Comprehensive Methodology for the Investigation of Mercury Adsorption on Activated Carbons

Abstract

In mercury adsorption on activated carbons both physisorptive and chemisorptive mechanisms play a role. The systematic investigation of Hg0 chemisorption is difficult because equilibrium capacities cannot be determined due to slow adsorption mechanisms. Therefore, the present publication suggests a three‐step approach: 1) Breakthrough curves are used to assess the dynamics of Hg0 adsorption. 2) The contributions of physisorption and chemisorption can be distinguished by coupled adsorption and desorption experiments. 3) Temperature programmed desorption (TPD) experiments are performed to get information about specific chemisorptive binding sites on the surface. This approach was tested on four characteristic examples of impregnated and non‐impregnated activated carbons.

Impact of H2O on the Adsorption of Hg0 on Activated Carbon

“…In previous publications, 31,32 we have extensively reviewed the literature on physisorptive and chemisorptive singlecomponent adsorption of Hg 0 . Mercury can react chemisorptively with surface groups of activated carbons in the presence of other components such as water, oxygen, sulfur, or chlorine.…”

Influence of Oxygen on Hg0 Adsorption on Non-Impregnated Activated Carbons

“…In an earlier publication, we have shown that these activated carbons have predominantly physisorptive sites for the adsorption of Hg 0 . 28 …”

“… Flow diagram of fixed bed test unit; a = water bath; b = evaporator; c = cooler; d = tempered reactors 1 and 2; MFC = mass flow controller; AAS = atomic absorption spectrometer according to refs ( 28 ) and ( 29 ). …”

“…The lower limit of the activation energy of desorption E A is equal to the adsorption enthalpy of physisorption of Hg 0 , 28 assuming that chemisorption must be stronger than physisorption. The upper limit corresponds to the averaged reaction enthalpy of several chemisorptive adsorption processes, which has been extended by a tolerance range.…”

“…In previous publications, we have already reported on the current status of literature on adsorption of Hg 0 . 28 , 29 To sum up, thermodynamic and kinetic investigations of the adsorption of Hg 0 are very fragmentary in the literature because of difficult experimental conditions. Many times, only single aspects of physisorption and chemisorption of Hg 0 were considered, which often led to antithetical interpretations of adsorption mechanisms.…”