Adsorption studies and effect of heat treatment on porous glass microspheres

This paper investigates the effect of heat treatment on porous glass microspheres produced via a novel flame spheroidization process, followed by exploring their suitability for dye removal from water. The effect of simple use of smaller porogen (≤5 µm) followed by heat treatment on the overall changes in textural and porosity profiles was quantified. Heat treatment was applied at different temperatures between 510°C and 540°C and cross-sectional SEM and nitrogen adsorption–desorption confirmed pore sizes had narrowed significantly from microporous (55 ± 8 µm) to mesoporous to macroporous range (≥2 nm) yet retained their interconnectivity. This decrease in pore morphologies led to an increased specific surface area and pore volume (by 51%). In addition, dye separation studies were explored using anionic Acid Red 88 (AR88), utilizing batch and column adsorption experimental processes. This study showed that the heat-treated microspheres achieved higher dye adsorption rates (i.e., 125 mg/g in batch adsorption studies, while column adsorption studies revealed 153 mg/g and 76 mg/g for flow rates 2.2 ml/min and 0.5 ml/min, respectively) in comparison with the nonheat-treated microspheres. Furthermore, the dye separation profiles were achieved via electrostatic interaction, hydrogen bonding, and Lewis acid–base interaction, without any internal or external functionalization of the microspheres required