Complex processing of phosphatic ores enrichment waste
The production of high-quality phosphate fertilizers, in particular calcium acid phosphates, requires the use of ore rich in phosphates (above 28 wt.% P2O5) and containing a minimum amount of impurities, including harmful ones. The absence of such large natural deposits leads to the need to enrich the existing phosphate ore containing an average amount of phosphates (14-23% P2O5) and contaminated with various impurities. Enrichment of polymineral phosphate ores leads to the production of their concentrates and waste (sludge). Sludge is a mixture of clay impurities, iron compounds, phosphate substances contained in the original ore, as well as toxic surfactants used in its flotation enrichment. This prevents the use of sludge as a secondary source of raw materials in any industry and its return to waste deposits. The lack of methods for processing sludge leads to their accumulation and environmental pollution: the area of fertile land is shrinking, pollution of nearby natural water bodies increases. The proposed integrated physicochemical technology for processing phosphate ore dressing wastes using nitric acid is aimed at improving the environmental situation in the regions producing phosphate raw materials and obtaining a number of valuable products important for the national economy: glauconite sand, clay, hydrogen phosphate and calcium nitrate. The yield of sludge processing products was experimentally established, which amounted to: 68.6% glauconite, 6.91% clay, 12.9% technical calcium hydrogen phosphate, 18.2% technical calcium nitrate. Processing products - clay and glauconite sand are most widely used in the construction industry, in particular, in the production of bricks and concrete. Glauconite sand and clay are used in the production of sorbents, paints and primers. Hydrophosphate and calcium nitrate are used in agriculture as phosphorus and nitrogen fertilizers, respectively.