| Airborne particulates such as dust, can cause human health problems and environmental damage. There is a national search for effective measures of dust emission control. In this research, potentially effective polymer solutions were evaluated with respect to their physico-chemical interactions with soils during desiccation processes that impact upon dust generation. Clay soils supply the fine particulates which could become airborne under dry condition. The capacity of the soil to hold liquids and remain relatively wet for reasonably long periods of time is hereby considered to be an index of the dust control potential of substances that are dissolved in the liquid phase in soils. Sodium carboxymethyl cellulose (CMC), polyacrylamide (PAM), polyethylene oxide (PEO) with two different molecular weights, were tested with Na-montmorillonite and kaolinite at aqueous polymer concentrations ranging from 0g/L to 10 g/L. Physico-chemical interactions between polymer solutions and clay soils were investigated through measurements and analyses of viscosity, dielectric constant, chamber desiccation, polymer/swelling, polymer sorption, Fourier Transform-Infrared (FT-IR) spectrum, X-ray diffraction patterns, Scanning electron microscopic (SEM) images, and optical microscopic images. It was found that the addition of polymer solutions improves the retention of liquid on clay soils. The time to reach half of the total liquid loss of 6 g/L of CMC (molecular weight, MW, 80,000) on Na-montmorillonite was 100 hours, 1 g/L of PEO (MW, 7,000,000) was 81 hours, and 6 g/L of PEO (MW , 8,000,000) was 110 hours while water was 54 hours, which were valid for the duration of 890 hours. The sorption of PAM and PEO onto Na-montmorillonite and kaolinite followed the Langmuir isotherms. The maximum amount of adsorption for PAM (MW, 4,000,000) was 0.2380 gram per gram of Na-montmorillonite, and for PEO (M, 8,000,000) was 0.3042 gram per gram of kaolinite. Hypotheses were proposed and validated through SEM and optical microscopic images, viscosity and dielectric constant measurements. The net effects of polymer addition on liquid retention in clays during desiccation could be explained as deriving from the combined effect of the viscosity increase and change in dielectric constant/charge concentration ratio. |
