New glass‐based binders from engineered mixtures of inorganic waste

Abstract

Aluminum is one of the most important strategic resources, but the Bayer process, typically applied for the purification of ores, leads to vast amounts of alkaline slurry waste, known as red mud. Though interesting for potential reprocessing, red mud is still predominantly stored in big slurry pools, due to high levels of toxic metals. Toxic ions can be easily immobilized by vitrification, but the high costs of this solution need to be balanced by the reuse of the obtained glass. The present paper is dedicated to the transformation of waste‐derived glass into new binders for the construction industry, according to both “conventional melting” and “smelting” approaches. In the first case, red mud was included in a mixture of waste, designed to yield a reactive glass (CMG), that is, forming stable gels after activation in an alkaline aqueous solution. In the second approach, red mud was subjected to a thermal treatment in a reductive atmosphere, implying the separation of molten iron alloy. The remaining glassy slag, according to its chemical composition (CaO and Al2O3‐rich) underwent gelation by simple interaction with pure water, without any alkaline activator, thus configuring a new “glass cement.”

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

“…Alkalis could react also with atmospheric CO 2 (M. [ 22 ]). The C–O stretching signal at around 1410 cm −1 (asymmetric stretching vibration), detected after activation but not after washing, is consistent with the formation of soluble (hydrated) carbonates.…”

Upcycling waste derived glass into high-performance photocatalytic scaffolds by alkali activation and direct ink writing

“…Hujova et al have found out that glasses from industrial residues, composed primarily of red mud, can be applied as precursors for inorganic binders, at nearly room temperature [ 11 ], by interaction with pure water or with a highly concentrated alkaline solution. In the latter case, glass is designed to undergo a substantial dissolution, followed by condensation reactions (‘polymerization’) between dissolution products.…”

Waste Glass Upcycling Supported by Alkali Activation: An Overview

“…In alkali activation, precursors dissolve in the activating medium, -consisting of a concentrated aqueous solution of alkali hydroxides or alkali silicates-where the degradation products condense and polymerise, leading to products with variable molecular structures. A three-dimensional, continuous, highly interconnected structure is available in the subset of AAMs known as "geopolymers" [15,16]. These products feature a "zeolite-like" network, i.e., they feature a specific connectivity between structural units, finding analogies in the same zeolites, in feldspar minerals, or in alkali aluminosilicate glasses [17].…”