Showing papers on "Sodium dichromate published in 2010"
TL;DR: In this article, the authors used response surface methodology (RSM) to optimize the process parameters for the extraction of chromium from aqueous solution of waste sodium dichromate recovered from the pharmaceutical industry wastewater using emulsion liquid membrane technique.
Abstract: Response surface methodology (RSM) is used to optimize the process parameters for the extraction of chromium from aqueous solution of waste sodium dichromate recovered from the pharmaceutical industry wastewater using emulsion liquid membrane technique. The liquid membrane used was composed of kerosene oil as the solvent, SPAN-80 as the surfactant and potassium hydroxide as internal reagent and trioctylamine as carrier. The process parameters namely, feed concentration, pH, internal reagent concentration and surfactant concentration on the extraction of chromium were optimized using Box–Behnken design. The optimum conditions for the extraction of chromium (VI) were: feed concentration (224.04 ppm), pH (2.76), internal reagent concentration (0.71 N) and surfactant concentration (1.92%, w/w). At the optimized condition the maximum chromium extraction was found to be 92.50%.
58 citations
TL;DR: It is demonstrated that the addition of chromate or dichromate sodium salts to growth medium at neutral pH ended-up in two different solutions with a different balance of chemical species.
Abstract: Studies of Cr(VI) toxicity are generally performed using chromate salts in solution, both when studying the effects on prokaryotes and eukaryotes. Some studies on human carcinogenesis and toxicology on bacteria were done using dichromate, but comparison with chromate was never reported before, and dichromate existence was never taken into consideration and usually overlooked. This paper studied comparatively the effect of dichromate and chromate on the physiology of Ochrobactrum tritici strain 5bvl1, a highly Cr(VI)-resistant and reducing microorganism. This study demonstrated that the addition of chromate or dichromate sodium salts to growth medium at neutral pH ended-up in two different solutions with a different balance of chemical species. Cr(VI) was toxic to O. tritici strain 5bvl1, as clearly shown on growth, reduction, respiration, glucose accumulation assays and by comparing cell morphology. Moreover, the addition of sodium dichromate was always more toxic to cells when compared to chromate and achieved a higher inhibition of every parameter studied. The toxicity differences between the two Cr(VI) oxyanions indicate the possibility of a different impact of Cr(VI) contamination on the environment. This may be of major importance, considering the slight acidity of most of the arable lands which favours the presence of dichromate, the more toxic species.
32 citations
TL;DR: The obtained results have shown that this is the first successful attempt to achieve desired base properties of the product and there is an opportunity to utilize the dangerous wastes and reused them in the production scheme by minimizing or annulling the environmental impact and to attend a sustainable process development concept.
31 citations
Patent•
14 Apr 2010
TL;DR: In this paper, a process for producing the sodium dichromate through a carbonization method comprising of converting the sodium chromate into the mixture via carbon dioxide under a pressurizing condition, delivering the mixture to a tower after a cascade reaction of more than three continuous towers.
Abstract: The invention provides a process for preparing sodium dichromate, namely producing the sodium dichromate through a carbonization method comprising: converting sodium chromate into the sodium dichromate via carbon dioxide under pressurizing condition; delivering sodium chromate neutral liquor with impurities removed to a carbonization tower after a cascade reaction of more than three continuous towers; obtaining carbonizing liquor by controlling different gradient parameters (concentration and temperature of the carbonizing liquor, partial pressure of the carbon dioxide, carbonizing time and the like), continuously carbonizing and separating under pressure; obtaining sodium dichromate finished products through concentrating, filtering, evaporating, crystallizing and centrifugal dehydrating.
7 citations
TL;DR: In this article, the effects of various extraction and stripping parameters, such as equilibrium pH (7.0, 8.5 and 10), extractant concentration (5, 10 and 20 volume %), organic-to-aqueous (O/A) ratio and stripping agent type and concentration were studied on chromium recovery from chromium electroplating rinse bath wastewater using Aliquat 336.
Abstract: In this study, the effects of various extraction and stripping parameters, such as equilibrium pH (7.0, 8.5 and 10), extractant concentration (5, 10 and 20 volume %), organic-to-aqueous (O/A) ratio and stripping agent type and concentration were studied on chromium (VI) recovery from chromium electroplating rinse bath wastewater using Aliquat 336. Results showed that these parameters all had significant effects on chromium (VI) recovery. A pregnant strip solution from a chromium electroplating rinse bath wastewater with 33.4 g/L chromium content, suitable for sodium dichromate production, was generated by 20 vol. % Aliquat 336 in commercial kerosene. The O/A ratio was 1/4 and the equilibrium pH value was 0.87, the as-received pH value. The wastewater was treated with a two-stage countercurrent extraction process to produce a loaded organic phase, which was later stripped at the O/A ratio of two with a 4-M NaOH solution in a two-stage countercurrent stripping process using Taguchi’s optimization technique.
