Water desalination by forward osmosis: Dynamic performance assessment and experimental validation using MgCl2 and NaCl as draw solutes

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-2 h-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-2 h-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.

Impact of temperature and forward osmosis membrane properties on the concentration polarization and specific energy consumption of hybrid desalination system

This study investigates how temperature and forward osmosis (FO) membrane properties, such as water permeability (A), solute permeability (B), and structural parameter (S), affect the specific energy consumption (SEC) of forward osmosis-reverse osmosis system. The results show that further SEC reduction beyond the water permeability of 3 LMH bar-1 is limited owing to high concentration polarization (CP). Increasing S by 10-fold increases FO recovery by 177.6%, causing SEC decreases by 33.6%. However, membrane with smaller S also increases external CP. To reduce SEC, future work should emphasize mixing strategies to reduce external CP. Furthermore, increasing the temperature from 10 to 40 °C can reduce SEC by 14.3%, highlighting the energy-saving potential of temperature-elevated systems. The factorial design indicates that at a lower temperature, increasing A and decreasing S have a more significant impact on reducing SEC. This underlines the importance of developing advanced FO membranes, particularly for lower-temperature processes.