Covalent organic framework/PVA membranes for efficient phosphoric acid concentration via pervaporation

Membrane-based methods offer a promising alternative for phosphoric acid concentration, addressing the limitations of conventional techniques. In this study, we employ a pervaporation system to achieve phosphoric acid concentration, evaluating its efficiency and stability under industrial-relevant conditions. Composite PVA-COF membranes were successfully prepared through vacuum filtration of TpPa-SO 3 H nanosheets and PVA on hydrophilic polytetrafluoroethylene (PTFE) support membranes and the followed crosslinking with glutaraldehyde. The incorporation of PVA effectively eliminates boundary defects and enhances the mechanical and operational stability of the composite membrane. The optimum COF-PVA composite membrane exhibits excellent rejection of NaCl (99.9 %) and an ultrafast water flux of 268.6 kg m −2  h −1 . The water flux surpasses that of most reported membranes. Moreover, the membrane exhibited outstanding acid resistance and durability in phosphoric acid concentration tests, maintaining stable operation for 420 min at 40 °C with no phosphorus leakage detected in permeate. The membrane demonstrated notable concentration efficiency, achieving an increase in phosphoric acid concentration from 20 % to 25 % during a sustained 180-min operational period at 70 °C. This work helps to explore the prospects for the application of pervaporation membranes in the fields of seawater desalination and phosphorus chemical industry. Synopsis The hybrid membrane composed of poly (vinyl alcohol) and covalent organic framework, which is characterized by high permeate flux, salt rejection rate and acid stability.