Semi-interpenetrating polymer network (semi-IPN) cryogels based on polyacrylamide (PAAm) and anionically modified potato starch (PA) were synthesized and tested as sorbents for heavy metal ions like: Cu2+, Cd2+, Ni2+, and Zn2+ from aqueous solutions by batch-mode under noncompetitive conditions. Experimental data obtained from batch equilibrium tests have been analyzed using four models: Langmuir, Freundlich, Temkin, and Sips isotherms. The equilibrium data obtained for the sorption of heavy metal ions onto the semi-IPN cryogels were well fitted in the Sips nonlinear regression model with a maximum theoretical sorption capacity of 40.72 mg Cu2+/g composite, 19.27 mg Cd2+/g composite, 9.31 mg Ni2+/g composite, and 7.48 mg Zn2+/g composite.