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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]

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]