Adsorption of gold nanoparticles on illite under high solid/liquid ratio and initial pH conditions

Abstract Adsorption of nanoparticles on minerals affects the fate and transport of nanoparticles directly and is of great significance to many fields, including research into ore deposits, geochemistry, the environment and mineral materials. Whereas many previous studies have been conducted under the equilibrium pH and low solid (mineral) to liquid (nanoparticle suspension) ratio conditions, adsorption processes under initial pH and high solid/liquid ratio conditions may represent many important yet underexamined complex scenarios. To fill in this research gap, the adsorption of gold nanoparticles on illite was investigated experimentally at a relatively high solid/liquid ratio of 5 g L –1 and the effects of initial pH, ionic strength, citrate concentration, temperature and illite particle size were evaluated. The adsorbed amount of gold nanoparticles (from <5% to nearly 100%) increased with increasing ionic strength, temperature and citrate concentration and decreased with increasing pH and illite particle size. The presence of illite resulted in the dynamic evolution of the pH of the suspension, which, along with solution chemistry parameters, controlled the electrostatic interaction of illite and gold nanoparticles. The adsorption results, scanning electron microscopy observations and surface properties of illite suggest that the negatively charged gold nanoparticles were adsorbed predominantly on the positive illite edges through electrostatic interaction. The electrostatic attraction between illite and gold nanoparticles appeared to be strong, supported by the minor amount of desorption. These research findings are expected to provide a valuable reference regarding many critical issues in the geosciences as well as for industrial applications.