The paper suggests a method of synthesizing a granulated sorbing agent for sewage purification from ions of heavy metals (copper and zinc). The raw material mixture includes iron sludge produced by water treatment, liquid glass, caustic limestone, and water. The optimum mass ratio of 10:1:14:4 (dry iron sludge, calcium oxide, liquid glass, water) is selected for the mixture composition which provides the high strength and water resistance of sorbing agent. The paper considers the preparation and the optimum thermal treatment conditions which ensure the strength, appropriate porosity and specific surface of specimens. Research results are obtained for mechanical-and-physical properties of synthesized granular sorbing agent. The static exchange capacity and the extraction degree of copper and zinc ions from model saline solutions are detected herein. Research results contribute to the problem of the efficiency improvement of closed water utilization systems and can be used in utilization of large-tonnage water treatment wastes, thereby providing sewage purification facilities with inexpensive sorbing agents.