The article presents the results of generalization of known information on various methods of enrichment of low-grade phosphate raw materials in the world. Based on the review of literature materials, scientists propose several methods of enrichment: mechanical, calcination at high temperatures, flotation, chemical enrichment with various acids and salts. Analyzing and summarizing these data, the article describes the advantages and disadvantages of each proposed method of enrichment of low-grade phosphorites. It is known that the sphere of production of phosphorus-containing products is important for many agricultural countries that produce these products themselves or import from others. This review material is very important for those who are interested in the problems of attracting low-grade phosphates into the production cycle by enriching them.

No abstract

No abstract

The article presents the results of studies of the process of obtaining NPK fertilizer from low-grade phosphate raw materials with P2O5 of about 18%. Phosphate raw materials were leached with a mixture of nitric-phosphoric acids with the addition of potassium carbonate, which serves as a source of potassium in the final product. The main parameters determined were the content of the main nutrients P2O5:N:K2O, temperature and time of the leaching process. According to the graphical method, the “apparent” activation energy of the heterogeneous process is found, which is equal to 3.8 kJ/mol indicates the intradiffusion nature of the process. Methods of chemical analysis, scanning electron microscopy and XRD analysis were used for a comprehensive study of raw materials and final products.

The results of physico-chemical and microscopic investigations of phosphorus sludge are considered. It was established that phosphorus sludge does not meet regulatory requirements for mineral fertilizing on granulometric composition. On chemical composition, phosphorus sludge is close to original phosphate raw material of Karatau deposit, but it differs from latter by its less content of phosphate component and presence of constituents of charge mixture -quartzite and coke. The results of microscopic investigations show that phosphorus sludge structure contains mainly calcium silicates, diopside, and potassium aluminosilicates. The presence of latter ones allows that phosphorus sludge is a valuable secondary phosphate raw material, quite suitable for recycling of it into phosphorus, potassium containing complex mineral fertilizer.