Highly porous activated carbon from recycled tobacco waste: a promising adsorbent for thiamethoxam removal.

This work aimed to use illicit tobacco residues for the production of activated carbon (AC) with a large surface area to remove thiamethoxam from water. We successfully produced tobacco-derived activated carbons (ACs) through thermal and chemical activation, including AC800-4-KOH, AC900-4-KOH, and AC900-5-KOH. AC900-4-KOH, in particular, displayed an exceptional surface area of 3294 m² g⁻¹, with surface functional groups indicating its aptitude for adsorption. In our comprehensive adsorption analysis, we observed rapid thiamethoxam removal, with over 95% adsorption occurring within just 5 minutes. The Freundlich model best described the adsorption process, revealing multilayer adsorption on the inherently heterogeneous AC surfaces. Additionally, Langmuir isotherm results highlighted AC900-4-KOH's superior maximum adsorption capacity at 150.5 mg g⁻¹, underscoring its exceptional adsorption potential. KLangmuir constants further illustrated the robust thiamethoxam-AC interaction, with AC900-5-KOH exhibiting the highest affinity. Our findings demonstrate the spontaneous, exothermic, and temperature-dependent nature of thiamethoxam adsorption (ΔGº<0, ΔHº<0, ΔSº>0), emphasizing its favorable thermodynamic feasibility. Furthermore, water elution experiments confirmed the absence of significant metal release from the adsorbents. This study pioneered the use of recycled tobacco waste to produce AC, showcasing exceptional thiamethoxam adsorption capacities. These findings position the AC as a promising candidate for water treatment and environmental remediation applications.