The report describes the development of a new process for regenerating activated carbon, using supercritical CO2 as a desorbent. Supercritical CO2 in the range of 30-250 C and at pressures > 80 atm. is a good solvent for organics. A series of pesticides was tested for treatment by carbon adsorption and supercritical CO2 regeneration. Alachlor and atrazine, selected for further study, both permitted regeneration over multiple cycles with a low average loss per cycle. All pesticides tested showed a substantial capacity decline (30-plus%) after one generation, but after several cycles both alachlor and atrazine exhibited a stable working capacity. Regeneration is rapid. Water in the carbon pores is not detrimental, at least not at 120 C. Shorter exposure time of carbon to adsorbent resulted in less first-cycle decline. Desorption rates increased increased with temperature, and higher regeneration pressures (150-275 atm.) gave improved regenerability. Treatability studies on a plant sample of atrazine manufacturing wastewater indicated a stable but low working capacity of carbon. Working capacities of 0.05 to 0.08 g TOC per g carbon were obtained at regeneration pressures of 150-275 atm. at 120 C.

"Arthur D. Little, Inc." "March 1980." Includes bibliographical references (pages 152-155). "Grant no. R804554, program element no. 1BB610."