Development of Pistachio Shell-Based Bioadsorbents Through Pyrolysis for CO₂ Capture and H₂S Removal

The development of sustainable waste management for environmental remediation has highlighted the potential of biochar produced from agricultural wastes as an effective adsorbent for gas pollutant capture. This work focuses on the production and activation of biochar derived from pistachio shells for CO₂ and H₂S adsorption. Adsorbents were obtained by pyrolysis and subsequently activated through two methods: chemical activation with KOH and physical activation with CO₂. Adsorption studies were conducted to evaluate the influence of these activation methods on textural properties and adsorption capacities. Chemical activation enhanced microporosity and increased the specific surface area (531 m²/g), resulting in a better performance, obtaining adsorption capacities of 87 mgCO₂/g_adsorbent and 9.6 mgH₂S/g_adsorbent. Non-linear kinetic models were identified as the most suitable for fitting CO₂ adsorption data, with the Avrami model presenting the best fit results. Dynamic H₂S adsorption tests revealed the influence of moisture present in the adsorbent, favoring H₂S dissociation and thus improving capture processes, especially when chemical activation biochar is employed. This enhancement is attributed to the greater development of active centers on its surface, including micropores and heterogeneous atoms introduced though impregnation.