Experimental and Kinetic Study of Mercury Adsorption on Various Activated Carbons in a Fixed-Bed Adsorber

Abstract

This study investigated experimentally and theoretically the characteristics of mercury sorption by activated carbons. Experiments were carried out in a fixed-bed mercury sorption facility composed of a mercury permeation tube embedded in an isothermal water bath, a fix-bed adsorber enclosed in a furnace, and an on-line GC for mercury measurements. The proposed sorption model involved the coupling of a kinetic model based on the mechanisms of surface equilibrium and external mass transfer, and a material balance model based on the tank-in-series approach. Three different equilibrium expressions were used in the model, i.e., the Henry's Law, the Langmuir isotherm, and the Freundlich isotherm. In additional to kinetic simulations using the developed model, an equilibrium model was also used to simulate the thermodynamically preferred mercury species under the experimental conditions. The experimental results have indicated that the factors affecting the adsorption efficiency include the type of activated carbon, the adsorption temperature, the inlet mercury concentration, and the gas flow rate. The developed kinetic model has been found to describe well both the current experimental results and those reported in the literature.

A Detailed Investigation of Adsorption Isotherms, Enthalpies, and Kinetics of Mercury Adsorption on Nonimpregnated Activated Carbon

“…Well-established large-scale processes (absorptive gas scrubbing, flue gas adsorption) are rather suited for the separation of mercury from large, continuous volume flows with uniform loading. For the separation of mercury from fluctuating waste gas streams, fixed-bed adsorption is a proper method, which has been investigated in many scientific studies. − For economic and technical reasons, particularly suitable adsorbents for Hg 0 adsorption are nonimpregnated − ,− ,, and impregnated activated carbons, ,,,− the development and investigation of which make up the largest part of the literature. − ,,,− , Most references focus on specific technical applications and compare breakthrough curves on different adsorbents in a small temperature and concentration range. Therefore, despite the large number of publications, there is no deep scientific understanding of adsorption mechanisms.…”

“…The group of Ho et al published experimental data on the adsorption capacity of raw activated carbon at 25 °C and mercury concentrations of 25.3 μg m –3 in a fixed bed adsorber. The results were used along with data from Korpiel and Vidic and Krishnan et al , to fit isothermal parameters. − …”

“…Ho et al, − Meserole et al, and Karatza et al ,, performed dynamic simulations of adsorption processes on activated carbons using a kinetic approach and incremental solving of mass balances. Ho et al and Meserole et al.…”

Adsorption of mercury from single and multicomponent metal systems on activated carbon developed from cherry stones

“…Among the activating agents used most frequently are H 3 PO 4 , ZnCl 2 , KOH, etc. A wealth of literature is devoted to studies of the adsorption of mercury from a single solute solution by AC (Valenzuela Calahorro et al 1990;Gómez-Serrano et al 1998;Pulido et al 1998;Hsi et al 2002;Yardim et al 2003;Li et al 2003;Ho et al 2004;Nabais et al 2006; and so on). However, the use of ACs prepared by chemical activation with various activating agents has been much less frequent (Zhang et al 2005).…”