Catalytic ozonation of an azo-dye using a natural aluminosilicate

INCHAURRONDO, N.; DI LUCA, C.; ?ERJAV, G.; GRAU, J.M.; PINTAR, A.; HAURE, P.

CATALYSIS TODAY

ELSEVIER SCIENCE BV

Año: 2019

0920-5861

Catalytic ozonation of Orange II (100 mg/L) was studied using aluminosilicate Montanit300® (M) modified with H2SO4 (MS) and HCl (MH). Characterization of these samples was performed through several techniques: SEM/EDX, FTIR, XRD, FRX, TPD pyridine, surface area, pHPZC. Acid treatment increased surface area, Si:Al ratio and quantity of acid sites, but reduced pHPZC and Fe and Mn content. Ozonation experiments achieved complete decoloration and remarkable TOC conversions of 66, 65, 88 and 91% by single ozonation and catalytic ozonation with MH, MS and M, respectively. Higher M and MS activity under acidic pH was attributed to Mn leaching. Decreased mineralization efficiency in the presence of tert-butanol suggested a radical mechanism. At neutral pH, M showed no activity, while MS presented mild activity owing to its enlarged hydrophobicity. The M sample sustained mineralization levels over 20 h, whereas MS deactivated quickly. However, it was reversed through calcination and increasing the ozone dose managed to delay deactivation.Mn is naturally found in Montanit300®, thus making it an inexpensive catalyst. The development of a dynamic cycle combining reduced and oxidized forms of Mn was key to the outstanding activity observed.