract: In present investigation we are studied the kinetics and mechanism of oxidation of ester by potassium dichromate in acid medium. In the present paper we reported the effect of oxidant K2Cr2O7, effect of substrate (ester), effect of sulphuric acid and effect of temperature on oxidation of ester. The reaction is first order with respect to oxidant and substrate, as temperature increases rate of the reaction also increases

The Identification Of Local Anæsthetic Drugs Of The Benzoic Ester Group

Abstract: Summary 1 A scheme is described for the characterisation and identification of the eleven local anaesthetic drugs of the benzoic ester group at present commercially available in this country. 2 The complete scheme is designed in five distinct stages, any of which may be omitted if identification is otherwise satisfactorily achieved: (i) purification of the crude material by precipitation of the hydrochloride from an ethereal solution of the base; (ii) reactions with the common alkaloidal reagents; (iii) demonstration of the presence of the benzoic ester structure; (iv) simple crystal tests and colour reactions with the three reagents, potassium iodide, potassium permanganate and potassium dichromate. (v) final identification by micro-mixed melting-point determination.

Detailed Studies on the High Temperature Corrosion Reactions between Potassium Chloride and Metallic Chromium

Abstract: Recovery of energy from biomass and various waste–derived fuels by combustion has become important due to reduction of detrimental CO2 emissions. Biomass does, however, release significant amounts of chlorine and alkali metals, as e.g. HCl(g), KCl(g), KOH(g) and NaCl(g), into the gas phase during combustion. The alkali chlorides may cause deposits on superheater tubes, which interfere with operation and can lead to corrosion and/or blockage of the gas path. To prevent and diminish the problems mentioned above, better and more detailed knowledge of the reactions between potassium chloride and the tube materials during combustion is needed. These materials commonly contain, among other metals, chromium, which is thought to protect the rest of the material since it forms a very dense but thin oxide layer on the surface of the tube material. It has been suggested that the reaction between solid or partly molten KCl and chromium oxide is the one responsible for starting the complex series of corrosion reactions. In this work, the overall reaction between potassium chloride and chromium was studied through partial reactions with compounds known to participate to the overall reaction or to be formed during it. The reactions were studied in synthetic air by heating sample mixtures in a DTA/TGA (Differential Thermal Analysis/ Thermogravimetric Analysis) apparatus. Selected samples were also studied and analyzed with a scanning electron microscope equipped with an energy dispersive x-ray analyzer (SEM/EDXA). Under the used conditions both potassium chloride and potassium chromate reacted with pure chromium and chromium oxide. In the case of chromium, chromium oxide was formed via the formation of potassium chromate. In reactions including chromium oxide as reactant also potassium dichromate was detected.

Detection of micronuclei and other nuclear abnormalities in Oreochromis niloticus exposed to potassium dichromate.

Abstract: The objective of this paper was to analyze the micronuclei (MNs) and other nuclear abnormalities (NAs) frequencies in peripheral blood of Nile tilapia (Oreochromis niloticus) treated with potassium dichromate via contaminated water. Blood samples were collected from caudal vessels after potassium dichromate 12 mg.L expositions for 24 and 48 hours. The typical micronuclei were not found in control group. 1 In the exposed groups the frequencies were 1.0 ± 1.15 at 24h and 2.43 ± 0.98 at 48h. The nuclear morphological alterations frequencies in control, 24h and 48h were 4.29 ± 4.50, 5.86 ± 3.02 and 11.0 ± 3.74, respectively. The parametric ANOVA showed a very significant difference (p < 0.01) in MNs frequencies between control and 48h groups; also there was significant difference (p < 0.05) between the two exposition times. In the NAs, there was significant difference only between control and exposed for 48h groups (p < 0.05). Results confirm the potentially adverse effects of potassium dichromate. The demonstrated sensitivity to this ion shows that Oreochromis niloticus can be used to monitor for the acute effects of pollutants on the basis of hexavalent chromium in freshwater ecosystem.

Polyaniline-poly(vinyl alcohol) IPN-composite prepared from potassium dichromate embedded PVA film: a material for humidity sensing application

Abstract: Polyaniline-polyvinyl alcohol (PANI-PVA) interpenetrating network composite film is successfully prepared by in situ polymerization of aniline within PVA film embedded with different concentrations of potassium dichromate (K2Cr2O7). The resulted composite is characterized by UV-Visible spectroscopy, SEM and XRD, TGA techniques and confirmed the formation of interpenetrating network formation of PANI within PVA matrix. Electrical conductivity of the composite films increase from 10−6 to 10−2 S/cm with the increase in the loading of dichromate from 10−4 to 10−2M. Further, exposing in humidity environment, the conductivity of the composite films increases from 14 to 100% with the increase in humidity conditions from 11.3 to 84.3%.

