Optimization and modeling of zinc borate (2ZnO·3B2O3·3.5H2O) production with the reaction of boric acid and zinc oxide

Production of zinc borate from boric acid was investigated in aqueous media. Zinc oxide and zinc borate are used as seed crystal to convert all the zinc oxide and to get a high reaction rate. The effect of some parameters such as temperature, stirring speed, H3BO3-to-ZnO ratio, % seed crystal/(H3BO3 + ZnO) and time was studied on zinc borate production by using the 25−1 fractional factorial design and central composite design methods. The chosen experimental parameters and their ranges were as follows: reaction temperature, 68–102 °C; stirring speed, 333–767 rpm; H3BO3-to-ZnO ratio, 3–10; % seed crystal/(H3BO3 + ZnO), 0–1; time, 60–200 min. A statistical model for production of zinc borate was developed between the zinc oxide conversion and relevant parameters by means of variance analysis by using the Matlab computer software. This model was used to determine optimum production conditions. The optimum conditions for production of the zinc borate from boric acid in aqueous media were determined to be as follows: reaction temperature, 85 °C; stirring speed, 766 rpm; H3BO3-to-ZnO ratio, 10; % seed crystal/(H3BO3 + ZnO), 1 × 10−3, reaction time, 183 min. Under the optimum conditions, the calculated zinc oxide conversion was approximately 99%.