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.

In this study, an adsorptive electrospun polyamide membrane (ESPA) and electrospun polyamide–weathered basalt composite membrane (ESPA-WB) were prepared by an electrospinning process at room temperature. Hence, the WB structure was built as a polymeric membrane separation film in combination with the ESPA matrix as a composite nano-filtration membrane. Then, the ESPA and ESPA-WB membranes were characterized using BET surface area analysis, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy (SEM). To avoid cracks forming during the sintering process, the WB should be added in certain percentages. The microstructures of the prepared membranes were investigated to evaluate their efficiency for basic and acidic dyesʼ removal and their permeation flux. Compared with the ESPA, the ESPA-WB membrane combines the characteristics of WB and ESPA, which greatly enhances the performance of both methylene blue (MB) and methyl orange (MO) dyes removal from synthetic wastewater. The outcomes of this study indicated that the dye uptake in the case of ESPA-WB is higher than that of ESPA, and it decreases with an increase in dye concentrations. The obtained membrane ESPA-WB showed both an excellent anti-dye fouling and a good rejection property for both dyes (i.e. 90% rejection for MB and 74% for MO) with no sign of contamination by the applied dyes. It was found that the structure of the ESPA-WB membrane contains a large number of several adsorption sites which leads to an increase in the removal rate of dyes. Hence, this study demonstrated a non-conventional strategy to prepare an effective adsorptive nano-composite membrane that can be applied as a highly recyclable one for the removal of organic dyes. Graphic abstract

Sustainable serpentine/polyamide nanocomposite (SP/PAM) was fabricated using malicious mining (serpentine chrysotile, SP Ctl) and industrial (polyamide, PA6) wastes via the electro-spinning technique. Before fabrication, the fibrous nature of Ctl was demolished through intensive grinding into nano-fractions. The successful impregnation of Ctl within PA6 via the electro-spinning technique at fixed ratios of precursor raw materials in the dissolving agent (7.5/92.5% SP/PA wt/wt solid/solid) created an internal network structure within the polymer fibers by molecular self-assembly. SP/PAM showcased its prowess in tackling the remediation of diverse dyes and Fe(III) from synthetic solutions in a batch system. Based on correlation coefficient outcomes (R2 ≈ 0.999), the pseudo-second-order equation justified the sorption data in an adequate way for all contaminants. In addition, intra-particle diffusion was not the only driving factor in the sorption process. Similarly, the Langmuir equation with maximum removal capacity (qmax) 5.97, 4.33, and 5.36 mg/g for MO, MB, and Fe(Ⅲ), respectively, defined the sorption data better than Freundlich.

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The dyeing of recycled polyamide nonwoven fabrics based on nanofibers (PA-NWNF), which were fabricated from polyamide wastes, was conducted in this study. Since PA-NWNF exhibited a high surface area to volume ratio, it was dyed with different particle sizes of Disperse Red 167 dye (DR 167, DR 167-B, and DR 167-C) without auxiliary agents to prevent further environmental pollution. The undyed and dyed PA-NWNF, as well as the applied dyes, were characterized by SEM, BET, XRD, and FT-IR techniques. Both color yield (K/S) and fastness of dyed PA-NWNF were also evaluated. The morphology of dyed DR 167-C owned homogeneity and smooth nanofibers. In addition, DR 167-C dye (the smallest particle size) provided numerous advantages, including high particle dispersion, low dyeing temperature, minimum processing time, and greater color yield. At a concentration of 15%, DR 167-C produced 55.1 and 33.18% color yields which were higher than DR 167 and DR 167-B, respectively. Also, DR 167-C achieved a better colorfastness to washing (very good, 4) compared to other studied dyes.