Kinetics of oxidation of aliphatic alcohols by potassium dichromate in aqueous and micellar media

Abstract: The kinetics of oxidation of four aliphatic alcohols in acidic aqueous and micellar media were investigated. The reaction was found to be first-order with respect to both alcohol and oxidant. Pseudo-first-order kinetics were found to be perfectly applicable with ethanol, 1-propanol and 2-propanol while deviation was observed at intermediate stages of the reaction with methanol. The pseudo-first-order rate constants were found to be independent of concentration of the oxidant. The presence of TX-100 enhanced the rate of the reaction for all alcohols. Negative salt effects were observed with addition of KCl to the reaction mixture. A suitable mechanism for the reaction was suggested which agrees with the experimental findings.

Thermal decomposition of ammonium nitrate with three-component additives

Abstract: Results of a thermal analysis of a system constituted by ammonium nitrate and a three-component additive with Mg(NO3)2 as a promising ecologically clean oxidizing agent for high-energy condensed systems are presented.

Microarray analysis of global gene expression in Caenorhabditis elegans exposed to potassium dichromate

Abstract: Hexavalent chromium [Cr (VI)] can be considered as carcinogen heavy metal to human population. Especially, potassium dichromate [K2Cr2O7; Cr (VI)] induces DNA damage response and oxidative stress. It also causes inhibition of protective process including DNA repair as well as apoptosis. However, genomic responses to Cr (VI) exposure in Caenorhabditis elegans (C. elegans) have not been performed yet. As an alternative animal model, C. elegans is well known model for genetical studies including mRNA expression (etc.) and also serves as a living biomonitor in ecotoxicological field. Moreover, recognition of chromium biomarkers for the toxicity assessment is of prime importance. In present study, we have investigated the changes of gene expression in C. elegans in response to potassium dichromate exposure using microarray consisting of 22K nematode-specific oligonucleotide probes. We have found 28 genes as a Cr (VI) responsive genes that were differentially expressed (>2 fold) following 24 hours exposure to potassium dichromate. In addition, using the comparative toxicogenomics database, we have deduced molecular targets including cyclin B, alpha-B crystalline, G-protein coupled receptor kinase, nucleobindin, U2AF splicing factor, and SR protein (splicing factor) in response to potassium dichromate toxicity in C. elegans. In consistency with previous studies in human, it has also found that alteration in expression level of these genes contributes to particular syndromes including cataract, prostatic neoplasms, liver disease and neurotoxicity syndromes. In conclusion, our investigation would be able to present precise route to figure out important biomarkers in response to potassium dichromate in the field of ecotoxicology.

Research on the Role of Pre-Oxidation in the Separation of Cu-Pb in the Presence of Potassium Dichromate

Abstract: It is the most effective method to use potassium dichromate to separate copper from lead when galena is oxidized. However, it needs long time to oxidize galena by potassium dichromate. The efficiency of five oxidants on potassium dichromate depressing ability to galena have been studied completely in this paper, and results suggest that separation of Cu-Pb can be carried out effectively in short time in the presence of potassium dichromate when galena is pre-oxidized by oxidants. Sodium hypochlorite is the best oxidant, and after the interaction of 15 min., the grade and the recovery of copper concentrate are 24.02% and 81.93% respectively, and the grade and the recovery of lead concentrate are 17.88% and 84.98% respectively.

Study on Clean Production Technologies of Electrolysis Manganese Passivation

Abstract: The passivator of potassium dichromate is one of the main electrolysis manganese passivation technologies in China. The biggest problem of hexavalent chromium passivation is chromium emission. The end-pipe treatment of Cr-containing effluents can be understood as detoxification and precipitation. Here the highly toxicity Cr(Ⅵ) is reduced to low toxicity Cr(Ⅲ) . In alkaline conditions, Cr (Ⅲ)is precipitated in the type of chromium hydroxide and produce chromium residue. The landfill of Chromium residue is a big problem to environment safety. The measures of clean process were reviewed around with emission reduction of Cr.

Analysis of Potassium Dichromate Method for Determining COD in Water

Abstract: The potassium dichromate method is the national standard method for determining COD in the industrial wastewater.Based on massive experiments,accuracy,recovery of the method,standard solution's stability and the sampling method are discussed in this paper.The problems in the practical work are analyzed.The effective adjustment and control methods are adopted to reduce errors and to ensure reality of the determined water sample.

