Preparation of Carbon Dot-Modified Polyacrylonitrile Fiber Membranes Capable of Loading Titanium Dioxide and Investigation of Their Photocatalytic Performance

Addressing the critical issues of inevitable agglomeration and unsatisfactory photocatalytic efficiency inherent to powdered photocatalysts during water treatment, the idea to develop a robust nanofiber membrane carrier that can achieve uniform loading of photocatalysts and enhance their activity is valuable. The modified polyacrylonitrile (P-CPAN) was synthesized first by pomegranate peel carbon dots (PCDs) with acrylonitrile (AN) and acrylic acid (AA) through the in situ polymerization, then the hierarchical composite membrane, i.e., TP/CT@P-CPAN, was fabricated via electrospinning followed by a subsequent preimpregnation/solvothermal synthesis method. Compared with the reference sample, i.e., titanium dioxide (CT) powder, the heterojunctional TiO2@PCDs (TP) powder formed by the combination of TiO2 and PCDs has better photocatalytic ability, as TP could significantly expand the light absorption range to the visible-light region and reduce the recombination of photoinduced electron–hole pairs. Both PCDs and −COOH groups on the surface of P-CPAN nanofibers were suitable anchor points for amorphous CT during preimpregnation, TP and CT crystals through solvothermal synthesis could then attach firmly on the membrane. Hence, the TP/CT@P-CPAN membrane demonstrated good photocatalytic performance and durability. Even after 4 h of ultrasonic treatment, no significant shedding of the supported photocatalyst was observed. It can remain relatively stable even under acidic (pH = 2), alkaline (pH = 12), and high-salinity (10 g·L–1) conditions. Research on this kind of TP/CT@P-CPAN material that can be applied to complex usage environments has certain reference value for the development of fiber membrane-based photocatalyst materials.