Physical mechanism of sono‐Fenton process

Abstract

Hybrid advanced oxidation processes (AOPs), where two or more AOPs are applied simultaneously, are known to give effective degradation of recalcitrant organic pollutants. This article attempts to discern the physical mechanism of the hybrid sono-Fenton process with identification of links between individual mechanism of the sonolysis and Fenton process. An approach of coupling experimental results with simulations of cavitation bubble dynamics has been adopted for two textile dyes as model pollutants. Fenton process is revealed to have greater contribution than sonolysis in the overall decolorization of both dyes. H 2 O 2 added to the liquid medium as a Fenton reagent scavenges• OH radicals produced by cavitation bubbles. Addition of only H 2 O 2 to the medium during sonolysis does not yield marked difference in decolorization. Elimination of transient cavitation with application of elevated static pressure to the medium does not alter the extent of decolorization. The synergy between sonolysis and Fenton process is, thus, revealed to be negative. The dissolved oxygen in the medium is found to play an important role in decolorization through conservation of oxidizing radicals.

Numerical Simulation and Investigation of System Parameters of Sonochemical Process

“…The results showed that as the static pressure increases the radical formation decreases drastically; even it becomes zero at higher ambient static pressure. This is due to at elevated static pressure, the sonochemical effects get eliminated which directly affects the generation of radical formation, provided the applied pressure must be greater than or equal to the acoustic pressure amplitude ( ≥ AW ) [9,38]. The highest…”

“…At transient collapse, temperature and pressure reach extreme conditions, which result in dissociation of molecules to form various chemical species. To calculate the composition of the bubble at the time of collapse, we assume that thermodynamic equilibrium is attained [9]. The equilibrium mole fraction of different chemical species in the bubble at the peak conditions reached at transient collapse is estimated using Gibbs free-energy minimization technique [33].…”

“…The bubble collapse occurs within as small time as 50 ns, and it is almost adiabatic. During the collapse of the bubble, many species are formed such as H 2 • OH radical is the most predominant radical species [21,22] having an oxidizing potential of 2.33 V [9,23]. For greater details in cavitation concepts, we would like to refer the readers to see the state of art reviews by Xu et al [4], Apfel [24], Gong and Hart [25], Suslick et al [26], and Gogate and Pandit [27].…”

“…In the last few decades, sonochemical process became one of the most popular techniques for synthesis of catalysts as well as different types of materials [4][5][6][7], degradation of pollutants [8][9][10][11][12], synthesis of biodiesel [13,14], and so forth. Numerous literatures on sonochemistry have already been published [15][16][17][18] which reported the various beneficial effects of sonochemistry.…”

Synthesis and Application of Magnetic Photocatalyst of Ni-Zn Ferrite/TiO2from IC Lead Frame Scraps

“…Among them, semiconductor TiO 2 's simultaneous photocatalytic oxidation and reduction show significant potential due to being photoreactive, nontoxic, chemically and biologically inert, photostable, and lower in cost. Among different advanced oxidation processes (AOPs), a brand new AOP, sonolysis or hybrid AOP, combined with sonolysis has drawn increasing attention as it generates ⋅ OH free radical through transient cavitation by ultrasound irradiation [18][19][20]. Cavitation is essentially the nucleation, growth, and transient implosive collapse of gas bubbles driven by ultrasound wave.…”