电解电渗析法制备硅溶胶

PREPARATION OF SILICA SOLS BY ELECTRODIALYSIS

以RuO_x／Ti为阳极、铁镀镍为阴极与Nafion901阳离子交换膜组装成两室的电解电渗析槽，探讨了电解电渗析法制备硅溶胶过程中槽电压和pH值变化的基本规律，证实了增大电流密度和阳极液的进料液流速率可减少二氧化硅在阳极上的吸附沉积，增大二氧化硅的收率．在滴加操作中，通过实验找到了制备浓硅溶胶的较佳的初始组成和操作条件，基本上解决了二氧化硅在阳极上的沉积问题，最高槽电压不超过10V，最高电流密度可达150mA·cm^(-2)，膜的平均电流效率在93％左右．

An electrodialytic cell system equipped with a steel cathode,a RuOx/Ti anode and a piece of Nafion 901 cation-exchange membrane was set up in the process of producing silica sols by eletrodialysis of sodium silicate.It was confirmed that the deposition of silica on anodes can be minimized by increasing current density and the velocity of anolyte.The yield of silica was above 97% in the case of i＞50mA·cm^(-2), u＞0.3lm·s^(-1).The current efficiency of membrane was more than 90% when temperature was higher than 20℃ and current density was greater than 30mA·cm^(-2).Concentrated silica sols can be produced by electrodialysis in the process of adding concentrated sodium silicate (Xsio2=30%) into anolyte.The Optimal initial anolyte composition and operating conditions were obtained.The deposition of silica on anodes during the process can be overcome mainly if initial anolyte was dilute aqueous silica sols with particle size less than 5nm.The highest cell voltage was less than 10V,the greatest current density was about 150mA·cm^(-2) and the mean efficiency of membrane was about 93%.