Electrospinning of UiO-66-ZrO₂/chitosan/polythiophene hybrid for efficient 4-chloro-2-methylphenoxyacetic acid herbicide removal at various pH levels

Abstract 4-Chloro-2-methylphenoxyacetic acid (CMPA) is a widely used herbicide whose persistence at elevated levels poses serious environmental and health risks. To address this challenge, a Zirconium based organic framework/ZrO 2 /Chitosan/Polythiophene nanofiber (UiO-66-ZrO 2 /CS/PTh.(2) NF) was designed for CMPA adsorption. The UiO-66-ZrO₂/CS/PTh.(2) hybrid was prepared by combining different ratios of the UiO-66-ZrO 2 with chitosan, followed by in-situ oxidative polymerization of thiophene. The UiO-66-ZrO 2 /CS/PTh.(2) NF was fabricated via electrospinning of UiO-66-ZrO 2 /CS/PTh.(2) into nonwoven fibrous mats using a Polyvinyl alcohol/Polyvinyl pyrrolidine (PVA/PVP) blend to enhance viscosity and conductivity. Physical characterization confirmed the successful formation of UiO-66-ZrO 2 /CS/PTh.(2) NF, which exhibited a specific surface area of 593.13 m 2 g −1 and a total pore volume of 4.26 cc g −1 , corresponding to an average pore diameter in the mesoporous range. SEM analysis showed fiber diameters ranging from 286 to 429 nm, whereas TEM analysis revealed fiber diameters ranging between 32 and 55 nm. Adsorption studies showed CMPA capacities of 229.0, 253.0, and 290.87 mg g −1 for UiO-66-ZrO₂/CS/PTh.(1), UiO-66-ZrO₂/CS/PTh.(2), and UiO-66-ZrO₂/CS/PTh.(2) NF, respectively. The removal efficiency of UiO-66-ZrO₂/CS/PTh.(2) NF was systematically evaluated over a pH range of 2–12. The material achieved 98.6% CMPA removal at pH 2, maintaining 86.9% efficiency at pH 12, attributed to its positive zeta potential. Kinetic and isotherm analyses indicated pseudo-second-order behavior and Freundlich multilayer adsorption. High performance was retained over 10 reuse cycles, demonstrating stability and cost-effectiveness.