Synthesis and application of fe-doped tio₂-halloysite nanotubes composite and their potential application in water treatment

In this work, the potential application of TiO₂-Fe-HNT photocatalyst-adsorbent composite in water treatment technologies was confirmed. The photocatalyst-adsorbent composite (TiO₂-Fe-HNTs) was synthesized by the hydrothermal method and characterized by X-ray diffraction, thermogravimetric analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy, and diffuse reflectance spectroscopy. The adsorption and photocatalysis mechanism by the TiO₂-Fe-HNT composite were examined on methylene blue dye, rhodamine blue dye, naproxen sodium (pharmaceutical drug waste), and imidacloprid (pesticide). The TiO₂-Fe-HNT composite was active in UV and visible regions of the electromagnetic spectrum. The adsorption and photocatalytic efficiency increased with increasing amount of HNTs. The photocatalyst-adsorbent composite exhibited excellent removal efficiency for pharmaceutical waste (naproxen sodium) and pesticides (imidacloprid). An adsorption equilibrium data fitted well with the pseudo-second-order kinetics for both methylene blue and rhodamine blue dyes with the intraparticle model describing its rate-controlling steps. The Langmuir and Freundlich isotherm models further described the adsorption of methylene blue and rhodamine blue molecules, respectively.