Quantitative evaluation of heel accumulation and regeneration performance of beaded activated carbon during cyclic VOCs adsorption–desorption

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Activated carbon adsorption–thermal desorption systems are widely applied for volatile organic compound (VOC S ) control; however, irreversible heel accumulation during cyclic operation leads to progressive deterioration of adsorption capacity and regeneration performance. This study systematically investigates the effects of adsorption mode, VOC S characteristics, and regeneration conditions on heel accumulation in beaded activated carbon. Both gas-phase aeration and liquid-phase soaking adsorption exhibited comparable heel accumulation (>30% after five cycles), suggesting that soaking adsorption can serve as a rapid evaluation approach under controlled conditions. Among the tested VOCs, cyclohexanone showed the highest heel accumulation (>40%), attributed to its high boiling point and strong adsorption affinity. Regeneration at 150°C was ineffective, resulting in persistent heel accumulation (25–35%), whereas regeneration at 300°C under oxygen-free conditions with controlled water vapor reduced heel accumulation to approximately 6–8% while preserving pore structure. The presence of oxygen significantly promoted heel formation and hindered regeneration. Spectroscopic and thermal analyses revealed that oxygen-containing conditions facilitated oxidative transformation and formation of thermally stable residues, leading to irreversible pore blockage. Strong correlations among specific surface area, apparent density, and cumulative heel accumulation (R² > 0.90) further demonstrate that apparent density can serve as a rapid indicator of carbon deactivation under cyclohexanone adsorption–desorption conditions. These findings provide mechanistic understanding and practical guidance for optimizing regeneration strategies in cyclic VOC S adsorption systems.

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