Journal of Hazardous Materials 252–253 (2013) 419–427 Contents lists available at SciVerse ScienceDirect Journal of Hazardous Materials jou rn al hom epage: www.elsevier.com/locate/jhazmat Adsorption kinetic and equilibrium study for removal of mercuric chloride by CuCl 2 -impregnated activated carbon sorbent Xin Li, Zhouyang Liu, Joo-Youp Lee ∗ Chemical Engineering Program, School of Energy, Environmental, Biological, and Medical Engineering, University of Cincinnati, Cincinnati, OH 45221-0012, United States h i g h l i g h t s ◮ Intrinsic adsorption kinetics of HgCl 2 was obtained for raw and CuCl 2 -AC sorbents. ◮ Model includes adsorption kinetics, equilibrium, and internal and external mass transfer. ◮ Adsorption equilibrium confirms physical adsorption of HgCl 2 onto CuCl 2 -AC sorbents. ◮ High CuCl 2 loading can result in high binding energy of HgCl 2 adsorption on carbon. ◮ HgCl 2 desorption rate for CuCl 2 -AC sorbents was found to significantly decrease. a r t i c l e i n f o Article history: Received 17 January 2013 Received in revised form 23 February 2013 Accepted 25 February 2013 Available online 5 March 2013 Keywords: CuCl2-AC sorbent HgCl2 adsorption Adsorption kinetics Sorbent injection Mercury emissions control a b s t r a c t The intrinsic adsorption kinetics of mercuric chloride (HgCl 2 ) was studied for raw, 4% and 10% CuCl 2 - impregnated activated carbon (CuCl 2 -AC) sorbents in a fixed-bed system. An HgCl 2 adsorption kinetic model was developed for the AC sorbents by taking into account the adsorption kinetics, equilibrium, and internal and external mass transfer. The adsorption kinetic constants determined from the comparisons between the simulation and experimental results were 0.2, 0.3, and 0.5 m 3 /(g s) for DARCO-HG, 4%(wt), and 10%(wt) CuCl 2 -AC sorbents, respectively, at 140 ◦ C. CuCl 2 loading was found to slightly increase the adsorption kinetic constant or at least not to decrease it. The HgCl 2 equilibrium adsorption data based on the Langmuir isotherm show that high CuCl 2 loading can result in high binding energy of the HgCl 2 adsorption onto the carbon surface. The adsorption equilibrium constant was found to increase by ∼10 times when CuCl 2 loading varied from 0 to 10%(wt), which led to a decrease in the desorption kinetic constant (k 2 ) by ∼10 times and subsequently the desorption rate by ∼50 times. Intraparticle pore diffusion considered in the model showed good accuracy, allowing for the determination of intrinsic HgCl 2 adsorption kinetics. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Many previous studies have shown that raw activated carbon (AC) cannot physically adsorb elemental mercury (Hg(0)) vapor in a post-combustion temperature window [1,2]. It is supposed that raw AC adsorbs HCl and NO 2 gases from flue gas first and then het- erogeneously oxidizes Hg(0) vapor to form oxidized mercury bound to the carbon surface [2–5]. Among chemically-promoted acti- vated carbon sorbents, halogenated activated carbons have been reported to significantly enhance Hg(0) vapor adsorption [1–3]. These halogenated AC sorbents have demonstrated excellent per- formances in the adsorption of both elemental and oxidized forms ∗ Corresponding author. Tel.: +1 513 556 0018; fax: +1 413 556 0018. E-mail addresses: li2x2@mail.uc.edu (X. Li), liuzy@mail.uc.edu (Z. Liu), joo.lee@uc.edu, jooyoup@gmail.com (J.-Y. Lee). of mercury vapor from the coal combustion flue gases of subbitu- minous and lignite coals with relatively low HCl gas concentrations (e.g., <∼10 ppmv). A fundamental understanding of mercury reaction and adsorp- tion mechanisms and the subsequent determination of kinetic parameters play a critical role ultimately in the prediction of mer- cury removal for sorbent injection. However, it is difficult to find mercury adsorption modeling studies for the prediction of elemen- tal and oxidized mercury vapor removal by chemical and physical sorbents in the ductwork and fabric filter primarily due to a dif- ficulty in finding the equilibrium and kinetic data associated with reaction and adsorption mechanisms between mercury vapor and a sorbent [6,7]. Karatza et al. studied the adsorption kinetics of HgCl 2 onto raw and sodium sulfide (Na 2 S)-impregnated AC in a lab-scale fixed bed without taking into account the external and internal mass transfer from the bulk gas to the solid [8]. The adsorp- tion of HgCl 2 on raw AC was identified as physical adsorption. It 0304-3894/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jhazmat.2013.02.049