Evaluation of two sulfur impregnation methods on activated carbon and bentonite for the production of elemental mercury sorbents

Adsorption of vapor-phase elemental mercury by virgin and modified bentonit e and activated carbon was evaluated at 140 degreesC, empty-bed contact tim e in a fixed-bed adsorber of 0.011 s, and influent mercury concentration of 55 mug/m(3). Acid-treated bentonite had somewhat higher capacity than the virgin bentonite due to higher surface area and perhaps some active surface sites created by acid treatment. Sulfur impregnation through hydrogen sulf ide oxidation enhanced mercury removal efficiency over the nonimpregnated b entonite. However, mercury removal efficiency was promoted to a limited ext ent, due to predominance of nonreactive sulfur allotropes and significant r eduction in surface area. Sulfur impregnation of bituminous coal-based carb on (BPL) was performed using thermal deposition of elemental sulfur (BPLS) at high temperature (600 degreesC) or hydrogen sulfide oxidation (BPLHS) at low temperature (150 degreesC). Both BPLS and BPLHS performed significantl y better than virgin BPL carbon. Although sulfur content of BPLHS increased with an increase in impregnation time, impregnation for 0.25 h produced th e most effective sorbent (BPLHS-0.25). Although BPLS and BPLHS-0.25 had sim ilar sulfur content, BPLS performed significantly better due to greater sur face area and predominance of more reactive sulfur allotropes. However, app lication of BPLHS sorbents for mercury control may be justified by the poll ution prevention efforts for a number of industrial processes that generate H2S waste streams.