Scientists propose a universal method for recycling gypsum production waste

An international group of scientists has proposed a comprehensive method for obtaining synthetic gypsum from filtration products of natural water sources. From the waste remaining after gypsum production, researchers suggest manufacturing sorbents for oil removal from rivers, seas, and oceans, as well as photocatalytic materials for wastewater treatment from dyes. Tests of the obtained materials showed that they not only meet all the requirements for substances of this class but can also be used as fertilizer. The work was published in the scientific journal Environmental Science and Pollution Research.

Industrial waste often poses a problem for enterprises, requiring additional costs for storage or disposal. Neutralizing spent sulfuric acid and chemical precipitates from natural water discoloration not only reduces the volume of waste material but also creates a new product that can be used in construction, medicine, or other industries. However, in this case, besides synthetic gypsum, an acidic filtrate is formed — a liquid with high acidity and high iron content.

Scientists from the MISIS University, together with colleagues from Belarus, proposed to process the acidic filtrate not only into magnetic sorbents capable of removing oil products from aquatic environments but also into photocatalytic materials for wastewater treatment from dyes. As the researchers note, the water remaining after the neutralized filtrate can be used as a complex fertilizer, as it contains sulfur, calcium, magnesium, and sodium.

Photocatalytic materials were obtained by combustion synthesis in a solution, and glycine, citric acid, urea, and hexamethylenetetramine were used as reducers.

“High concentration iron sulfate obtained after gypsum production is an excellent source for synthesizing magnetic sorbents and photocatalysts. The best results as photocatalytic materials for the destruction of harmful organic substances were shown by samples obtained using citric acid and hexamethylenetetramine as reducers. To manufacture the most effective oil sorbents, it is better to use glycine as a reducer. The remaining neutralized filtrate also underwent tests as a complex fertilizer. Oil radish shoots watered with this solution accelerated growth by 15% compared to untreated samples,” notes co-author of the study Valentin Romanovsky, an employee of the Research Center “Structural Ceramic Nanomaterials” at MISIS University.

Further research by scientists will be aimed at testing the technology of obtaining synthetic gypsum from other calcium-containing wastes and producing high-quality binders based on them.