SYNTHESIS OF SODIUM THIOSULFATE PENTAHYDRATE BY MECHANICAL ACTIVATION OF S−Na2SO3 SYSTEM

Abstract

The mechanochemical synthesis of sodium thiosulfate pentahydrate (Na2S2O3·5H2O) in the ball 2-drum planetary mill "Activator-2SL" owing to mechanical activation of an aqueous sulfur suspension (S) in the equimolar solution of sodium sulfite (Na2SO3) was carried out by the Na2SO3 + S = Na2S2O3 reaction for the first time. As the mechanochemical reactors for the synthesis of Na2S2O3·5H2O, the following accessories were chosen (drum balancing was carried out with the appropriate ball loading): (i) A stainless steel drum of 250 ml volume and a combined ball charge (diameter of balls was 1 cm) of silicon nitride (Si3N4, 30 pieces) and tungsten carbide (WC, 20 pieces); (ii) Silicon nitride drum of 80 ml in volume and a ball charge of tungsten carbide (30 pieces). This choice minimized the corrosion of the hardware in the alkaline solution. The synthesis process is carried out by mechanical activation of sulfur for at least 35 min at a rotational speed of the mill carrier of at least 350 rpm. The preparation of Na2S2O3·5H2O involves the reaction of elemental sulfur with a solution of sodium sulfite in the presence of ammonia, filtration of the suspension and crystallization of the desired product. X-ray phase analysis for the crystallization products of filtrates from drums (i) and (ii) showed the presence of only one phase, namely Na2S2O3·5H2O reflexes. By thermal analysis, it was determined that the difference in the crystallization products in drums (i) and (ii) is in the different content of the crystallization water: the weight loss percentage of the sample from drum (i) is many times greater than that of drum (ii). Using the method of iodometric titration, it was found that under relatively mild and short-term conditions of mechanical activation, the degree of transformation for the reaction of formation of sodium thiosulfate pentahydrate in the slurry solution is ~95%. Forcitation:Urakaev F.Kh. Synthesis of sodium thiosulfate pentahydrate by mechanical activation of S−Na2SO3 system. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 8. P. 37-42.