A parametric study on the synergistic impacts of chemical additives on permeation properties of thin film composite polyamide membrane

An investigation into electrochemical properties of poly(ether sulfone)/poly(vinyl pyrrolidone) heterogeneous cation-exchange membranes by using design of experiment method

Poly(ether sulfone) (PES)/poly(vinyl pyrrolidone) (PVP) blend heterogeneous cation exchange membranes were prepared by solution casting technique using dimethylformamide as solvent and cation exchange resin powder as functional groups agent. In this study, Taguchi experiment design method was employed for investigating the effects of controlling variables including polymer binder (PVP + PES) to total casting solution ratio, blend ratio of polymer binders (PVP to PES), resin to polymer binder ratio, and casting temperature on electrochemical characteristics of PES/PVP heterogeneous membranes. To this aim, each factor was considered at 4 different levels and therefore, 16 experiments were designed. To improve the quality of the membranes ultrasonic was used for appropriate dispersing of resin particles in the matrix of the membranes. According to the results, the averaged maximum values of 1.535 meq/g and 46.6 mV were obtained for IEC and membrane potential, respectively. Also, the highest obtained value of ion permeability tests was equal to 1.33 m/s. Finally, the synthesis conditions was optimized by considering the IEC and membrane potential as the objective functions which gave the values of 1.55 meq/g and 1.39 m/s for IEC and membrane potential, respectively, which proved that the synthesized membrane can be considered as a promising heterogeneous membrane.

Impact of bacterial streamers on biofouling of microfluidic filtration systems

We investigate the effect of biofouling in a microfluidic filtration system. The microfluidic platform consists of cylindrical microposts with a pore-spacing of 2 μm, which act as the filtration section of the device. One of our key findings is that there exists a critical pressure difference above which pronounced streamer formation is observed, which eventually leads to rapid clogging of the device with an accompanying exponential decrease in permeate flow. Moreover, when streamers do form, de-clogging of pores also occurs intermittently, which leads to small time scale fluctuations [O(10¹ s)] superimposed upon the large time scale [O(10² min)] clogging of the system. These de-clogging phenomena lead to a sharp increase in water permeation through the microfluidic filtration device but rates the water quality as biomass debris is transported in the permeate. Streamer-based clogging shares similarities with various fouling mechanisms typically associated with membranes. Finally, we also show that the pH of the feed strongly affects biofouling of the microfluidic filtration system.

Recent Advances in Nanoporous Membranes for Water Purification

Nanoporous materials exhibit wide applications in the fields of electrocatalysis, nanodevice fabrication, energy, and environmental science, as well as analytical science. In this review, we present a summary of recent studies on nanoporous membranes for water purification application. The types and fabrication strategies of various nanoporous membranes are first introduced, and then the fabricated nanoporous membranes for removing various water pollutants, such as salt, metallic ions, anions, nanoparticles, organic chemicals, and biological substrates, are demonstrated and discussed. This work will be valuable for readers to understand the design and fabrication of various nanoporous membranes, and their potential purification mechanisms towards different water pollutants. In addition, it will be helpful for developing new nanoporous materials for quick, economic, and high-performance water purification.

Robust fabrication of thin film polyamide-TiO2 nanocomposite membranes with enhanced thermal stability and anti-biofouling propensity

The development of nano-enabled composite materials has led to a paradigm shift in the manufacture of high-performance nanocomposite membranes with enhanced permeation, thermo-mechanical, and antibacterial properties. The major challenges to the successful incorporation of nanoparticles (NPs) to polymer films are the severe aggregation of the NPs and the weak compatibility of NPs with polymers. These two phenomena lead to the formation of non-selective voids at the interface of the polymer and NPs, which adversely affect the separation performance of the membrane. To overcome these challenges, we have developed a new method for the fabrication of robust TFN reverse osmosis membranes. This approach relies on the simultaneous synthesis and surface functionalization of TiO₂ NPs in an organic solvent (heptane) via biphasic solvothermal reaction. The resulting stable suspension of the TiO₂ NPs in heptane was then utilized in the interfacial (in-situ) polymerization reaction where the NPs were entrapped within the matrix of the polyamide (PA) membrane. TiO₂ NPs of 10 nm were effectively incorporated into the thin PA layer and improved the thermal stability and anti-biofouling properties of the resulting TFN membranes. These features make our synthesized membranes potential candidates for applications where the treatment of high-temperature streams containing biomaterials is desirable.

Parametric study on the stabilization of metal oxide nanoparticles in organic solvents: A case study with indium tin oxide (ITO) and heptane

The tendency of nanoparticles (NPs) to form large aggregates has been a major limitation to their widespread applications where utilizing monodisperse and stable suspension of NPs is essential. The aggregation of NPs becomes more challenging when there is less affinity between the dispersed phase (NPs) and the continuous phase (solvent), such as, dispersion of hydrophilic metal oxide NPs into a nonpolar (organic) solvent. The objective of this study is to systematically investigate the synergistic effects of eight dispersion parameters on the size and stability of indium tin oxide (ITO) NPs in heptane. The matrix of experimentation was designed using an L₁₈ Taguchi method. The analysis of variance (ANOVA) of the experimental results revealed that the most significant factors on the size and stability of NPs were the mass of ITO NPs and the volume of the dispersing agent. Taguchi signal-to-noise (SN) ratio analysis was used to determine the optimal factor levels for the preparation of well-dispersed and stable NP suspensions. Confirmation tests were carried out at the suggested levels of the ANOVA predictive model, and highly stable ITO NPs in heptane with the size distribution of 43.0-68.3nm were obtained. The results of the present parametric study can be used for a broad range of applications where effective stabilization of metal oxide NPs in organic solvents is desired.