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Recently, feed spacer research for improving the performance of a membrane module has adopted three-dimensional (3D) printing technology. This study aims to improve the performance of membrane feed spacers by using various materials and incorporating 3D printing. The samples were fabricated after modeling with 3D computer-aided design (CAD) software to investigate the mechanical strength, water flux, reverse solute flux, and fouling performances. This research was performed using acrylonitrile butadiene styrene (ABS), polypropylene (PP), and natural polylactic acid (PLA) as printing material, and the spacer model was produced using a diamond-shaped feed spacer, with a commercially available product as a reference. The 3D printed samples were initially compared in terms of size and precision with the 3D CAD model, and deviations were observed between the products and the CAD model. Then, the spacers were tested in terms of mechanical strength, water flux, reverse solute flux, and fouling (alginate-based waste water was used as a model foulant). Although there was not much difference among the samples regarding the water flux, better performances than the commercial product were obtained for reverse solute flux and fouling resistance. When comparing the prominent performance of natural PLA with the commercial product, PLA was found to have approximately 10% less fouling (based on foulant volume per unit area and root mean square roughness values), although it showed similar water flux. Thus, another approach has been introduced for using bio-degradable materials for membrane spacers., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

In membrane processes, a spacer is known to play a key role in the mitigation of membrane fouling. In this study, the effect of electric polarization on a graphene-blended polymer spacer (e.g., poly(lactic acid), PLA) for organic fouling on membrane surfaces was investigated. A pristine PLA spacer (P-S), a graphene-blended spacer (G-S), and an electrically polarized graphene-blended spacer (EG-S) were successfully fabricated by 3D printing. Organic fouling tests were conducted by the 5-h filtration of CaCl2 and a sodium alginate solution through commercially available membranes, which were placed together with the fabricated spacers. Membranes utilizing P-S, G-S, and EG-S were characterized in terms of the fouling amount on the membrane surface and fouling roughness. Electrostatic forces of EG-S provided 70% less and 90% smoother fouling on the membrane surface, leading to an only 14% less water flux reduction after 5 h of fouling. The importance of nanomaterial blending and polarization was successfully demonstrated herein. [ABSTRACT FROM AUTHOR]

In this study, electrospun nanofiber was continuously sandwiched between two rubber rollers at high temperature (150 °C). The prepared nanofiber support layer possessed a pore size of 0.4 μm (with narrow distribution) and a fiber diameter of 292 ± 94 nm. Afterward, an interfacial polymerization was employed to deposit the selective polyamide layer on the nanofiber support layer. For the first time, engineered osmosis (EO) was used as a platform for verifying the presence of a polyamide selective layer on a nanofiber support layer. We found that the membrane prepared exhibited an excellent combination of permeability (30 L/m 2 h) and selectivity (17 g/m 2 h and 0.57 g/L) under a net pressure of 49 bar at the EO platform. The membrane developed can be applied to generate renewable energy using the EO process. In addition, the EO method can be used to detect selective polymer having a nano-scale thickness. [ABSTRACT FROM AUTHOR]

A thin film composite (TFC) forward osmosis (FO) membrane with high performance and superb durability was fabricated on a polydopamine (PDA)-modified polyethylene (DPE) support via an unconventional aromatic solvent-based interfacial polymerization (IP) method. The PDA coating uniformly hydrophilized the hydrophobic pristine polyethylene (PE) support, which enabled the long-term operation stability. The thin (∼8 μm) and highly porous support structure with interconnected pores was preserved after the PDA modification, leading to a remarkably low structural parameter (∼168 μm) of the support. In addition, the use of the toluene-based IP process allowed for the formation of a highly permselective polyamide selective layer on the hydrophilic DPE support, which was challenging with the conventional aliphatic solvent-based IP process. Hence, the prepared DPE-supported TFC (DPE-TFC) membrane exhibited unprecedented high FO performance, i.e., ∼4.5 times higher FO water flux and ∼63% lower specific salt flux (in FO mode) compared to the commercial HTI-CTA membrane. Furthermore, the DPE-TFC membrane possessed superior mechanical robustness, which guarantee durable operability and potential application even in mechanically harsh environments. Hence, the PE-supported FO membrane presents a new paradigm in FO membrane technology. Image 1 • FO membranes were fabricated using polydopamine-modified PE (DPE) supports. • DPE supports were uniformly hydrophilic while preserving their original structures. • The thinness, high porosity and enhanced hydrophilicity of DPE supports reduced ICP. • Toluene-based interfacial polymerization produced a highly permselective layer. • The prepared DPE-TFC membranes showed excellent FO performance and high durability. [ABSTRACT FROM AUTHOR]

Abstract In this study, a thin-film composite (TFC) membrane with a polysulfone (PSf) support layer comprising an ultrathin polydopamine/graphene oxide (PDA/GO) interlayer was fabricated by phase inversion, self-polymerization, and interfacial polymerization to improve water permeability of the TFC membrane for forward osmosis (FO) application. The surface of the support layer exhibited greater hydrophilicity because of the hydrophilic functional groups of PDA and GO. For longer PDA coating time, the permeability decreased due to pore blocking by PDA and GO. The TFC membrane with the PSf support layer coated with the PDA/GO interlayer showed great improvement of water flux (57.6%) without severe loss of the reverse solute flux under an optimum condition of 1 h of PDA coating time and 0.5 g/L of GO concentration. The results of this study are expected to contribute to the development of TFC FO membranes containing a hydrophilic interlayer to achieve improved membrane performance for water treatment and seawater desalination. Graphical abstract Unlabelled Image Highlights • TFC membrane with PDA/GO interlayer was synthesized. • TFC membrane with PDA/GO interlayer was firstly applied to FO operation. • Support layer with PDA/GO interlayer increased hydrophilicity. • TFC membrane with PDA/GO interlayer enhanced water flux. [ABSTRACT FROM AUTHOR]

Functionalized multi-walled carbon nanotube blended cellulose acetate (fCNT-CA) membranes were synthesized for forward osmosis (FO) through phase inversion. The membranes were characterized through SEM, FTIR, and water contact angle measurement. AFM was utilized to investigate alginate fouling mechanism on the membrane. It reveals that the fCNT contributes to advance alginate fouling resistance in FO (57% less normalized water flux decline for 1% fCNT-CA membrane was observed than that for bare CA membrane), due to enhanced electrostatic repulsion between the membrane and the alginate foulant. Furthermore, it was found that the fCNT-CA membranes became more hydrophilic due to carboxylic groups in functionalized carbon nanotube, resulting in approximately 50% higher water-permeated flux than bare CA membrane. This study presents not only the fabrication of fCNT-CA membrane and its application to FO, but also the quantification of the beneficial role of fCNT with respect to alginate fouling in FO. [ABSTRACT FROM AUTHOR]