Reusability of Spent Adsorbents for a Circular Materials Economy in a Chemical and Sustainable Industry

Abstract

Circular adsorption systems, particularly the management of spent adsorbents, are reaching a pivotal stage in industrial adoption and large-scale implementation. Simultaneously, the production and scaling of spent adsorbents are increasingly aligning with commodity applications. However, the prevailing approach to spent adsorbents at the end of their lifecycle primarily focuses on disposal or recycling to mitigate secondary pollution. A more economically favourable alternative involves prioritizing efficient reprocessing and recycling over disposal. In this context, the review underscores the decisive role of cost management in both the synthesis and regeneration of adsorbents. The synthesis stage has a strategic and multifaceted impact on adsorption performance, with several parameters, either individually or jointly, exerting a direct influence on cost. Key economic determinants include preparation and modification expenses, process complexity, and overall yield, all of which are essential in assessing the feasibility of adsorbent technologies. The review also combines scientific and strategic perspectives by grouping adsorbents according to their synthesis and regeneration cost profiles. Materials such as graphene oxide, silica, carbon nanotubes, and MOF-based composites fall into the high-cost category due to their costly production and regeneration requirements. In contrast, agricultural waste-based adsorbents emerge as a cost-effective solution, offering low synthesis and regeneration costs. Although composites hold strong potential, their high cost remains a major obstacle to large-scale implementation. On the top of that, we present strong economic incentives for adopting spent adsorbent reclamation over alternative pathways. The sustainable management of spent adsorbents—including recovery and regeneration processes—is reviewed through the lens of circular economy.