From Hazardous Waste to Resource: Upcycling Barium Slag as Valuable Industrial Materials for the Circular Economy

Barium slag (BS) is an industrial hazardous solid waste generated during the production of barium salts. It is primarily derived from the reduction roasting of barite. BS itself contains a large amount of heavy metals and alkaline substances, which are highly toxic and can pose a threat to human health and the environment. BS is increasingly recognized as a valuable resource because of its abundant content of useful constituents, including BaO, SiO2, CaO, SO3, unreacted barite, quartz (SiO2), clay minerals, and residual carbon. However, the reuse of BS faces several critical challenges, including its attributes of hazardous waste or risks, technical treatment difficulty, product application safety and economic constraints. This systematically reviews the key pathways and multi-dimensional evaluation of the resource utilization of BS. Specifically, it encompasses four major technical routes: recovery of valuable components, production of building materials, preparation of environmental materials, and design of other functional materials. It also delves into performance optimization strategies, chemical reaction mechanisms, and core scientific challenges. Meanwhile, it conducts a comprehensive review from the perspectives of environmental benefits, economic feasibility, technical limitations, and future research directions in the circular economy. In summary, by analyzing the current status of BS resource utilization, existing deficiencies, improvement recommendations, and future prospects can be identified. This, in turn, clarifies the pathway for recycling resources and ultimately achieves the integration of environmental and economic benefits.