Synergetic adsorption-photocatalysis process for water treatment using TiO 2 supported on waste stainless steel slag.

This study presents an economical and efficient method to decolourise dye wastewater using industrial waste stainless steel slag (SSS). Titanium dioxide was immobilised on SSS by a precipitation-calcination method. Samples with different TiO 2 loadings (prepared using either titanium isopropoxide precursor or commercial TiO 2 nanoparticles) were used to decolourise an organic contaminant (methylene blue) under dark and UV conditions in aqueous solution, and their adsorption and photocatalytic performances were compared. Samples with 15 and 25 TiO 2 wt% prepared by the precursor method had normalised photocatalytic efficiencies per gram close to that of bare TiO 2 ; using an adsorption-photocatalysis process led to efficiencies 4.4 and 1.6 times higher than that of pure TiO 2 . The improvement in catalytic performance (greater for samples with less than 50% TiO 2 content) may be due to better UV absorption ability (related to with the improvement of TiO 2 particle dispersion) and the close TiO 2 support interaction, which can eventually cause a photocatalysis-enhancing shift towards more negative oxidation potentials. The SSS also acted as an efficient adsorption trap for organic compounds. The pollutant was thus transferred to the TiO 2 surface and photodegraded more rapidly and efficiently. The outstanding synergetic adsorption-photocatalysis capacities of TiO 2 waste stainless steel slag composites for dye water treatment made the proposed conversion approach have great potential in practical applications.