In the present study bulk NiO(x) and supported NiO(x)/ZrO(2) catalysts have been prepared. The bulk NiO(x) was synthesized using the precipitation-oxidation method with reverse order of precipitation while deposition-precipitation technique was used for the preparation of zirconia supported catalyst. The as-prepared samples were characterized by means of XRD, HRTEM, SAED, IR-spectroscopy, and chemical analyses. It was found that under the applied synthesis procedure nanosized and highly dispersed oxide materials with high active oxygen content were obtained. The catalytic activity and selectivity of these oxide catalysts have been studied in reaction of low-temperature oxidation of phenol in aqueous phase. The effects of several parameters such as catalyst amount, temperature and solution pH on the degradation efficiency of the process were also investigated. Experimental results demonstrated that phenol could be completely degraded under all reaction conditions, except at pH = 12.