4 citations
Patent•
19 May 2010
TL;DR: In this paper, a method for jointly producing chromium salt and ferrochromium alloy by sintering with the wet-fire methods is described, comprising of four steps: grinding coarse ferro chromium ore into fine finchromium ore powder, mixing the fine ferrochrome ore powder and sodium carbonate into mixture, and sintering the mixture into primary sintered clinker, extracting primary sodium chromate solution from the primary sinterered clinkers and obtaining the left primary chromium slag, and separating, sinting and crushing the primary chrom
Abstract: The invention discloses a method for jointly producing chromium salt and ferrochromium alloy by sintering with the wet-fire methods, comprising the following steps: grinding coarse ferrochromium ore into fine ferrochromium ore powder; mixing the fine ferrochromium ore powder and sodium carbonate into mixture, and sintering the mixture into primary sintered clinker; extracting primary sodium chromate solution from the primary sintered clinker and obtaining the left primary chromium slag; separating, sintering and crushing the primary chromium slag into primary chromium slag powder, and mixing the primary chromium slag powder and sodium carbonate into mixture, and sintering the mixture into secondary sintered clinker; extracting secondary alkaline sodium chromate solution from the secondary sintered clinker and obtaining the left secondary chromium slag; adding acidic solution to neutralize the alkaline sodium chromate solution; adding sodium dichromate to the sodium chromate solution, adjusting the acidifying with sulfuric acid to form sodium dichromate solution, and separating sodium dichromate crystals from the sodium dichromate solution; mixing the secondary chromium slag and iron ore with coke powder and auxiliary materials and sintering the mixture into sintered ore; and mixing the sintered ore and coke in a blast furnace to smelt the ferrochromium alloy.
4 citations
Journal Article•
TL;DR: The Oxidation of m-toluidine by sodium dichromate has been studied both spectrophotometrally and iodometrically in aqueous nitric acid medium and the reaction shows substrate inhibition at low H+ concentration.
Abstract: The Oxidation of m-toluidine by sodium dichromate has been studied both spectrophotometrically (640nm) and iodometrically in aqueous nitric acid medium. The reaction is said to follow consecutive reaction mechanism. The reaction shows substrate inhibition at low H+ concentration. Oxidation proceeds by two routes and both routes give the colored product. Suitable mechanism is proposed. The rate constants, equilibrium constants and kinetic parameters are calculated.
4 citations
Patent•
02 Nov 2010
TL;DR: In this article, a hydrothermal oxidation method for producing alkali metal dichromate from carbon ferrochrome is described. But the method is not suitable for industrial use.
Abstract: The present invention provides a hydrothermal oxidation method for producing alkali metal dichromate from carbon ferrochrome, and the method comprises the following steps: formulating an initial reaction liquid by mixing carbon ferrochrome, an alkaline substance and water, in which the actual addition amount of the alkali is controlled smaller than the theoretically required amount; adding the initial reaction liquid into a reaction kettle, charging an oxidizing gas into the reaction kettle, and allowing the reaction to proceed for 0.5 to 3 h at a temperature of 150° C. to 370° C. and a pressure of 2 Mpa to 24 MPa; carrying out solid-liquid separation, cooling the resultant filtrate to a temperature of −12° C. to −20° C. to precipitate crystals, and carrying out separation by centrifuge to obtain alkali metal dichromate solution; adding CrO3 to the alkali metal dichromate solution until the degree of acidification reaches 100% or greater, concentrating the solution by evaporation, and cooling it to precipitate crystals, so as to afford alkali metal dichromate. The method has a simple process, is easy to control, and can directly produce sodium dichromate under hydrothermal conditions.
3 citations
Patent•
15 Dec 2010
TL;DR: In this article, a continuous preparation method for sodium dichromate crystal solution is proposed, which consists of first-step electrolysis: electrolyzing alkali sodium chromate solution serving as anode raw material solution and sodium hydroxide solutions serving as cathode raw materials solution.
Abstract: The invention relates to a continuous preparation method for sodium dichromate crystal solution. The method comprises the following steps of: (1) first-step electrolysis: electrolyzing alkali sodium chromate solution serving as anode raw material solution and sodium hydroxide solution serving as cathode raw material solution in a continuous preparation device for the sodium dichromate crystal solution with a filter at the temperature of 70 DEG C to obtain neutral sodium chromate solution and oxygen at the anode and obtain sodium hydroxide solution and hydrogen at the cathode; filtering the neutral sodium chromate solution to obtain anode raw material solution for the second step, and introducing the anode raw material solution to a next continuous preparation device for the sodium dichromate crystal solution without the filter; and (2) second-step electrolysis: electrolyzing the anode raw material solution obtained in the step (1) and the sodium hydroxide solution serving as cathode raw material solution at the temperature of 70 DEG C to obtain the sodium dichromate crystal solution and oxygen at the anode and obtain the sodium hydroxide solution and hydrogen at the cathode. The method greatly shortens the process, realizes continuous production and effectively improves the production efficiency by using the continuous preparation device for the sodium dichromate crystal solution.
1 citations
Patent•
24 Nov 2010
TL;DR: In this paper, a method for continuously preparing sodium dichromate by an ionic membrane electrolysis was proposed, which comprises the following steps of neutralizing industrial alkaline sodium chromate solution, removing impurities, and collecting filtrate serving as feed solution of electrolysis process.
Abstract: The invention relates to a method for continuously preparing sodium dichromate by an ionic membrane electrolysis. The method comprises the following steps of: firstly, neutralizing industrial alkaline sodium chromate solution, removing impurities, and collecting filtrate serving as feed solution of electrolysis process; secondly, introducing the filtrate into an anode chamber in a one-membrane two-chamber ionic membrane electrolyzer, and introducing sodium hydroxide solution into a cathode chamber, wherein anions and cations migrate to the anode and the cathode respectively under the action of an electric field, sodium dichromate acidizing fluid is obtained in the anode chamber, high-concentration sodium hydroxide solution is obtained in the cathode chamber, and hydrogen and oxygen are produced on a positive electrode and a negative electrode respectively; and finally, performing evaporation concentration and natural cooling crystallization on the sodium dichromate acidizing fluid to separate out dehydrate sodium dichromate products. The method has the advantages of short process, low cost, high purity of the obtained sodium dichromate products, near 100 percent of raw material utilization rate, and high economic value of byproducts.
1 citations