Using ultrasonic and microwave devices to dry and disperse soils with high Fe2O3 content from Brazil

Abstract

Our aim was to use the domestic microwave to dry different tropical soils with an iron oxide (Fe2O3) content in the clay fraction, as well as to disperse them using ultrasonic energy. We used nine soils with different Fe2O3 content in the clay fraction (31–663 g kg−1) from horizons (A-Bi-Bw) of the Inceptisols and Oxisols in Brazil. The study was separated into two experiments: 1- soil drying time modeling (classic oven methods v. domestic microwave), 2- Soil dispersion: particle size and clay dispersed in water, by ultrasound energy v. standard method (NaOH 1 N + mechanical dispersion). Data were submitted to Gompertz non-linear regression model, ANOVA, Scott Knott's test, and Pearson's correlations. The domestic microwave was efficient for eigth soils studied, being limited when the Fe2O3 content exceeds 50%. The optimum drying time was between 30 and 40 min. The dispersion carried out by sonification, with the energy of 127.5 Jml−1, in five minutes, increased the clay content, showing greater efficiency in relation to the standard dispersion method, in soils with high Fe2O3 content. The use of the domestic microwave and the ultrasonic to disperse the soil allows a particle size analysis to be carried out in one hour with good precision compared to the standard method.