Enhanced Tetracycline Degradation by a GaOOH@PDA/PES Photocatalytic Membrane through S-Scheme Heterojunction Formation: A DFT-Guided Experimental Study

Abstract

In this work, we rationally designed and fabricated an S-scheme GaOOH@PDA heterojunction under the guidance of density functional theory (DFT) calculations. Compared with pristine GaOOH, the as-fabricated GaOOH@PDA heterojunction exhibited nearly doubled photocurrent density and lower charge-transfer resistance, which indicated highly efficient separation and migration of photogenerated carriers. Thereafter, the obtained GaOOH@PDA composite was immobilized on a poly(ether sulfone) (PES) substrate to fabricate a novel photocatalytic membrane (GaOOH@PDA/PES). Under the optimal conditions screened via response surface methodology (RSM), the as-prepared photocatalytic membrane achieved a high removal efficiency of 94.5% toward tetracycline hydrochloride. Moreover, when assembled in a self-built continuous-flow photocatalytic membrane reactor (PMR), the GaOOH@PDA/PES membrane exhibited outstanding long-term stability and sustainable degradation capability, verifying its promising feasibility for practical wastewater remediation. The remarkable photocatalytic performance originates from the synergistic contribution of three pivotal factors: the S-scheme heterojunction endows efficient spatial separation of photoinduced charge carriers, the heterostructure optimizes the adsorption energy toward target pollutants, and polydopamine (PDA) imparts a prominent photothermal effect. Ecotoxicity evaluation further demonstrated that the designed catalytic system can efficiently eliminate pollutants while exerting favorable antibacterial activity and posing negligible ecological risk. This study underscores the significance of DFT-guided rational design in exploiting high-efficiency photocatalysts. More importantly, it establishes a comprehensive research route covering theoretical prediction, material synthesis, membrane fabrication, reactor integration, mechanism clarification, and ecotoxicity assessment. This work lays the theoretical and practical foundation for the further development and application of advanced photocatalytic membrane technology in sustainable water purification.