Cerium water treatment

Gadolinium is produced from both its ores, monazite and bastnasite. After the initial steps of crushing and beneficiation, rare earths in the form of oxides are attacked by sulfuric or hydrochloric acid. Insoluble rare earth oxides are converted into soluble sulfates or chlorides. When produced from monazite sand, the mixture of sand and sulfuric acid is initially heated at 150°C in cast iron vessels. Exothermic reaction sustains the temperature at about 200 to 250°C. The reaction mixture is cooled and treated with cold water to dissolve rare earth sulfates. The solution is then treated with sodium pyrophosphate to precipitate thorium. Cerium is removed next. Treatment with caustic soda solution fohowed by air drying converts the metal to cerium(lV) hydroxide. Treatment with hydrochloric or nitric acid sol-... 

Mediated electrochemical oxidation (MEO) is an ex situ treatment technology that uses electricity, acid, and a metal catalyst to destroy organic wastes at low temperatures and pressures. The proprietary CerOx Corporation MEO configuration uses cerium metal as a catalyst to oxidize organic waste into carbon dioxide and water. The process occurs in an acidic solution, typically nitric acid. The first step involves the generation of an oxidant at the anode, followed by the reduction of water or another chemical species at the cathode. This technology serves as a nonthermal alternative to incineration. 

The cerium hydroxyl carbonate could be obtained through hydrothermal treatments, for example the hydrothermal treatment of cerium oxalate (Li et al., 1996). The most feasible way is to utilize the sealed reaction of Ce with urea CO(NH2)2 in aqueous solution. The hydrolysis of urea in water leads to (NH4)2C03 and provides the base to change the... 

Wang et al., 1996, 2002). Zhang et al. reported the solvothermal s)mthesis of ceria nanoparticles in ethanol (Zhang et al., 2003a). Ce(N03)3 6H2O and (NH4)2Ce(N03)g are used as cerium source respectively with KOH or NaOH powders. The alcohothermal treatment was performed at 180 °C to produce ceria nanocrystals. To attain full crysfallization via a dissolution and recrystallization mechanism, small amount of water is required in the reactions. 

The products were readily converted to free 8-amino ketones and esters. Thus, treatment of the products with cerium ammonium nitrate in acetonitrile-water (9 1) at room temperature induced smooth deprotection of the 2-methoxyphenylamino group to give free /5-amino carbonyl compounds [71,72]. 

Cerium (IV) oxide nanoparticles were synthesized by Masui et al [236] by use of a two-microemulsion technique. One of the microemulsions contained polyoxyethylene(lO) octylphenyl ether (OP-10) as the surfactant, n-hexyl alcohol as the co-surfactant, cyclohexane as the continuous phase, and an aqueous solution of cerium nitrate as the droplet phase. The second microemulsion was the same except that the droplet phase was an aqueous ammonia solution. The two were mixed to cause precipitation the particles thus obtained were gathered by centrifugation and washing under sonication with methanol, deionized water and acetone. The final treatment involved freeze-drying and vacuum drying. The mean particle size varied with experimental conditions in the range 2.5-4.0 nm. 

An alternative American process uses a feed produced by oxalate precipitation of thorium and rare earths. This precipitate is calcined to the oxides and dissolved in nitric acid for extraction with undiluted TBP. After stripping with 8N nitric acid, a high proportion of cerium extracts with the thorium, but the other rare earths are eliminated. The cerium is then back-washed in a separate extractor by means of 0 1 N sodium nitrite solution, which reduces it to the solvent-insoluble cerous condition. Thorium is then backwashed in the last extractor with either water or 2 per cent sulphuric acid. In order to make this process economic it was necessary to devise an efficient system of oxalic acid recovery. This was based upon treatment of the thorium and rare earth oxalates with sodium hydroxide and recycling the resulting sodium oxalate to the precipitation stage. 

A paint grade of cerium sulfide has also been developed. The pigment has been evaluated in several coatings formulations such as automotive refinish (acrylic-isocyanate binders), general industrial solvent-based systems (polyester-melamine binders), oil-based architectural coatings, and water-based paint. In the latter, performance may be improved by treatment with organics during formulation. 

Depending on the solvent, different reaction products form when alkenes react with iodine in presence of cerium(IV) triflate 1,2-hydroxy iodides in water, 1,2-alkoxy iodides in alcohols and 1,2-acetoxy iodides in acetic acid (Iranpoor and Shekarriz, 2000). Treatment of a mixture of styrene and sodium p-toluene sulfinate in anhydrous acetonitrile with CAN af-... 

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