Sustainable environmentally friendly approaches to the recycling of spent selective catalytic reduction (SCR) catalysts

The chapter deals with the problem of the recycling of a spent selective catalytic reduction (SCR) catalyst used originally to convert nitrogen oxides into N₂ to comply with the environmental air emissions regulations. Spent SCR catalysts are considered hazardous waste due to the presence of vanadium and tungsten, which are also strategic metals in the international market and worthy of recycling alongside the titanium present. Every country deals with the problem of waste disposal, in the case of solid waste in landfills which bring environmental and social burdens. In addition, the multiple uses of vanadium and tungsten coupled with the depletion of primary ores bring a necessity for recycling of the metals from spent SCR catalysts. Finally, there is an approach to the current recycling methods and the research necessary to attain selectivity for the separation of vanadium and tungsten by several hydrometallurgical routes. A complete review and literature survey on the current techniques of vanadium and tungsten recycling is shown, both from the author’s research laboratory as from other researchers.