Upcycling of Pharmaceutical Glass into Highly Porous Ceramics: From Foams to Membranes

Abstract

The present COVID-19 emergency has dramatically increased the demand for pharmaceutical containers, especially vials. End-of-life containers, however, cannot be easily recycled in the manufacturing of new articles. This paper presents some strategies for upcycling of pharmaceutical glass into various porous ceramics. Suspensions of a fine glass powder (70 vol%) are used as a starting material. Highly uniform cellular structures may be easily prepared by vigorous mechanical stirring of partially gelified suspensions with added surfactant, followed by drying and firing at 550–650 °C. Stabilization of the cellular structures at temperatures as low as the glass transition temperature (Tg) of the used glass is facilitated by thermal decomposition of the gel phase, instead of viscous flow sintering of glass. This finding enabled the preparation of glass membranes (∼78 vol% open porosity), by direct firing of hardened suspensions, avoiding any surfactant addition and mechanical stirring. The powders obtained by crushing of hardened suspensions, even in unfired state, may be used as a low-cost sorbent for dye removal.

Novel glass-based membranes for Cu adsorption: From alkali activation to sintering

“…As observed previously, alkaline attack of BASG yields quite specific results [ 6 ]. Unlike in Ca-rich and Al-poor common soda-lime glass, alkali activation does not promote formation of calcium silicate hydrated (CSH) compounds.…”

“…Immobilization of heavy metals using glass-based membranes shows a highly convincing alternative to solve this problem. The required materials (membranes) can be fabricated by a low-temperature consolidation process [ 6 ] of suitable alkali activated materials Luukkonen, 2019 [ 7 ].…”

“…In the vast range of cullet, i.e., material recovered from the dismantling of a variety of glass articles, the (Ca-free) alkali boro-alumino-silicate glass (BASG) adopted for pharmaceutical containers (e.g., vials) has been recently found to offer unprecedented opportunities. The glass forms stable gels, even by the activation with diluted alkali hydroxide solutions, according to a mechanism proposed by Mehta et al [ 6 ]. The activation results in the formation of a hydrated layer at the surface of fine glass particles; the particles are later bound to each other through condensation reactions.…”

“…Activated BASG from the pharmaceutical industry has been already tested for the adsorption of dyes: the new glass-based gels have been successfully tested in one of the emerging environmental applications of geopolymers, [ 6 ]. The present research aims at extending the applications of activated BASG in the remediation of wastewaters beyond organic pollutants; in particular, the immobilization of copper ions was considered.…”

Waste Glass Upcycling Supported by Alkali Activation: An Overview

“…Alkali ions in foams likely did more than stabilise the AlO 4 and BO 4 units in the gel; they also likely encouraged the construction of a highly depolymerised network, inhibiting the condensation of silanol groups and the development of robust Si-O bridges. Glass particles were most likely "glued" together by the condensation of silanol groups since alkali ions entered the gel significantly less often in denser bodies [37][38][39].…”