Membrane vis-LED photoreactor for simultaneous penicillin G degradation and TiO2 separation

The hybrid membrane photoreactor (MPR) combining a photoreactor irradiated with visible-light-emitting diode (vis-LED) and a cross-flow microfiltration (MF) membrane module was investigated in both closed-loop and continuous flow-through modes for the simultaneous degradation of penicillin G (PG) and separation of visible-light responsive TiO2 particles, namely C-sensitized-N-doped TiO2 (T300) and C–N–S tridoped TiO2 (T0.05-450). The turbidity of permeate water was <0.2 NTU for both T300 and T0.05-450 suspensions in the MPR system operated at different transmembrane pressures (TMPs) and cross-flow velocities (CFVs), indicating effective separation of TiO2 particles by the MF membrane. The operations at a higher TMP or lower CFV were more prone to induce TiO2 deposition on the membrane surface without backwashing, which resulted in the membrane fouling, the loss of TiO2 from the photoreactor and the decrease of PG photocatalytic degradation efficiency. 75% and 84% of PG were degraded in the closed-loop MPR without backwashing operated at 10 kPa and 0.15 m s−1 after 4 h of vis-LED irradiation using 1.0 g L−1 of T300 and T0.05-450, respectively. With backwashing of the membrane, the PG photocatalytic degradation efficiencies in the closed-loop MPR could be significantly enhanced to achieve 93% and 95% using 1.0 g L−1 of T300 and T0.05-450, respectively, which were almost comparable to those achieved in the batch photoreactor. Due to its shorter hydraulic residence time in the photoreactor, the PG degradation efficiency in the continuous flow-through MPR with backwashing was lower than that achieved in the closed-loop MPR.

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► TiO2 was effectively separated by the MF membrane.
► The effects of TiO2 dosage, TMP and CFV on the MPR performances were investigated.
► Backwashing dislodged TiO2 particles from the membrane surface efficiently.
► The performance of continuous flow-through MPR was compared to that of closed-loop MPR.