Chemical Activation of Khojakul Phosphorites by Ammonium Salts

Aims: To investigate chemical activation of low-grade phosphorite from Karakalpakstan, Khojakul by ammonium salts in order to obtain slow-acting phosphate fertilizers.

Study Design: The content of the total form N (Nt.) was determined by method Kjeldahl method. Determination of total and acceptable forms (on 0.2 M solution of Trilon B) of phosphorus (P2O5tot., P2O5wat.) was performed widely in the analysis of phosphate ores by differential method on photo colour meter PCM-3 (made in Russia, l = 440 nm) as phosphorus-vanadium-molybdenum complex. This method is based on measuring the light transmission of yellow phosphorus-vanadium-molybdenum complex relative to the reference solution containing a certain amount of phosphates. The method allows analyzing the products with a relative error of determining ±1%. The activation rate (Ka) was defined by relation acceptable P2O5 form to total P2O5 form. Decarbonization degree (Kd) was determined by changing C02 in the phosphate rock and final product. pH of ammonium salts solution and final products were defined after their agitation in 10% distiller water suspension. Further suspension obtained was measured by potentiometric method on ionomer I-130M (made in Russia) with electrode system of electrodes ESL 63-07, EVL-1M3.1.

Place and Duration of Study: The laboratory of phosphate fertilizers of the Institute of General and Inorganic Chemistry under Academy Science of the Republic of Uzbekistan, from July to August in 2016.

Methodology: Model laboratory device that obtains fertilizers consists of five-liter screw mixer made from stainless steel 12X18H10T equipped with stirrer, moved by electric motor. The laboratorial experiment is done in the following way: in the beginning measured sample of phosphorite was charged in screw mixer and then it was fed to 2, 5, 10 and 20% of ammonia solutions at different ratios proportions of mineral fertilizers (MF) and phosphorite powder (PHP), for 30 min with vigorous stirring components. Products obtained from interaction of components were analyzed for nitrogen content and different forms of phosphorus. The weight ratio of MF:PHP was in the range from 1: 1 to 1: 10. After completing activation process for 30 minute, wet products were dried in muffle oven at 90°C until dry condition.

Results: The chemical compositions of final products were determined during the experiment. Based on chemical activation of low-grade phosphorite fertilizers containing high acceptable form of phosphorus (v) oxide (P2O5) can be obtained. It had been found that degree of activation (Ka) of phosphorite powder depends on the nature of the ammonium solution and the pH of the medium. Ammonium sulphate is more acidic than ammonium nitrate, ammonium phosphate, and ammonium chloride. The pH of ammonium sulphate (10% of its solution) is 3.80. The decarbonization degree (Kd) of the fertilizers obtained from ammonium sulphate is in a range from 6.33 to 35.39%, which is higher than for other types. Therefore, there had been obtained the fertilizers containing high acceptable form of phosphorus (v) oxide in a range 35.30 – 59.07%. It was revealed that the more phosphate raw is used for activation process, the less is acceptable P2O5 in fertilizers obtained. Moreover, the fertilizers have high content of nitrogen, depending on the type of ammonium salts used, in a range 1.06 – 17.33% in the composition.

Conclusion: Based on the results it is possible to obtain effective slow-acting complex phosphate fertilizers with different ratios of nutrients by the activation of low-grade phosphate rock from Karakalpakstan, which do not have an industrial value, mineral salts, used in agriculture as a standard mineral fertilizer.