Recycling and characterization of spent catalyst: Carmoisine dye removal from water and carbon monoxide conversion to carbon dioxide in air

[Display omitted] •Economic recycling of spent Co-Mo-Al2O3 catalysts.•Characterization of the recycling of catalysts by EDX, XPS and BET methods.•Fast removal (98%) of carmoisine azo dye from water.•Carbon monoxide conversion (100%) to carbon dioxide.•Catalyst useful to remove carmoisine and carbon monoxide from water and air. This study describes the recycling of the spent Co-Mo-Al2O3 catalysts in hydro-treating diesel fuel and subsequent application in purifying wastewater and air from harmful contaminants. A sodium carbonate solution was used for the selective extraction of molybdenum with an extraction efficiency of at least 90 %. As a result, Mo-Al2O3 material was obtained. The material was characterized by EDX and low-temperature nitrogen adsorption. The materials showed high activity and stability as a Fenton-type catalyst in the oxidative degradation of the carmoisine azo dye in aqueous solution with 98 % removal in 30 min having 8.0 g/L catalyst at pH 2.0 and 60 °C temp. The carbon monoxide conversion to carbon dioxide was 100 % at 475 °C. The present work is very useful for the purification of water by removing carmoisine dye and air by converting carbon monoxide to carbon dioxide.