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<p>The development of new methods for the elimination of dissolved pollutants, especially organic dyes in wastewater, has recently received much attention. Membrane technology with photocatalytic activity is one of the new solutions for treating wastewater containing dyes. In the present study, a novel nanocomposite membrane with photocatalytic activity was developed based on deposition of a layer of polydopamine containing blue TiO₂ nanotubes (BTNTs). First, BTNTs were synthesized by two stage electrochemical and anodizing methods. A porous polyethersulfone (PES) membrane was prepared using the phase inversion method, and finally, a thin layer of polydopamine containing BTNTs was deposited on the membrane surface. Characterization of BTNTs was performed using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and diffuse reflectance spectroscopy (DRS). The results showed the successful synthesis of BTNTs with a diameter of 90&#xa0;nm. BTNTs also showed significant photocatalytic activity in the visible light region with a band gap energy of 2.24&#xa0;eV. A series of experiments such as swelling, water contact angle, flux, fouling, rejection, and degradation tests were performed to evaluate membrane performance, with all measurements performed in triplicate (<i>n</i> = 3) and reported as standard deviation. The results indicated that the hydrophilicity, flux, and fouling resistance of the membrane were improved after deposition of the polydopamine–BTNT layer. Water contact angle measurements confirmed this improvement, decreasing from 55° for the pristine PES membrane to 41° after polydopamine coating and further to 34° for the membrane containing 20 wt% BTNTs relative to dopamine hydrochloride (0.01&#xa0;g BTNTs, M5). The flux recovery ratio (FRR) also increased compared to the pristine PES membrane, which had an FRR of about 60%. In comparison, the BTNT-containing membrane achieved an FRR of 95% under visible light irradiation due to reduced dye adsorption and the photocatalytic self-cleaning effect. The filtration and photocatalytic degradation of methylene blue (MB) solution were studied, and it was found that the nanocomposite membrane containing 0.01&#xa0;g BTNTs (M5) could eliminate up to 98.78% of MB dye under visible light irradiation. Furthermore, the advanced oxidation process significantly reduces secondary waste generation while promoting mineralization of organic pollutants.</p>

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Fabrication of a polydopamine/blue TiO₂ nanotube thin-film nanocomposite membrane for visible-light photocatalytic degradation of methylene blue

  • 期刊论文

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  • 发表日期：

    2026年7月22日

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  • Ehsan Sadeghzadeh,
  • Mehdi Mahmoudian,
  • Masoud Faraji,
  • Nasrin Shadjou

摘要

The development of new methods for the elimination of dissolved pollutants, especially organic dyes in wastewater, has recently received much attention. Membrane technology with photocatalytic activity is one of the new solutions for treating wastewater containing dyes. In the present study, a novel nanocomposite membrane with photocatalytic activity was developed based on deposition of a layer of polydopamine containing blue TiO₂ nanotubes (BTNTs). First, BTNTs were synthesized by two stage electrochemical and anodizing methods. A porous polyethersulfone (PES) membrane was prepared using the phase inversion method, and finally, a thin layer of polydopamine containing BTNTs was deposited on the membrane surface. Characterization of BTNTs was performed using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and diffuse reflectance spectroscopy (DRS). The results showed the successful synthesis of BTNTs with a diameter of 90 nm. BTNTs also showed significant photocatalytic activity in the visible light region with a band gap energy of 2.24 eV. A series of experiments such as swelling, water contact angle, flux, fouling, rejection, and degradation tests were performed to evaluate membrane performance, with all measurements performed in triplicate (n = 3) and reported as standard deviation. The results indicated that the hydrophilicity, flux, and fouling resistance of the membrane were improved after deposition of the polydopamine–BTNT layer. Water contact angle measurements confirmed this improvement, decreasing from 55° for the pristine PES membrane to 41° after polydopamine coating and further to 34° for the membrane containing 20 wt% BTNTs relative to dopamine hydrochloride (0.01 g BTNTs, M5). The flux recovery ratio (FRR) also increased compared to the pristine PES membrane, which had an FRR of about 60%. In comparison, the BTNT-containing membrane achieved an FRR of 95% under visible light irradiation due to reduced dye adsorption and the photocatalytic self-cleaning effect. The filtration and photocatalytic degradation of methylene blue (MB) solution were studied, and it was found that the nanocomposite membrane containing 0.01 g BTNTs (M5) could eliminate up to 98.78% of MB dye under visible light irradiation. Furthermore, the advanced oxidation process significantly reduces secondary waste generation while promoting mineralization of organic pollutants.