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This study proposes using membrane distillation (MD) as an alternative to the conventional multi-stage flushing (MSF) process to concentrate a semi-product of organic fertilizer. By applying a unique asymmetric polyvinylidene fluoride (PVDF) membrane, which was specifically designed for MD applications using a nonsolvent thermally induced phase separation (NTIPS) method, the direct contact membrane distillation (DCMD) performance was investigated in terms of its sustainability in permeation flux, fouling resistance, and anti-wetting properties. It was found that the permeation flux increased with increasing flow rate, while the top-surface facing feed mode was the preferred orientation to achieve 25% higher flux than the bottom-surface facing feed mode. Compared to the commercial polytetrafluoroethylene (PTFE) membrane, the asymmetric PVDF membrane exhibited excellent anti-fouling and sustainable flux, with less than 8% flux decline in a 15 h continuous operation, i.e., flux decreased slightly and was maintained as high as 74 kg·m-2·h-1 at 70 °C. Meanwhile, the lost flux was easily recovered by clean water rinsing. Overall 2.6 times concentration factor was achieved in 15 h MD operation, with 63.4% water being removed from the fertilizer sample. Further concentration could be achieved to reach the desired industrial standard of 5x concentration factor. [ABSTRACT FROM AUTHOR]

ABSTRACT The influence of nanosilica on the concentration fluctuation of polystyrene/poly (vinyl methyl ether) (PS/PVME) mixtures was investigated during phase separation. The amplitude of concentration fluctuation was quantified by dielectric spectrums based on the idea of Lodge-Mcleish model and the linearized Cahn-Hilliard theory could describe the amplitude evolution of concentration fluctuation at the early stage of phase separation. Hydrophilic nanosilica A200 dispersed in PVME-rich phase behaved an obvious inhibition effect on the concentration fluctuation of blend matrix, while hydrophobic nanosilica R974 dispersed in PS-rich phase had little effect on the concentration fluctuation. The kinetics and amplitude evolution of concentration fluctuation during phase separation for PS/PVME/A200 nanocomposites were remarkably restrained due to the surface adsorption of PVME on A200. As the segmental dynamics of PVME and PS in homogeneous matrix was hardly influenced by A200 and R974, the enhanced miscibility and the significantly constrained flow relaxation of PVME chains might contribute to the retarded concentration fluctuation of PS/PVME/A200 nanocomposites. While the weak interaction between R974 and components of blend matrix and little effect of R974 on the molecular dynamics of PS chains may result in the weak retardation of concentration fluctuation for blend matrix. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1337-1349 [ABSTRACT FROM AUTHOR]

This study proposed a novel strategy to fabricate highly permeable and robust supported membranes for membrane distillation, via a nonsolvent thermally induced phase separation method. Different from traditional supported membranes cast on non-woven fabrics, a well-integrated fabric-embedded PVDF (FE-PVDF) membrane was successfully obtained using polyamide 66 gauze supports. The optimal FE-PVDF membrane PA-120 exhibited an interesting structure with pseudo Janus function, which entailed hydrophobic bulk membrane property but a pseudo hydrophilic bottom surface due to the presence of water-filled "50 μm grade" pores. The PA-120 exhibited a DCMD flux of 68.5 kg.m−2.h−1 at 70 °C with synthetic saline solution and exceptional tensile strength of 21 MPa (lateral)/21 MPa (longitudinal), which was 1.4-fold and 23-fold higher than that of the unsupported benchmark, respectively. The concentration of 10 wt% monosodium glutamate solution with PA-120 was demonstrated at 70 °C up to 55 wt% when crystallization was observed, The flux showed a minor decrease by 16.3% until 40 wt% and a subsequent decline towards 55 wt%. Repeated concentration cycles were conducted with intermediate membrane rinsing by fresh feed, demonstrating highly recoverable performance. This preliminary study brings new perspectives towards pushing the limits of current lab-made MD membranes. [Display omitted] • Ultra-robust fabric-embedded PVDF membranes were obtained by a facile NTIPS method. • FE-PVDF membrane offered tensile strength 21 MPa and DCMD flux 68.5 kg.m−2.h−1 (70 °C). • Membrane structure with a pseudo Janus function led to greatly enhanced mass transfer. • Successful concentration of MSG solution was conducted towards crystallization. • Reversible MD performance demonstrated in repeated cycles with no additional cleaning. [ABSTRACT FROM AUTHOR]

Abstract Nano-pore size is the key factor to determine the performance of porous membrane in various applications. The programmable and continuous manipulation of it remains as a great challenge. In this work, nano-porous shape memory polymer (SMP) membrane has been fabricated successfully in ternary blend of PVDF, PBSU and random copolymer (BMG) based on the special interface interaction and complicated phase behaviors among them. On one hand, phase separation takes place, producing bicontinuous structures with the characteristic size of microns including BMG rich phase and PVDF/PBSU mixed phase. The former provides shape memory effect in which cross-linked points and network play the roles of shape fixed phase and recovery phase respectively; on the other hand, exclusion of PBSU during crystallization of PVDF contributes to bicontinuous structures in nanoscale. The removal of PBSU based on double bicontinuous structures results in the interconnected nano-pores. The obtained nano-porous PVDF/BMG composite membranes possess not only shape memory performance, but also the interpenetrated channels. The pore size has been manipulated successfully by means of biaxial tension based on the proportional deformation in macro- and micro-scales. Our results provide a new strategy for the fabrication of nano-porous SMPs and the manipulation of pore size in them. Highlights • Double bicontinuous structures have been obtained based on the complicated phase behaviors in ternary blend. • Nano-porous shape memory membranes were prepared successfully. • Pore-size in microscale has been tailored programmably by macroscopic deformation. [ABSTRACT FROM AUTHOR]