Kinetics study on the capture of elemental mercury in flue gas by KI‐impregnated clays

Abstract

To understand the capture of elemental mercury (Hg 0 ) on potassium iodide-impregnated clays, a variety of kinetic models including pseudo-firstorder, pseudo-second-order, Elovich, and intraparticle diffusion models were used to analyze the experimental data and discuss the mechanism. A strong correlation was observed between the pseudo-second-order kinetic model and the experimental data for a range of parameters (KI loading, adsorption temperatures, and O 2 concentrations). This suggests that chemisorption may be a rate-limiting mechanism during the adsorption process on KI clays. Further, the results of the pseudo-first-order model and the intraparticle diffusion model both indicate that mass transfer limitations should not be ignored during the initial stage of adsorption. Thermodynamic investigation shows that the adsorption reaction of Hg 0 on the KI clays is inherently spontaneous and endothermic, corresponding to a process involving both physisorption and chemisorption, and the chemisorption is the dominant adsorption.

Mercury adsorption in the gas phase by regenerable Au-loaded activated carbon foams: a kinetic and reaction mechanism study

“…In the adsorption experiments, the concentration of Hg 0 at the exit of the adsorption reactor was recorded at 3 minute intervals, and the cumulative concentration of Hg 0 in the sorbent (q t , mg g À1 ) at an adsorption time t (min) was calculated with the following equation: 42,43…”

“…Adsorption on the surface of a porous material is considered to take place via three steps: 29,43,44 (i) diffusion through the fluid surrounding the solid particles to the external surface of the adsorbent, controlled by external mass transfer, (ii) diffusion through the fluid within the pores of the sorbent particles to the sorption sites, in a pore diffusion mechanism, and (iii) adsorption at the active sites on the surface of the sorbent.…”

Experiment and Kinetic Study of Elemental Mercury Adsorption over a Novel Chlorinated Sorbent Derived from Coal and Waste Polyvinyl Chloride

“…The intraparticle diffusion could be described by the Web–Morris model when internal diffusion dominates the adsorption process . The Web–Morris model could be presented as follows: where q t (μg/g) is the mass of Hg 0 captured on sorbent at time t (min), k id is the rate constant of the intraparticle diffusion model, and C is a constant that depends on the effect of the boundary layer on adsorption . The values of k id and C were calculated from the slope and the intercept of the straight line plots of q t versus t 1/2 , respectively.…”

“…where q t (μg/g) is the mass of Hg 0 captured on sorbent at time t (min), k id is the rate constant of the intraparticle diffusion model, and C is a constant that depends on the effect of the boundary layer on adsorption. 44 The values of k id and C were calculated from the slope and the intercept of the straight line plots of q t versus t 1/2 , respectively. The experimental data of T7Char, T7C9P1, T7C3P1, T8C9P1, and T8C3P1 were fitted with the Web−Morris model, pseudo-first-order model, and pseudo-second-order model in Figure 7.…”

Noble metal-based sorbents: A way to avoid new waste after mercury removal

“…In the adsorption experiments, the concentration of mercury at the exit of the adsorption chamber was recorded at 2 minute intervals. The concentration of mercury accumulated in the sorbent (q t ) at adsorption time t was calculated by means of the following equation [60]:…”