الفهرس 
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Abstract
This work describe the synthesis of a novel dye adsorbent by electrospinning technique to produced non-woven Polyamide nanofibers from Polyamide yarn waste. Polyamide nanofiber accompanied by chemical modification with critic acid (CA), by taking the advantage of low cost of raw materials, merits of the large specific surface area and highly open-porous structure of nonwoven nanofiber and plentiful active carboxyl groups introduced by CA and superior chemical stability.
The electrospinning parameters are polymer concentrations (15, 18, 22, 24 and 28 % wt/wt respect to solvent), applied voltages (5, 10, 15, 20, and 25 KV) and collector distance (5, 10, 15, 20 and 25 cm) have been studied. The obtained PA-nanofiber mats were modified with citric acid at various conditions such as CA concentrations (1, 3, 6, 8 and 15 %), curing temperature (90, 105, 120 and 130 °C) and Sodium hypophosphite monohydrate (SHP) concentrations (2, 4, 8 and 15 %) as a catalyst. The optimum conditions of this modification were investigated by Methylene Blue (MB) uptake efficiency. The obtained data illustrate a positive relationship between CA concentration and MB uptake using the modified PA-nanofiber.
The produced nonwoven adsorbent was well characterized using number of techniques, the morphology of surface for each of the PA-fiber waste, PA-nanofiber as well as modified PA-nanofiber with CA was determined using scanning electron microscopy(SEM), The functional groups on the surface of the PA-fiber waste, PA-nanofiber as well as modified PA-nanofiber were detected by Attenuated total reflections Fourier transform infrared (ATR-FTIR) and Surface areas of PA-fiber waste, PA-nanofiber as well as modified PA-nanofiber were measured using the Brunauer–Emmett–Teller (BET) equation. Also, UV–Vis spectroscopy used to determine the absorbance of produced samples toward MB. 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.
The obtained CA grafted PA-nanofiber present an excellent methylene blue (MB) adsorption performance with high efficiency, short equilibrium time.The MB separation capability of the modified PA-nanofiber was considerably higher than that of the PA-nanofiber. Kinetics and isotherms analysis were investigated as well. 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 to be ascribed as a 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.