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• An acid-stable polyamine NF hollow fiber module was prepared for phosphorus recovery via the IP method. • Tannic acid interlayer was first constructed onto the PES substrate to assist the spreading of the aqueous phase. • The resultant NF membrane shows only 9.6% rejection of phosphorus, alongside over 93.5% rejection of metal ions at pH 2. • Membrane water permeability can reach 20.3 LMH/bar. The hazardous heavy metals coexisting with phosphorus-containing sewage sludge seriously limit phosphorus recovery. Nanofiltration (NF) membrane, which can selectively separate heavy metals and phosphorus, has a promising potential for recovering high-quality phosphorus from sewage sludge. In this work, we utilized the undissociated form of H 3 PO 4 at pH <2 and customized an acid-stable polyamine NF membrane via interfacial polymerization (IP) for separating phosphorus and heavy metals under acidic conditions. An interlayer formed via co-deposition of tannic acid (TA) and diethylenetriamine (DETA) was firstly coated onto the polyethersulfone (PES) hollow fiber module to assist the spreading of aqueous phase on the substrate surface. Consequently, a tight and positively charged polyamine layer with a mean pore size of 0.77 nm was successfully constructed on the PES substrate, which is smaller than that of the membrane without interlayer (1.39 nm). This polyamine membrane maintained excellent stability during 15-day acid testing with 0.1 M HCl as feed solution. When it was used to recover phosphorus at acidic condition (pH 2), the phosphorus rejection of the NF membrane was only 9.8 %, much lower than that at neutral pH (46.7 %), which is due to the fact that most phosphorus existed in the undissociated form of H 3 PO 4 at pH 2. Meanwhile, given the fine-tuning pore size and Donnan exclusion effect of this membrane, it could effectively retain 96.9 % of Mg2+ and over 93.5 % of most heavy metal ions such as Pb2+, Cu2+, Fe3+, Zn2+, and Cr3+, alongside outstanding water permeability of 20.3 LMH/bar at 2-bar operation pressure. This result demonstrates the potential of our homemade polyamine membrane in phosphorus recovery. [ABSTRACT FROM AUTHOR]

[Display omitted] • Microfiltration PTFE hollow fibres were transformed into durable, high value OSN membranes. • A PEI/PIP based polyamide thin film was successfully synthesized on PTFE hollow fibre substrates. • A two-time interfacial polymerization was conducted to obtain a defect-free polyamide layer. • The resultant membranes could withstand strong aprotic solvents like DMF and DMSO. • The membranes had high solute rejections, of up to 95 % methyl orange (327 Da) rejection in DMF. Polymeric membranes have been extensively studied for organic solvent nanofiltration (OSN) but many fail to show sufficient chemical resistance in strong solvents like dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). This study focuses on harnessing the outstanding chemical resistance of polytetrafluoroethylene (PTFE), to develop polyamide-PTFE thin film composite (TFC) membranes that are resistant to such aprotic solvents. A defect-free polyamide thin film layer was successfully synthesized on the microfiltration PTFE hollow fibre substrates, overcoming challenges such as large and uneven pore size, and hydrophobicity of the PTFE substrates. A simple polydopamine (PDA) coating was carried out to improve the substrate's hydrophilicity prior to the polyamide synthesis via interfacial polymerization (IP). Polyethyleneimine (PEI) and trimesoyl chloride (TMC) were used as the monomers and a two-time IP method was employed to obtain a defect-free polyamide coating. The synthesized membranes showed high acetonitrile (ACN) and DMF permeabilities of 7.94 and 3.70 lm−2h−1bar−1, respectively, with acid fuchsin (585 Da) rejections of > 90 %. The molecular weight cut-off (MWCO) of the membranes could be further reduced to ∼300 Da by the addition of piperazine (PIP) monomers. The membranes also showed excellent stability and performance in a 72-hour OSN test performed in DMF indicating their great potential in effective molecular separation in harsh solvents. This study demonstrates how a simple modification and coating technique can transform commercially available microfiltration PTFE hollow fibres into durable and high value OSN membranes. [ABSTRACT FROM AUTHOR]