Heteroatoms doped iron oxide-based catalyst prepared from zinc slag for efficient selective catalytic reduction of NO_x with NH₃

Excessive emissions of nitrogen oxides from flue gas have imposed various detrimental impacts on environment, and the development of deNO_x catalysts with low-cost and high performance is an urgent requirement. Iron oxide-based material has been explored for promising deNO_x catalysts. However, the unsatisfactory low-temperature activity limits their practical applications. In this study, a series of excellent low-temperature denitrification catalysts (Ha-FeO_x/yZS) were prepared by acid treatment of zinc slag, and the mass ratios of Fe to impure ions was regulated by adjusting the acid concentrations. Ha-FeO_x/yZS showed high denitrification performance (> 90%) in the range of 180–300 °C, and the optimal NO conversion and N₂ selectivity were higher than 95% at 250 °C. Among them, the Ha-FeO_x/2ZS synthesized with 2 mol/L HNO₃ exhibited the widest temperature window (175–350 °C). The excellent denitrification performance of Ha-FeO_x/yZS was mainly attributed to the strong interaction between Fe and impurity ions to inhibit the growth of crystals, making Ha-FeO_x/yZS with amorphous structure, nice fine particles, large specific surface area, more surface acid sites and high chemisorbed oxygen. The in-situ DRIFT experiments confirmed that the SCR reaction on the Ha-FeO_x/yZS followed both Langmuir-Hinshelwood (L-H) mechanism and Eley-Rideal (E-R) mechanism. The present work proposed a high value-added method for the preparation of cost-effective catalysts from zinc slag, which showed a promising application prospect in NO_x removal by selective catalytic reduction with ammonia.