Polystyrene-Supported Amines: Affinity for Mercury(II) as a Function of the Pendant Groups and the Hg(II) Counterion

Amine ligands (-CH 2 NR 2, where R = H, CH 3, or CH 2 CH 2 OH) 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 (HNO 3 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 NO 3 -, Cl -, and SO 4 2- 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 HNO 3 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).