Harmless disposal of phosphogypsum synergized red mud: Harmful element control and material utilization

Abstract

Soluble P2O5 and fluorine in phosphogypsum can jeopardize the environment and even human health. The application in building materials is a pathway to consume phosphogypsum on a large scale. However, the presence of soluble phosphorus causes significant retardation that reduces the early strength of building materials containing phosphogypsum. In this study, the mechanism of soluble phosphorus removal from phosphogypsum by red mud were studied. The synergistic effect of phosphogypsum, red mud and blast furnace slag for the preparation of high-sulfur cementitious materials was also investigated. The results demonstrated that the soluble phosphorus was transformed to inert material and was completely stabilized when red mud dosing reached 20 %. The slow setting was significantly improved, causing an increase in 3-d compressive strength. More hydration products were generated to enhance the early strength, indicating that the optimal synergistic effect of phosphogypsum, red mud and blast furnace slag occurred. In addition, the compressive strength reached 21.40 MPa (3 d), 29.60 MPa (7 d), and 48.60 MPa (28 d) when the total admixture of phosphogypsum and red mud was 45 %. The environmental performance research also shows that the material was green and non-polluting. This paper advocates the use of the physicochemical properties of different solid wastes to dispose of hazardous substances in phosphogypsum rather than the use of natural resources.