Optimized CWPO oxidation of natural organic matter in continuous fixed bed reactor catalyzed by an extruded Al/Fe-PILC clay catalyst

Abstract Catalytic wet peroxide oxidation of dissolved natural organic matter (NOM) has been optimized in a continuous-flow, fixed bed reactor by using an extruded Al/Fe-pillared clay catalyst using a Synthetic Surrogate of NOM (SS-NOM) resembling typical composition and molecular weight distributions in real surface waters. Proper humidity of the extrudate’s precursor mix was found to be 38 %. Mass fraction of catalyst (xc = 0.5), absolute humidity (H = 0.6), and a height/diameter ratio = 2.0 (particle ϕ ∼ 3.0 mm and height ∼ 6.0 mm) showed the best combined mechanical and textural properties (compression strength 121 N, tenacity 1.1325 mJ, attrition 1.45 (%), BET surface 76 m2/g, and microporous surface 52 m2/g) and catalytic performance. The main parameters governing the catalytic wet peroxide oxidation (height of the catalyst bed and the ratio (H2O2/SS-NOM) were optimized in terms of mineralization of the total organic carbon and H2O2 reaction efficiency, under constant and rather short 9.2 min of residence time. Inlet concentrations of the SS-NOM (TOC = 6.63–13.7 mg C/dm3), pH (5.9–7.8) and temperature (20.0 °C – 24.0 °C) were covariates within the typical ranges exhibited by surface waters. The optimal multi-response catalytic performance using desirability function (d = 0.73) displayed 24.3 % of TOC mineralization and 51.2 % of reacted H2O2 with a height of catalyst bed 22 cm and inlet ratio (H2O2/SS-NOM) = 5.9 (mg H2O2/mg TOC), room temperature (20.0 ± 1.0 °C), and circumneutral pH.