Application of low-cost adsorbents for dye removal – A review

Electrospinning is a versatile and viable technique for generating ultrathin fibers. Remarkable progress has been made with regard to the development of electrospinning methods and engineering of electrospun nanofibers to suit or enable various applications. We aim to provide a comprehensive overview of electrospinning, including the principle, methods, materials, and applications. We begin with a brief introduction to the early history of electrospinning, followed by discussion of its principle and typical apparatus. We then discuss its renaissance over the past two decades as a powerful technology for the production of nanofibers with diversified compositions, structures, and properties. Afterward, we discuss the applications of electrospun nanofibers, including their use as "smart" mats, filtration membranes, catalytic supports, energy harvesting/conversion/storage components, and photonic and electronic devices, as well as biomedical scaffolds. We highlight the most relevant and recent advances related to the applications of electrospun nanofibers by focusing on the most representative examples. We also offer perspectives on the challenges, opportunities, and new directions for future development. At the end, we discuss approaches to the scale-up production of electrospun nanofibers and briefly discuss various types of commercial products based on electrospun nanofibers that have found widespread use in our everyday life.

Electrospinning and Electrospun Nanofibers: Methods, Materials, and Applications

 Many atmospheric chemicals occur in the gas phase as well as in liquid cloud droplets and aerosol particles Therefore, it is necessary to understand the distribution between the phases According to Henry's law, the equilibrium ratio between the abundances in the gas phase and in the aqueous phase is constant for a dilute solution Henry's law constants of trace gases of potential importance in environmental chemistry have been collected and converted into a uniform format The compilation contains 17 350 values of Henry's law constants for 4632 species, collected from 689 references It is also available at http://wwwhenrys-laworg 

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Compilation of Henry's law constants (version 4.0) for water as solvent

Utilization of polymers as biomaterials has greatly impacted the advancement of modern medicine. Specifically, polymeric biomaterials that are biodegradable provide the significant advantage of being able to be broken down and removed after they have served their function. Applications are wide ranging with degradable polymers being used clinically as surgical sutures and implants. In order to fit functional demand, materials with desired physical, chemical, biological, biomechanical and degradation properties must be selected. Fortunately, a wide range of natural and synthetic degradable polymers has been investigated for biomedical applications with novel materials constantly being developed to meet new challenges. This review summarizes the most recent advances in the field over the past 4 years, specifically highlighting new and interesting discoveries in tissue engineering and drug delivery applications.

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Biomedical Applications of Biodegradable Polymers

Solar photocatalytic degradation of azo dye: comparison of photocatalytic efficiency of ZnO and TiO2

Aligned, electrospun polymer fibers have shown considerable promise in directing regenerating axons in vitro and in vivo. However, in several studies, final electrospinning parameters are presented for producing aligned fiber scaffolds, and alignment where minimal fiber crossing occurs is not achieved. Highly aligned species are necessary for neural tissue engineering applications to ensure that axonal extension occurs through a regenerating environment efficiently. Axonal outgrowth on fibers that deviate from the natural axis of growth may delay axonal extension from one end of a scaffold to the other. Therefore, producing aligned fiber scaffolds with little fiber crossing is essential. In this study, the contributions of four electrospinning parameters (collection disk rotation speed, needle size, needle tip shape and syringe pump flow rate) were investigated thoroughly with the goal of finding parameters to obtain highly aligned electrospun fibers made from poly-L-lactic acid (PLLA). Using an 8 wt% PLLA solution in chloroform, a collection disk rotation speed of 1000 revolutions per minute (rpm), a 22 gauge, sharp-tip needle and a syringe pump rate of 2 ml h(-1) produced highly aligned fiber (1.2-1.6 microm in diameter) scaffolds verified using a fast Fourier transform and a fiber alignment quantification technique. Additionally, the application of an insulating sheath around the needle tip improved the rate of fiber deposition (electrospinning efficiency). Optimized scaffolds were then evaluated in vitro using embryonic stage nine (E9) chick dorsal root ganglia (DRGs) and rat Schwann cells (SCs). To demonstrate the importance of creating highly aligned scaffolds to direct neurite outgrowth, scaffolds were created that contained crossing fibers. Neurites on these scaffolds were directed down the axis of the aligned fibers, but neurites also grew along the crossed fibers. At times, these crossed fibers even stopped further axonal extension. Highly aligned PLLA fibers generated under optimized electrospinning conditions guided neurite and SC growth along the aligned fibers. Schwann cells demonstrated the bipolar phenotype seen along the fibers. Using a novel technique to determine fiber density, an increase in fiber density correlated to an increase in the number of neurites, but average neurite length was not statistically different between the two different fiber densities. Together, this work presents methods by which to produce highly aligned fiber scaffolds efficiently and techniques for assessing neurite outgrowth on different fiber scaffolds, while suggesting that crossing fibers may be detrimental in fostering efficient, directed axonal outgrowth.

https://iopscience.iop.org/article/10.1088/1741-2560/6/1/016001/pdf

Creation of highly aligned electrospun poly-L-lactic acid fibers for nerve regeneration applications.

Varying the diameter of aligned electrospun fibers alters neurite outgrowth and Schwann cell migration.

Photoactive catalysts, when illuminated with UV-light, generate highly reactive radicals that can oxidize the organic contaminants in water. One method to increase the efficiency of the process, and thereby reduce the light energy requirements, is by developing more active catalysts. Several catalysts that were obtained commercially and/or prepared in the laboratory were examined for their photoactivity, and they are: TiO 2 , Pt-TiO 2 with platinum loading varying from 0.5% to 10% by weight, SrTiO 3 , and 1.5% NiO-SrTiO 3 . The organic compounds used to identify the best catalyst were trichloroethylene (TCE), toluene, methyl ethyl ketone (MEK), salicylic acid, and 2,4-dichlorophenol, with initial concentration varying from 0.1 to 10.0 mg/L

Heterogeneous photocatalytic oxidation of hazardous organic contaminants in water

The preparation and analysis of zeolite ZSM-5 membranes on porous alumina supports

Heterogeneous advanced oxidation involves the use of photoactive metal oxide catalysts illuminated with near-UV light to generate highly reactive species that can oxidize organic chemicals. This study examined the technical feasibility of using heterogeneous advanced oxidation for the regeneration of spent adsorbents. Adsorbability and regenerability of nonimpregnated and photocatalyst-impregnated adsorbents were evaluated. The nonimpregnated adsorbents were regenerated in titanium dioxide suspensions, whereas the photocatalyst impregnated adsorbents were regenerated in water in which no suspended photocatalyst particles were present. The results showed that the regeneration rates for the impregnated adsorbents were much faster than those for the nonimpregnated ones. To obtain adsorption capacity recoveries of >90%, a regeneration time of about one-fifth of the adsorption time was required for the regeneration of an adsorbent impregnated with platinized titanium dioxide whereas regeneration times longer than the adsorption times were required for the regeneration of the nonimpregnated adsorbents.

Michael E. Mullins

Papers

Creation of highly aligned electrospun poly-L-lactic acid fibers for nerve regeneration applications.

Varying the diameter of aligned electrospun fibers alters neurite outgrowth and Schwann cell migration.

Heterogeneous photocatalytic oxidation of hazardous organic contaminants in water

The preparation and analysis of zeolite ZSM-5 membranes on porous alumina supports

Regeneration of Adsorbents Using Heterogeneous Advanced Oxidation