Hydrothermal carbonization of digested sewage sludge coupled with Alkali activation: Integrated approach for sludge handling, optimized production, characterization and Pb(II) adsorption

Background: Integrated sewage sludge handling and heavy metal management are important issues that scientists are working to solve today. Methods: Hydrothermal carbonization of dewatered digested sewage sludge (DDSS) under various conditions is carried out in this work, followed by alkali activation. The response surface methodology is used to investigate the operating process conditions and optimize them in order to produce hydrochar with the highest modified adsorption capacity (yield and Pb2+ adsorption). Significant Findings: The ideal conditions are 182.4 degrees C, 4.9 hours, 5.025 (w/w) water/DDSS ratio, and 3.5 (w/w) ZnCl2/DDSS ratio. In addition, the Langmuir isotherm (q(max) =109.3 mg/g) and pseudo-second-order models (q(eq)=110.7 mg/g) fit the experimental results better. The thermodynamics research confirmed that the adsorption process is spontaneous and endothermic. The findings revealed that hydrothermal carbonization of DDSS may be used to make effective adsorbents for heavy metal removal and waste management. (c) 2022 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.