Removal of Ciprofloxacin by Borophene-Incorporated Mixed Matrix Membranes

Pharmaceutical wastewater has become a global concern. Ciprofloxacin (CIP) and similar antibiotics can promote the emergence of antibiotic-resistant microbes and superbugs, along with their own associated side effects. CIP removal using 2D materials with an elevated surface area offers a promising approach. Among 2D materials, borophene with an unoccupied p z orbital emerges as an attractive option for electron-rich CIP removal. In this study, freestanding borophene was synthesized sonochemically by adding boron in DMF, and the performance of borophene-integrated ultrafiltration membranes for the removal of CIP was investigated. Phase inversion kinetics indicated that the addition of borophene caused delayed demixing of the solvent and nonsolvent, resulting in a denser membrane morphology compared to that without borophene. The M2 membrane with 7.2 mg/L borophene concentration in the polymer dope solution exhibited the desired morphology with a permeability of 24 L/m 2 ·h·bar and a molecular weight cutoff of 21 kDa. The average pore diameter was reduced from 12.8 to 8.5 nm up to the M2 membrane, and then, it again increased to 11.5 nm due to agglomeration (M3 membrane) of borophene, drawing more water during phase separation. The membrane became more hydrophilic, and the surface potential was more negative with the addition of borophene. The strong interaction between polysulfone and borophene in the polymer matrix prevented leaching. The ultimate stress increased from 13.3 (M0 membrane) to 54 N/mm 2 (M2 membrane) upon incorporation of borophene (4 times). The detailed performance of the M2 membrane was evaluated for CIP removal using the HPLC method. In deionized water, CIP rejection of 97.8% was observed after 15 min of filtration with a feed concentration of 10 mg/L, a transmembrane pressure drop of 1 bar, and a cross-flow rate of 50 L/h. Overall, the borophene-incorporated membrane demonstrated significantly enhanced mechanical strength, tunable morphology, and adequate ciprofloxacin removal efficiency, indicating the potential for treating pharmaceutical wastewater.