Box–Behnken Experimental Design for Zinc Borate Zn2B6O11•7H2O

The present study investigated the effect of the operating conditions on the crystallization of zinc borate. For zinc borate crystallization, sodium tetraborate decahydrate and zinc sulfate heptahydrate were used as reactants. In the first part of the study, the crystals were characterized by X-ray diffraction spectroscopy (XRD), Fourier-transform infrared spectroscopy (FTIR), light microscopy, and particle size and thermogravimetric analysis. The results show that the obtained crystals were in the form of Zn2B6O11•7H2O, and the operating conditions had a significant effect on the size, morphology, and filtration characteristics of the zinc borate crystals. In the second part of the study, Box–Behnken design (BBD) with response surface methodology (RSM) was employed to determine the optimal operating conditions for zinc borate crystallization. The effects of stirring rate, temperature, and reactant feed rate on the average particle size were investigated. The results show that the data sufficiently fit the second-order polynomial model. The crystallization conditions, including stirring rate, temperature, and reactant feed rate, were studied at 400–500 rpm, 45–85oC, and 300–900 mL/h, respectively. The minimum particle size (3.3 µm) was obtained at a stirring rate of 450 rpm, a temperature of 85oC, and a reactant feed rate of 300 mL/h.