Exploring the self-cleaning and antimicrobial efficiency of the magnesium oxychloride cement composites

Abstract

Composites of magnesium oxychloride cement (MOC) functionalized with TiO2 nanoparticles are proposed here as an alternative technology to maintain clean building surfaces from airborne pollutants and microorganisms. The MOC composites were characterized by different techniques such as XRD, FTIR, SEM, EDS, UV–Vis, compressive strength, and nanoindentation tests. According to the results, phase 3 (3 Mg(OH)2.MgCl2.8H2O) with needle-like morphology was the primary crystallized hydration product for the MOC composites. Also, the samples exhibited good mechanical properties and good light absorption, allowing them to activate under solar light irradiation. The self-cleaning efficiency of the MOC composites was evaluated by measuring the removal of three types of pollutants: methylene blue (MB), rhodamine B (RhB), and reactive black 5 (RB5), under two scenarios: natural sunlight and accelerated weathering conditions. The self-cleaning tests revealed outstanding efficiencies of the composites to remove MB (82%), RhB (88%), and RB5 (91%) under solar light and accelerated weathering tests. On the other hand, the antimicrobial activity was evaluated against E. coli (gram-negative) and S. aureus (gram-positive) under irradiation. The zone of inhibition (ZOI) showed diameters higher than 21 mm to E. coli for samples with 5% of TiO2 or superior, revealing a high microbial inhibition of the gram-negative bacteria. Also, the structural and morphological stability of the MOC composites was confirmed after several cycles for the accelerating weathering tests, demonstrating their potential to be used outdoors to reduce environmental pollution.