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.