Polystyrene-supported amines: Affinity for mercury(II) as a function of the pendant groups and the Hg(II) counterion

Amine ligands (-CH2NR2, where R = H, CH3, or CH2CH2OH) immobilized on cross-linked polystyrene beads have a high affinity and selectivity for Hg(II) from aqueous solutions. The high affinity is dependent on solution pH and the background acid (HNO3 or HCl). There is no affinity for Pb(II), Cu(II), Cd(II), Zn(II), and Ca(II) cations from solutions up to pH 3.5; high background levels of NO3-, Cl-, and SO42- anions do not affect complexation of Hg(II) by the resins. Key results include the following: (1) simple monoamines have a high affinity for Hg(II); (2) tertiary amines have a higher affinity than the primary amine resin; (3) electron donors on the nitrogen allow for high levels of Hg(II) complexation but the trend is affected by the counterion in solution; and (4) linear correlations in the log-log plot of the distribution coefficient and solution acidity with a slope of 0.6-0.8 from HNO3 and 1.3-1.5 from HCl suggest that Hg(II) uptake occurs through ion exchange and coordination with Hg(II) speciation as a function of pH being an important variable. Solution measurements of mercuric ions were done by inductively coupled plasma atomic emission spectroscopy (ICP-AES).