Polyelectrolyte modification of ultrafiltration membrane for removal of copper ions

Alternating electrostatic adsorption of polyanions and polycations onto porous substrates, using the layer-by-layer technique, provides a convenient way to modify ultrafiltration membranes. That is why polyethersulfone ultrafiltration membranes have been coated by alternating deposition of poly(allylamine hydrochloride) and poly(acrylic acid) to modify the membranes by a thin polyelectrolyte multilayer film. The polyelectrolyte-modified membranes were characterized by using infrared spectroscopy, water angle measurements and laser reflectometry. In an attempt to develop membrane modification as a new alternative method allowing the removal of heavy metal ions by ultrafiltration, these modified membranes were used to perform the filtration of aqueous solutions contaminated by copper (II) cations. These filtration experiments led to a good retention of the copper ions by the modified membranes, thus proving the usefulness of polyelectrolytes adsorption on organic membranes. It also demonstrated the importance of several operating conditions including: polyelectrolyte concentration, polyelectrolyte pH, polyelectrolyte multilayer film thickness, number of polyelectrolyte layers and pH of copper solutions.