Abstract
Mercury (Hg 2+ ) is one of the most toxic and persistent heavy metals in aquatic environments, driving the need for the development of efficient and sustainable adsorbents from low-cost biomass resources. Herein, activated carbons derived from olive stones, a major Mediterranean agricultural waste, were prepared using H 3 PO 4 , NaOH, and ZnCl 2 as activating agents under identical preparation conditions and denoted as AC-H 3 PO 4 , AC-NaOH, and AC-Zn, respectively. The prepared adsorbents were comprehensively characterized, compared for Hg 2+ adsorption from aqueous solution, and their environmental sustainability was evaluated through cradle-to-gate life cycle assessment (LCA). While AC-Zn presented the lowest surface area (321 m 2 g⁻ 1 ), the Langmuir maximum adsorption capacity (162.0 mg g⁻ 1 ) was found to be substantially higher than that of AC-NaOH (69.3 mg g⁻ 1 ) and AC-H 3 PO 4 (17.0 mg g⁻ 1 ), demonstrating that surface chemistry and pore accessibility play a more critical role in Hg 2+ uptake than total surface area alone. LCA results showed that AC-H 3 PO 4 had the lowest production-based global warming potential (GWP; 7.25 kg CO 2 eq kg⁻ 1 AC), followed by AC-NaOH (7.28 kg CO 2 eq kg⁻ 1 AC) and AC-Zn (9.49 kg CO 2 eq kg⁻ 1 AC). However, when normalized by Hg 2+ adsorption capacity, AC-Zn showed the lowest GWP (59 kg CO 2 eq kg⁻ 1 Hg 2+ capacity), highlighting the importance of assessing adsorbents based on both production impact and pollutant-removal performance. This study presents a sustainable waste-valorization strategy for converting agricultural waste into high-performance adsorbents for Hg 2+ remediation while integrating adsorption performance with life cycle thinking, supporting United Nations Sustainable Development Goals 3, 6, 12, and 13.