Application of Fenton sludge coupled selective acid leaching in selective catalytic reduction of NOx: Performance and mechanisms

Abstract

• Fenton sludge is used to prepare SCR iron-based catalyst. • Physical and chemical properties of the catalyst are characterized in detail. • An alternative method was provided to dispose Fenton sludge. • The optimum acid leaching conditions were explored in detail. • NO x conversion can reach 100% at 301–450 °C. Fenton sludge is a type of industrial hazardous waste produced after the Fenton reaction treats industrial wastewater that contains a large amount of iron oxide and other metallic elements. In this study, an efficient treatment method for preparing a selective catalytic reduction catalyst from Fenton sludge is proposed. Fenton sludge was treated using a selective acid leaching method, and the effects of four main factors were systematically studied. The experimental results showed that the dealkalization extent reached 94.8% and the retention extent of active components was 90.46% under the condition of the liquid-to-solid ratio of 6 mL/g, acid leaching temperature of 80 °C, acid leaching time of 60 min and acid dosage of 20%. The modified Fenton sludge catalyst (MFS) achieved 100% NO x conversion in the temperature range 301–450 °C, which is a wide reaction temperature range and excellent low-temperature catalytic activity. The selective dealkalization treatment can effectively inhibit the high-temperature sintering of the catalyst, increase the specific surface area and porosity of the catalyst and improve the redox performance of the catalyst. Moreover, the high O β concentration, Fe 3+ /Fe 2+ ratio and number of oxygen vacancies contributed to the excellent catalytic performance of MFS.