Oxidation products of fused 2-hetarylimidazole derivatives

Abstract: Oxidation of 5-(1-methyl-1H-benzimidazol-2-yl)thiophene-, and -selenophene-2-carbaldehydes with potassium dichromate in 20% aqueous sulfuric acid afforded the corresponding carboxylic acids. Analogous reaction with 5-(1-methyl-1H-benzimidazol-2-yl)furan-2-carbaldehyde led to the formation of 1-methyl-1H-benzimidazole as a result of decarboxylation of the primary oxidation product and subsequent decomposition of the furan ring. Probable factors responsible for instability of 5-(1H-benzimidazol-2-yl)-hetarene-2-carboxylic acids were considered. The oxidation of 2-furylnaphtho[2,3-d]- and 2-hetarylphenanthro-[9,10-d]imidazoles gave, respectively, an anthraquinone analog and 6,7-quinones. π-Electron-rich heterocycles in 2-furyl- and 2-pyrrolylphenanthro[9,10-d]imidazoles were oxidized completely, being replaced by hydrogen.

A Comparison of Two Methods for Quantitative Analysis on Ethanol Content: Gas Chromatography Method and Potassium Dichromate Colorimetric Method

Abstract: Two common quantitative analysis methods on ethanol content,including gas chromatograpy(GC) method and potassium dichromate colorimetric method,are compared when they are applied to analyze the standard solution with certain ethanol concentration and fermentation liquor with unknown ethanol concentration.The analysis results show the GC method is more accurate and comes up with higher cost in quantitatively analyzing the ethanol concentration of fermentation liquor;and that the potassium dichromate colorimetric method can be applied as a cheaper alternative method to GC method in batch quantity analysis on ethanol contents of fermentation liquors.

Research on the acute toxicity of imidazolium ionic liquids on the brine shrimp.

Abstract: In this paper,the effects of three imidazolium ionic liquids,1-butyl-,1-octyl-and 1-dodecyl-3-methylimidazolium chloride on the inhibiting concentration to the growth of brine shrimp in artificial sea water were carefully studied.At the same time,toxic organics such as methanol and acetonitrile and toxic inorganics like potassium dichromate were selected as positive control for the investigation of the effect of ILs on the brine shrimp.Dose-response curve fittings were established for the ionic liquids and the positive control toxins.The experimental results showed that with increasing the alkyl chain length of the ionic liquids,their toxicity to brine shrimp accordingly increased(LC50-24h values were 171.1,133.6,17.76μg/mL for the three ionic liquids,respectively).The LC50-24h values of the three imidazolium ionic liquids were found to be 10-2 to 10-3 of the values of methanol and acetonitrile while being much close to that of potassium dichromate.

Method for preparing vacuum superconductive liquid

Abstract: The invention relates to combustion systems, in particular to a method special for preparing vacuum superconductive liquid. The method for preparing the vacuum superconductive liquid adopts the technical scheme that the vacuum superconductive liquid comprises the following components: potassium sulfate, potassium dichromate, calcium chloride, ethanol, sodium perborate, boric acid, manganese dioxide, aluminium hydroxide, cobalt trioxide, sodium peroxide, potassium chloride, and the like. The technical process comprises the following steps of: heating distilled water, then adding boric acid to be stirred and dissolved; adding potassium dichromate to be dissolved; then adding sodium perborate; reacting for about 20min and then slowly adding sodium peroxide; reacting until the liquid is transparent; and then sequentially adding the other components to be stirred uniformly.

Method for preparing chromic anhydride from potassium chromate

Abstract: The invention relates to a method for preparing chromic anhydride from potassium chromate. The method comprises the following steps: 1) dissolving and acidizing the potassium chromate to obtain saturated potassium dichromate solution; 2) adding concentrated sulfuric acid in the potassium dichromate solution in the step 1 so that the mole ratio of the dichromate solution to the concentrated sulfuric acid is 1:1-7, stirring, reacting for 0.5-2 hours at the temperature of 20-150 DEG C, precipitating chromic anhydride crystals, filtering to obtain chromic anhydride macro crystals and mother liquor; 3) feeding 40%-60% of mother liquor in the step 2) back to the step 1) for the acidification of the potassium chromate, and carrying out crystallization and reduction on the residual parts to prepare chromic oxide; and 4) rinsing and filtering the chromic anhydride macro crystals in the step 2) with saturated chromic anhydride solution to obtain the chromic anhydride crystals and filtrate, recycling the filtrate to rinse the chromic anhydride macro crystals, and drying the chromic anhydride macro crystals to obtain the chromic anhydride. The invention has the advantages that the method is operated at the temperature lower than the decomposition temperature of the chromic anhydride and under normal pressure, and the obtained product has the advantages of high quality, high yield and low energy consumption.

KINETIC AND MECHANISTIC STUDY OF OXIDATION OF ESTER BY K2Cr2O7

Abstract: In present investigation we are studied the kinetics and mechanism of oxidation of ester by potassium dichromate in acid medium. In the present paper we reported the effect of oxidant K2Cr2O7 , effect of substrate (ester), effect of sulphuric acid and effect of temperature on oxidation of ester. The reaction is first order with respect to oxidant and substrate, as temperature increases rate of the reaction also increases.