Synergistic upcycling of blast furnace slag: Cobalt sequestration and catalytic enhancement of thermochemical energy production

Abstract

The continuous growth of the global steel industry has resulted in a substantial increase in slag residue generation, emphasizing the urgent need for more efficient and sustainable management strategies. This study proposes a feasible approach to upcycle blast furnace slag (BFS) into a dual-purpose material: an effective sorbent for cobalt (Co) removal from wastewater and a catalyst for enhancing syngas production via biomass pyrolysis. BFS underwent alkali activation and silylation to produce a calcium silicate material (CSM), which was used for Co removal from aqueous solution. Sorption experiments demonstrated that CSM effectively sequestered Co through chemisorption and ion-exchange, achieving a maximum adsorption capacity of 147.8 mg g−1. The Co-laden CSM (CoCSM) was thermally treated and applied as a catalyst in the thermochemical conversion of spent coffee grounds (SCG). CoCSM enhanced H2-rich pyro-gas production by >3-fold compared to pyrolysis without CoCSM, while concurrently decreasing the yield of pyrogenic oil. This research demonstrates a practical strategy integrating resource upcycling, water treatment, and energy production processes in the management of BFS, contributing to a more sustainable circular economy for industrial waste.