Highly efficient degradation of berberine chloride form wastewater by a novel three-dimensional electrode photoelectrocatalytic system

Fe₂O₃/graphite (Fe₂O₃/C) and nano-TiO₂-coated glass bead were prepared by impregnation and sol–gel method respectively and employed as the catalyst of a novel three-dimensional electrode photoelectrocatalytic (3-D PEC) system. The photoexcited electrons can transfer from TiO₂, Fe₂O₃ to counter electrode. It improves the migration of photoexcited charges, retards the fast recombination of electron–hole, and increases the lifetime of photogenerated holes (h⁺). In addition, the cycle reaction of Fe³⁺/Fe²⁺ on Fe₂O₃/C surface enhanced the Fenton reaction which can produce more hydroxyl radicals (·OH) and promote the capacity of mineralization of the pollutants. This novel 3-D PEC system showed excellent performance for the degradation of berberine chloride form (BCF). At the pH value of 3, 93% BCF was removed within 60 min; besides, 98.64% COD removal rate, 78.96% mineralization, 21.47% mineralization current efficiency, and just 3.16 kW h g⁻¹TOC energy cost were obtained in 120 min. In this study, we proposed the 3-D PEC mechanism. Electron spin resonance (ESR) and scavenging experiments suggest that the major reactive oxygen species (ROS) are superoxide radicals (O₂^·−), ·OH, and h⁺, while the role of sulfate radical (SO₄^·−) is insignificant. This work provides a new dimension for the design of reactors for wastewater treatment and the construction of the 3-D PEC system can potentially be utilized in water purification.