Combination effects of various oxidants and immobilization on lightweight expanded clay aggregate concrete on the photocatalytic activity of UV/TiO₂ system

The widespread industrial use of dyes like malachite green and golden yellow poses environmental and health risks. This study evaluated the efficacy of several oxidants, namely sodium periodate, sodium chlorate, and sodium persulfate, combined with immobilized titanium dioxide nanoparticles on lightweight expanded clay aggregate concrete under ultraviolet radiation in removing these dyes from water. The immobilization of this type of concrete addresses challenges like nanoparticle separation during photodegradation and electron–hole recombination. Characterizations revealed a thin layer of titanium dioxide on the concrete, enhancing photocatalytic properties. Critical factors like dye concentration, pH, and oxidant dosage were considered. Notably, golden yellow removal was mainly through photocatalysis, whereas malachite green removal involved an additional adsorption mechanism. Best color removal efficiencies were achieved with sodium persulfate and sodium periodate for golden yellow (99.36% and 99.91%) and with sodium persulfate and sodium chlorate for malachite green (99.61%). The optimal oxidant concentration was 0.008 mol/L across all tests. Kinetic studies showed different orders for both dyes. Reusability tests affirmed the method's efficiency, with up to 97% and 99% color removal for the respective dyes. The study underscores the potential of using immobilized titanium dioxide on lightweight expanded clay aggregate concrete with oxidants for treating dye-laden water.