Removal Of Organic Compounds From Sodium Aluminate Solution By Oxidation ?H₂O₂? And Its Effect On Seed Decomposition Of Sodium Aluminate Solution

The process of alumina production by Bayer process has the advantages of simple process, convenient operation, high quality of products and so on,so that it is widely used.But with the production cycle process running, there was a series of negative impacts which were usually caused by organics accumulation in production processes.Therefore,the problem of remove organic matter has aroused more and more attention of people.Wet oxidation method has many advantages such as high removal rate,simple operation,low cost, etc.It is a very good application prospects to Wet oxidation method.This thesis is based on the method of wet oxidation for removal of organic compounds,and H₂O₂ oxidation method is proposed for the removal of organic compounds from sodium aluminate solution.The main research contents include the effect of H₂O₂ oxidation on organic matter removal,the change rule of the form of organic matter before and after oxidation,depth analysis of the mechanism of H₂O₂ oxidation of organic compounds,and study the effect of sodium aluminate solution after removal of organic matter on the crystal seed decomposition.Providing reference basis to industrial utilization of the method.?1?By studying on removing organics from sodium aluminate solutions by H₂O₂,the results show that the times of circulating high pressure dissolution has a significant effect on the removal of organic compounds by H₂O₂ oxidation,the Tc removal rate and Na2C2O4 removal rate decreased with the increase of the number of circulating.This shows that the organic compounds in sodium aluminate solution is not conducive to the removal by H₂O₂ oxidation after circulating high pressure digestion.This is also illustrated why it is difficult to remove the organic compounds in sodium aluminate solution in the actual production process.The organic composition of sodium aluminate solution is more complicated in the actual production process after years of recycling.There is a new batch of organic matter just brought by bauxite,an old batch of organic matter brought by bauxite which has changed complex,and there are also a large number of organic compounds which aredifficult to be oxidated.?2?Analysing the Organic speciation of H₂O₂ before and after oxidation of sodium aluminate solution with circulating high pressure.The results show that the kinds of organic compounds in sodium aluminate solution are very complicated.And the humic acid organic matter has been changed in the high pressure digestion process of sodium aluminate solution.The speciation of organic compounds in sodium aluminate solution before and after H₂O₂ oxidation mainly contains organic acids such as butyric acid,butanedioic acid,phthalic acid,hexadecanoic acid and octadecanoic acid,etc.The alkyl type organic matter mainly contains 1,1-dibutoxy-butane,and the relative percentage content of 1,1-dibutoxy-butane and butyric acid is still higher before and after H₂O₂ oxidation.It is showed that the oxidation of H₂O₂ to this kind of organic matter is weak.There are many different kinds of organic acids containing phenyl before H₂O₂ oxidation.At the same time,it contains less organic acids phenyl after H₂O₂ oxidation.This means that H₂O₂ had oxidative decomposition on the decomposition of organic acid containing phenyl.Studying the effect on seed decomposition of sodium aluminate solution after oxidated by H₂O₂.The results showed that the sodium aluminate solution after H₂O₂ oxidation removal of some organic compounds is beneficial to the process of crystal seed decomposition in the same crystallization conditions.The decomposition rate of sodium aluminate solution was significantly higher than that of sodium aluminate solution before H₂O₂ oxidation.The crystallization product of sodium aluminate solution which was oxidated the organic matter by H₂O₂ is large particles, fewer small particles, the particles surface is smooth, and crystal particle diameter is significantly higher than the particle diameter of crystal containing humic acid sodium aluminate solution.It means that it reduce the amount of organic aluminium hydroxide crystal surface,the crystal surface is smooth in the crystallization process,and the particle surface is not easy to damage after the organic compounds in sodium aluminate solution were oxidized by H₂O₂.