Photocatalytic hydrogel layer supported on alkali modified straw fibers for ciprofloxacin removal from water

Abstract Rice straw is a potential green resource due to its low cost and high renewability. From the perspective of waste reutilization and green chemistry, an alkali-cooking modified rice straw fiber (AMSF) was prepared as a biosorbent to remove ciprofloxacin (CPFX) from water. To gain the ability of self-generation, a TiO2 hydrogel layer was coated on the surface of AMSF. The adsorption equilibrium was reached at approximately 35 min for AMSF, and the maximum adsorption capacity was 93.5 mg/g. The CPFX removal ability was enhanced by the TiO2-gel layer, especially under ultraviolet, and the CPFX removal quantity by TiO2@AMSF can be 153, 112, and 60 mg/g under ultraviolet, natural light and dark, respectively. The whole adsorption-degradation reaction lasted up to 450 min, and the pseudo-second-order model showed better linearity compared to the Langmuir-Hinshelwood. The CPFX removal ability of TiO2@AMSF in fluoroquinolone antibiotics system was also evaluated, and the adsorption and photodegradation effects were the removal mechanism. Providing more TiO2-gel layers or adding a UV irradiation can be an effective way to regenerate saturated TiO2@AMSF.