One-step electrospinning of cellulose acetate/chitosan/TiO₂ fibrous membranes: efficient humic acid removal by synergistic adsorption and photocatalysis

The removal of contaminants in water purification is limited by the adsorption equilibrium, while the efficiency of photocatalytic oxidation is highly dependent on the adsorption process at the surface of photocatalysts. What would happen if photocatalytic oxidation were combined with biopolymer-based adsorbents? In this work, nano-sized TiO₂ was employed as a model photocatalyst and incorporated in our previously developed highly efficient adsorbents - cellulose acetate (CA)/chitosan (CS) fibrous membranes by one-step electrospinning to continuously and synergistically remove humic acid (HA) from aqueous solutions. The effect of TiO₂ contents on the structure and properties of TiO₂-CA/CS composites was studied by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and tensile testing, and the adsorption-photocatalysis experiment was carried out as a function of TiO₂ content, pH level, fiber composition, and irradiation time. The results indicated that TiO₂ was uniformly fixed in the electrospun CA/CS fibers. When the content of TiO₂ was 2 wt %, the composite fabric exhibited the highest tensile strength (21.84 ± 0.85 MPa) and could continuously remove HA (87.79% in 3 h without obvious saturation or fiber damage) at a low adsorbent dosage of 0.3 g/L. The HA removal efficiency of the TiO₂-CA/CS fibers under UV irradiation was higher than those of TiO₂-CA and CA/CS fibers, which also indicated a successful synergistic strategy.