Enhanced methylene blue adsorption by double alkali activation of highly porous glass microspheres prepared from waste glass

The remediation of water from organic pollutants, such as dyes and related compounds and the reuse of discarded glasses, represents fundamental challenges in highly industrialized countries. Porous glass microspheres have been proposed as efficient adsorbents in wastewater treatment, but their real application is problematic, especially from the perspective of their reuse and recycling. For the first time, the present paper describes the process of preparation and use of highly porous bodies with a specific surface area of nearly 20 m2/g fabricated from alkali activated glass microspheres and applicable for the removal of methylene blue as a model organic dye from wastewater. Alkali activation is applied both as an intermediate step (using 9 M KOH) for the conversion of waste glass into porous microspheres by flame spheroidization process, and as a final step (using 2.5 M NaOH), facilitating low temperature consolidation of the microspheres, and their transformation into porous structures. The experimental adsorption capacity of porous glass microspheres pellet was 122 mg/g. The high correlation coefficient indicates the applicability of Langmuir isotherm adsorption model.