Calcium Oxide Surface Research Articles

Synthesis of graphene mesosponge using CaO nanoparticles formed from CaCO3

While graphene mesosponge (GMS) is a new type of mesoporous material with the potential for a variety of applications, its synthesis process requires costly templates such as Al2O3 and MgO nanoparticles. In this study, we present a new synthesis method for GMS, which achieves a high specific surface area of 1720 m2 g1 by employing calcium oxide (CaO) nanoparticles as templates. The CaO nanoparticles with an approximate diameter of 86 nm are formed through the thermal decomposition of calcium carbonate nanoparticles. However, the calcium carbonate nanoparticles contain a small amount of Mg (2 wt %), and the thermal decomposition process also yields impurities, including Mg. When the CaO nanoparticles, including the Mg-based impurities, are subjected to chemical vapor deposition, the CaO surface can be coated with a thin carbon layer, primarily consisting of single-layer graphene through the specific catalysis of the CaO surface in facilitating the CH4-to-C conversion reactions. However, at the same time, the presence of Mg-based impurities leads to the formation of low-crystalline carbons, which have a detrimental effect on the subsequent high-temperature annealing at 1800 °C, following the template removal process, resulting in an excessive number of edge sits in the GMS. We have found that the harmful low-crystalline carbons can be eliminated through heat treatment in air at 350 °C. By adopting such a removal process, high-quality GMS with a minimal number of edge sites can be produced.

Unveiling the dynamic thermal separation process of CO2 on the surface of calcium oxide: An ab-initio molecular dynamics study with experimental verification

Heating to release CO2 captured by Calcium oxide is one of the crucial steps in CO2 capture technology. However, the molecular mechanism underlying CO2 thermal desorption and the impact of CaO hydration on CO2 desorption remain unclear. Based on ab initio molecular dynamics (AIMD), a comprehensive analysis of the desorption and regeneration mechanism of carbonized CaO surfaces was conducted. Temperature is the primary factor responsible for CO2 thermal desorption on CaO surfaces. Simulations of CO2 thermal-dynamic desorption indicate that the desorption temperature range of CO2 from a dry CaO surface was between 400 and 500 °C. The explicit solvent model was utilised to simulate the desorption of CO2 under hydration condition. In the temperature range of 25–800 °C, the desorption behaviour of CO2 is substantially inhibited in the presence of water layers and Ca(OH)2. Consistent with the AIMD results, the thermal desorption experiment following CO2 adsorption confirmed that the desorption temperature of CO2 increases considerably when the adsorbed sample hydrates. Consequently, the desorption process of CO2 on CaO surface was comprehensively elucidated by a combination of theoretical study and experimental validation, thereby guiding the development and regeneration of CaO-based adsorbents.

Investigation of adsorption performance of calcium oxide particles upon various treatments.

This study describes the improvements of adsorption capacities for raw calcium oxide (CaO) particles subjected to ultrasonication, activation with nitric acid and thermal treatments. The influence of acids and bases on CaO particle surface was assessed with respect to several variables including treatment methods, adsorption contact times, particle size and specific surface area characteristics, concentration and temperature along with various thermodynamic parameters. Structural analyses and physical characteristics of CaO particles were evaluated using FT-IR and SEM methods. SEM micrographs of samples revealed uniform distributions of CaO particles of average diameter 0.5-2.0µm. The CaO surfaces showed CH3COOH as having the greatest amounts of adsorbate and modeling of the experimental adsorption isotherm data agreed well with the Freundlich adsorption isotherm. Enhancements in adsorption performance of untreated CaO particles were noted with the ultrasonication, activation with HNO3 and thermal treatment processes. The Langmuir-type adsorption demonstrated that single layer adsorption capacities of adsorbate CH3COOH at 25oC on sonicated CaO (386.6mg/g), with nitric acid and thermal activation (354.9 and 320.8mg/g, respectively) were greater than that of the unsonicated CaO (296.3mg/g) particles. Adsorption spontaneities of the processes were confirmed by the decreases in adsorption free energy values, ΔGads0, changing from -16.1 to -17.1kJmol-1 with temperature range 283-338K.

