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.

Design of Nano-Catalyst for Removal of Phenolic Compounds from Wastewater by Oxidation Using Modified Digital Basket Baffle Batch Reactor: Experiments and Modeling

“…Incipient Wetness Impregnation (IWI) [12][13][14][15][16] technology was employed in preparing the novel nano-catalyst. At first, AC was treated and dried so as to eliminate any impurities before being utilized in the IWI process.…”

Assessment of Pretreatments for Highly Concentrated Leachate Waters to Enhance the Performance of Catalytic Wet Peroxide Oxidation with Sustainable Low-Cost Catalysts

“…It is known that the activity of catalysts in CWPO strongly depends on the capacity of electron exchange of their active sites for the generation of hydroxyl and hydroperoxyl radicals from hydrogen peroxide decomposition and further oxidation of organic substances present in the aqueous matrix [37]. Several works have reported the role of oxygen-containing groups and related acid-base characteristics [38], residual metallic particles [38,39], defect sites [40], the presence of heteroatoms [41,42] and textural properties [43] in the abatement of different pollutants. We observed that both catalysts led to similar conversions since removals of 43% and 41% for TOC, 52% and 45% for COD, 93% and 91% for BOD 5 , 82% and 79% for aromaticity, and 43% and 42% of η H 2 O 2 were obtained with HC and PC, respectively.…”

The influence of active carbon contaminants on the ozonation mechanism interpretation

“…However, there are some evidence that carbon nanotubes impurities can enhance redox properties of carbon and improve electrooxidation of organics 34 , 35 . In turn, iron impurity of activated carbons can enhance phenol removal in catalytic wet peroxidation 36 . In our previous work 29 , it was shown that the mineral matter presence in activated carbon enhances the ozone decomposition.…”