Adsorption Performance of Cu-Fe Bimetallic-Modified Coconut Shell Activated Carbon for Ultra-Low-Concentration SO₂

In this study, Cu-Fe bimetallic-supported adsorbents were prepared using alkali-activated coconut shell activated carbon (AC-OH) as a carrier by impregnation method. To optimize the adsorption effect, the effects of the second metal type, Fe loading amount, Cu/Fe ratio, and operating conditions on the adsorption effect of extremely low-concentration SO₂ (1 ppm) were systematically investigated. The results showed that when the Cu loading was 5% by mass and the Fe loading was 3% by mass, the adsorbent exhibited optimal adsorption performance, with a breakthrough time of up to 36.5 h and a corresponding breakthrough sulfur capacity of 14.424 mg/g. Further exploration of the conditions shows that the coexistence of O₂ and H₂O can significantly promote the adsorption of SO₂, while reducing the space velocity is beneficial for prolonging the breakthrough time. In terms of regeneration stability, after two adsorption-regeneration cycles, the adsorption activity of the adsorbent decreased to 72.7% of the fresh sample, and the deactivation was mainly attributed to the accumulation of sulfate species and the loss or aggregation of active components. By combining XRD, FT-IR, XPS, SEM and other characterization techniques, the structure-activity relationship and deactivation mechanism of the adsorbent were analyzed. This bimetallic-modified activated carbon has shown great potential for deep purification of extremely low concentrations of SO₂.