Experimental and mechanistic study on the enrichment of heavy metals by modified calcium oxide during MSW pyrolysis

ABSTRACT Experimental and density functional theory (DFT) calculations show that NaCl modified can promote the adsorption of heavy metals Cr, Cd, and Pb by CaO in the municipal solid waste (MSW) pyrolysis. CrCl3 (g), CdCl2 (g) and PbCl2 (g) are the main form of Cr, Cd and Pb in MSW pyrolysis gas. The DFT calculations show that the adsorption energy of NaCl modified CaO (NaCl/CaO) increased from 285.37 kJ/mol, 130.58 kJ/mol and 145.72 kJ/mol to 373.80 kJ/mol, 216.03 kJ/mol and 214.67 kJ/mol for Cr, Cd and Pb compared with CaO. Similarly, the experimental average adsorption rates increased from 43.32%, 40.13% and 25.54% to 56.42%, 46.44% and 46.22%. The bondings between CaO and CrCl3, CdCl2, PbCl2 molecules are the outermost 2p orbitals of O in CaO hybridizes with the 3d and 3p orbitals of Cr, the 5s and 4d orbitals of Cd, and the 6p and 6s orbitals of Pb. After the adsorption of NaCl, the total charge change on the CaO surface changed from 0.12e to 0.01e, and the number of electrons obtained by CrCl3, CdCl2 and PbCl2 molecules from the adsorbent increased from 0.51, 0.26 and 0.22 e to 0.94, 0.53 and 0.34 e. NaCl promoting the electron-losing ability of calcium oxide surface. Meanwhile the Cl atom of NaCl form new chemical bonds with heavy metal atoms, increasing adsorption sites of heavy metal molecules with calcium oxide. This study contributes to the adsorption of heavy metals during MSW pyrolysis by CaO and NaCl/CaO.

Carbon Nanofibers Grown in CaO for Self-Sensing in Mortar.

Intelligent cementitious materials integrated with carbon nanofibers (CNFs) have the potential to be used as sensors in structural health monitoring (SHM). The difficulty in dispersing CNFs in cement-based matrices, however, limits the sensitivity to deformation (gauge factor) and strength. Here, we synthesise CNF by chemical vapour deposition on the surface of calcium oxide (CaO) and, for the first time, investigate this amphiphilic carbon nanomaterial for self-sensing in mortar. SEM, TEM, TGA, Raman and VSM were used to characterise the produced CNF@CaO. In addition, the electrical resistivity of the mortar, containing different concentrations of CNF with and without CaO, was measured using the four-point probe method. Furthermore, the piezoresistive response of the composite was quantified by means of compressive loading. The synthesised CNF was 5–10 μm long with an average diameter of ~160 nm, containing magnetic nanoparticles inside. Thermal decomposition of the CNF@CaO compound indicated that 26% of the material was composed of CNF; after CaO removal, 84% of the material was composed of CNF. The electrical resistivity of the material drops sharply at concentrations of 2% by weight of CNF and this drop is even more pronounced for samples with 1.2% by weight of washed CaO. This indicates a better dispersion of the material when the CaO is removed. The sensitivity to deformation of the sample with 1.2% by weight of CNF@CaO was quantified as a gauge factor (GF) of 1552, while all other samples showed a GF below 100. Its FCR amplitude can vary inversely up to 8% by means of cyclic compressive loading. The method proposed in this study provides versatility for the fabrication of carbon nanofibers on a tailored substrate to promote self-sensing in cementitious materials.

Influence of Vacancy Defects of the Calcium Oxide Surface on the Nonequilibrium Phase Transition of Alkali Metal Salts.

