Oxidation of polyaniline-derived carbon using microwaves for adsorptive removal of pharmaceuticals with an amino group

Carbonaceous materials, especially oxidized ones, have been frequently used as adsorbents. Oxidation of carbons has usually been carried out using ammonium persulfate/H2SO4 solution under electric heating. In this work, polyaniline-derived carbons were oxidized with both the conventional method and HNO3 under microwaves. The obtained carbons, after thorough characterization, were applied to the adsorptive purification of water polluted with emerging contaminants, especially basic pharmaceuticals with amino groups (like atenolol (ATNL) and diphenhydramine (DPHA)). The carbon oxidized under microwave was much more effective in the adsorption than the carbon oxidized by the conventional method using electric heating. Both the adsorbed quantities and adsorption kinetic constants increased with increasing oxidation (by microwaves) temperatures up to 100 °C. The best performing MPDC(100) was recyclable and highly competitive in the adsorption of ATNL and DPHA. The mechanism of ATNL and DPHA adsorptions over MPDC(100) was investigated by checking surface charge and adsorbed quantities under wide pH conditions. Electrostatic interaction with π-π interaction and hydrogen bonding (adsorbent: hydrogen-acceptor) was the major mechanism for the effective adsorption over MPDC(100). Finally, porous carbon with a high concentration of anionic sites like carboxylates can be suggested as an effective adsorbent to remove basic pharmaceuticals with amino groups.