Double-layered hydroxides (LDHs) represent a unique class of compounds characterized by a crystal structure formed through the juxtaposition of two-dimensional units held together by relatively weak van der Waals forces. LDHs are commonly synthesized in nanoparticle form using straightforward and cost-effective methods. These LDH nanoparticles have found applications in various industries, particularly in the treatment of dye-contaminated wastewater. One noteworthy approach to enhance the properties of LDH nanoparticles involves the modification of the interlayer spacing within LDH structures, achieved through techniques such as calcination. In this research, LDH nanoparticles were synthesized using the co-precipitation method and subsequently subjected to calcination at 500℃, resulting in the formation of LDO nanoparticles. The produced nanoparticles were incorporated into nylon 6 nanofibers to eva‎luate their effectiveness in the photocatalytic degradation of methylene blue. The nanofibers were fabricated using the electrospinning technique, employing nylon 6 polymer solutions with concentrations of 10%, 12%, and 14% by weight, which contained varying proportions of LDH (or LDO) nanoparticles (ranging from 0% to 6% by weight). Analysis through FTIR, XRD, and EDX confirmed the successful integration of LDH (or LDO) within the nanofibers. Scanning electron microscopy (FESEM) images revealed an increase in nanofiber diameter with rising solution concentration of polymer and LDH (or LDO) nanoparticles. Additionally, calcination of LDH nanoparticles was observed to reduce the nanofiber diameter, as evidenced by the FESEM images. Diffuse reflectance spectroscopy (DRS) confirmed a reduction in band width following calcination. The study on the photocatalytic degradation of methylene blue revealed that elevating LDH (or LDO) concentrations, nanofiber weight, and the concentration of nylon 6 polymer led to enhanced dye degradation. The most favorable results was observed when employing 40 mg of nanofibers produced through electrospinning a solution of 12% nylon 6, which included 2% by weight of LDH (or LDO). The impact of the light source on the photocatalytic degradation of the optimal sample was investigated, and it observed degradation efficiencies of 93% under UV irradiation and 73% under visible light irradiation. Furthermore, the influence of pH on methylene blue degradation was assessed, with the highest efficiency (100%) being achieved at pH=10. Subsequently, in the case of photocatalytic degradation employing 40 mg of nanofibers containing 2% LDH, the degradation efficiency reached 62%, while the sample containing LDO achieved an impressive 94% efficiency. Consequently, the latter sample was designated as the optimal choice for subsequent experiments. A comprehensive analysis was conducted on the kinetics and isotherm of the photocatalytic degradation of methylene blue, using 40 mg of nanofibers containing 2% LDO. The results revealed that the kinetics of photocatalytic degradation of methylene blue followed the pseudo-second-order kinetic model, while the isotherm of the photocatalytic degradation of methylene blue adhered to the Langmuir isotherm model. Notably, the analysis of chemical oxygen demand (COD) in the effluents after 120 minutes of photocatalytic degradation revealed not only effective dye degradation but also an improvement in effluent quality, thanks to the produced nanofibers. Ultimately, the photocatalytic degradation process utilizing the optimal sample was shown to be reproducible, and the optimal sample demonstrated the ability to be regenerated for future use.

صديقه برهاني

محمد ديناري

حسين ايزدان , كميل نصوري