Molten alkali metal salt effectively promotes the performance of calcium looping (CaL). Deep insight into the nonequilibrium phase-transition characteristic of alkali metal salt is better for the control of the temperature in CaL, which not only ensures the complete melting of metal salt but also prevents the reaction from inhibiting caused by higher temperatures. In this work, therefore, the molecular dynamics simulation method is used to explore the nonequilibrium phase-transition characteristic of Na2SO4. The results show that the equilibrium melting temperature of nanosodium sulfate on the calcium oxide surface is 810 K, which is lower than the macroscopic melting temperature. Meanwhile, the high heating rates led to the atoms in Na2SO4 unable to break through the thermal stability limit, resulting in overheating of the crystal. Both the surface premelting and overheating melting temperature of the crystal are increased. When the heating rates are 0.25, 0.5, and 1.0 K/ps, the overheating melting temperatures are 845, 885, and 930 K, respectively. More than that, the surface defects enhance the interaction between CaO and Na2SO4 because of the surface being charged. The increases in the interaction not only effectively break the stability of the crystal lattice of Na2SO4 on the defective surfaces but also promote the energy transport inside Na2SO4. Therefore, as the defect concentration increases from 0 to 3% and 5%, the overheating melting temperature of Na2SO4 gradually decreases from 845 to 836 and 815 K.

The influence of the local environment on the electron accepting ability of the cation: induced Lewis acidity

The effect of adsorption of acid gases CO2, SO2 and SO3 on the electron accepting ability of cations on the surface of calcium oxide was studied by low-temperature IR spectroscopy of adsorbed CO. It is shown that the formation of carbonate, sulfite and sulfate anions in the surface layer leads to the appearance of Lewis acid sites, the strength of which, estimated by the shift in the vibration frequency of CO molecules associated with them, increases in the appropriate order, approaching that for calcium-containing zeolites. The results of the calculation of cluster models by the DFT method confirm the observed trends in the variation of the vibrational frequency and the absorption coefficient of CO molecules bound through both the carbon and oxygen atoms, and also demonstrate the dependence of the ability of a cation for CO linkage isomerism on its local environment. Keywords: surface, adsorption, acidity, IR spectroscopy, quantum chemical calculation, electron accepting ability.

Влияние локального окружения на электроноакцепторную способность катиона: индуцированная льюисовская кислотность

The effect of adsorption of acid gases CO2, SO2 and SO3 on the electron-accepting ability of cations at the surface of calcium oxide was studied by low-temperature IR spectroscopy of adsorbed CO. It is shown that the formation of carbonate, sulfite and sulfate anions in the surface layer leads to the appearance of Lewis acid sites, the strength of which, estimated by the shift in the vibrational frequency of CO molecules bound to them, increases in the corresponding order, approaching that for calcium- containing zeolites. The results of calculation of cluster models by the DFT method confirm the observed trends in the variation of vibrational frequency and the absorption coefficient of CO molecules bound both via carbon atom or via oxygen, and also demonstrate the dependence of the ability of a cation to linkage isomerism on its local environment.

Influence of Vacancy Defect of Calcium Oxide Surface on the Wettability of Molten Alkali Metal Salt in Calcium Looping Process.

The influence of the vacancy defect of the CaO surface on the wettability of molten alkali metal salt was studied by molecular dynamics simulations. The results indicated that in the temperature range of 800-1100 K, the molten Na2SO4 on both VDcalcium and VDoxygen defect surfaces presented a poor wettability compared to that on the complete surface. Measurement of the density profile and the contact angle of the molten Na2SO4 showed that the higher the temperature and defect concentration, the worse the wettability. The micromechanism was revealed by calculating the polarization intensity that the vacancy defect surface led to the formation of the induced dipole moment in the molten Na2SO4. Induced polarization caused by defect surfaces reduces the wettability of Na2SO4. More importantly, as the temperature and defect concentration increase, various defect surfaces form loose and local weak liquidity structures. These structures are beneficial for the diffusion of carbon dioxide into the solid, but the reduction in the spreading area caused by poor wettability causes the efficiency of the CaL to decline. The vibration difference between Na2SO4 and CaO increases with the increased temperature and defect concentration. This means that the thermal energy transportability at the interface is suppressed by poor wettability.

