Utilization of polypyrrole coated iron-doped titania based hydrogel for the removal of tetracycline hydrochloride from aqueous solutions: Adsorption and photocatalytic degradation studies

• Novel adsorbent cum photocatalyst, poly(IA)-(Fe–TiO2–PPy) was prepared and characterized.
• Doping of iron species and polypyrrole coating enhances the absorption maximum to visible region.
• Presence of COOH functionality on surface makes the material a hydrogel.
• Adsorption properties of poly(IA)-(Fe–TiO2–PPy) for tetracycline hydrochloride were evaluated.
• Photocatalytic degradation ability of the material was investigated under solar light.

The removal of tetracycline hydrochloride (TCH) from aqueous solutions with a novel photocatalyst, polypyrrole coated iron-doped titania polymerised with itaconic acid [poly(IA)-(Fe–TiO2–PPy)] was investigated in a batch system. All the prepared samples were characterized using scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and Diffuse reflectance spectroscopy (DRS) techniques. The effects of pH, contact time, adsorbent dose and ionic strength on the adsorption of TCH onto poly(IA)-(Fe–TiO2–PPy) were investigated. The kinetic data were found to follow pseudo-second-order kinetic model. The equilibrium adsorption data were fitted to Langmuir isotherm model, with maximum adsorption capacity 149.25 mg/g. Swelling capacity of the adsorbent relative to pH and time were also investigated. The photodegradation kinetics of TCH by the photocatalyst was found to follow Langmuir–Hinshelwood mechanism of first-order kinetics. Regeneration experiments and repeated use of adsorbent were tried for four cycles. From the results, it can be concluded that the prepared poly(IA)-(Fe–TiO2–PPy) could be an efficient adsorbent-cum-photocatalyst for the degradation of TCH form aqueous solutions under solar light.

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