Green and Eco-Friendly Egg White–TiO2 Hydrogel with Enhanced Antimicrobial, Adsorptive, and Photocatalytic Properties

Abstract

The design of multi-purpose decontaminants with environmentally friendly characteristics, low cost, and high efficiency in removing pollutants from the environment is an effective and economic strategy for maintaining the long-term development of the ecosystem. Based on the strategy of killing two birds with one stone, an egg white (EW)/TiO2 hydrogel with a porous structure is devised as a bio-adsorbent using waste eggs nearing their expiration date for simultaneously achieving the efficient removal of organic dyes and the inactivation of microorganisms from industrial wastewater. The characterizations of its morphology and composition using scanning electron microscopy (SEM), the Brunauer–Emmett–Teller (BET) theory, energy-dispersive spectrometry (EDS), Fourier transform infrared spectroscopy (FTIR), and a thermogravimetric analyzer (TGA) validate the successful synthesis of EW/TiO2. The maximum adsorption capacity of EW/TiO2 is 333.172 mg∙mL−1 according to the Langmuir model. The photodegradation of a methyl blue (MB) solution under irradiation via a xenon lamp is used to assess the photocatalytic behavior of EW/TiO2. Among the different samples, the 5 wt% TiO2-doped EW/TiO2 hydrogel shows an efficiency of 99% for 120 min of irradiation. Finally, the antibacterial properties of the EW/TiO2 hydrogel are evaluated by calculating its bacterial survival rate against Escherichia coli (E. coli). The EW/TiO2 photocatalyst exhibits a photocatalytic inactivation efficiency of 90.4%, indicating that the EW/TiO2 hydrogel possesses positive antibacterial activity via effectively inhibiting the growth of the bacteria, which is suitable for industrial wastewater treatment over a long period of time.