Jixiang Xu

Effects of sodium salts organic acids modification on the microstructure and dispersion behavior of palygorskite nano-powder via high-pressure homogenization process

High-pressure homogenization could disaggregate the crystal bundles of palygorskite and favor the adsorption of electrolyte ions onto its surface through the produced cavitation, shear, and turbulence forces, and has evident influences on the micromorphologies and properties of clay. In this work, a series of palygorskite samples modified with sodium citrate, sodium benzoate, sodium lactate, sodium acetate, and sodium propionate were obtained under the condition of high-pressure homogenization. The effects of type and concentration of sodium salts organic acids on the microstructure, morphology, surface charge, and physicochemical property of palygorskite were studied through x-ray diffraction (XRD), N2 adsorption–desorption isotherm, field emission scanning electron microscopy, zeta potential, rotational viscosity, and rheological measurements. XRD results confirmed that the crystal structure of homogenized palygorskite was not changed after introduction of sodium salts organic acids, but the aggregates were effectively disaggregated. Modification of palygorskite with sodium citrate made the surface more negatively charged, and the samples exhibited higher specific surface area and rheological properties. This work provided a method to improve the rheological properties of palygorskite suspension through dispersion of clay in sodium citrate solution followed by homogenization at 30 MPa.

Effect of Solvents Treatment on Microstructure and Dispersion Properties of Palygorskite

Palygorskite was dispersed by various organic solvents and water, and the effects of solvent types on its microstructure, dispersion degree, and colloidal properties were investigated by infrared spectroscopy (IR), x-ray diffraction (XRD), and nitrogen adsorption-desorption isotherm (BET), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and rheological analyses. It was found that dimethyl sulfoxide and dimethyl formamide molecules may attach onto the surface of palygorskite and cause a complete disappearance of micropores. Solvent parameters govern the dispersion degree of palygorskite, and dimethyl sulfoxide and dimethyl formamide are good solvents to disperse palygorskite aggregates in contrast to ethanol and isopropanol. Colloidal stability and rheological tests suggested dimethyl sulfoxide-dispersed palygorskite can form more stable suspension with higher shear stress and modulus, but isopropanol-dispersed palygorskite may rapidly subside in suspension and show poor colloidal properties.