Synthesis and Adsorption Performance of Ag/γ-Al₂O₃ with High Adsorption Capacities for Dibenzyl Disulfide

The removal of dibenzyl disulfide (DBDS) from transformer oils is vital to the sustainable operation of transformers. Here, Ag/γ-Al₂O₃ samples were prepared by a planetary mixer-assisted impregnation method and characterized. The effect of adsorption time and temperature on the equilibrium adsorption of DBDS onto Ag/γ-Al₂O₃ was discussed. The kinetics and isotherms of DBDS adsorption on the samples were studied. The desorption activation energy of DBDS was also estimated through temperature-programmed desorption (TPD) experiments. Results indicated that the DBDS adsorption capacities on Ag/γ-Al₂O₃ increased quickly within the first 3 h, and the highest DBDS adsorption capacity was 69.5 mg/g, which was 232, 107, and 5.6 times higher than that of active bentonite, γ-Al₂O₃, and active carbon, respectively. The adsorption isotherms were well fitted by the Langmuir model, and the adsorption kinetics followed the pseudo-second-order model. The desorption activation energy of DBDS on Ag/γ-Al₂O₃ was much higher than that on active carbon, indicating a strong interaction between DBDS and Ag/γ-Al₂O₃. Finally, the hard–soft acid–base (HSAB) principle was used to explain the adsorption mechanism, confirming that DBDS as a soft base can be preferentially adsorbed by Ag/γ-Al₂O₃ because Ag⁺ is a soft acid.