Resource Utilization of Spent Activated Coke as an Efficient Material for Simultaneous Removal of COS and H2S

The desulfurization of blast furnace gas (BFG) is highly desired by iron and steel enterprises to realize its resource utilization with no environmental pollution. In this work, spent activated coke (SAC) modified by NaOH was innovatively reused as an efficient material for the removal of carbonyl sulfide (COS) and sulfuretted hydrogen (H2S) from BFG with admirable breakthrough sulfur capacities of 126.58 and 141.62 mg/g, respectively, and 100% removal efficiency of both COS and H2S could be reached with the total sulfur capacity of COS and H2S as high as 116.60 mg/g in the purification of the simulative BFG gas. The removal behaviors manifested that the removal process included catalytic hydrolysis of COS to H2S and subsequent oxidation of H2S to immobilize these sulfur species in the form of S8. The multiple structural characterizations (X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), H2-temperature-programmed reduction (TPR)) further revealed that the surface carbonyl and pyridine/pyrrolic groups together with the loaded hydroxyl ion enhanced the COS hydrolysis and the subsequent oxidation of H2S. The modified SAC possessed much richer pore structures and active groups than either fresh activated coke (FAC) or high specific surface area activated carbon (HAC). At the same time, a recycling scheme suitable for SAC after removing H2S and COS was proposed. The demonstrated excellent simultaneous removal capacity of COS and H2S over the modified SAC will provide a promising technical route for desulfurization of BFG with high efficiency and low cost.