Cyanide is highly toxic, and although various approaches have been employed for its remediation, these methods do not have the required performance. This report describes the synthesis of titanium dioxide nanoparticles with maximum photocatalytic properties and their application for the treatment of cyanide in wastewater. Three types of crystalline titanium nanoparticles were synthesized: anatase, rutile, and a biphasic mix of rutile and anatase. The phase and microscopic properties were characterized by X-ray diffraction and scanning electron microscopy. The specific surfaces of the particles were determined, and their photocatalytic activity was studied under the ultraviolet irradiation for cyanide degradation. The results indicate that an increase in sulfate ion leads to changes in the phase ratios of rutile to anatase. The diameter of the nanoparticles was between 18 and 22 nm, and they displayed high photocatalytic properties. The biphasic form of the titanium dioxide nanoparticles demonstrated the highest removal of cyanide. Complete degradation of cyanide was observed in a pilot scale experiment.