Influence of excess KMnO4 on the adsorption of powdered activated carbon

The effects of KMnO4 or powdered activated carbon (PAC) treatment and a combination of these treatments on the removal of natural organic matter (NOM) have been investigated in this research. The experiments were carried out using two processes: Process 1: organic matter oxidized by KMnO4 (from 0 to 8 mg L-1), and then adsorbed onto PAC, and Process 2: PAC oxidized by KMnO4 (from 0 to 2 mg L-1) before the organic matter was adsorbed onto PAC in raw water. The results showed that both processes had acceptable organic matter removals, that is, the CODMn reduction was more than 18% and the UV254 reduced by more than 25%, respectively, at a KMnO4 concentration of 2 mg L-1 and PAC at 30 mg L-1 However, the organic matter characteristics were obviously different during the two processes. In Process 2, although the EEM picture exhibited lower fluorescence in the humic-like and fulvic-like regions than it did in Process 1, it was not correlative with the decrease of CODMn and UV254, which was assumed that KMnO4 oxidation altered the structure of some organic matter with a transformation to other structures with high fluorescence intensity in the two regions. Compared to the original PAC, KMnO4 oxidation did not change the PAC surface chemical and physical characteristics obviously according to nitrogen gas adsorption and FTIR spectral analysis. The results indicate that KMnO4 oxidation had little influence on the PAC characteristics, whereas the characteristics of the NOM were changed significantly. (C) 2013 Published by Elsevier B.V.