Eggshell recycling for fabrication of Pd@CaO, characterization and high-performance solar photocatalytic activity.

Recycling of waste materials into useful products is a promising strategy for environmental protection. Eggshell is one of the globally produced huge wastes. In this work, calcium oxide (CaO) nanoparticles were recycled via calcination of chicken eggshells at 1100 °C for 2 h. A novel nanocomposite, made of loading palladium nanoparticles on calcium oxide surface (Pd@CaO), is successfully fabricated through solid-solid interaction. The materials were characterized using different physicochemical techniques: Fourier-transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-Vis), photoluminescence (PL) analysis, ultra-high resolution field emission scanning electron microscope (FE-SEM), transmittance electron microscope (TEM), and X-ray diffraction (XRD). The study sheds light on the ability of the materials to be used for detoxification of crystal violet dye as pollutant model under solar irradiation. The effects of operational conditions, such as catalyst mass, initial dye concentration, pH, and illumination time, have been tested. The optimum conditions for crystal violet photocatalytic degradation in the presence of Pd@CaO were mild conditions. Control experiments studied the effect of sunlight in the absence of the catalyst, and the effect of the catalyst in the absence of sunlight does not provide the significant removal exhibited in the presence of catalyst under solar irradiation.

Influence of rheological behavior of molten sodium sulfate on adherent heterogeneous surface on performance of high-temperature thermochemical energy storage

Molecular dynamics simulations were carried out to investigate the influence of the rheological behavior of molten sodium sulfate on the adherent heterogeneous surface on the performance of high-temperature thermochemical energy storage. It was found that the molten salts occurred to migrate on a nanoscale adherent heterogeneous surface due to the energy gradient of the heterogeneous surface. Molten salts underwent three spreading stages during the entire migration process. Poor wettability of the molten salt on the CaO surface came out in the climb spreading stage, and good wettability came out in the fall spreading stage. More importantly, the motion of molten salt caused an additional enhancement effect of potential energy at the interface compared to the pure CaO surface. The enhancement mechanism was the kinetic energy caused a more violent collision of ions between the molten salt and the solid surface, which lead to a local overheat at the interface to promote the ionization of the surface. The structural analysis illustrated that the calcium oxide ions of the heterogeneous surface appear stronger fluidization compared with the calcium oxide ions of the pure calcium oxide surface. The enhancement effect worked on the CaO based adsorbent rather than the inert solid supports.

Carbon dioxide gas sensing, capture, and storage potential of calcium oxide surface and single walled carbon nanotube: insights from ab initio simulation

Single walled carbon nanotube (SWCNT) and alkaline metal oxide have been identified as potential materials for management of CO2 emission. Yet the underlying operating mechanism is still not well understood, while an in-depth understanding would possibly lead to development of superior CO2 monitoring, capture, and storage devices. Here we present ab initio density functional theory calculations to provide a comprehensive description of CO2 gas interaction with SWCNT and CaO surface. In particular, our results revealed that CO2 is chemisorbed on CaO surface with negligible effect on electronic properties of the absorbent, while CO2 interaction with SWCNT can be categorized as physisorption interaction a process that can be easily reversed using thermal treating of the tube at 150 °C. Thus CaO is found to be ideal for long term storage of CO2 while SWCNT reported superior performance in CO2 sensing and capture. This work may guide the development of better devices based on CaO and SWCNT for CO2 sensing, capture, and storage.

Molecular simulation study of strontium doping on the adsorption of methanol on CaO(100) surface

The influence of strontium doping on the adsorption of methanol on calcium oxide surface was investigated by molecular simulation. The model for methanol adsorption onto the CaO(100) and CaO(100)-Sr surfaces was constructed; the adsorption energy and activation energy were then calculated and the density of states was portrayed for the methanol bond on the calcium oxide surface. The methanol activation degrees on the calcium oxide surface before and after strontium doping were then compared by analyzing the Mulliken atomic charge population and deformation density. The results illustrate that the adsorption of methanol onto the calcium oxide surface can be significantly enhanced through the strontium doping; moreover, the enhancement increases with an increase in the doping content of strontium. After doping calcium oxide with strontium, the energy required for methanol activation is reduced; as a result, the strontium doping can also enhance the activation degree of methanol, as methanol is activated upon adsorption onto the calcium oxide surface.

