Salicylic acid and derivatives anchored on poly(styrene-co-divinylbenzene) resin and membrane via a diazo bridge: Synthesis, characterisation and application to metal extraction

New materials for chelating solid-phase extraction have been prepared by grafting of salicylic acid and derivatives on poly(styrene-co-divinylbenzene) based sorbents. These sorbents are either resin bead-shaped Amberlite® XAD-4 or membrane disk-shaped Empore™ SDB-XC. Grafting has been achieved via -NN- spacer. The grafted ligands are salicylic acid (SA), its dimer form methylenedisalicylic acid (MDSA) and trimer form aurintricarboxylic form (ATA) in order to study the influence of multi-functionalization on chelating properties. Grafting scheme was validated on a model molecule (4-ethylaniline) for optimisation of experimental conditions. The resulting sorbents have been characterised by FTIR, Py-GC/MS analysis and 13 C CP-MAS NMR. Grafting rates are higher for SA (25-38%) than for MDSA (16-17%) and ATA (9%), still the number of SA entities remains almost constant. Metallic sorption abilities of the two new sorbents - determined by ICP-AES - have been succcessfully assessed by means of flow-through experiments with synthetic solution of multielement cations (Cd2+, Co2+, Cu2+, Mn2+, Ni2+, Pb2+, Zn2+, Fe2+ and Al3+). It evidenced the influence of the PTFE matrix, contained in Empore disks, for acidic pH. Finally, complexing capacities for Fe(III) were found to be higher for membranes (13.4 ± 0.7 for SA) than for resins (11.6 ± 0.6): this allows to consider grafted polymer membranes as competitive materials for SPE applications.