Comparative study on the toxic elements in spent selective catalytic reduction (SCR) catalyst from different industries: Occurrence, leaching behavior, and detoxification strategy

Selective catalytic reduction (SCR) is currently the most effective control method for NOx emission after fuel combustion. Spent selective catalytic reduction (SCR) catalysts from various industries have emerged as a novel solid waste. Toxic elements in spent SCR catalysts from various industries have not been given sufficient attention, resulting in its irrational disposal and potential environmental threats. This study investigates the presence and leaching behavior of toxic elements in spent SCR catalysts samples from four distinct industries: coal-fired power plants, flat glass manufacturing, cement manufacturing, and waste incineration plant. The experimental findings reveal that spent SCR catalysts contain toxic elements including V, As, Pb, Tl, Cu, and Zn. The types and concentrations of these toxic elements are contingent upon the composition of flue gas and operational conditions of NOx removal units employed in each industry. The environmental mobility and chemical speciation of these toxic elements are determined by diverse characterization techniques. Based on the analysis results, an acid-alkali leaching detoxification strategy is proposed. Following detoxification, the leaching concentrations of toxic elements in catalysts from coal-fired power plants, flat glass manufacturing, and waste incineration conform to the requirements of hazardous waste landfill standards. This study reveals the toxic element composition in spent SCR catalysts and provides a foundation for the rational disposal and management of these catalysts across diverse industries.