Effective catalytic ozonation for oxalic acid degradation with bimetallic Fe‐Cu‐MCM‐41: operation parameters and mechanism

Abstract

BACKGROUND The formation of carboxylic acid, especially oxalic acid (OA), limits the complete mineralization of organic pollutant in both ozonation and catalytic ozonation. Bimetallic catalyst is well known for its catalytic activity. In this study, bimetallic Fe‐Cu‐MCM‐41 is synthesized to accelerate ozone decomposition to ·OH and enhance OA degradation. RESULTS After the employment of Fe‐Cu‐MCM‐41/O3, 95% OA was removed at 60 min, which was much higher than that in Fe‐MCM‐41/O3 (23.4%), Cu‐MCM‐41/O3 (69.7%) and a single ozonation process (16.5%). Using pyridine adsorption–IR, ESR and XPS, a relationship was found between catalytic activity of catalysts, Lewis acid sites and electron transfer effect. OA degradations were found to follow a hydroxyl radical mechanism. The Fe‐Cu‐MCM‐41/O3 process was sensitive to pH value; a higher removal efficiency was achieved under alkaline conditions. Fe‐Cu‐MCM‐41 significantly accelerated ozone decomposition, hydroxyl radicals and hydrogen peroxide generation. CONCLUSIONS Co‐incorporating Fe and Cu successfully increased the number of Lewis acid sites on MCM‐41. Electron transfers between Fe(II/III), Cu(I/II) and O3 were also found. The joint function of Lewis sites and the electron transfer effect enhanced ·OH generation and OA degradation. Fe‐Cu‐MCM‐41 showed bright prospects for use in water treatment processes. © 2017 Society of Chemical Industry

Hybrid oxidation separation technology (HOST) for synergistic removal of recalcitrant pollutants in water

“…2.1). Conversely, ≡Me-O − was proposed as the active site of bimetallic Fe-Cu-MCM-41 and responsible for catalytic O3 decomposition at pH > pHpzc (Chen et al, 2017c). As shown in the resonance structure of O3 molecule (Fig.…”

“…Proposed reaction mechanism of heterogeneous catalytic ozonation with surface hydroxyl group as active site: (a) ≡Me-OH (adapted from Zhao et al (2009a)); (b) ≡Me-OH2 + (adapted from Zhao et al (2009b)); and (c) ≡Me-O − (Chen et al, 2017c).…”

“…The O3(aq) could then adsorb onto the deprotonated surface hydroxyl group (≡Me-O − ) for electron transfer and further react with H2O to produce HO • , owing to the electrophilic nature of O3 molecule (Eqs. 5.13-14) (Chen et al, 2017c). Meanwhile, the 1 O2 could be generated by homolytic dissociation of dimerised HO2 • (Eq.…”