Reactive sorption of mercury(II) on to poly(m-phenylenediamine) microparticles

Poly(m-phenylenediamine) (PmPD) microparticles, from the monomer with two amino groups, were synthesized through chemical oxidation, and the strong adsorbability of mercury ions on to PmPD was systematically examined. The results revealed a rapid adsorption process with an equilibrium time of 30 minutes. Also, the adsorption behaviour showed that the adsorption kinetics was in good agreement with the pseudo-second-order equation. The maximum uptake capacity for mercury (Q(max)) reached approximately 955 mg g(-1) at 0.02 M NaNO3 and 25 degrees C, which decreased appreciably with the increasing of salt concentration. The amount of mercury sorbed at equilibrium steadily increased as the temperature rose from 25 to 45 degrees C, which can be indicative of an endothermic process. The pH value of the solution seemed to exhibit little influence on the adsorption capacity. The adsorption mechanisms, including Hg2+ complexation with nitrogen and ion exchange between Hg2+ and H+ on PmPD chains, are proposed on the basis of Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis.