An evaluation of the use of the spex mixer mill unit for soil particle dispersion

Abstract

Abstract The Spex Mixer Mill (Model-1800) for soil particle breakdown was evaluated, and its effectiveness was compared with that of ultrasonic vibration (Brownwell Biosonik IV) using three soils developed from the same volcanic ash deposits but under different climatic conditions on the Island of Hawaii. The Akaka and Hilo soils (Typic Hydrandepts) were developed under high rainfall (3,500-7,600 mm/year) and consisted of large amounts of amorphous materials. The Kawaihae soil which was developed under low rainfall (150-500 mm/year) contained mainly dehydrated halloysite. The study revealed that the soil : water ratio and the total soil suspension volume strongly influenced on the particle dispersion. At maximum dispersion, the soil : water ratios were 1 : 4, 1 : 6, and 1 : 8 for the Kawaihae, Hilo, and Akaka soils, respectively, and nearly half of the given container volume was best. The soil : water ratios for maximum dispersion were closely and positively related to the specific surface areas of the soils. It is postulated that the functions of water were to sustain the interaggregate frictional forces and water film thickness around the particles to maintain an interparticle distance for colloidal stability. The estimated minimum water film thicknesses were 430, 233, and 277 Å. for the Kawaihae, Hilo, and Akaka soils, respectively. The shaking obtained using the Spex Mixer Mill technique was far more effective than the ultrasonic vibration technique for soil particle breakdown. It was also found that the P2O5 dried Typic Hydrandept soils required a much longer period of time, compared to the original (wet) soils, to reach a plateau of recovered clay-sized particles. Even so, the amount of clay-sized particles recovered from the P2O5 dried soils was significantly lower than the amount recovered from the original (wet) soils.