Preparation and application of wood-supported piezocatalyst with high efficiency and stability via partial hydrolysis of wood cellulose and hemicellulose with Lewis acid

The conveniently recoverable piezocatalyst with self-floating and stable performance has drawn wide attention. Herein, MoS₂ was anchored on 1-cm-square eucalyptus wood blocks via a facile hydrothermal/solvothermal process to fabricate two floating piezocatalysts, i.e., MoS₂/unpretreated wood (MUW) and MoS₂/pretreated wood (MPW). FeCl₃ solution was used as a Lewis acid to pretreat the wood through partial hydrolyzing cellulose and hemicellulose for an purpose to creat rich micropores for MoS₂ loading in the wood and to form MoFe heterojunction. The piezocatalytic properties and performance of the prepared wood were systematically studied. The scanning electron microscopy confirms MoS₂ was anchored on wood surface. The macroscopic photos show that MoS₂ penetrated through the MPW interior whereas it was only loaded on the wood surface layer. The X-ray photoelectron spectroscopy reveals the shift of Mo 3d and S 2p, verifying the heterojunction formation of MPW. The Fourier transform infrared spectra prove the partial hydrolysis of wood matrix. In comparison to MUW, MPW had excellent piezocatalytic property, wide pH adaptability, convenient recyclability and high stability. Sildenafil and Cr⁶⁺ ions could be completely removed in 20 and 15 min, respectively, by MPW. Contrastly, the removal efficiency of sildenafil and Cr⁶⁺ by MUW was 78.6 % and 68.3 % in 20 and 15 min, respectively. After five cycles of use, the removal ratio of sildenafil was 62.4 % by MUW and 90.5 % by MPW in 20 min. The mineralization efficiency of sildenafil reached 99.2 % in 30 min by MPW, and various types of N/S-containing intermediates were effectively degraded. The electron spin resonance characterization and active species scavenging experiments displayed that e^- and ^•O₂^- were major active species responsible for Cr⁶⁺ piezoreduction by MUW and MPW, while ^•O₂^- and ^•OH were the dominant species accounting for sildenafil degradation by MUW and MPW, respectively. And ^•OH was not generated in the MUW piezocatalysis process. MPW had higher piezoelectric current and lower resistance at the electron transfer interface than MUW. Conclusively, this study paves a new pathway for preparing new floating piezocatalysts with easy recyclability and high stability from biomass for wastewater treatment.