Removal of Methylene Blue from Simulated Wastewater Based upon Hydrothermal Carbon Activated by Phosphoric Acid

• DOI: 10.3390/w17050733
• Publication Date: 2025-03-03T15:15:03Z
• Authors: Jing Hong; Jia Bao; Yang Liu

Cationic dyes pose potential health risks to humans due to their higher toxicity levels. Most current research focuses on the utilization of biomass waste in the preparation of multifunctional materials to mitigate the adverse impact of cationic dye wastewater on the environment. However, conventional methods of biochar preparation require elevated pyrolysis temperatures and greater energy consumption. Accordingly, this study aims to investigate the effectiveness of the removal of methylene blue (MB) from simulated wastewater using a one-step phosphoric acid activation hydrothermal carbonization technique. SEM, BET, XRD, FTIR, and XPS analyses were conducted to investigate the surface morphology and chemical composition of pine sawdust (PS) biomass as a raw material, pine sawdust with hydrothermal carbon (HTC-PS), and pine sawdust with phosphoric acid-activated hydrothermal carbon (PHTC-PS). The results demonstrate that PHTC-PS exhibits a maximum adsorption capacity of 268.4 mg/g for MB at 298 K. The experimental data demonstrate its consistency through both the Langmuir isotherm model and pseudo-second-order kinetic model, suggesting that its adsorption mechanism predominantly involves monolayer formation through chemical interactions. Additionally, thermodynamic parameters reveal that the MB adsorption of PHTC-PS is a spontaneous endothermic reaction. Thus, this study demonstrates that the one-step phosphoric acid activation hydrothermal carbonization method can achieve satisfactory adsorption efficiency with the advantages of lower energy consumption, simplicity to the operation, and mild preparation conditions.