Activated carbon derived from shrimp waste enhanced by ball milling: a green solution for CO2 capture and waste valorization

Shrimp waste-derived biochar (BC), pretreated with HCl, was chemically activated with KOH at varying mass ratios and subjected to ball milling to engineer high-performance CO₂ adsorbents. Comprehensive characterization, including TGA, BET surface area analysis, DLS zeta potential, FT-IR, FE-SEM, and EDS, revealed significant structural enhancements. Textural analysis showed a dramatic surface area increase from 3 m² g⁻¹ for raw biochar to 924.4 m² g⁻¹ for the T-AC1:2 sample (HCl-treated BC and KOH-activated at a 1 : 2 ratio). The optimized sample, n-T-AC1:1 (HCl-treated, KOH-activated 1 : 1, and ball-milled), achieved the highest CO₂ adsorption capacity of 5.14 mmol g⁻¹ at 0 °C and 1 bar. Nonlinear isotherm modeling indicated Freundlich behavior at 0 °C and Redlich–Peterson behavior at 25 °C and 40 °C, while thermodynamic analysis confirmed spontaneous, exothermic physisorption. The optimized adsorbent also demonstrated excellent cycling stability over multiple adsorption–desorption cycles, confirming its regeneration potential. These findings demonstrate that the shrimp waste valorization strategy, combined with chemical and mechanical treatments, offers a scalable and sustainable route for developing high-performance carbon capture materials, contributing to waste reduction and climate change mitigation.