In-situ growth of silver particles in polyethersulfone (PES) ultrafiltration membrane for concentrating mangosteen rind extract

Mangosteen rind, often discarded as solid waste, contains bioactive compounds beneficial to public health. Commercial membranes can concentrate these compounds to enhance storage and transport, but prolonged filtration of organic-rich solutions causes biofouling. As process innovation, a mixed-matrix antibacterial membrane was developed by in-situ growth of silver (Ag) particles in a polyethersulfone (PES) ultrafiltration matrix. Ag particles were uniformly distributed on the membrane surface, with cross-sectional EDX mapping showing migration of Ag–PVP complexes to the water interface during phase inversion, driven by hydrophilicity. The triple role of polyvinylpyrrolidone (PVP) as reducing, dispersing, and capping agent was highlighted, with N and O atoms in PVP forming coordinate bonds with Ag⁺ ions. The membrane with 0.1 wt% Ag precursor achieved the highest flux (15.52 L/m²·h·bar) and concentration efficiency (13.80 %), and lowest energy use (0.3560 W·h/L) after two hours of filtering the mangosteen rind extract. Total phenolic content rejection was 81.78–89.28 %, while total monomeric anthocyanin rejection was lower (29.48–58.70 %), indicating the PES/Ag membrane’s potential for fractionating both compounds. Disk diffusion tests confirmed antibacterial resistance of the 1.0 wt% AgNO₃ membrane against Staphylococcus aureus and Escherichia coli with inhibition ring diameters of 0.6 mm and 0.7 mm, respectively. In conclusion, the PES/Ag membrane effectively concentrated phenolic compounds and improved biofouling resistance, with future work focusing on optimizing Ag synthesis and assessing particle leaching.