A novel self-cleaning ceramic waste-slag geopolymer with nano-SiO2-TiO2 photocatalytic coating

Abstract

In this investigation, a geopolymer based on ceramic waste (CW) and granulated blast furnace slag (GBFS) was synthesized. To confer the geopolymer with self-cleaning functionality, a nano-SiO2-TiO2 coating with hydrophobic and photocatalytic properties was applied onto the surface of CW-GBFS-based geopolymer. The effect of both the CW content and the alkali activator modulus (molar ratio of SiO2/Na2O) on the compressive strength of the geopolymer was evaluated. The highest compressive strength of 45.6 MPa was attained at 7 days with a composition containing 40 wt% of CW and an alkali activator modulus of 1.4. Furthermore, the geopolymer with the most desirable compressive strength was selected for the preparation of SiO2–TiO2/CW-GBFS-based geopolymer (ST/CGG). The effect of nano-SiO2-TiO2 dosage on the self-cleaning performance of ST/CGG was explored. The self-cleaning surface of the ST/CGG had a maximum water contact angle of 118° when the addition of SiO2 and TiO2 was 5.8 wt%. Moreover, the surface of the ST/CGG underwent testing for methyl orange degradation, ultraviolet–visible diffuse reflectance spectral analysis, oleic acid decomposition, and bauxite residue removal, validating its superior photocatalytic self-cleaning efficacy. Overall, this work not only highlights the potential of ceramic waste utilization for geopolymers, but also provides a feasible strategy for developing functional geopolymers with self-cleaning ability.