The recycling glass industry is identified as a model to follow in order to advance towards a circular economy. The recycling glass rate in Europe is around 74 %, meanwhile in Spain is considered 70 %, as reported elsewhere.... [ view full abstract ]
The recycling glass industry is identified as a model to follow in order to advance towards a circular economy. The recycling glass rate in Europe is around 74 %, meanwhile in Spain is considered 70 %, as reported elsewhere. However, during the glass selection process by an optical sorting equipment a waste called CSP (Ceramic, Stone, Porcelain) is generated, being less than 2 % wt. in Catalonia. Although this type of equipment should only separate ceramics, stone, and porcelain, around 84 % wt. of glass is found in the CSP. This is mainly because optical sorting equipment does not recognize the glass with stickers, nor the bottom of bottles, neither the bottlenecks as glass. The CSP separation process is crucial because ceramics and porcelain hinder the recast of the glass. In this way, in Catalonia CSP is mainly considered a non-profitable material, and its useful life ends in the landfill, where the accessibility in Europe is increasingly restricted.
The main CSP composition is SiO2, alkali metals, and Al2O3; key components for the geopolymer development. Hence, in this study, the potential use of CSP as unique precursor to synthesize different geopolymers has been analysed. This research has studied the parameters which affect the formulation and behaviour of new CSP geopolymers. The concentration (1M, 4M, and 8M) of the alkali activator, the curing temperature (30 ºC and 40 ºC), and finally the liquid-to-solid ratio (L/S) were the parameters under study. The CSP was first milled below 80 µm particle size and was characterized by means of specific surface (BET), XRF, and XRD, among others. Then, the CSP powder was mixed with the alkali solution to obtain the final CSP geopolymer. After curing, the properties in terms of physical (density and porosity) and mechanical (compressive and flexural strength) were evaluated. The results obtained show the feasibility to use CSP as unique precursor to develop new geopolymers.
