Electro-activation of peroxymonosulfate by β-PbO2 partial filling/covering TiO2 nanotube arrays anode for alkaloid berberine degradation: Performance, mechanism and practicability

An interlocking “T-shape” structure was built by uniform filling β-PbO2 crystalline inside the trace Ti3+ self-doping TiO2 nanotube arrays (TNAs) channels and depositing the cauliflower-like β-PbO2 clusters on its upper surface through a facile current pulse deposition method. We elaborated the interfacial engineering strategy for generating compact oxide layers at TNAs bottoms and growing β-PbO2 crystalline from the selectively conductive TNAs bottoms. Different characterization techniques and electrochemical analyses were conducted to characterize the morphology, structure, and electrochemical property of the β-PbO2 partial filling/covering TNAs (β-PbO2/TNAs/Ti) materials. We also systematically investigated and elucidated the performance and mechanism of β-PbO2/TNAs/Ti anode activated peroxymonosulfate (PMS) system via berberine removal/mineralization, reactive oxygen species (ROS) identification/contribution, intermediates analysis, energy consumption and practical applicability estimation. Results illustrated that filling β-PbO2 inside TNAs can efficiently improve the directional electron-transfer efficiency, oxygen evolution over-potential, tolerance to the varied water matrices and service lifetime of β-PbO2/TNAs/Ti anode activated PMS system. The ROS including •OH, SO4∙- and 1O2 that generated from PMS electro-activation are responsible for efficient berberine degradation through two pathways. This study will provide a general approach to construct the versatile tube-filled TNAs-based materials for wide applications in water/wastewater treatment.