Study on Preparation of Zinc Pyrithione Ultrafine Particles via Rapid Precipitation in Microchannel Reactor

Aiming at the problems of large particle size (2-5 μm) and broad particle size distribution of zinc pyrithione (ZPT) particles prepared by traditional tank reactors, ultrafine ZPT particles were synthesized via rapid precipitation method in a microchannel reactor using sodium pyrithione (SPT) and zinc sulfate as raw materials. The effects of key parameters including reactant concentration, microchannel flow velocity and channel dimension on particle size and size distribution were systematically investigated by single-factor experiments, and the drying strategy was further optimized. The results showed that under the optimal conditions-SPT concentration of 0.5 mol/L, zinc sulfate concentration of 0.25 mol/L, channel flow velocity of 21.7 m/s, channel inner diameter of 0.8 mm, room temperature reaction and pressure of 1 MPa-the particle size of wet-state ZPT reached 180 nm, which was reduced by 40% compared with that prepared in tank reactors, and the corresponding polydispersity index (PDI) was 0.18. Spray drying was verified as the optimal drying method, by which the dried particles maintained a stable size of 600 nm with favorable dispersibility, and the Zeta potential was -20.6 mV. X-ray diffraction (XRD) and thermogravimetric analysis (TGA) characterizations confirmed that the as-prepared products possessed high purity and outstanding thermal stability with stable structure below 200 °C. This work provides an efficient technical route for the fabrication of narrow-dispersed ultrafine ZPT particles, and offers reliable experimental data for the industrial application of microchannel technology in ZPT synthesis.