Photocatalytic degradation of a textile dye in aqueous phase over ZnO nanoparticles embedded in biosilica nanobiostructure

In the present study, ZnO nanoparticles immobilized on biosilica nanobiostructure were used for the photocatalytic degradation of Acid Red 88 (AR88) in aqueous phase. UV-induced ZnO/biosilica nanocomposite (78.84%) was more efficient than visible light-induced ZnO/biosilica nanocomposite (21.87%). The results of UV–vis diffuse reflectance spectra (DRS) indicated that the enhanced UV–vis absorption of the nanocomposite could be attributed to biosilica support. Increasing the adsorbent dosage from 0.1 to 1.5 g/L caused a sharp increase in the decolorization efficiency from 15.30 to 98.54%, respectively, while further increase in the amount of photocatalyst to 2 g/L led to a little drop in the decolorization efficiency, decreasing to 93.63%. Decreasing the initial AR88 concentration from 70 to 10 mg/L enhanced the apparent reaction rate constant (k_ap) from 0.0078 to 0.1579 min⁻¹ and diminished the consumption of electrical energy (EE₀) from 2,813 to 139 kW h/m³, respectively. The decolorization and mineralization efficiency of 96.32 and 65.57% were obtained, respectively, thereby confirming an acceptable mineralization of AR88 within 30 min.