Palladium nanoparticles supported on biochar/graphitic carbon nitride as a heterogeneous catalyst for pharmaceutical degradation

Sonocatalysis is a promising method for degrading organic pollutants in aqueous media. However, practical applications require the development of low-cost, green, and efficient sonocatalysts. This study investigated the removal of pharmaceutical compounds, such as tetracycline (TC), from water and wastewater via ultrasound (US)-based decomposition by Pd nanoparticles protected on biochar/graphitic carbon nitride (Pd@BC/g-C₃N₄). The constituents and characteristics of the catalysts were evaluated, and BC/g-C₃N₄ and Pd@BC/g-C₃N₄ were found to have bandgaps of 2.61, and 2.21 eV, respectively. Furthermore, the Pd@BC/g-C₃N₄ nanocomposite was confirmed to consist of Pd nanoparticles uniformly distributed on BC/g-C₃N₄. Pd@BC/g-C₃N₄ attained a degradation performance of 94.23 % after 120 min under the optimum conditions ([TC]₀ = 10 mg/L, [Pd@BC/g-C₃N₄] = 0.03 g/L, and pH 6), whereas the degradation efficiency was only 78.33 % with BC/g-C₃N₄. The sonocatalytic activity did not decrease significantly during reusability experiments, demonstrating the high stability of the Pd@BC/g-C₃N₄ structure. The hydroxyl radicals (^•OH) production during the sonocatalytic degradation of TC via the US/Pd@BC/g-C₃N₄ process was confirmed using photoluminescence measurements and scavenging experiments with o-phenylenediamine. Gas chromatography-mass spectrometry analysis of the TC degradation intermediates revealed short-chain compounds, suggesting considerable progress toward mineralization during the sonocatalytic process. Thus, Pd@BC/g-C₃N₄ has the potential as an efficient heterogenous sonocatalyst for wastewater remediation.