Catalytic regeneration of chloroorganics-saturated activated carbon using hydrodechlorination

A new two-step catalytic process is suggested as viable means for exhaustive regeneration of spent granular activated carbon (AC) saturated with chloroorganic compounds: it incorporates hydrodechlorination (HDC) by hydrogen or by hydrazine followed by oxidation in air. Complete dechlorination of p-chlorophenol (4-CP) was achieved with hydrogen over an AC/Pd catalyst at temperatures in excess of 200 degrees C. Complete recovery of the adsorption capacity was achieved in three tested cycles of adsorption of 4-CP and regeneration in batch and column studies. Pd is the most suitable catalyst for both HDC and oxidation steps, but the limiting factor of Pd is the possible oxidation of the carbon support and there is a need to increase the oxidation resistance of AC. Dechlorination of 4-CP with an equimolar solution of hydrazine sulfate and ammonium hydroxide is possible over AC/Pd, but the process is much slower.