Environmental pollution on a global scale is expected to be the greatest problem that chemical scientists will face in the 21st century, and an increasing number of these scientists are looking to new photocatalytic systems for the solution. Existing photocatalytic systems are effective for the decomposition of many unwanted organics through the use of efficient semiconductor photocatalysts activated by ultra-violet (UV) irradiation. The demand for visible light activated photocatalytic systems is increasing rapidly. Currently, however, the efficiency and availability of photocatalysts which can be activated effectively by the solar spectrum and especially indoor lighting is severely limited. The purpose of this project is to investigate the potential of a TiO2-ZnFe2O4 alloyed nanocomposite for use as a visible light activated photocatalyst. An overview of the principles of photocatalysis is first provided. Relevant properties of pure and modified TiO2 are next discussed, and results of studies on structural and photocatalytic properties are presented. Alloyed TiO2-ZnFe2O4 nanocomposites are discussed in detail and their crystal structure, particle size, particle interaction, optical characteristics, and photoactivity are discussed in detail. Measurements characterizing the alloys are carried out using XRD, SEM, EDS, UV-Vis spectroscopy, and photodegradation procedures. The photoactivity of the alloys is carefully studied through phenol degradation experiments, and recommendations are provided to improve the photocatalysts under investigation.