Optimized conversion of waste cooking oil to biodiesel using modified calcium oxide as catalyst via a microwave heating system

Homogeneous catalysts have been commonly utilized during the production of biodiesel in industrial applications. However, a homogeneous catalysis system has several disadvantages, including difficulties related to the separation of the reactant and products and the pollution of wastewater after the chemical washing process. However, transesterification through heterogenous catalysis avoids the aforementioned drawbacks in the homogeneous catalysis process. In this study, a novel modified calcium oxide (CaO) is proposed as an alkaline solid catalyst. The surface of commercial CaO is chemically modified using bromooctane through a microwave approach to improve its catalytic ability. The physiochemical characteristics of the modified CaO are analyzed using a Fourier transform infrared (FTIR) spectrometer, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The results show that microwave heating significantly reduces the synthesis time for the modified CaO, which was found to be one twelfth that of traditional water-bath heating. In addition, calcium hydroxide (Ca(OH)2) was rarely generated during the modification procedure, and microwave-modified CaO was found to have better thermos-stability. The optimal reaction conditions are as follows: a 4 wt% catalyst, a methanol-to-oil molar ratio of 8:1, a reaction temperature of 65 °C, and a reaction time of 75 min. Under these conditions, the biodiesel conversion reaches 98.2%, while the reaction time (75 min) is only 53.6% of the traditional water bath heating transesterification reaction (140 min).

Wettability of molten sodium sulfate salt on nanoscale calcium oxide surface in high-temperature thermochemical energy storage

Molecular dynamics simulations were carried out to originally investigate wettability of molten sodium sulfate salt on nanoscale calcium oxide surfaces at high temperature and micro-mechanisms on the molten salt promoting the performance of thermochemical energy storage. It was found that in terms of the molten sodium sulfate salt, the nanoscale calcium oxide surface was hydrophilic, and became more and more hydrophilic with increasing temperatures. More importantly, average diffusion coefficients and radial distribution functions of various ions illustrated that the molten sodium sulfate activated the calcium ions and the oxygen ions on the calcium oxide surface, resulting in weak fluidization of the surface at a temperature below the melting temperature. This promoted potential energy of the atom interaction at the contact interface. Additionally, it was observed that the sodium sulfate transited from partial coverage to complete coverage on the spherical nanoscale calcium oxide surface. Higher temperatures induced better coverage performances due to the decreasing surface tension of the molten salt. Therefore, the molten salt formed a screen on the surface to effectively prevent the calcium oxide particles from sintering. This study provides a theoretical foundation to further utilize the molten salt to promote the performance of the thermochemical energy storage.

Thermal Analysis and SEM Microscopy Applied to Studying the Efficiency of Ionic Liquid Immobilization on Solid Supports.

Ionic liquids (ILs) are widely used in elastomer composites, primarily as vulcanization activators or accelerators, crosslinkers, conductive additives, or dispersing agents of fillers. The aim of this work was to study the efficiency of ionic liquid immobilization on filler surfaces using different techniques of thermal analysis and scanning electron microscopy (SEM). Ionic liquid, such as 1-decyl 3-methylimidazolium bromide (DmiBr) was grafted on the surface of silica, calcium oxide, and carbon black to improve the dispersion degree of their particles in the elastomeric matrix. Thermal analysis and SEM microscopy revealed a key role in determining the efficiency of the filler modification with ILs dissolved in acetone. Identifying the weight loss associated with thermal decomposition of DmiBr in modified fillers, allowed the calculation of the efficiency of their modification and compare the surface reactivity of studied fillers with DmiBr. Silica and carbon black exhibited high and comparable ability for interaction with ionic liquid. SEM images showed that particles of DmiBr-modified fillers were quite homogeneously dispersed in the elastomer matrix and exhibited good adhesion to the elastomer.

