Preparation of spherical tungsten trioxide by spray pyrolysis of peroxotungstic acid

This paper proposes a short-process, environmentally friendly approach for preparing spherical tungsten oxide powder using peroxotungstic acid solution, and investigates the factors influencing the spray pyrolysis, as well as the underlying pyrolysis mechanism. The experimental results demonstrate that varying the concentration of peroxotungstic acid did not significantly affect droplet atomization efficiency, but more WO₃ led to the formation of coarser particles in a high-concentration solution. Droplets underwent uniform contraction at l80 °C, yielding smaller particles, whereas the formation of porous structures was promoted at 300 °C. Rapid carrier gas velocity (120 L/min) induced particle adhesion and the generation of secondary particles, yet it also facilitated the collection of finer particles. Furthermore, an increase in ultrasonic frequency correlated with a reduction in the particle size of the pyrolysis product. Solid spherical monoclinic tungsten trioxide could be obtained through low-temperature calcination at 400 °C without altering the particle morphology. This paper presents a promising solution to address the challenges of ammonia nitrogen pollution and process complexity in conventional tungsten refining.