The effect of thermal treatment on the structural and electrokinetic properties of porous glass membranes

摘要

The properties of porous glass membranes prepared by acid leaching of sodium borosilicate glasses 8B and 8V and also 8B glass containing small amounts of fluorine and phosphorus (SFP) are comprehensively studied. The effect of the composition and conditions of thermal treatment of the original and porous glasses on their structural (specific surface area, structure resistance coefficient, average pore radius, volume porosity, and filtration factor) and electrokinetic characteristics (conductivity, counterion transport numbers, and electrokinetic potential) in KCI solutions at neutral pH values is studied. It is shown that an increase in thermal treatment temperature T-TT of the porous glasses from 120 to 750 degrees C leads to a decrease in structure resistance coefficient P of 8B membranes. For membranes prepared from SFP glass, P values, efficiency coefficients, and counterion transport numbers are virtually independent of T-TT at 120-600 degrees C and increase at T-TT = 750 degrees C. Specific surface area and volume porosity decrease with a rise in T-TT for all studied membranes. The observed regularities of variations in the membrane characteristics are explained by the increasing fraction of large pores because of sintering of small pores with an increase in T-TT and by the different amounts of secondary silica in the pore space of porous glasses.