Investigating the impact of activation temperature and time on the adsorption properties of activated biochar

Biochar is a sustainable, eco-friendly, and cost-effective material that has gained considerable interest for its potential as an efficient adsorbent. Its pore and surface characteristics are greatly influenced by the choice of biomass source and activation conditions, with temperature and time emerging as pivotal factors in determining biochar's structural characteristics. This study investigates how physical activation temperature and time impact the pore structure, surface area, and adsorption capabilities of biochar derived from Loblolly pine. Biochar samples were physically activated under nitrogen (N 2 ) and carbon dioxide (CO 2 ) atmospheres at temperatures ranging from 550 °C to 850 °C and activation times from 1 h to 3 h. N 2 was utilised as an inert purge gas during the thermochemical conversion, while CO 2 was introduced exclusively at the target temperature to serve as the physical activating agent. Results indicate that increased activation temperature and time improved the pore and surface characteristics of the biochar. The N 2 adsorption isotherms exhibited Type I characteristics, confirming a predominantly microporous structure, with mesopore development at higher activation conditions. Brunauer–Emmett–Teller (BET) surface area and pore volume increased with both temperature and time, reaching a maximum of 756.33 m 2 /g and 0.39 cm 3 /g, respectively, at 850 °C and 3 h. The proximate analysis demonstrated that the precursor maintained exceptionally low ash content (≤ 2.13 wt-%) while yielding a highly carbonaceous matrix (fixed carbon up to 85.74 wt-%). Prolonged activation increased carbon content and reduced volatile matter, enhancing the material's structural stability. Scanning electron microscope (SEM) analysis demonstrated the development of porous structures at higher magnifications. These findings underscore the effectiveness of physical activation in refining the pore structure and adsorption capabilities of activated biochar, offering valuable insights for optimising its use as a sustainable and efficient adsorbent.