The effect of heat, adsorption and mechanochemical treatments on stuck structure and adsorption properties of fumed silicas

The structural characteristics of fumed silicas synthesised under varied conditions and standard fumed silicas subjected to different types of pre-treatment, such as heating, suspending–ball-milling–drying, ball-milling of dry powder, and immobilisation of polymers, were studied using adsorption–desorption methods. Variations of preparation conditions and applied treatments influence the structure of finished samples in respect of both micropores and mesopores in primary particle swarms (aggregates, agglomerates) dependent on the treatment time nonlinearly. However, pre-treatments change the mesopore parameters of final adsorbents to a greater extent than those of micropores due to significant rearrangement of the primary particle agglomerates and gaps between aggregates. Application of the regularisation procedure to compute the pore size distributions using overall adsorption equation based on the combination of the Kelvin equation and the statistical adsorbed film thickness allows us to study the dependence of the structural characteristics of fumed silicas on treatment conditions in details.