Известия Томского политехнического университета: Инжиниринг георесурсов (May 2019)
The research of particle size of calcium oxalate obtained by precipitation from nitrate solutions
Abstract
The relevance of the research is conditioned by the fact that calcium ions precipitation in the form of oxalate is widely used for its quantitative determination, concentration and preliminary separation of transplutonium elements from a range of elements (Mg, Mn, Al, Cr, Fe, Ni etc.). Calcium oxalate being the least soluble of all oxalates of alkaline-earth metals, can quantitatively purify solutions from radionuclides by entrapping them in the precipitate and leaving the concomitant impurities in the solution. Awareness of the size of calcium oxalate crystals obtained in production conditions makes it possible to avoid the sediment entrainment while filtrating. It also increases the separation degree, thereby improving cost-performance characteristics of production. The main aim of the research is to study the effects of the solution acidity and the precipitant concentration (oxalic acid) on the size of the resulting particles of calcium oxalate, and to choose the type of filter for entrapping particulates of sediment formed from acidic nitrate solutions, that provides the most complete separation of the solution from the precipitate without using additional filtration or refiltration of the solution. The methods used in the research: co-precipitation method, adsorbtion, quartering technique, determination of the particle size of calcium oxalate precipitate, obtained by precipitation of oxalic acid calcium salts from nitrate solutions, X-ray spectrometry analysis and scanning electron microscopy technique by means of the electron microscope "Inspect S" with the microanalyser Edax. The results. The paper considers the mechanisms of crystal growth depending on various factors and conditions. The authors have studied the size of the particles of calcium oxalate, obtained by precipitation with oxalic acid from nitrate solutions of calcium salts. The photographs of the precipitation were made; the dispersion analysis of the examined system of particle allocation according to size was carried out. It was ascertained that by reducing the acidity of the solution from 2,0 to 0,01 mol/l, the size of the resultant particles of calcium oxalate decreases from 42,0-35,0 to 1,0-0,1 m.
