Self-regeneration hybrid hydrogel for bisphenol a adsorption in water

Hybrid hydrogel was synthesized by immobilizing TiO₂ in polyethylene glycol diacrylate (TiO₂@PEGDA) as an efficient adsorbent with photocatalysis property for bisphenol A (BPA) elimination. TiO₂@PEGDA exhibited spherical and rough structure with limited crystallinity and abundant functional groups. The contact angle increased to 61.96° (TiO₂@PEGDA) from 46.73° (pristine PEGDA), indicating that hydrogel hydrophilicity decreased due to the presence of TiO₂. The swelling capacity of TiO₂@PEGDA (9.0%) was decreased compared with pristine PEGDA (15.6%). Adsorption results demonstrated that the maximum adsorption capacity of TiO₂@PEGDA (101.4 mg/g) for BPA was slightly higher than that of pristine PEGDA (97.68 mg/g). The adsorption capacity was independent with pH below 8 and decreased obviously when the value of pH was higher than 8. The adsorption behavior was fitted well with the pseudo-second-order kinetic and the Langmuir isotherm model. Both ΔG₀ and ΔH₀ were negative, indicating that BPA adsorbed on TiO₂@PEGDA was an exothermic and spontaneous process. Regeneration study was performed by photocatalysis, and the adsorption capacity was 85.6% compared with the initial capacity after four-cycle use, indicating that TiO₂@PEGDA could be recycled without significant adsorption capacity loss. Consequently, TiO₂@PEGDA can serve as an eco-friendly and promising material for efficiently adsorbing BPA with self-clean property.