Geopolymerization: a promising technique for membrane synthesis

Abstract

Ceramic membranes are considered superior over their polymeric counterparts for applications at high temperature, pressure, and in aggressive environments with additional advantages of cleaning at high temperature. Preparation of porous ceramic membrane is expensive because the ceramic materials cannot be processed in a liquid state as polymers. Ceramic membrane synthesis involved solid powder preparation, consolidation, suspension formation, calcination, and sintering temperature which makes its synthesis very expensive. Geopolymerization is a heterogeneous reaction of aluminosilicate materials and chemical activators to form a three-dimensional structure having high mechanical strength without sintering. The overall percent energy and cost-saving of geopolymeric membranes were compared with conventional ceramic membranes. Recently, the geopolymerization technique has been used for membrane synthesis to replace conventional ceramic membrane synthesis. The objective of this review article is to discuss the potential opportunities and challenges in the synthesis and application of geopolymeric membranes.

Ceramic-like membranes without sintering via alkali activation of metakaolin, blast furnace slag, or their mixture: Characterization and cation-exchange properties

“…The purpose of the support and intermediate layers (e.g., steel or alumina with a thickness of few mm) is to overcome the brittleness of the ceramic material while the selective layer (e.g., metal oxides) is responsible of the separation (Garmash et al, 1995;Komolikov and Blaginina, 2002). The manufacturing of ceramic membranes involves solid powder preparation, consolidation, suspension J o u r n a l P r e -p r o o f formation, dispersion of particles in liquid, pressing, calcination, and sintering at temperatures frequently more than 1500 °C (Qiu et al, 2017;Sadiq et al, 2021). Additionally, many raw materials for ceramics, such as zirconia, mullite, or titanium dioxide are also relatively expensive.…”

“…The preparation of alkali-activated membranes follows a simple procedure consisting of mixing of aluminosilicate precursor and aqueous alkali-activator solution, casting, and curing at 20-80 °C (Chen et al, 2020;Daud et al, 2021;Ge et al, 2015;Mohammadi and Mohammadi, 2017;Xu et al, 2019Xu et al, , 2015Zhang et al, 2021). Consequently, the material costs of an alkali-activated membrane in one recent case example (fly ash activated with sodium silicate and hydroxide with a hydrogen peroxide addition) was J o u r n a l P r e -p r o o f estimated to be ~2 $ per m 2 while a comparable alumina-based ceramic membrane cost ~120 $ per m 2 (Sadiq et al, 2021).…”

Why geopolymers and alkali‐activated materials are key components of a sustainable world: A perspective contribution

“…Another reported application is the pervaporation of water/ethanol 118 . What is especially interesting is that the cost of geopolymer or alkali‐activated membranes can be just ∼2% of that of a comparable ceramic membrane 119 (which can be approx. 10 times that of an organic polymer membrane 120 ).…”

The Capacity of Alkali‐Activated Industrial Wastes in Novel Sustainable Ceramic Membranes

“…The elevated cost of ceramic membranes can be attributed to the use of costly raw materials, including sodium carbonate, silica, alumina, zirconia, and boric acid. Sadiq et al [167] compared the costs of conventional alpha-alumina ceramic membranes with FA-based geopolymeric membranes in terms of raw materials. The total cost for synthesizing the FA-based geopolymeric membrane was found to be $2.37 m −2 , while it amounted to $120.58 m −2 for the alpha-alumina ceramic membrane [167].…”