Photocatalysis is a process in which the rate of photoreaction is accelerated in presence of a catalyst. It has gained much interest due to its ability to completely mineralise a variety of organic compounds into carbon dioxide and water. This paper describes the basics of heterogeneous photocatalysis, mainly on TiO2 and the application of the photocatalytic process to water purification, mainly to remove phenol as well as special emphasis on the effects of; solution pH, dissolved oxygen, catalyst load, initial phenol concentration and UV radiation on the photoactivity. Photocatalytic degradation of phenol was conducted in 1 L solutions of phenol (20 mg/L) in ultrapure water in a batch system. Catalyst concentration was constant at 8 mg/L Titanium dioxide (TiO2). Concentration of phenol was monitored on a Waters High Performance Liquid Chromatograph (HPLC) and Gas Chromatogram- Mass Spectrometer (GC-MS). Results showed that photo degradation is an effective method for the removal of phenol from wastewaters. The efficiency of the process depends strongly on the experimental conditions.