Experimental optimization of microwave drying zinc oxide leach residues by response surface methodology

Abstract

AbstractResponse surface methodology (RSM) and Box-Behnken design (BBD) were applied to experiment optimization of microwave drying zinc oxide leach residues (ZOLR). The effects of different factors involving temperature, drying time, material mass, material thickness and their interaction on moisture content and dehydration rate of ZOLR were investigated. Two second-order polynomial models for moisture content and dehydration rate of ZOLR were established by multivariate regression analysis. Analysis of variance shows that all independent variable and quadratic terms of the four factors have significant influence on moisture content and dehydration rate of ZOLR. The optimum drying conditions are as follows: temperature is 93.41°C, drying time is 15.9 min, sample mass is 77.91 g and material thickness is 17 mm. The predicted values of moisture content and dehydration rate were 10.98% and 1 g/min, which were close to experimental values 11±0.03% and 1±0.01 g/min under the optimal conditions. Infrared spectra analysis show that no chemical reactions took place in the process of microwave dying ZOLR and only a part of the absorbed water was removed in the sample.