pHEMA membranes carrying 25.6 mmol Procion Blue MX-3G/m(2) were used for removal of heavy metal ions (i.e., copper, arsenic, cadmium, and mercury) from aqueous media containing different amounts of these ions (0.1-4.5 mmol/L) and at different pH values (2.0-8.0). The maximum adsorption capacities of heavy metal ions onto Procion Blue MX-3G-attached membranes under noncompetitive conditions were 5.6 mmol/m(2) for Cu(II), 19.6 mmol/m(2) for As(III), 46.2 mmol/m(2) for Cd(II), and 119.6 mmol/m(2) for Hg(II). The competitive adsorption capacities of the heavy metal ions were 6.9 mmol/m(2) for Cu(II), 21.2 mmol/m(2) for As(III), 33.9 mmol/m(2) for Cd(II), and 52.5 mmol/m(2) for Hg(II). The same affinity order was observed under noncompetitive and competitive adsorption: Hg(II) > Cd(IT) > As(III) > Cu(II). The adsorption of heavy metal ions increased with increasing pH and reached a plateau value at around pH 6.0. Adsorption of heavy metal ions from artificial wastewater was also studied. The adsorption capacities are 3.5 mmol/m(2) for Cu(I), 10.2 mmol/m(2) for As(III), 24.7 mmol/m(2) for Cd(II), and 37.3 mmol/m(2) for Hg(II). Desorption of heavy metal ions was performed using 0.1 M HNO3. Procion Blue MX-3G-attached membranes are suitable for repeated use of more than 5 cycles without noticeable loss of capacity.