Degradation of oxytetracycline using hydroxyl radicals produced by metastable aluminium ions

In this work, a new homogenous Fenton-like reaction, using metastable aluminium ions $\left(\right[\mathrm{Al}\left(H_{2}O{)}_6^{3+}\right]\ast )$, was adopted to decompose H₂O₂ into HO^• and degrade OTC in an aqueous solution. It was found that $\left[\mathrm{Al}\right(H_{2}O{)}_6^{3+}]\ast$ ions can efficiently degrade and mineralize OTC across a wide pH range of 2.5-12.0 without precipitates. Under optimal conditions, OTC can be degraded within ∼10 min, and >60% of total organic carbon (TOC) was removed after reaction for 24 h. Even in a neutral solution, the degradation ratio of OTC can be up to ∼80%. Meanwhile, $\left[\mathrm{Al}(H_{2}O{)}_6^{3+}\right]\ast$ ions exhibited good recyclability, with no significant decrease in the degradation efficiency of OTC even up to six cycles. The reaction byproducts were determined, which indicates that the pathway of OTC degradation in $\left[\mathrm{Al}(H_{2}O{)}_6^{3+}\right]\ast$ solution includes decarbonylation, hydroxylation and dehydration. The present study provides a new homogeneous method to remove OTC in the aqueous solution.