Sonocatalytic oxidation of EDTA in aqueous solutions over noble metal-free Co3O4/TiO2 catalyst

Abstract

The sonocatalytic degradation of EDTA in aqueous solution was studied under ultrasound irradiation (345 kHz, 73 W, acoustic power 0.20 W•mL −1 , Ar and Ar/O 2 saturating gases, T = 20-50°C) in the presence of Co 3 O 4 /TiO 2 and Pt/TiO 2 nanocatalysts. About 90% of EDTA (C 0 = 5 10-3 M) was oxidized during ultrasonic treatment at 40°C in the presence of the Co 3 O 4 /TiO 2 catalyst and Ar/O 2 gas mixture. By contrast, Pt/TiO 2 catalyst exhibited much lower sonocatalytic activity in this system. Suggested mechanism of EDTA oxidation in the presence of Co 3 O 4 /TiO 2 catalyst involved the generation of oxidizing radicals by acoustic cavitation and Co(II)-Co(III) redox process. Quite low apparent activation energy of the sonocatalytic process (E a = 19 kJ mol −1) was attributed to diffusion of reagents in the vicinity of the active sites of catalyst. Sonocatalytic degradation of EDTA is accompanied by formation of iminodiacetic acid, formic acid, oxalic acid, glycolic acid and acetic acid as intermediate products in an agreement with radical-driven mechanism.

Nanostructured TiO2 cavitation agents for dual-modal sonophotocatalysis with pulsed ultrasound

“…The use of ultrasound to generate these transient, high energy events is distinct from conventional synthetic chemistry methods and has allowed for the development of unique materials under ambient conditions [6] , [7] . Thus, sonochemistry has shown potential in a broad spectrum of applications including green polymer synthesis [8] , waste water treatment [9] , and biomedical therapies [10] , [11] , [12] .…”

Selective radical depolymerization of cellulose to glucose induced by high frequency ultrasound

“…Close to a surface, the implosion of cavitation bubbles is very asymmetric and generates high-speed jets of liquid towards the surface, a good mean to concentrate radicals on a particle. 17 Applied to cellulose, this physical principle should be an efficient mean to control the reaction selectivity by concentrating radicals on the cellulose particle surfaces, thus preventing side reactions of released glucose into the bulk solution.…”

Photocatalytic and Sonocatalytic Degradation of EDTA and Rhodamine B over Ti0 and Ti@TiO2 Nanoparticles

“…• ) and superoxide (O 2 ) radicals in solution and bubble/solution interface or by the catalytic degradation of EDTA at the surface of the catalyst (Ti or Ti@TiO 2 ) by oxygen activated initially by the power US at the surface of titanium [17]. It was reported that sonocatalytic EDTA degradation yields several intermediate products shown in Figure S5a [21]. On the other hand, photocatalytic EDTA degradation process is initiated upon photon absorption by Ti@TiO 2 NPs in a similar manner reported previously for the photothermal production of H 2 using the same catalyst [18].…”