Tailored GQDs heterojunction membranes for photocatalytic degradation of metronidazole from wastewater

BACKGROUND: Metronidazole is a persistent antibiotic pollutant in aquatic environments, posing ecological and health risks due to its chemical stability and low biodegradability. This study evaluates the influence of three graphene quantum dot (GQD) modifications (heteroatom-doped N,S-GQDs, surface-hydroxylated NaOH-GQDs, and polymer-modified PANI-GQDs) and MIL-100(Fe) synergy in a hybrid PVDF/PEI membrane for efficient antibiotic removal. RESULTS: The modified membranes exhibited Metronidazole rejection rates of 51%, 90%, and 63% for N,S-GQD, NaOH-GQD, and PANI-GQD coatings, respectively, compared to 68% for the uncoated hybrid membrane. The photocatalytic efficiency followed the order NaOH-GQD > N,S-GQD > uncoated membrane > PANI-GQD, with the NaOH-GQD-coated membrane showing the highest degradation rate (K₁ = 0.0119 min⁻¹, R² = 0.99). CONCLUSION: The heterojunction NaOH-GQD coating on the MIL-100(Fe) framework facilitated pollutant interaction and enhanced photocatalytic degradation, enabling efficient and stable antibiotic removal through a coupled nanofiltration and photocatalytic process. This work introduces a scalable and durable membrane photocatalyst platform that couples nanofiltration and visible-light photocatalysis, offering a promising route for sustainable water purification.