Efficient removal of tebuconazole from wastewater by zinc-modified passion fruit peels: Adsorption behaviour and mechanism

In this research, an effective adsorbent, ZnCl2-modified biochar (Zn-PFPB), was prepared from unprocessed passion fruit peel (PFP) for the removal of tebuconazole (TE) from wastewater. The synthesized Zn-PFPB was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), N₂ adsorption/desorption curves, and point of zero charge, which suggested that Zn-PFPB had an amorphous structure and high porosity. Optimal TE removal occurred at pH 2 with an adsorbent dosage of 0.5 g L⁻¹. The kinetics of the adsorption process followed the pseudo-second-order model while the isotherm model used was the Langmuir model, suggesting monolayer chemisorption. The maximum adsorption capacity reached 201.32 mg g⁻¹ for TE. The adsorption mechanisms were pore filling, hydrogen bonding, π-π interactions, and surface complexation. Importantly, Zn-PFPB maintained removal efficiency of more than 65% over a broad pH range (2–10), which can be considered as a promising candidate for practical applications. The regeneration rate of Zn-PFPB was determined to be 70% after the third cycle when using 1 mol L⁻¹ NaOH. The cost analysis showed a fabrication cost of $5.093/kg for Zn-PFPB. Batch mode scale-up design showed that 18 g of Zn-PFPB can remove 95% TE from 50 L of wastewater containing 50 mg L⁻¹ TE. This work proposes a new, economical, and eco-friendly way of managing agricultural waste in wastewater treatment and soil management.