Sustainable Thermal Regeneration of Spent Activated Carbons by Solar Energy: Application to Water Treatment

Our aim was to assess the feasibility of using solar energy for the thermal regeneration of spent activated carbons (ACs). The context was water treatment, for which ACs are commonly used. The target pollutant was perchloroethylene (PCE). Preliminary experiments were performed to select the best-suited adsorbent among five ACs (Aquacarb, surface area Brunauer-Emmett-Teller, 1100 m(2) g(-1); micropores areas, 870 m(2) g(-1)). Water properties influence adsorption capacity; this is lower with natural water (groundwater) than with ultrapure water. The competition between natural organic matter (found in groundwater but not in ultrapure water) and the target pollutant accounts for this difference. Groundwater was used in regeneration tests so as to approximate to field conditions. Operating conditions for regeneration were determined: the working temperature ranged between 130 and 400 degrees C, and the treatment time was set so as to prevent any kinetic limitation. Four regeneration cycles showed the same decrease in adsorption capacity over the cycles in the working temperature range. The adsorption capacity recovered was about 60% after the fourth cycle. Solar thermal regeneration was then performed. The solar and classical regenerations gave similar results. This first solar thermal regeneration test is promising for its environmental and economical advantages.