Transition metal-modified alkali-activated aluminosilicate foams as catalysts for peracetic acid in phenol abatement

Abstract

Abstract

The use of peracetic acid (PAA, CH3C(O)OOH) in advanced oxidation processes has recently attracted attention for the abatement of micropollutants. Radical formation from PAA can be activated by transition metals and to achieve sustained catalytic performance, one strategy is to immobilize the metals on a support. In this study, alkali-activated aluminosilicate foams (AAFs) synthesized from metakaolin, glass wool, stone wool, or blast furnace slag at 22 or 60 °C were compared as supports for Mn(II), Fe(III), Cu(II), and Co(II) either with or without calcination at 400 °C and tested for aqueous phenol abatement. The best precursor was metakaolin (MK) cured at 22 °C, showing a compressive strength of 0.67 MPa, ∼82 % porosity, and stable pH after treatment with 0.1 M acetic acid. Among the four metals, Co(II)-modified MK-AAFs dried at 60 °C showed the best PAA activation performance due to high metal content (2.7 wt%), minimal leaching (0.09 %), and stable neutral pH. Flow-through column experiments using crushed Co(II)-modified MK-AAF pieces (20 g, 5.6–10 mm size) were investigated to assess the effects of empty bed contact time (15–25 min) and PAA dose (0.4–1.2 mM) on phenol (10 μM) abatement at a pH of 7.4. Under optimal conditions (1.2 mM PAA and 15 min contact time), up to ∼97 % of phenol abatement was achieved. In a long-term experiment (180 bed volumes of treated water), the phenol abatement decreased from ∼94 % to ∼70 % after 120 bed volumes and remained stable after that. This study demonstrates that Co(II)-containing MK-based geopolymer foams could be an effective catalyst for developing PAA-based advanced oxidation processes.