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Article Dans Une Revue Electrochimica Acta Année : 2024

Assessment of an hybrid process coupling ozonation and anodic oxidation in a monophasic configuration

Résumé

This prospective study assessed a hybrid process that combines ozonation with anodic oxidation (AO/O3) with two boron-doped diamond (BDD) electrodes to treat a model aqueous solution containing 30 ppm of alachlor at pH 5 in a phosphate buffer. An innovative monophasic configuration, operated batch-wise, in which an ozone-stock solution was injected at t0 in the electrochemical reactor, was proposed in order to avoid introduction of ozone-enriched gas bubbles. The alachlor parent molecule was almost entirely degraded within around 150 min of reaction time by anodic oxidation alone, whatever the applied current intensity (200, 500 and 800 mA). The mineralization efficiency varied from 50 % at 200 mA to 80 % at 800 mA after 120 min. The results emphasized that the anodic oxidation was a diffusion-controlled process. Addition of ozone at a low ozone dose of 1.9–2.3 mol of ozone per mol of alachlor allowed to decrease the ozone half-life time 2.7 times with the hybrid process compared to ozonation alone. This faster ozone consumption was concomitant with an enhanced alachlor degradation rate, with a corresponding half-life time around two-times lower. However, owing to the low ozone dose applied and the short ozone lifetime in solution (around 25–30 min), similar mineralization efficiencies were noticed for both AO/O3 and AO processes. Thus, the application of pulse ozone-stock solution re-injections every 20 min to prolong the ozone exposure was assessed to overcome this limitation. However, the effect on the mineralization rate remained small, even if it allows to enhance even more the alachlor parent molecule degradation rate. The low influence of the hybrid process on the mineralization rate was attributed to the production of aliphatic fatty acids by-products that are poorly reactive with hydroxyl radicals, and whose the degradation by AO is the rate limiting step.
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hal-04506309 , version 1 (29-04-2024)

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Helios Yasmine, Florence Fourcade, Fares Zouaoui, Pierre-Francois Biard. Assessment of an hybrid process coupling ozonation and anodic oxidation in a monophasic configuration. Electrochimica Acta, 2024, Electrochimica Acta, 484, pp.144049. ⟨10.1016/j.electacta.2024.144049⟩. ⟨hal-04506309⟩
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