Tailoring Y-doped ZnO loaded onto eco-friendly support alginate-hectorite for azo dye removal

Abstract

Yttrium-doped zinc oxide nanocomposites supported on an alginate-hectorite matrix were synthesized via an eco-friendly process and tested for the degradation of direct blue 71 and reactive black 5 azo dyes. The structural analysis confirmed a reduction in crystallite size from 34 nm in the sample with 2 % yttrium doping (ZAHY02) to 26 nm in the sample with 3 % yttrium doping (ZAHY03). Fourier-transform infrared spectroscopy revealed strong chemical interactions between the doped zinc oxide, the biopolymer, and the clay mineral. Scanning electron microscopy showed a well-dispersed morphology with smaller particle sizes in the nanocomposite doped with 3 % yttrium. Nitrogen adsorption–desorption analysis indicated a surface area of 77.4 m²/g and a pore volume of 0.179 cm³/g for the 2 % yttrium-doped nanocomposite, which decreased with higher doping levels. Optical measurements showed a narrowed band gap of 3.236 eV for the 2 % yttrium-doped sample, enhancing light absorption and photocatalytic activity. The Gaussian PL spectra deconvolution quantified V_Zn, V_O, and V_O⁺ structural defects. Photocatalytic experiments achieved significant efficiency, exceeding 90 % to remove direct blue 71 and 79 % for the reactive black 5 within 120 min under optimized conditions, with hydroxyl radicals identified as the primary reactive species. Stability tests confirmed the material’s high reusability, maintaining efficiency over three cycles. This study demonstrates the potential of these nanocomposites as sustainable and effective photocatalysts for wastewater treatment applications.