Photo-Assisted Removal of Tetracycline Using Bio-Nanocomposite-Immobilized Alginate Beads

In the present study, we report an efficient method for tetracycline (TC) removal from contaminated wastewater using alginate beads, immobilized with bio nanocomposite (BNC) consisting of Fe₃O₄ (iron oxide) and TiO₂ (titanium dioxide) nanoparticles along with dead biomass of TC-resistant bacteria Acinetobacter sp. Chemically synthesized Fe₃O₄ nanoparticles and commercially available TiO₂ (P₂₅) nanoparticles were combined to form nanocomposite followed by encapsulation within alginate beads along with heat-killed biomass of Acinetobactersp. for the efficient degradation and adsorption of the target pollutant. The primary characterization of chemically synthesized nanoparticles was carried out with Fourier transform infrared, scanning electron microscopy-energy-dispersive X-ray spectrometry, transmission electron microscopy, and X-ray diffraction techniques. The batch studies for TC removal were performed by varying the reaction parameters such as bead weight, initial TC concentration, and pH in a photoreactor with UV-C irradiation. TC concentration of 10 mg/L, bead weight 10 g, and pH 6 were fixed as the optimum condition where 98 ± 0.5% of TC was removed from the solution. The possible removal mechanism was investigated with the help of UV-visible, total organic carbon, oxidation-reduction potential, Brunauer-Emmett-Teller, and liquid chromatography-mass spectroscopy analyses. The applicability of the process was successfully tested with the natural water systems spiked with TC at 10 mg/L. To assess the ecotoxic effects of the treated effluents, the cell viability assay was performed with the algal strains, Chlorella, and Scenedesmussp. and the bacterial strains, Pseudomonas aeruginosaand Escherichia coli. Finally, the reusability of the BNC bead was successfully established up to the 4th cycle.