In this work, the processes of purification of oily waters using magnetites were investigated: magnetite synthesized according to the classical method and magnetites modified with hydrophobizing agents (sulphonol or alkylimidazolin). It is shown that magnetite modified with alkylimidazolin in doses of 50–200 mg/dm3 provides a high degree of oil removal from waters of various mineralization. The degree of water purification reaches 97.5–99.8%. Sulphonol-modified magnetite shows greater efficiency than conventional magnetite only at high concentrations (200 mg/dm3) and only in fresh water. Three hours is enough to ensure the maximum degree of purification of water-oil solutions. Changing the amount of hydrophobizing agent (alkylimidazolin) during the synthesis of magnetite reduces the effect of pH on the purification of both fresh and mineralized waters