Hydrothermal carbonization derived hydrochar from industrial waste as an efficient adsorbent for toxic dye removal and process optimization.

This study focuses on the removal of Red F2B dye from aqueous solutions using hydrochar prepared from industrial waste via hydrothermal carbonization (HTC). The synthesized hydrochar was thoroughly characterized to assess its structural and surface features (FTIR, XRD, and FESEM-EDS). A series of adsorption trials was performed to examine the influence of pH, temperature, contact time, dye concentration, and hydrochar dosage on dye elimination efficiency. The results indicated that dye removal was highly dependent on pH, achieving optimal removal at pH 3, and that it exhibited endothermic characteristics. The adsorption equilibrium data aligned well with the Langmuir model, with a calculated maximum adsorption capacity of 44.24 mg/g. Kinetic modeling suggested a pseudo-second-order mechanism, indicating that chemisorption governed the adsorption rate. Thermodynamic evaluations confirmed that the process was spontaneous and energy-absorbing. Process optimization was performed using Response Surface Methodology (RSM), which identified pH, hydrochar dose, contact time, and initial dye concentration as key influencing factors. Overall, this study demonstrates the feasibility of utilizing HTC-derived hydrochar from industrial sludge as a sustainable and efficient adsorbent for dye-contaminated wastewater, promoting circular economy and resource recovery concepts.