Contribution of Irradiation and Dihydroxybenzenes on Iron(III) Reduction in Fenton Process

Abstract

The contribution of irradiation and the dihydroxybenzenes (DHB), catechol (CAT) and hydroquinone (HQ), added or formed as phenol oxidation intermediates, was evaluated for the reduction of Fe III and for phenol degradation via Fenton processes. The formation of CAT and HQ was observed during phenol degradation starting with Fe 2+ or Fe 3+ in the presence or absence of irradiation and their presence increased the rate of phenol degradation, more remarkably when initially added. Initial phenol degradation rate in the presence of DHB in the dark was much higher in comparison to their absence due to the initial higher and faster formation of Fe 2+. However, degradation slows down due to the rapid oxidation of DHB, while under irradiation of free iron or citrate complex much higher mineralization is achieved in shorter time.

Influence of dihydroxybenzenes on paracetamol and ciprofloxacin degradation and iron(III) reduction in Fenton processes

“…In the dark, although at much lower extent, Fe(III) reduction also occurred generating 0.021 mmol L −1 Fe 2+ (Fig. 2, green line), a different behavior as previously observed with phenol and Fe(III), when no Fe 2+ was detected in the dark (Silva and Nogueira 2016), suggesting that other dihydroxylated products generated during PCT degradation contributed to iron reduction.…”

“…1d), which is able to reduce Fe(III) to Fe(II) that decomposes H 2 O 2 forming • OH. Generation of DHB intermediates as HQ was previously observed during PCT and phenol Fenton degradation, which may influence reaction rate (Trovó et al 2012;Moctezuma et al 2012;Silva and Nogueira 2016).…”

“…The effect on degradation may vary depending upon the position of the substituents and formation of intermediates that can improve or decrease Fe(III) reduction (Nichela et al 2010). It was previously observed that HQ and catechol (CAT) accelerated significantly the phenol degradation changing drastically the reaction kinetics after their generation as intermediate in the dark (Silva and Nogueira 2016).…”

Kinetic Study of Methyl Orange Azo Dye Discoloration by Fenton Processes in the Presence of Di-hydroxybenzenes and Gallic Acid

“…5 Diversos compostos fenólicos redutores têm sido testados, sendo comprovadas as suas propriedades prooxidantes, desde fenóis derivados de lignina, 8,9 o ácido 3-hidroxiantranílico, 10 além dos mais estudados, os di-hidroxibenzenos. [11][12][13][14][15] O aminoácido alifático cisteína, único redutor dentre os vinte aminoácidos proteinogênicos, também tem proporcionado incrementos na degradação de um corante por processos Fenton. 16 O mecanismo que demonstra a redução de Fe 3+ pelo dihidroxibenzeno catecol está ilustrado na Figura 1.…”