Currently, various industrial enterprises produce large amounts of gypsum-containing waste. It is not surprising that researchers and industry specialists pay special attention to the problem of disposal and recycling of gypsum waste.
One of the most promising approaches to gypsum waste processing is the development and implementation of technologies for obtaining gypsum binders from these materials. Such binders are in great demand among construction material production facilities. The implementation of this approach may significantly reduce pollution of soil and air, water bodies and groundwater. In many regions of Russia that do not have their own gypsum deposits, this method will be beneficial for the environment. It will also supply local construction material production facilities with raw materials at a lower price than those shipped from other regions (long-distance transportation of gypsum significantly increases its cost).
Phosphogypsum, borogypsum, and fluorogypsum are all recycled. The main process used is boiling the waste in liquid media. If gypsum waste contains too many impurities (more than 0.5%), especially phosphorus or fluorine, which can significantly reduce the quality of the binder, then the raw material is pre-washed. Recycling of citrogypsum, a waste product of the manufacture of citric acid, is a very complex technological process. And the most common type of gypsum waste is phosphogypsum, a by-product of processing phosphorite and apatite ores. For example, in the production of one ton of superphosphate, one of the most popular agricultural fertilizers, four tons of phosphogypsum are formed.
Specialists offer various methods of processing — both focused on energy-intensive technologies, and more economical non-autoclave ones based on the dehydrating effect of sulfuric acid. As a rule, processing technologies involve the production of modified gypsum binders, which are more in demand in the industry. The primary target of the modification is water resistance of gypsum plaster.
Though recycling technologies are constantly evolving, and more and more enterprises are introducing them in the production to a certain degree, the processing and reuse of gypsum waste is far from forming a full production cycle — most regions continue to accumulate gypsum waste.