Influence of humic acid on colloidal illite stability and attachment and transport of nTiO₂ in water saturated sand columns

Abstract

Effects of pH and humic acid on the attachment of illite particles to sand, and effects of surfactant and grain size of the porous media on the transport of nTiO₂ in sand columns were investigated. Results showed that illite colloids were stable in 1 mM NaCl solutions at pH 5 and 9 at HA concentrations of 0-20 mg/L. The attachment of illite colloids to quartz sand was not influenced by HA or pH, but illite attachment to Fe coated sand at pH 5 decreased with increasing HA concentration. Stability of TiO₂ particles were influenced by pH, ionic strength and surfactant. Transport of nTiO₂ was influenced by pH, xanthan gum, and higher in coarse-grained sand columns compared to that in fine-grained sand columns under certain conditions. Interaction energies between particles and between particles and sand calculated based on Derjaguin-Landau-Verwey-Overbeek theory agreed with the experimentally observed particle stability, attachment, and transport.