Removal Of Al And Si In Sodium Chromate And Dynamics Research On Sodium Chromate To Sodium Dichromate By Carbonation

Sodium dichromate was a kind of important chemical raw material, mainly used in metallurgy, materials, electroplating, tanning, dyeing, pigments, wood preservatives, catalysts, oxidants, flame retardants, matches and metal corrosion inhibitor, etc.. Sulfuric acid method was a traditional production method used in China for a long time and had a serious problem of the pollution, pressurized carbonization method could achieve cleaner production theoretically, so it had certain practical directive significance to simulate and improve carbonization process.Sodium chromate solution added trace impurities of Al-Si, made Si content is about50ppm, and Al100ppm:the removal of trace Si didn’t need to add CaO, A/S was6, reacted at60℃for40min, then almost removed the Si completely; Al was189.65mg/L in the solution of sodium chromate, Al could be completely removed in the autoclave by controlling CO2pressure0.4MPa for20min. Improved carbonization process by single factor analysis method, the process could make the first carbonation rate reached more than70%; the second carbonation rate reached more95%. The reaction was a first order reaction, the reaction rate formula was r=kc. The reaction activation energy Ea was46.38kJ/mol obtained by Arrhenius theorem. Through the analysis of the reaction mechanism in333.15K, the reaction rate equation could be expressed as:in the stage d<1.00mol/L,r1=10-2.84-0.0375d,the reaction rate decreased as the reaction before the sodium bicarbonate precipitation; in the stage d>1.00mol/L,r2=10-2945+0.067reaction rate became larger as the reaction after the sodium bicarbonate precipitation, explained the reaction phenomena by simulating reaction mechanism.The filtrate by removing impurity and the second carbonization process could meet the requirements of production. The removing impurity and carbonization process needed no additives, SO42-was greatly reduced and Al-Si impurity could be all removed in the solution, and all by-products could be recycled, and no corrosion of equipments, the process was the ideal cleaning method.