Enhancement of phosphogypsum mechanical block with the addition of iron and aluminum salts

Waste gypsum is one of the typical industrial solid waste in the world. Due to its treatment technical barriers, the existing treatment of waste gypsum is mainly stockpiled. And with the rapid development of industry, the treatment of waste gypsum has become one of the key issues of environmental protection. In this study, blocks of phosphogypsum were pressed by conventional mechanical methods, and subsequently, the effects of different pressing press pressures, curing times, moisture content and different added substances on the mechanical and waterproof properties of the block were investigated. The experimental results showed that when the pressing pressure is 300 MPa, curing time is 3 d, water content is 5%, and the content of elemental iron and aluminum is 1%, the mechanical properties and waterproof performance are the best. At this time, the compressive strength is 54 MPa, the flexural strength is 8 MPa, and the softening coefficient is more than 0.90. Through the leaching toxicity analysis, it was found that the pressed block has a better sealing effect on the toxic and harmful substances in the waste gypsum, and the toxic and harmful substances were not be released. This method provides an economic and simple way for high value-added resource treatment of solid waste gypsum.