Efficiency of Adsorption and Photodegradation of Composite TiO2/Fe2O3 and Industrial Wastes in Cyanide Removal

Abstract

This research focused on the evaluation of the Fe2O3/TiO2 composite and two industrial wastes, a kaolin (Clay-K) and a blast furnace sludge (BFS), as adsorbents and/or photocatalytic materials to enhance the removal of cyanide from aqueous solutions. Cyanide adsorption tests were conducted in the absence of light. In contrast, cyanide photodegradation tests were conducted under three types of irradiations: visible light, ultraviolet (UV) light, and natural sunlight. For the latter case, two irradiance conditions were evaluated. Cyanide adsorption from aqueous phases was similar for Clay-K and TiO2/Fe2O3 materials, which adsorbed almost twice as much cyanide compared to the BFS sample. The differences observed in cyanide removal were explained in terms of the material’s surface area and chemical composition, and a complexation of cyanide ions with surface metals was suggested as the most feasible adsorption mechanism. The set of cyanide photodegradation experiments promoted, in general, higher cyanide removal from the aqueous solution compared to the adsorption processes. Under the conditions used in this study and when using Clay-K and BFS as promoters, cyanide photodegradation progressively enhanced with the following radiations: visible light < visible light