Abstract:In the process of industrial production, the treatment process of arsenic-containing flue gas and wastewater often involves with the production and discharge of arsenic-containing gypsum sludge which has low resource value and is a hazardous waste. Thus, its low-cost and harmless treatment is an important development direction. Based on the idea of "treating waste with waste", lead smelting slag was used to prepare cementitious materials which was applied to solidify arsenic-containing gypsum sludge. Moreover, the microwave irradiation curing was introduced to replace the traditional constant temperature and humidity curing. The results show that the compressive strength and arsenic leaching concentration of the solidified body obtained after 500 W microwave irradiation for 1.5 minutes are comparable to the solidified body obtained at constant temperature and humidity curing for seven days. The compressive strength reaches 3.09 MPa, and the As leaching concentration reduces to 0.5 mg/L below, which meets the requirements of the "Hazardous Waste Landfill Pollution Control Standard" (GB 18598—2019). Further studies on the hydration reaction characteristics and arsenic solidification behavior show that the hydration products of the system are mainly C-(Al/Fe)-S-H (calcium silicate hydrate or aluminum silicon hydrate/calcium ferrite hydrate) gel and ettringite. However, the microwave irradiation can inhibit the formation of ettringite. Therefore, the solidification of arsenic mainly depends on the physical encapsulation and encapsulation of C-(Al/Fe)-S-H gel.