Recycling Waste Materials to Fabricate Solar-Driven Self-Cleaning Geopolymers

The design of photocatalytic building materials based on geopolymers (GPs) through recycling industrial by-products is an up-and-coming technology that provide durability during environmental exposure. Thus, this work aimed to design, fabricate, and characterized photocatalytic geopolymers based on recycling industrial wastes (slags and fly ash) and TiO2 nanoparticles to propose a strategy to contribute to a circular economy. Taguchi L9 orthogonal design was used to optimize the formulation of GPs to obtain higher self-cleaning efficiency under solar light irradiation. The factors modified during the GPs fabrication were %TiO2, %fly ash, and temperature. The main products of the slag activation were calcium aluminosilicate hydrate and Zeolite X. The self-cleaning efficiency of the GPs was optimized through the signal-to-noise ratio (S/N): Larger is better, which conditions were 3 wt% of TiO2, 300 degrees C, and no-fly ash. After 3 days of solar light exposure, the optimal GP removes up to 88.4% of the pollutant from its surface, which evidences its self-cleaning activity under real outdoor conditions. Also, the GP fabricated under the optimal conditions generated hydroxyl radicals under solar light, which can open a window of possibilities to remove a wide range of atmospheric pollutants by recycling industrial by-products.