Multifunctional MOF-808@PVDF microspheres for recovery of unidirectional flow phosphorus from either wastewater or fermented sludge

• The mass ratio of MOF-808 to PVDF of 1:10 shows optimal performance. • Binding force of P on MOF-808@PVDF is ligand exchange and electrostatic interaction . • P partition coefficient for MOF-808@PVDF is 3.47 ∼ 446.81 in wastewater and AF broth. • The P dynamic adsorption process follows the Thomas and Yoon-Nelson models. • MOF-808@PVDF achieved a + 6.99 % VFAs yield and 56.58 % P recovery in AF system. Recovering phosphorus (P) from actual wastewater and its by-product, waste activated sludge (WAS), is essential for mitigating environmental pollution and advancing resource sustainability. However, conventional adsorbents face challenges in efficiently recovering P during the anaerobic fermentation (AF) of WAS. This study synthesized three MOF-808@polymer composites using poly(vinylidene fluoride) (PVDF), polyethersulfone, and sodium alginate. Among these, MOF-808@PVDF (mass ratio 1:10) demonstrated superior performance in terms of P adsorption capacity and acid-base stability. In static experiments, its maximum adsorption capacity reached 4.61 mg/g at 25 °C, with MOF-808 contributing as the primary adsorption site (56.55 mg/g). The key mechanisms were identified as ligand exchange and electrostatic attraction. MOF-808@PVDF exhibited the highest P distribution coefficient, outperforming in actual wastewater by 19.74 to 446.81 times and in fermentation broth by 3.47 to 54.84 times. Dynamic adsorption in actual wastewater conformed well to the Thomas and Yoon-Nelson models. While PVDF itself showed limited P adsorption, it can retain impurities in various complex aqueous environments, minimizing MOF-808 contamination. Additionally, PVDF with high mechanical strength effectively promoted WAS dissolution through friction and supported bacterial enrichment and metabolism via its proton transfer and rough surface with adsorbed organics, resulting in increased volatile fatty acids yield (+6.99 %) and enhanced P release. The reduced pH of the AF system and the fermentation temperature of 35 °C further improved the P adsorption capacity of MOF-808@PVDF. This study provides valuable insights into the design and application of innovative multifunctional adsorbents for wastewater treatment and resource recovery.