Polydopamine-Coated Adsorptive Ultrafiltration Membrane with In Situ Grown β-FeOOH for Phosphorus Recovery from Wastewater

Abstract

This study describes the preparation and characterization of a polydopamine-coated UF membrane with in situ grown akageneite using a two-step mineralization process that employs NaOH for precipitation. This PAN-PDA-Ak/ NaOH membrane showed superior phosphorus uptake capacity, higher wettability, and surface roughness compared to PAN-PDA-Ak/HCl membranes, which were fabricated using the conventional forced hydrolysis with HCl and at elevated temperatures. The Langmuir model accurately described isotherm data, indicating a homogeneous adsorbent surface with a maximum phosphorus uptake capacity of 10.4 mg P/g. Under dynamic filtration conditions using 0.3 bar pressure, the membrane removed over 64% of phosphorus from both single-contaminant and synthetic wastewater solutions. The PAN-PDA-Ak/NaOH membrane demonstrated a high affinity for phosphorus, excellent reusability, and stability, with complete restoration of its uptake capacity after five cycles and negligible Fe leaching. This membrane also had a high permeability (199 LMH/bar), offering a unique opportunity to combine low-pressure operations with the high selectivity of adsorbents.