Hydrogels based on N-acryloyl-N'-methylpiperazine (AcrNMP) swelled extensively in solutions of low pH due to the protonation of the tertiary amine. The water transport in the gels under an acidic condition was non-Fickian and nearly Fickian in neutral pH with the collective diffusion coefficients determined as 2.08 x 10(-7) and 5.00 x 10(-7) cm(-2) s(-1), respectively. These gels demonstrated good metal-uptake behavior with various, divalent metal ions, in particular, copper and nickel, with the uptake capacity increased with increasing pH. The swelling ratio of the gel in the presence of metal ions decreased with increasing metal ion uptake. The results suggest that high metal ion uptake can lead to physical crosslinking arising from the interchain metal complex formation. The metal-loaded gels could be stripped easily with 1M H2SO4 without any loss in their uptake capacity.