Abstract
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 TiO2 loadings (prepared using either titanium isopropoxide precursor or commercial TiO2 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 TiO2 wt% prepared by the precursor method had normalised photocatalytic efficiencies per gram close to that of bare TiO2; using an adsorption–photocatalysis process led to efficiencies 4.4 and 1.6 times higher than that of pure TiO2. The improvement in catalytic performance (greater for samples with less than 50% TiO2 content) may be due to better UV absorption ability (related to with the improvement of TiO2 particle dispersion) and the close TiO2 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 TiO2 surface and photodegraded more rapidly and efficiently. The outstanding synergetic adsorption–photocatalysis capacities of TiO2 waste stainless steel slag composites for dye water treatment made the proposed conversion approach have great potential in practical applications.Graphical abstract
Highlights
Stainless steel production is one of the most dynamic sectors in the manufacturing industry
In pure T iO2 synthesised by Method 1 (M1) (100M1), anatase and rutile crystalline phases were formed
The X-ray diffraction (XRD) pattern of the 100M2 sample confirmed the presence of anatase along with the rutile phase, as certified by the catalyst’s producer company
Summary
Stainless steel production is one of the most dynamic sectors in the manufacturing industry. The world production of stainless steel in 2019 exceeded 52.2 Mt (data reported by the International Stainless Steel Forum, ISSF). Stainless steel is a recyclable material; for every 2 to 4 t produced, approximately 1 t of slag is generated (Das et al 2007). The large amount of waste generated is an inconvenience, and an environmental risk. New technologies for waste slag reuse must be developed to achieve a sustainable metallurgical industry
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