Engineered ZIF-8 Grown on Polydopamine-Functionalized Melamine Foam for Enhanced Adsorption of Chlortetracycline Hydrochloride from Wastewater

A macroscopic P-ZIF-8/PDA/MF adsorbent was fabricated by substituting conventional zinc precursors with layered porous zinc oxide (P-ZnO) on polydopamine (PDA)-functionalized melamine foam (MF). The composite exhibited exceptional adsorption capacity for chlortetracycline hydrochloride from wastewater, with a Langmuir-modeled maximum of 1320 mg/g at pH 6. Systematic evaluation of environmental parameters─including pH gradients, ionic strength variations, and competitive ion interference─revealed robust performance under various aqueous conditions. In addition, FT-IR and XPS analyses were performed to characterize P-ZIF-8/PDA/MF both prior to adsorption and following the adsorption process in order to clarify its adsorption behavior. The analysis indicates that the uptake by P-ZIF-8/PDA/MF mainly proceeds through monolayer chemisorption, which results from the combined contributions of hydrogen-bond interactions, π–π stacking, and pH-dependent electrostatic attraction.