Xanthan gum templated hydrothermal synthesis of Bi₂O₃ nano-photocatalyst for the mineralization of chlorophenols prevalent in paper pulp mill

This study effectively synthesized monoclinic bismuth oxide nano-photocatalyst (α-Bi₂O₃) using both template-assisted and template-free methods, employing the hydrothermal process. Xanthan gum, a type of soft biopolymeric material, was used as a sacrificial template to promote the regulated growth of nano-photocatalysts. The structure, morphology, surface features, optical properties, and catalytic activity of both templated and non-templated Bi₂O₃ were analyzed using XRD, FESEM-EDX, IR, and UV–Vis (DRS) spectral analysis techniques. Additionally, the chemical oxygen (COD) analyzer methodology was used to assess the catalytic activity. The combination of synthetic technique and template has successfully produced Bi₂O₃ nano-photocatalyst with a consistent and granular shape. Specifically, the template-assisted processes have produced nanostructures of bismuth oxide that are highly crystalline and low band gap (2.76–2.71 eV). The use of template-assisted metal oxide nanostructures has shown potential as very effective photocatalysts for breaking down developing pollutants, such as 2,4-dichlorophenol (2,4-DCP), which is found in paper and pulp mills, when exposed to sunlight. The xanthan gum templated α-Bi₂O₃ nano-photocatalyst almost completely photodegraded 2,4-DCP within 90 min under sunlight. The remarkable catalytic capability of bismuth oxide (Bi₂O₃) templated by xanthan gum has been confirmed by their high-rate constants of 0.01–0.05 min⁻¹. As the treatment duration increased to 90 min, the degradation of 2,4-DCP resulted in a maximum elimination rate of 97.5% for COD. As a result, the template-assisted approaches have successfully produced nanostructures with customized features, which makes them very efficient in photocatalysis for quickly breaking down certain emergent organic pollutants present in paper and pulp mill wastewater. These eco-friendly synthetic photocatalysts can be efficiently used for treating wastewater that is contaminated with emerging organic contaminants.