Excellent performance of novel superhydrophobic composite hollow membrane in the vacuum membrane distillation

Separation techniques for manufacturing fruit spirits: From traditional distillation to advanced pervaporation process

Separation process is one of the key processes in the production of fruit spirits, including the traditional distillation method and the new pervaporation membrane method. The separation process significantly determines the constituents and proportions of compounds in the fruit spirit, which has a significant impact on the spirit quality and consumer acceptance. Therefore, it is important and complex to reveal the changing rules of chemical substances and the principles behind them during the separation process of fruit spirits. This review summarized the traditional separation methods commonly used in fruit spirits, covering the types, principles, and corresponding equipment of distillation methods, focused on the enrichment or removal of aroma compounds and harmful factors in fruit spirits by distillation methods, and tried to explain the mechanism behind it. It also proposed a new separation technology for the production of fruit spirits, pervaporation membrane technology, summarized its working principle, operation, working parameters, and application in the production of fruit spirits, and outlined the impact of the separation method on the production of fruit spirits based on existing research, focusing on the separation of flavor compounds, sensory qualities, and hazard factors in fruit spirits, along with a preliminary comparison with distillation. Finally, according to the current researches of the separation methods and the development requirement of the separation process of fruit spirits, the prospect of corresponding research is put forward, in order to propose new ideas and development directions for the research in this field.

Nanoparticle-Enhanced PVDF Flat-Sheet Membranes for Seawater Desalination in Direct Contact Membrane Distillation

In this study, hydrophobic functionalized carbon nanotubes (fCNTs) and silica nanoparticles (fSiO₂NPs) were incorporated into polyvinylidene fluoride (PVDF) flat-sheet membranes to improve their performance in membrane distillation (MD). The performance of the as-synthesized membranes was evaluated against commercial reference polytetrafluoroethylene (PTFE) flat-sheet membranes. The water contact angle (WCA) and liquid entry pressure (LEP) of the PVDF membrane were compromised after incorporation of hydrophilic pore forming polyvinylpyrrolidone (PVP). These parameters were key in ensuring high salt rejections in MD processes. Upon incorporation of fCNTS and fSiO₂NPs, WCA and LEP improved to 103.61° and 590 kPa, respectively. Moreover, the NP additives enhanced membrane surface roughness. Thus, an increase in membrane roughness improved WCA and resistance to membrane wetting. High salt rejection (>99%) and stable fluxes (39.77 kg m^-2 h^-1) were recorded throughout a 3 h process evaluation where 3.5 wt% NaCl solution was used as feed. These findings were recorded at feed temperature of 60 ℃. Evidently, this study substantiated the necessity of high feed temperatures towards high rates of water recovery.

Scale Up and Validation of Novel Tri-Bore PVDF Hollow Fiber Membranes for Membrane Distillation Application in Desalination and Industrial Wastewater Recycling

Novel tri-bore polyvinylidene difluoride (PVDF) hollow fiber membranes (TBHF) were scaled-up for fabrication on industrial-scale hollow fiber spinning equipment, with the objective of validating the membrane technology for membrane distillation (MD) applications in areas such as desalination, resource recovery, and zero liquid discharge. The membrane chemistry and spinning processes were adapted from a previously reported method and optimized to suit large-scale production processes with the objective of translating the technology from lab scale to pilot scale and eventual commercialization. The membrane process was successfully optimized in small 1.5 kg batches and scaled-up to 20 kg and 50 kg batch sizes with good reproducibility of membrane properties. The membranes were then assembled into 0.5-inch and 2-inch modules of different lengths and evaluated in direct contact membrane distillation (DCMD) mode, as well as vacuum membrane distillation (VMD) mode. The 0.5-inch modules had a permeate flux >10 L m−2 h−1, whereas the 2-inch module flux dropped significantly to <2 L m−2 h−1 according to testing with 3.5 wt.% NaCl feed. Several optimization trials were carried out to improve the DCMD and VMD flux to >5 L m−2 h−1, whereas the salt rejection consistently remained ≥99.9%.

Fabrication of a novel one-step coating hyper-hydrophobic fluorine-free TiO2 decorated hollow composite membrane for use in longer-term VMD with enhanced flux, rejection, anti-wetting and anti-fouling performances

Despite recent efforts, there are still significant challenges in preparing hyper-hydrophobic membranes using environmental-friendly materials and simple methods. In this work, using phase separation theory, we prepared a fluorine-free hyper-hydrophobic porous hollow composite membrane using one-step ultrasound dip-coating. Then, fluorine-free modified titanium dioxide, polydimethylsilane and polypropylene was used to construct the porous membrane with a water contact angle of 161°. The distribution of surface elements, morphology, wetting and the scale of titanium on the membranes was characterized using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), the water contact angle and acid-alkali stability, wetting resistance, and so on. The membrane was evaluated for desalination in the presence of organic-pollutants. Under longer-term vacuum membrane distillation, compared with the general polypropylene membrane, the flux of the hyper-hydrophobic membrane increased to 12.17 kg (m² h)^-1, and the rejection rate reached 99.99%. These results indicated that the free-fluorine hyper-hydrophobic membrane could be used for seawater desalination. Finally, our results indicate that the hyper-hydrophobic modified membrane has good potential for use in industrial desalination.