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%.