Synthesis of zinc borate using water soluble additives: Kinetics and product characterization

Abstract

Abstract Zinc borate was synthesized from the reaction of zinc oxide and boric acid in the absence or presence of seven different water soluble additives. Additive concentration and zinc oxide particle size were varied to investigate their effect on the growth kinetics of zinc borate particles. Zinc borate particles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Samples taken from the reaction mixture during the synthesis were analyzed for determining the concentration of zinc oxide, boron oxide, and zinc borate. The results reveal the formation of zinc borate with the molecular formula 2ZnO·3B2O3·3H2O in the form of irregular platelets. The product retains its hydrate up to 300 °C. The reaction rate was found to increase when additives or nanosize zinc oxide were used. However, a lag time is observed in the presence of additives while the reaction completion time remains unaffected. The experimental kinetics data were fit to the logistic model. The variation of the model parameters with experimental conditions was also investigated. The results reveal that the specific reaction rate increases with the increasing concentration of additives and the decreasing size of zinc oxide particles.