Abstract: A method for recycling a scrapped polyvinylidene fluoride (PVDF) membrane through chemical cleaning-structural transformation-hydrophilicity is disclosed, which can extend the service life of scrapped PVDF membrane materials (namely, membrane at the end of service life). The method includes the following steps: cleaning a scrapped membrane with sodium hypochlorite and citric acid; treating the membrane with a structural transformation agent, where, irreversible contaminants are washed away while the PVDF membrane is subjected to pore expansion and hydrophilization; and with self-polymerization of dopamine on a membrane surface, further improving the hydrophilicity of the membrane surface, enhancing the anti-contamination performance, and repairing damaged points on the surface of the scrapped PVDF membrane produced during long-term operation.

Abstract: A polyamide (PA) nanofiltration (NF) membrane and a preparation method thereof by regeneration from a scrapped microfiltration (MF) membrane are provided. The method adopts a cleaning-repairing-interfacial polymerization upgrading strategy, where, sodium hypochlorite and oxalic acid are used for deeply cleaning a scrapped MF membrane. PDA is used as a repairing agent to construct a reaction platform on the membrane surface, and finally a reaction system of piperazine and trimesoyl chloride (TMC) are used to form a PA NF membrane with a PA active layer. The repairing can construct a coating with a given thickness and prominent hydrophilicity on the membrane surface, which provides favorable base membrane conditions for upgrading and preparing an NF membrane.

Abstract: A method for recycling a scrapped polyvinylidene fluoride (PVDF) membrane through chemical cleaning-structural transformation-hydrophilicity is disclosed, which can extend the service life of scrapped PVDF membrane materials (namely, membrane at the end of service life). The method includes the following steps: cleaning a scrapped membrane with sodium hypochlorite and citric acid; treating the membrane with a structural transformation agent, where, irreversible contaminants are washed away while the PVDF membrane is subjected to pore expansion and hydrophilization; and with self-polymerization of dopamine on a membrane surface, further improving the hydrophilicity of the membrane surface, enhancing the anti-contamination performance, and repairing damaged points on the surface of the scrapped PVDF membrane produced during long-term operation.

Abstract: A polyamide (PA) nanofiltration (NF) membrane and a preparation method thereof by regeneration from a scrapped microfiltration (MF) membrane are provided. The method adopts a cleaning-repairing-interfacial polymerization upgrading strategy, where, sodium hypochlorite and oxalic acid are used for deeply cleaning a scrapped MF membrane. PDA is used as a repairing agent to construct a reaction platform on the membrane surface, and finally a reaction system of piperazine and trimesoyl chloride (TMC) are used to form a PA NF membrane with a PA active layer. The repairing can construct a coating with a given thickness and prominent hydrophilicity on the membrane surface, which provides favorable base membrane conditions for upgrading and preparing an NF membrane.