Abstract: Contaminated adsorbent particles, preferably activated carbon particles, are regenerated in water at supercritical conditions. The particles are preferably mixed in water prior to treatment. The mixture is preferably heated to a temperature at least about 900.degree. F. (482.degree. C.) and pressurized to a pressure sufficient to achieve supercritical conditions for water. The mixture is preferably flowed through a first reactor for a time sufficient to substantially remove the organic contaminants from the particles. The particles are separated from the water and the mixture of water and organic contaminants may be transferred to a second reactor. Within the second reactor the organic contaminants are preferably substantially oxidized by supercritical water oxidation.