high concentration of contaminants to be removed relatively The interaction of hydrolyzable lead ions with thermosensitive rapidly. Previous studies of poly(N-isopropylacrylamide) microgel dispersions of N-isopropylacrylamide modified with a [poly(NIPAM)] microgels have shown their potential for range of acrylic acid comonomer concentrations has been investiremoval of heavy metal ions from aqueous environments (3, gated. The hydrodynamic diameter of the microgel particles was 4). Very little, however, is known regarding the mechanism observed, by dynamic light scattering, to reversibly alter due to of adsorption of the metal ions with the microgel particles.
changes in either temperature or pH, or due to the presence of
This paper aims to provide some understanding of the physilead ions. The hydrodynamic diameter of all the microgel particles cochemical principles involved in this type of process.
decreases with increasing temperature. However, upon increasing Temperature-sensitive microgels can be prepared from the pH, the anionic microgel particles increase in diameter at a fixed temperature, while in the presence of Pb(II) at pH 5, the NIPAM which has a lower critical solution temperature of hydrodynamic diameter of the anionic microgel particles de-32ЊC in the uncrosslinked, homopolymer form in aqueous creases. The size of the homopolymer microgel does not vary with solution (5). Hence, poly(NIPAM) microgels crosslinked pH, nor in the presence of Pb(II). The adsorption isotherms of with bisacrylamide rapidly swell and deswell upon warming hydrolysable Pb(II) with the microgel particles were established and subsequent cooling, in an aqueous medium (6). At low as a function of pH. Lead ion adsorption was observed to not temperatures (i.e., below 32ЊC), the poly(NIPAM) microsignificantly alter with temperature and was demonstrated to be gel has an expanded, ''sponge-like'' structure with the intercompletely reversible to pH adjustment.