Chromium recovery

The SRS process is versatile in chlorate plant production. The design and operating conditions can be adapted to meet the need of the different plant requirements, e.g. production of R8 solution with reduced chromium, recovery of chlorate from the purge liquor sent to effluent, or removal of sulphate from the liquor loop. 

The annual operating cost for a tin mill plant with a new waste treatment plant is more than 1,450,000, with more than 700,000 in sludge disposal costs. Lewis asserts that, in comparison, the ENVIRO-CLEAN process treatment cost includes chromium recovery valued at more than 190,000 and water savings valued at more than 50,000 per year. According to Lewis, a large-scale ENVIRO-CLEAN system complete with electrolytic recovery has an annual operating cost of less than 800,000 a year (D135035, p. 1). 

Ding et al. [88] used anion-exchange chromatog-raphy-ICP-MS to determine different forms of chromium in chromium picolinate products which are used as dietary supplements and appear to assist in weight loss. A Dionex AS7 anion-exchange column was used to separate Cr(III)-EDTA chelate and Cr(VI) in the supplements. Only 1% total chromium recoveries were obtained and this was attributed to retention of the chromium species on-column. The use of RP-HPLC proved to be more effective and complete chromium recoveries were obtained, based on the amounts stated on the manufacturer s product labels. 

Sonawane, J.V., Pabby, A.K., and Sastre, A.M., Hexavalent chromium recovery by pseudo-emulsion based hollow fiber strip dispersion with Cyanex-923 from acidic media, Chemosphere, 2008 (submitted). 

Panswad T Chavalparit O, Chandung C and Anotai j (2001) Economic considerations of chromium recovery from tanning wastewater. Waste Manag Res 19 450-455. 

Babcock ( ) also reported pilot plant uranium and chromium recovery projects using ILMs. Membrane modules were constructed with hollow fiber polysulfone supports containing kerosene solutions of commercially available hydrometallurgical complexatlon agents such as tertiary amines. Operating coats for the extraction step calculated from uranium recovery data were 0.8/kg Ur for a 3.8 x 10 ra /day plant which were superior to costs associated with solvent extraction and ion-exchange. 

Shaalan HF, Sorour MH, and Tewfik SR. Simulation and optimization of a membrane system for chromium recovery from tanning wastes. Desalination 2001 14 315-324. 

Integrated membrane process for chromium recovery in the leather industry. UF = ultrafiltration NF= nanofiltration. 

Panswad T, Chavalparit O, Sucharittham Y, Charoenwisedsin S (1995) A bench-scale study on chromium recovery fi om tanning wastewater. Water Sci Technol 31 73-81. doi 10.1016/0273-1223(95) 00408-F... 

Pilot plant uranium and chromium recovery data for a SLM system was reported by Babcock (65). Polysulfone hollow fibers were used in the module and a tertiary amine in kerosene was the organic phase. Operational costs for the separation of uranium were 0.8/Kg for a 3.8 X 10 m /day plant. This cost estimate was lower than those for uranium recovery by solvent extraction and ion exchange. 

The AOD refining cycle also includes a short reduction period where argon is injected into the metal to recover chromium from the slag. In effect, the spinel phases are substantially reduced. This cycle also employs an increased slag Ca0/Si02 ratio to facilitate chromium recovery. 

The sodium chlorate manufacturing process can be divided into six steps (/) brine treatment 2 electrolysis (J) crystallisation and salt recovery (4) chromium removal (5) hydrogen purification and collection and (6) electrical distribution. These steps are outlined in Figure 3. 

Where appropriate, the direct precipitation of hexavalent chromium with barium, and recovery of the Cr(VI) value can be employed (166). Another recycling (qv) option is ion exchange (qv), a technique that works for chromates and Finally, recovery of the chromium as the metal or alloy is... 

The suitability of gas absorption as a pollution control method is generally dependent on the following factors 1) availability of suitable solvent 2) required removal efficiency 3) pollutant concentration in the inlet vapor 4) capacity required for handling waste gas and, 5) recovery value of the pollutant(s) or the disposal cost of the unrecoverable solvent. Packed-bed scrubbers are typically used in the chemical, aluminum, coke and ferro-alloy, food and agriculture, and chromium electroplating industries. 

Yourfacility is involved in chrome plating of metal parts, which produces an aqueous plating waste that is treated on-site to recover chromium sludge. The effluent from the on-site treatment plant, which contains chromium compounds (a listed toxic chemical), is piped to a POTW. The chromium sludge is transferred to an off-site, private ly owned firm tor the recovery of the chromium. 

The second term indicates that by increasing the melt temperature, e.g., by oxygen lancing, to 1850 °C, AG° for the reaction becomes more positive and the reverse reaction leading to retention of chromium in steel becomes favorable. Addition of a deoxidant, e.g., silicon as ferrosilicon, which forms an oxide stabler than Cr203, also leads to further recovery of chromium in steel ... 

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