Environmental devices I
The COVID-19 pandemic has become an extremely urgent global concern owing to the serious threat of an exponential increase in the number of infected patients and confirmed deaths. Even though COVID-19 vaccines are being successfully distributed in several countries, critical issues such as long-term vaccine preservation for worldwide distribution and the possibility of short supply remain. Therefore, temporary prevention methods, such as handwashing and social distancing are important. Electrospun nanofibers have been considered as the most feasible alternative owing to the simplicity of processing and compatibility with several polymers; fibers with a wide range diameter can be produced, which contributes to the diversity of fabrication systems. Electrospinning is a novel method that facilitates the construction of ultrathin nanofibrous-web membranes with a significantly high air permeability and relatively low pressure drop, owing to the well-known slip effect that occurs when the fiber diameters are similar to the size of air molecules.
Environmental devices II
CO₂ separation has emerged as an inevitable technology for the future to reduce global greenhouse gas emissions. Membrane-based CO₂ separation from other trace gases, such as N₂, CH₄, and H₂, is a fascinating technique in terms of cost-effectiveness and thermodynamic energy-saving processes, particularly compared with existing CO₂ capture technologies, such as pressure swing adsorption, absorption, or distillation. In particular, large amounts of N₂ and CH₄ are emitted along with CO₂ during thermal power plant operations, emphasizing that CO₂ separation from these mixtures is a likely future requirement for reducing global greenhouse gas emissions. Mixed-matrix membranes (MMMs), which are composed of a polymeric matrix and finely dispersed inorganic filler, are attracting attention, owing to their high levels of permeability and selectivity. The high permeability of MMMs while maintaining reasonable CO₂ selectivity is important, as the low permeability of neat polymeric membranes represents a limiting factor for membrane applications in industrial settings.
Environmental devices III
Over the past two decades, capacitive deionization (CDI) technology has been attracted numerous attentions and considered as one of the most economical and energy efficient desalination technology. In CDI, an external electrical field in typical range of 0.8 – 1.5 V is applied to the pair of porous electrodes, resulting in separating charged salt ions including sodium and chloride (charging process). These ions are physically adsorbed onto electrode surface based on electrical double layer (EDL) mechanism. The electrode capacity can be regenerated by applying reverse potential or removing the electric field (discharging process), resulting in the release of the adsorbed ions turn back to feed stream. Cell configuration and electrode material play an important role in the enhancement of desalination performance in the CDI process. Various progresses in cell design have recently been made to overcome limitation of conventional CDI system including low salt adsorption capacity, co-ion expulsion, and unavoidable side reactions. CDI using flowable electrode (FCDI), membrane CDI, inverted CDI, asymmetric CDI, hybrid CDI, 3D-CDI, and rocking-chair CDI cells have been significantly developed in over the past two decades.
