U TILIZATION of electrospinning technique accompanied by chemical modification as well as, the production of low-cost adsorbent based on polyamide nanofibers is the aim of our current work. The electrospinning parameters (polymer conc, applied voltage, and collector distance) have been studied. The obtained polyamide nanofiber mats were modified with citric acid at various conditions (concentration, temperature and catalyst concentration). The optimum conditions of this modification were investigated by MB uptake efficiency. The obtained data illustrate a positive relationship between citric acid concentration and MB uptake using the modified polyamide nanofiber. The produced adsorbent was well characterized using SEM, ATR-FTIR, and surface area measurement. Scanning Electron Microscopy clarifies minor swelling of nanofibers during the modification process which attributed to the increase in fiber diameter and therefore reduction in the fiber surface area. The adsorption performance of the nanofiber mat was assessed as a function of pH, nanofiber mat dosage, contact time, and initial dye concentration. Kinetics and isotherms analysis were investigated as well. The MB separation capability of the modified PA-nanofiber was considerably higher than that of the PAnanofiber. The kinetic data of both nanofiber mat was better fitted with the pseudo-second-order model. Also, the equilibrium data of PA-nanofiber was better fitted with Freundlich model and Langmuir model in case of the modified PA-nanofiber. The adsorption behavior was favorable chemisorption process as inferred from the kinetics, and the isotherms studies. The results of this study promote the modified PA-nanofiber as a potential adsorption filters for dyeing wastewater decolourization.

Electrospun micro-and nanofiber scaffolds have gained interest in biomedical applications, especially in tissue engineering, because they can be used to reproduce the structure of the extracellular matrix (ECM) of natural tissue. The selection of the solvent is an important factor which affects the diameter, the surface morphology and the crystallinity of the electrospun fibers, and, accordingly, their mechanical properties as well as their degradation kinetics. Furthermore, the surface morphology of the electrospun fibres can be controlled by solvent vapour pressure to produce porous structures which might be helpful for cell adhesion and proliferation. In the present work, poly (L-lactic acid) (PLLA) has been electrospun using solvents with different vapour pressures to investigate the influences of the solvent vapour pressure on morphology, diameter, crystallinity and mechanical properties of the electrospun fiber scaffolds. The results show that the vapour pressure of the solvents (or solvent mixtures) play an important role in the fiber diameter and crystallinity. Furthermore, the crystallinity of the fibers is increased by lowering the vapour pressure of the used solvent. In addition, the mechanical properties (e.g., tensile strength and Young's modulus) are strongly dependent on morphological features such average fibers diameter. The smaller the average diameter, the higher the tensile strength and Young's modulus.

A B S T R A C TWaste wool fibers (WF) were oxidized and ball milled to enhance the exchanging ability toward some metal ions, namely copper and zinc. Wool fibers were oxidized with hydrogen peroxide and tetra acetyl ethylene diamine, followed by grinding process. Optimization of the exchanging medium with regard to the metal ion concentration, pH, and exchanging time was performed. It was observed that the ability of the wool powder (WP) and oxidized wool powder (OWP) to exchange greater amount of metal ions than the ordinary waste wool fibers. Mostly, current results verify a significant ability of the OWP to exchange copper and zinc ions from their aqueous medium. Nevertheless, the ability of all wool substrates used to exchange copper is more than their ability to exchange zinc, and as the pH of the exchanging medium increases, the uptake % of both copper and zinc ions by WF or WP increases to reach its maximum at pH 6. The efficiency of WF, WP, or OWP to adsorb copper and zinc ions after a number of adsorption/desorption tests was also studied.

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REMOVAL of methylene blue (MB) from water using adsorbent developed from waste wool fiber has been investigated by batch adsorption experiments in the present work. Wool fiber waste (WF) was collected from a local Spinning and Weaving Company, cleaned and further treated with citric acid to increase its adsorption capacity toward basic dyes. Raw and treated WF were ball milled to produce wool powder (WP) and modified wool powder (MWP), respectively. The carboxyl content was increased steadily as the citric acid solution concentration increased. The introduction of the carboxyl groups also has been proved by streaming potential measurements. The effect of contact time, wool dose and dye solution pH on the adsorption process were studied too. The adsorption isotherm was examined using Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) models. The adsorption equilibrium was attained within 20 minutes with a maximum removal percentage of 70 and 78 for WP and MWP, respectively. The wool dose affects the adsorption process significantly, especially for MWP which removes a higher percentage of MB (86 %) compared to WP (75 %). Both Freundlich and D-R were well fitting the adsorption equilibrium data with R 2 > 0.9. The values of Freundlich exponent factor (n) and D-R adsorption energy (E) reveal the chemisorption nature of the MB adsorption on both WP and MWP. This work demonstrated that, chemical and physical modifications of the waste wool fiber with citric acid has enhanced the adsorption of MB.

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