Adsorption of lead ions in aqueous solution using silica–alumina nanoparticles

The adsorption of lead ions in aqueous solution on the surface of silica–alumina nanoparticles is reported. The removal of lead ions from simulated industrial wastewater was performed using silica–alumina particles synthesized by the sol–gel method with a molar ratio of 1:1. Small amounts of lead ions were added to the sol until the critical flocculation concentration was reached and the particles flocculated forming aggregates which sediment down, being removed from the sol. The flocculation kinetics was followed using Dynamic Light Scattering that measures the particle size as a function of time. The amount of lead ions adsorbed by the nanoparticles was determined using Atomic Absorption Spectroscopy. The lead concentration was reduced from 140 ppm to below 10 ppb; this final concentration fulfills the corresponding legislation requirements.