Impact of Chemical and Physical Treatments on the Structural and Surface Properties of Activated Carbon and Hydrochar

This study investigates the effects of various chemical and physical treatments on the structural and surface properties of activated carbon and hydrochar. Both materials were subjected to treatments with hydrochloric acid, sodium hydroxide, and ethylenediaminetetraacetic acid solutions, as well as microwave irradiation and hydrothermal processing. The resulting changes were analyzed using scanning electron microscopy, energy-dispersive X-ray spectroscopy, nitrogen adsorption–desorption isotherms, and X-ray photoelectron spectroscopy. Results indicate that activated carbon exhibits remarkable chemical resistance, maintaining its intrinsic porous framework across all treatments. However, subtle modifications in surface chemistry were observed, with acid and base treatments slightly increasing the surface area, while ethylenediaminetetraacetic acid treatment decreased it. Hydrochar exhibited more significant changes, notably a drastic reduction in surface area and porosity following sodium hydroxide treatment, indicating low alkaline resistance. Microwave and hydrothermal treatments showed potential as regeneration methods for both materials, slightly increasing the specific surface area while preserving the physical structure. X-ray photoelectron spectroscopy revealed increases in oxygen-containing functional groups for activated carbon after treatments, while hydrochar showed more variable changes, notably in carbonyl functionalities. This comprehensive study provides crucial insights for optimizing the regeneration and modification processes of carbon-based adsorbents, potentially enhancing their performance and sustainability in water treatment applications.