Screening of activated carbons for the treatment of highly concentrated phenol solutions using catalytic wet peroxide oxidation: The effect of iron impurities on the catalytic activity

Abstract

Activated carbons (ACs) have been used as metal supports for catalytic wet peroxide oxidation (CWPO) of organic compounds. A shortcoming is that added metals can undergo leaching, leading to catalyst deactivation and secondary contamination of the treated water. In the present study, CWPO of phenol aqueous solutions was investigated in the presence of five commercial ACs without added metals yet containing different extents of iron impurities resulting from their industrial preparation procedures (ROX 0.8, RX 3-Extra, C-Gran and PK 0.25-1 from Cabot Norit and HYDRAFFIN AS 12/450 from Degussa). Application of as-received ROX 0.8 leads to the best compromise between removals of phenol (79%) and total organic carbon (TOC; 50%) and iron leaching (0.22 mg L−1 ). In-house-modified ROX 0.8 materials, obtained by thermal treatment under inert atmosphere followed by activation under oxidative atmosphere, were also tested. The activity of ROX 0.8 oxidized at 673 K (ROXN673 ) was the highest among these materials (92% and 57% of phenol and TOC removals, respectively) and with iron leaching (0.67 mg L−1 ) well below the limits established by European regulations for discharge of treated waters. This enhanced performance was mainly explained by the more developed porous structure and higher specific surface area (SBET ) of ROXN673, thus promoting better accessibility to iron impurities, which act as active sites for CWPO at the surface of the catalyst.