Preparation And Mechanism Of Sodium Perborate Tetrahydrate

Sodium perborate tetrahydrate(SPT)is one of the most important boron compounds and find wide applications in daily chemical industry,textile,paper industry,organic syntheses and medicine fields etc.The traditional production methods,including electrolysis and botate synthesized,have remarkable problems of high energy consumption and serious pollution.With the intermediate product from the Sub-molten Salt process,sodium metaborate tetrahydrate(SMB),as the raw material,the preparation mechanisms of SPT through reaction crystallization of SMB with hydrogen peroxide were systematically investigated and the process optimization was performed as well.The obtained SPT products from the shortened process have a good quality and added value.The following innovative progresses were achieved in this paper.1.The experimental determination of the metastable zone width(MSZW)was performed using a laser method.The factors of stirring rate,feeding rate of H2O2,temperature,initial concentration and additives were considered in the MSZW measurement.The results showed that MSZW tended to narrow all with the increase of the temperature,initial concentration of SMB,stirring rate and addition rate,broadening with two additives.2.The crystallization kinetics of SPT was investigated.The nucleation of SPT in present of sodium hexametaphosphate(SHMP)and sodium polyacrylate(PAAS)had been studied by isothermal crystallization.The secondary nucleation and growth kinetics were determined by discontinuous dynamic method and moment analysis,and finally established crystallization kinetics model.The results revealed that both two additives had an effect on nucleation,which suppressed the nucleation of SPT.The nucleation mechanism was heterogeneous.The crystal growth model belonged to continuous growth model.The increase of suspension density,stirring rate and supersaturation is facilitating the nucleation rate.A higher supersaturation results from the higher crystal growth.3.The preparation process of SPT was optimized.SHMP and PAAS is considered to have effects on the properties of SPT,including stacking density,active oxygen content,morphology,and particle size.The optimum conditions were achieved as additions of 0.4%SHMP and 0.08%PAAS.