Effective removal of ammonia from wastewater using hollow fiber renewal liquid membrane

Effects of silica nanoparticle addition and PDMS coating on membrane performance and stability in the extraction of aromatic amines

This study investigates novel strategies to improve membrane performance and stability in the extraction of aromatic amines for chiral amine production. The effects of silica nanoparticle addition and polydimethylsiloxane (PDMS) coating were explored, with a focus on the selective extraction of α-methylbenzylamine (MBA) and 1-methyl-3-phenylpropylamine (MPPA) from isopropyl amine (IPA). This work introduces a comparative analysis between open and tight membrane extraction (ME) systems, with and without the ionic liquid (IL) [P6,6,6,14][N(Tf)2]. The results reveal that PDMS creates a uniform and dense coating, particularly on PTFE and PVDF supports, while silica nanoparticle coatings were less stable, retaining only 50 % of nanoparticles after ME testing. A PDMS-coated PTFE membrane achieved significantly higher solute fluxes of 1.12 ± 0.01, 1.66 ± 0.02, and 0.36 ± 0.08 g/(m2h) for MBA, MPPA, and IPA, respectively, compared to an IL-wetted PTFE membrane, which was found to have fluxes of 0.60 ± 0.06, 1.01 ± 0.04, and 0.33 ± 0.10 g/(m2h) for the same solutes. A reduction in the pore size of the PTFE support further increased the fluxes to 1.74 ± 0.28, 2.75 ± 0.25, and 0.45 ± 0.08 g/(m2h) for MBA, MPPA, and IPA, respectively, achieving selectivity values of 3.83 ± 0.65 for MBA/IPA and 6.24 ± 0.88 for MPPA/IPA. Although IL impregnation marginally improved selectivity, it caused a significant reduction in solute fluxes. The PDMS coating retained 92.1 % of its mass after 24 h, while the IL retained 87.2 % over the same period. Compared to the tested IL, which presents safety concerns due to its flammability and corrosiveness, PDMS coatings provide a safer and more environmentally friendly alternative, as PDMS is non-toxic and does not bioaccumulate. These findings underscore the superior performance and environmental benefits of novel PDMS-coated membranes in tight ME setups compared to IL-based open ME systems.

Utilization of green organic solvents in solvent extraction and liquid membrane for sustainable wastewater treatment and resource recovery-a review

Water pollution and depletion of natural resources have motivated the utilization of green organic solvents in solvent extraction (SX) and liquid membrane (LM) for sustainable wastewater treatment and resource recovery. SX is an old and established separation method, while LM, which combines both the solute removal and recovery processes of SX in a single unit, is a revolutionary separation technology. The organic solvents used for solute removal in SX and LM can be categorized into sole conventional, mixed conventional-green, and sole green organic solvents, whereas the stripping agents used for solute recovery include acids, bases, metal salts, and water. This review revealed that the performance of greener organic solvents (mixed conventional-green and sole green organic solvents) was on par with the sole conventional organic solvents. However, some green organic solvents may threaten food security, while others could be pricey. The distinctive extraction theories of various sole green organic solvents (free fatty acid-rich oils, triglyceride-rich oils, and deep eutectic solvents) affect their application suitability for a specific type of wastewater. Organic liquid wastes are among the optimal green organic solvents for SX and LM in consideration of their triple environmental, economic, and performance benefits.