Hydroxyl radical production in aerobic aqueous solution containing metallic tungsten

• HO is produced during the O2-induced dissolution of metallic W in aqueous solution.
• The formed intermediate H2O2 in the process accounts for the production of HO.
• H2O2 undergoes surface or solution reactions to produce HO.
• Surface reactions dominate in the methanol case.
• Both surface and solution reactions occur in the Tris case.

In this work, we investigate the production of hydroxyl radicals from the W(s)/air aqueous system by quantifying the amount of scavenging product formaldehyde via the modified Hantzsch method. Tris(hydroxymethyl) aminomethane (Tris) and methanol are used as probe for HO. Meanwhile, the amount of dissolved tungsten is determined by ICP-OES. A turnover point ([W] ≈ 200 μM) is observed in the Tris case after which the production rate of CH2O overwhelms the constant rate in the methanol case. Based on the results, a mechanism is proposed for the studied system including both surface and solution reactions.

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