Synthesis of solid sodium silicate from waste glass and utilization on one-part alkali-activated materials based on...

Alkali activated materials (AAMs) commonly known as geopolymers are considered ecofriendly substitutes for Portland cement. However, these materials still have a significant environmental impact, owing mainly to the use of activators based on commercial chemical products. In this sense, this research focuses on the production and use of waste glass-derived activators AAMs as an alternative to commercial activators. Using a thermochemical synthesis method, activator compositions were systematically designed to achieve predefined activator modulus (Ms = SiO₂/Na₂O = 0.5; 1.0 and 1.5). These alternative activators were studied by XRD, FTIR and SEM techniques. Additionally, one-part AAMs were manufactured using spent oil filtration earth (SOFE) as precursor and activator with optimum modulus Ms = 1.0. The influence of the Na₂O dosage was studied (10; 20 and 30 g of Na₂O per every 100 g of SOFE) as well as the influence of the activator modulus maintaining the optimum dosage of 20 g Na₂O per 100 g of SOFE. As a control, two-part AAMs were also synthetized with the optimum dosage and modulus employing commercial activators (NaOH + Na₂SiO₃ solution). Results indicate that the modulus of the alternative activator and especially the Na₂O dosage have a significant influence on the technological properties of AAMs based in SOFE, with an optimum compressive strength (35.8 MPa) for the addition of 20 g of Na₂O per every 100 g of SOFE using activator with modulus Ms = 1.0. This research embodies a sustainable approach to AAM production and suggests waste glass as a valuable raw material for sodium silicate synthesis intended for the one-part activation of spent filtering earth from the agri-food industry, aligning with the principles of circular economy and sustainable development goals.