Magnetron sputtering of niobium thin films onto wood biochar to increase the selectivity for electrostatic attraction of anionic brilliant blue dye

Abstract

Background

Magnetron sputtering was employed to deposit thin niobium films onto biochar surfaces to increase selectivity for electrostatic interactions.

Methods

Biochar samples were coated with niobium under various power levels and deposition times by magnetron sputtering. Each material was then characterized and tested for adsorption performance with an anionic model molecule.

Significant findings

Niobium impregnation raised the point of zero charge of the biochar by 0.33 to 0.94 pH units, expanding the pH range in which the niobium-coated adsorbents maintain a positively charged surface. Optimal adsorption was observed at 298 K with an adsorbent dose of 1 g L⁻¹ and pH 2.4. The highest adsorption capacity of 43.64 mg g⁻¹ was achieved with the sample produced at 150 W for 30 min. This study highlights that the efficacy of niobium-coated adsorbents depends on the balance between metal loading and accessible surface area, emphasizing that increased metal deposition can shift the dominant adsorption mechanism by modifying surface characteristics.