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Chromate Ion Exchange
Published in Arup K. Sengupta, Ion Exchange Technology, 2021
Chromic acid and chromates are oxyacids and oxyanions of hexavalent chromium, Cr(VI), and used widely in anodizing, electroplating, corrosion control, oxidation, wood treatment, and several other industrial applications [1,2]. Unlike other toxic metals, however, oxyanions of Cr(VI) or chromates are quite soluble in the aqueous phase almost over the entire pH range and, thus, quite mobile in the natural environment. Toxicity, accompanied by widespread industrial applications and high mobility, has earned Cr(VI) an unusual notoriety in the area of environmental pollution. Contrary to Cr(VI) species or chromates, Cr(III) is less toxic and very insoluble at neutral to alkaline pH. As a result, chemical reduction of Cr(VI) to Cr(III), followed by precipitation as chromic hydroxide, Cr(OH)3(S), has been the traditional approach for treating Cr(IV)-laden wastewater [3,4]. Such an approach, however, does not allow recovery of Cr(VI) and is not efficient both thermodynamically and kinetically when Cr(VI) species are present at very low concentrations (from mg/L to μg/L). Furthermore, there is scientific evidence suggesting that chromic hydroxide sludges disposed of at landfills may be oxidized to mobile Cr(VI) in natural environments, thus threatening contamination of groundwater [5,6].
Antineoplastic Drugs and Other Chemical Wastes
Published in Peter A. Reinhardt, Judith G. Gordon, Infectious and Medical Waste Management, 2018
Peter A. Reinhardt, Judith G. Gordon
Many laboratory and maintenance wastes are hazardous because they are ignitable or corrosive. Spent organic solvents (e.g., alcohols, acetone, petroleum distillates) are hazardous waste. Old picric acid from the microbiology laboratory that has been allowed to dry is potentially explosive (reactive characteristic). Chromic acid is sometimes used to clean laboratory glassware. Waste chromic acid is regulated as a hazardous waste because it is a dangerous oxidizer and contains chromium, thereby meeting the criteria of being corrosive, being reactive, and producing toxic leachate.
Ferroalloys Waste Production and Utilization
Published in Sehliselo Ndlovu, Geoffrey S. Simate, Elias Matinde, Waste Production and Utilization in the Metal Extraction Industry, 2017
Sehliselo Ndlovu, Geoffrey S. Simate, Elias Matinde
Chromium-based compounds have found widespread applications in the chemicals industry, particularly in the form of chromite (naturally occurring chromium-containing ore, FeCr2O4) for the production of industrial chemicals such as chromic acid, sodium dichromate (Na2Cr2O7) and other chromium chemicals and pigments. In addition, the various chromium-based chemicals, though consumed in small quantities, have found widespread industrial applications in niche areas such as in catalysts, corrosion inhibitors, metal plating and finishing, pigments and leather tanning compounds and in the production of high-purity chromium metal (Papp and Lipin, 2001, 2006; International Chromium Development Association, 2011a; Koleli and Demir, 2016). Chromic acid is one such typical example of an industrial chemical that is widely used in metal finishing and electroplating processes where metal surfaces are coated with a thin layer of chromium for decorative or for corrosion inhibition purposes.
Detoxification of toxic cations Pb(II) and Cd(II) from liquid phase by employing Pennisetum glaucum biowaste: a kinetic investigation
Published in International Journal of Phytoremediation, 2022
Amna Yousaf, Muhammad Salman, Rabia Rehman, Umar Farooq
Collection and pretreatment methods of selected biosorbent (P. glaucum) were same as mentioned in previous studies (Yousaf et al.2017, 2018). Double distilled water was used with conductivity less than 0.05µS/cm. Synthetic solutions of selected salts were obtained from reliable sources (PbCl2 from Aldrich and CdNO3 from Schawls). Glassware was washed with chromic acid and later with distilled water. Unmodified biosorbent was labeled as UPG. UPG was mixed with the modifying agent in 1:2. Thiourea was completely homogenized with biomass in the presence of distilled water. Mixture was allowed to stay for 24 h and after that 50-60˚C temperature was applied for 15 min. Dried biosorbent was stored, labeled as MPG Selected biomass was characterized by Scanning electron microscope ((FEI Nova Nano SEM 450), Energy dispersion x-ray spectroscope (Nova SEM 450) and Fourier transform infrared spectrophotometer (FTIR, Shimadzu). Metal content during batch biosorption study was analyzed by Atomic absorption spectrophotometer (Buck Model Scientific 210-VGP.
Process design and optimization of bioethanol production from cassava bagasse using statistical design and genetic algorithm
Published in Preparative Biochemistry and Biotechnology, 2018
Selvaraju Sivamani, Rajoo Baskar
Chromic acid was prepared by dissolving 34 g of potassium dichromate in 325 mL of concentrated sulfuric acid and the final volume was made to 1 L with distilled water. 5 mL of standard solutions of ethanol (0–1% (v/v)) were prepared from a stock solution and taken in test tubes (1–6) and test solution was taken in test tube (7). 5 mL of chromic acid was added in each test tube and incubated in water bath at 60 °C for 20 min. The test tubes were cooled and the absorbance was measured at 584 nm in UV-Vis spectrophotometer. Finally, ethanol concentration was determined by plotting a standard curve.
Surface tension studies of binary and ternary mixtures of tetradecyltrimethylammonium bromide, ditetradecyldimethylammonium bromide and synperonic PE/F68
Published in Journal of Dispersion Science and Technology, 2020
Maria Papadimitriou, Antonis Avranas
The plate and all glassware were cleaned using chromic acid. The plate and the vessel for the sample were flamed before each measurement. The solutions were poured into the vessel and the surface was sucked off with a syringe connected to a vacuum pump to create a fresh surface. In a few cases, two or three series of measurements were performed. The average accuracy of the surface tension values was ±0.1 mN/m.