Rapid regeneration of sulfanilic acid-sorbed activated carbon by microwave with persulfate

A combined granular activated carbon (GAC) adsorption and microwave (MW)/persulfate (PS) regeneration process was employed to treat sulfanilic acid (SA) wastewater. SA of 50 mg L−1 was used. Results indicate that GAC effectively removed SA within 8 h. Microwave irradiation under acidic condition (pH 2.8) did not effectively regenerate GAC within 60 s. In contrast, the MW/PS process rapidly regenerated GAC within 30 s. An increase in PS dose, GAC/solution ratio, and irradiation time enhanced the regeneration. The optimum operating conditions were initial solution pH (pH0) 6, PS of 8 × 10−3 M, and GAC/solution of 3 g/15 ml. The adsorption capacity and BET of GAC did not significantly decrease at the first seven cycles of adsorption/regeneration. The desorption solution did not contain observable SA concentration.The addition of t-butanol inhibited GAC regeneration by the MW/PS process. When SA solution was treated by MW/PS, the SA and PS did not decrease within 60 s. In the presence of GAC, PS decreased rapidly by MW and 80% of PS decayed within 30 s. The results suggest that degradation of the sorbed SA by generated free radicals was one of the important factors responsible for the rapid GAC regeneration by the MW/PS process.

► MW/PS rapidly regenerated SA-sorbed GAC within 30 s.
► The optimal S/L for GAC regeneration by MW/PS was 1:5.
► The adsorption of GAC did not obviously decrease after seven cycles of adsorption–regeneration treatment.
► T-butanol inhibited MW/PS regeneration of GAC.
► Desorption solution did not contain measureable SA.