Change in dispersion of synthetic magnetite particles from the conditions of precipitation from iron sulfate-containing solutions

Abstract

The paper analyzes the problems of the reagent method of wastewater treatment of machine–building enterprises, and the advantages of the magnetic sorption method in comparison with the reagent method are presented. The magnetosorption method, based on the treatment of a liquid with particles of a ferromagnetic material with the aim of sorption on their surface of substances to be extracted, has proven itself well not only in the purification of wastewater from impurities of heavy metals, but also from petroleum products, surfactants, radioisotopes, and suspended substances. The efficiency of water purification processes depends on the properties of the sorbent particles, such as dispersion, sorption capacity and magnetic properties of the particles. The paper presents the results on the dispersion of particles. Changes in the dispersion of synthetic magnetite particles obtained under various conditions, such as storage time, temperature, pH, K=[Fe2+]:[Fe3+] ratio, salt content, and nature of the precipitant, were studied. It is shown that with an increase in storage time, the number of small particles less than 10 μm decreases, and the number of large particles increases due to recrystallization processes. It has been determined that at 20 ℃ without the influence of a magnetic field, a suspension with a maximum content of particles with a diameter of 10 μm is formed, at a temperature of 40 –  70 ℃ particles with a size of 8 –  10 μm prevail in the suspension, and with an increase in the pH of the solution, the number of small particles in the suspension increases. Conversely, with an increase in salt content, the particle size increases with a decrease in the fraction of small particles by almost half. It is noted that at K = 0.8; 2.0, the largest number of particles (about 60 %) with a size of 10 μm are formed in the solution. It is shown that the maximum number of particles larger than 20 μm is formed using NaOH.