Electroactive polymer-SiO2 nanocomposites for metal uptake

The use of electroactive polymer-SiO2 nanocomposites for the uptake of gold and palladium from AuCl3 and PdCl2 in acid solutions respectively was investigated. The electroactive polymers used were polyaniline (PAN) and polypyrrole (PPY). The change in the physicochemical properties of the nanocomposites with metal uptake were of particular interest. In the case of gold uptake, the reaction rate increases with temperature from 0 to 60 degrees C. The accumulation of elemental gold on the nanocomposites increases the diameter and decreases the surface area. The surface Au/N ratio as determined using X-ray photoelectron spectroscopy (XPS) is highly dependent on the rate of reactions even for the same amount of gold uptake. The uptake of palladium from PdCl2 is much more difficult to accomplish. High rates of uptake can-only be achieved with the electroactive polymers reduced to their lowest oxidation state and unlike the case of gold uptake, the palladium on the microparticles does not exist in the elemental form but as a Pd(II) compound. (C) 1998 Elsevier Science Ltd. All rights reserved.