Custom-designed 3D printed feed spacers and TFN membranes with MIL-101(Fe) for water recovery by forward osmosis

In this work, a dual-pronged approach- (i) novel thin-film nanocomposite polyether sulfone (PES) membrane with MIL-101 (Fe) and (ii) 3D printed spacers were explored to enhance water recovery by forward osmosis. The concentration of PES, pore former, draw solution, and MIL-101(Fe) was optimised for maximum pure water flux (PWF) and minimum specific reverse solute flux (SRSF). The best membrane exhibited a PWF of 7.52 Lm^-2h^-1 and an SRSF of 0.33 ± 0.03 gL^-1 using 1.5 M NaCl and DI water feed. The M₂₂ membrane with the diamond-type spacer demonstrated a PWF of 2.53 Lm^-2h^-1 and SRSF of 0.75 gL^-1 for emulsified oily wastewater feed. The novel spacer design imparted significant turbulence to the feed flow and a lower foulant resistance of 1.3 m^-1 as compared to the ladder type (1.5 m^-1) or commercial spacer (1.7 m^-1). This arrangement could recover 19% pure water within 12 h of operation (98% oil rejection) with a ∼ 94% flux recovery after hydraulic wash.