Activated carbon enhanced ozonation of oxalate attributed to HO. oxidation in bulk solution and surface oxidation： Effect of activated carbon dosage and pH
Linlin Xing , Yongbing Xie
,
Daisuke Minakata
,
Hongbin Cao
,
Jiadong Xiao
,
Yi Zhang
,
John C. Crittenden
DOI:10.1016/j.jes.2014.08.009
Received December 09, 2013,Revised February 11, 2014, Accepted , Available online October 22, 2014
Volume 26,2014,Pages 2095-2105
Ozonation of oxalate in aqueous phase was performed with a commercial activated carbon (AC) in this work. The effect of AC dosage and solution pH on the contribution of hydroxyl radicals (HOU) in bulk solution and oxidation on the AC surface to the removal of oxalatewas studied.We found that the removal of oxalatewas reduced by tert-butyl alcohol (tBA)with lowdosages of AC, while it was hardly affected by tBA when the AC dosage was greater than 0.3 g/L. tBA also inhibited ozone decomposition when the AC dosage was no more than 0.05 g/L, but it did not work when the AC dosage was no less than 0.1 g/L. These observations indicate that HOU in bulk solution and oxidation on the AC surface both contribute to the removal of oxalate. HOU oxidation in bulk solution is significantwhen the dosage of AC is low,whereas surface oxidation isdominantwhenthedosageofAC ishigh.Theoxalate removaldecreasedwith increasingpHof the solution with an AC dosage of 0.5 g/L. The degradation of oxalate occurs mainly through surface oxidation in acid and neutral solution, but throughHOU oxidation in basic bulk solution.A mechanism involving both HOU oxidation in bulk solution and surface oxidation was proposed for AC enhanced ozonation of oxalate.
