Metamorphosis of waste sludge into functional membrane: Construction of aluminum sludge-derived MOF@FeOOH/PVDF composite membrane for enhanced phosphorus removal

In the field of water treatment, aluminum sludge (AIS) represents a substantial solid waste stream awaiting resource utilization-a largely untapped resource. Converting it into phosphate adsorbents offers a promising route for achieving “treating waste with waste”. However, its practical application is hindered by several challenges: raw aluminum sludge contains high impurity levels and has limited adsorption capacity, while its powdery form complicates recovery, rendering it unsuitable for engineering applications. To overcome these bottlenecks, this study introduces a “sludge-active metal component-composite membrane” conversion pathway: Initially, acid leaching is employed to purify the aluminum sludge and enrich its active aluminum component. Then, by leveraging the precise structure of aluminum-based metal-organic frameworks (MOFs) combined with FeOOH doping modification, a stable adsorbent material rich in active metal sites is constructed. Finally, a composite membrane was prepared with PVDF, which effectively encapsulates nanoscale adsorption performance within a macroscopically recoverable MOF@FeOOH/PVDF membrane, thereby achieving synergistic enhancement of adsorption performance and separation/recovery capabilities. Systematic characterization and adsorption experiments revealed that the composite membrane achieves a maximum phosphate adsorption capacity of 939.37 mg/m 2 . The adsorption mechanism involves a synergistic multi-pathway process, encompassing metal chelation, hydrogen bonding, and electrostatic attraction. Guided by the dual goals of “solid waste upgrading and pollution control”, this study successfully transforms aluminum sludge into high-performance macroscopic membrane materials, providing an efficient and easily recyclable technical solution for phosphate removal in eutrophic water bodies. This achievement is well aligned with circular economy (5R) principles, yielding a win-win outcome for resource recycling and water environment remediation.