Advances in the regeneration of spent adsorbents for gas-phase treatment: Thermal analyses and non-conventional approaches

Adsorption is one of the most widely used methods for the treatment of volatile organic compounds from gaseous effluents. When developing an effective adsorbent, it is essential to consider the entire lifecycle: besides achieving high removal efficiency, the potential for regenerating spent adsorbents must also be carefully evaluated. This review examines current technologies for the regeneration of spent adsorbents used in purification of gas streams or to limit emissions, with the goal of extending their functional lifespan. Here, thermal, non-thermal, and emerging technologies for the regeneration of spent adsorbents are presented, with particular emphasis on thermal approaches and their integration in adsorption-desorption cycles. Particular attention is devoted to the influence of key operational parameters such as temperature, purging gas, heating rate, and residence time on the regeneration efficacy. Moreover, thermal characterization analyses are highlighted as key tools for optimizing thermal regeneration strategies to ensure that regenerated materials retain their original adsorption capacity over multiple reuse cycles. The proper use of thermal analyses (thermogravimetry, differential thermal analysis, differential scanning calorimetry) is essential to develop efficient regeneration strategies of spent adsorbent materials. The importance of effective off-gas treatment during regeneration is also addressed, emphasizing its role in sustainable adsorbent management. Finally, the review addresses the lack of studies evaluating the life-cycle environmental impacts of regeneration processes and provides guidance for future research to support the sustainable and circular use of adsorbent materials.