Adsorption of Lead Ions onto N -Isopropylacrylamide and Acrylic Acid Copolymer Microgels

The interaction of hydrolyzable lead ions with thermosensitive microgel dispersions of N -isopropylacrylamide modified with a range of acrylic acid comonomer concentrations has been investigated. The hydrodynamic diameter of the microgel particles was observed, by dynamic light scattering, to reversibly alter due to changes in either temperature or pH, or due to the presence of lead ions. The hydrodynamic diameter of all the microgel particles decreases with increasing temperature. However, upon increasing the pH, the anionic microgel particles increase in diameter at a fixed temperature, while in the presence of Pb(II) at pH 5, the hydrodynamic diameter of the anionic microgel particles decreases. The size of the homopolymer microgel does not vary with pH, nor in the presence of Pb(II). The adsorption isotherms of hydrolysable Pb(II) with the microgel particles were established as a function of pH. Lead ion adsorption was observed to not significantly alter with temperature and was demonstrated to be completely reversible to pH adjustment.