Phosphogypsum, composition and application.
Phosphogypsum is produced as a by product (waste) in the production of phosphoric acid and phosphate fertilizers from Apatite and phosphorite. It is used in agriculture as ameliorant and fertilizer and in the manufacture of building materials and products.
Phosphogypsum – a fertilizerused for plastering of soils. Phosphogypsum contains at least 80% of gypsum (CaSO4·2H2O) in the form of small crystals and 0.4% water-soluble phosphorus oxide, which is its beneficial components. It also contains soluble impurities (sulfuric acid, phosphoric acid, mono – and dicalcium phosphate) and insoluble (silica, phosphates, fluorides) substances, including rare earth and radioactive elements, heavy metals and other harmful and toxic elements.
Unwanted impurity elements (e.g., uranium, thorium, radium, polonium, cadmium, radon, neodymium, dysprosium, terbium, cerium, lanthanum, praseodymium) as a valuable material can be extracted from the phosphogypsum.
Phosphogypsum is produced as a by product ( waste) in the production of phosphoric acid and phosphate fertilizers from Apatite and phosphorite. Currently in Russia in the dumps of industrial enterprises have accumulated approximately 320 million tons of phosphogypsum.
The main use of phosphogypsum is the use of it as fertilizer and meliorant in agriculture for sodic (saline) soils. Salinization is typical of irrigated land, but also areas with dry climate. The total area of saline lands in Russia currently is around 35-40 million hectare or about 20% of the farmland area. The area of arable saline land is 10 million hectares.
The cause of soil salinity is the predominance in the soil of sodium ions, which have a tendency over time to accumulate. Large concentrations of this element inhibit the activity of microorganisms and plants, makes the soil sticky, structureless and unsuitable for processing. On the soil surface forms a waterproof crust. Radical improvement of soils is achieved by the substitution of sodium for calcium ions. When applied to such soils phosphogypsum the formation of sodium sulfate, which are easily washed out, which helps to normalize the water permeability of the soil.
Unlike phosphogypsum natural gypsum is less soluble in the soil because of its chemical composition, therefore, in agriculture use of phosphogypsum soluble. It make the soil once every few years at 6-7 tons per 1 hectare. Besides the function of leaching and reduce alkalinity of soil, natural material and fertilizer. It includes calcium, phosphorus, sulfur, and other trace minerals that increase crop yields. In addition, before the introduction of the soil it does not require cleaning P2O5 as the phosphorus, which it contains in the form of P2O5, is absorbed by plants.
A single application of phosphogypsum dose provides an increase of wheat yields about 15 quintals per 1 hectare (during the action).
Gypsum, which is contained in phosphogypsum is a great knitting tool. It can be used for the production of various construction materials, including cementand construction products, for example, partition blocks, slabs, bricks, plasterboards, as well as in road construction.
Roads constructed with phosphogypsum, characterized by low cost, reliability and durability.
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