Synthesis, characterization, and application of a zinc oxide–pyrrole–thiophene nanocomposite as an efficient adsorbent for the removal of tetracycline

Abstract

An in situ oxidatively synthesized zinc oxide-based pyrrole–thiophene (ZnO–Py–Th) nanocomposite was characterized by various techniques, such as Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). Also, zeta potential (pH_PZC) and specific surface area measurements were carried out via a Zetasizer (Particle Size Analyzer) and Brunauer–Emmett–Teller (BET) method, respectively, and demonstrated a pore size of ∼4.45 nm and specific surface area of 142.16 m² g⁻¹. The nanocomposite exhibited a high adsorption property (q_m = 436.5 mg g⁻¹) for the removal of tetracycline (TC). The optimum adsorbent dosage of nanocomposite was 1.2 g L⁻¹. The isotherm and kinetic data were best fitted by Langmuir and pseudo-first-order kinetic models, respectively. The values of the thermodynamic parameters at different temperatures (298–318 K) for different concentrations from 50–90 mg L⁻¹, i.e., the enthalpy change (ΔH° = − 18.66 to − 22.11 kJ mol⁻¹) and free energy change (ΔG° = − 4.28 to − 12.23 kJ mol⁻¹), indicated that the overall adsorption process was exothermic and spontaneous. The adsorption–desorption study showed that the adsorption capacity of the nanocomposite over 5 adsorption–desorption cycles decreased to 80.36%. Based on these results, an adsorption mechanism for the removal of TC was also proposed.