Method for isolating a heavy metal ion from an aqueous solution

A method of isolating a heavy metal ion from an aqueous solution, the method comprising:

• contacting the aqueous solution with a sorbent device to form an aqueous mixture comprising a heavy metal loaded sorbent device;
• removing the heavy metal loaded sorbent device from the aqueous mixture thereby obtaining a purified solution having a reduced concentration of the heavy metal ion compared to an initial concentration;
• treating the heavy metal loaded sorbent device with an acid to desorb the heavy metal;
• wherein the sorbent device comprises:
• an alkaline-treated zeolite;
• and
• a porous membrane bag encapsulating the alkaline-treated zeolite,
• wherein the alkaline-treated zeolite comprises an ultrastable Y (USY) zeolite comprising a molar ratio of Si to Al in a range of 15:1 to 25:1, a Brunauer-Emmet-Taylor (BET) surface area in a range of 680 to 750 m2/g, and an adsorption capacity in a range of 2 to 100 mg Cr(III) per gram, 1 to 75 mg Pb(II) per gram, and 0.4 to 50 mg Cd(II) per gram.