Regenerable Ag/graphene sorbent for elemental mercury capture at ambient temperature

• Ag/graphene composite was synthesized by a facile method.
• The Hg0 capacity of Ag/graphene was 4.2 mg/g at ambient temperature (25 °C).
• The acid gases had no effect on Hg0 removal efficiency.
• Mercury could be collected by thermal separation after adsorption.

Elemental mercury (Hg0) is a widespread concern due to its high toxic and long residence time in the environment. Ag/graphene composite was synthesized as a high efficient and recyclable sorbent for Hg0 removal. Ag particles were doped on the surface of graphene by a facile in situ chemical synthesis method. FTIR, XRD, and TEM results showed that Ag nanoparticles successfully grew on the surface of graphene layers. The performance of Ag/graphene as a sorbent was tested under a fix-bed reactor and the results showed that it could completely capture Hg0 at ambient temperature (25 °C). The Hg0 capacity was as high as 4.2 mg/g. The Hg0 removal efficiency decreased from 94% to 60% when the temperature increased from 25 to 100 °C, respectively. SO2 and NO had nearly no effect on Hg0 removal, but the efficiency dropped by about 4% when O2 existed. Hg-TPD results showed that mercury can be rapidly and efficiently released from the composite by thermal separation. The adsorption capacity of Hg0 had no degradation after six cycles. The high Hg0 capacity and recyclability make the Ag/graphene a candidate for the removal at ambient temperature.

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