Turning fulvic acid into silver loaded carbon nanosheet as a regenerable sorbent for complete Hg-0 removal in H2S containing natural gas

摘要

The migration and agglomeration of Ag nanoparticles during high temperature regeneration processes were generally considered the key contributor for the decreasing of Hg-0 removal performance over Ag-based sorbents. In this work, a complexation pathway was developed for controllable synthesis of Ag loaded carbon nanosheet (Ag/Fvs) using fulvic acid as template and carbon source. The elemental Ag nanoparticles were highly dispersed and embedded in the carbon nanosheet with an average diameter of 7.12 nm and formed a special core-shell structure. The synthesized sorbent achieved a complete Hg-0 removal in H2S containing natural gas at ambient temperature. At 1% breakthrough, the Hg-0 capture capacity of Ag/Fvs was as high as 1.36 mg.g(-1), which is much higher than the sample prepared by traditional impregnation method (I-Ag/Fvs, 0.98 mg.g(-1)) and other existing commercial sorbents. More importantly, the spent Ag/Fvs could be easily regenerated by thermal treating process, its Hg-0 capture capacity only slightly decreased by 5.8% after 4 cycles. We considered the carbon layer prevented Ag nanoparticles from poisoning by H2S, and more active sulfur sites for Hg-0 capture could be formed on porous carbon nanosheets by chemical adsorption of H2S, which is beneficial for the strong tolerance to H2S. The excellent regeneration performance of Ag/Fvs mainly attributed to the nanoconfinement of carbon layer, which is conducive to prevent the agglomeration of Ag nanoparticles during high temperature regeneration processes. This work represented a practical and efficient pathway to utilize the cheap fulvic acid for applications of Hg-0 removal in H2S containing natural gas.