Regeneration of spent activated Carbon using wet air oxidation

Abstract

Wet Air Oxidation (WAO) Powdered Activated Carbon (PAC) loaded with a food dye, namely, Tartarazine, was studied. Attempts were made to regenerate the loaded carbon designated now as a spent carbon. Slurry of spent carbon in water was oxidized by WAO in the temperature range of 120-1500C using air pressures between 3- 7 Kg/cm2in a stainless stell autoclave. The percentage regeneration was determined from the ratio Xrc/Xfc, where Xrc and Xfc are the adsorption capacities of regenerated carbon and fresh carbon respectively. The adsorption period of 2 days was given for every adsorption experiments. It was possible to regenerate the spent PAC to an extent of more than 98% by WAO. Attempts were made to regenerate same stock of carbon. This same stock of carbon was subjected to ve cycles of adsorption and regeneration. It was obsereved that the same stock can be successfully regenerated for three times with minimal loss in adsorption capacity and carbon weight. The percentage regeneration was 98.34%, 98.09% and 98.07% respectively for rst, second and third regeneration cycles. The carbon loss obsereved during the rst, second and third consecutive adsorption and regeneration was 3.78% and after ve cycles was 15%. Also the regenerated carbon was compared with the fresh carbon for there ability to reduce the COD of the Tartarazine dye solution. This study was conducted with keeping in mind the fact that if carbon is regenerated 100%, then for the same adsorption period and under same conditions the regenerated carbon should reduce the same amount of COD as that of the fresh carbon. The regenerated carbon stock taken for this experiment was that regenerated at conditions of 150 0C, 7Kg/cm2 and 5 hours residence time. After 5 days of prolonged adsorption with both fresh carbon and regenerated carbon seperately it was found out that after 24 hours the COD reduction capacity of fresh carbon was 64.95% and that of regenerated carbon was 63.99%. And after 5 days it was 80.01% for fresh carbon and 79.63% for regenerated carbon. The COD reduction capacity of regenerated carbon was small when compared to that of fresh carbon. This is due to the fact that the carbon is regenerated only 98%. Lastly the nancial and environmental viability of this project is also checked.