Understanding HCN heterogeneous adsorption on CaO(1 0 0) surface for the pyrolysis of sludge: A first-principles study and GCMC simulation

Pyrolysis and combustion of the sludge can eliminate the secondary pollution, and achieve the recovery of resource. However, it will produce large amount of nitrogen oxide. HCN is one of the major NOx precursors, and calcium oxide, the dehydrating agent and desulfurizer, have positive effect for HCN emission. Thus, the HCN on the perfect and defect CaO(1 0 0) surface heterogeneous adsorption is investigated through a first-principles calculation and Grand Canonical Monte Carlo simulation. Compared with single molecular model in our previous work, the CaO slab model with periodical boundary conditions has a better effect on describing the solid phase surface. The adsorption of HCN molecule on perfect CaO(1 0 0) surface proves to be chemisorption, and the most stable configuration is H-downward at O top site with the binding energy of −1.09 eV. Furthermore, HCN molecule adsorbs more tightly on to the O vacancy and Ca vacancy surface, and the binding energy increases to −2.76 eV and −2.79 eV, respectively. With the electron population and PDOS analysis, it reveals that the more electrons transfer from defect calcium oxide surface to HCN molecule. In the GCMC results, it is obvious that multiple HCN molecules easily adsorb on Ca vacancy surface. Meanwhile, HCN molecules are inclined to adsorb on the hollow site of the defect CaO(1 0 0) surface. From the isothermal adsorption curves, the adsorption ability decreases with the temperature increasing, and the fitted equation is coincide with the Freundlich isothermal adsorption equation. The variation of adsorption equilibrium constant K in the fitted equation indicates that the Ca vacancy surface is the most activity surface and the temperature increase is negative for the HCN adsorption, conforming to the adsorption rule calculated in the first-principle study. Thus, the point vacancy surface caused by uneven temperature can increase the adsorption ability of HCN on CaO(1 0 0) surface.

Combined experimental and theoretical studies on adsorption mechanisms of gaseous mercury(II) by calcium-based sorbents: The effect of unsaturated oxygen sites

Accurate mercury speciation measurements are critical for developing methods for mercury removal from flue gas, but the lack of reliable adsorbents has made Hg2+ selective retention challenging. Calcium oxide (CaO) loaded on porous support is promising for HgCl2 selective adsorption because of its porosity and alkaline nature. The main hypothesis investigated in this paper is if the capacity of CaO sorbent for HgCl2 selective adsorption is attributed to its basic sites, then this will be drastically impacted by the calcium precursors. We synthesized a suite of CaO/SiO2 sorbents from different precursors, including hydrated calcium oxide (CaO-HS), calcium nitrate tetrahydrate (CaO-NS), and calcium acetate monohydrate (CaO-AcS), to investigate their performance on HgCl2 selective adsorption in a fixed-bed reactor. Compared with CaO-HS and CaO-NS, CaO-AcS was demonstrated to have the strongest affinity for HgCl2 and almost complete breakthrough for Hg0. Advanced porosity and surface basicity of CaO-AcS were confirmed by characterization analysis. CaO (001) and CaO (011) facet as well as surface defects that have different unsaturated O sites were observed using the high resolution transmission electron microscope (HRTEM). Combined theoretical and experimental methods were used to study the interaction mechanisms between HgCl2 and basic sites on CaO-AcS surfaces. Density functional theory (DFT) calculations indicated all CaO surfaces weakly interact with Hg0, while four robust bonding states of HgCl2 were predicted on different basic sites with the intensity in increasing order: Monodentate < Tridendate < Bidentate < Bridging. This was consistent with HgCl2-TPD experiments that demonstrated that the four HgCl2 adsorption configurations on CaO-AcS were attributed to different unsaturated O sites. The findings in this work highlight the application potential of CaO-AcS for gaseous Hg2+ sampling and measurement from coal-fired flue gas.

Manufacture of a hydrophobic CaO/polylactic acid composite

ABSTRACTIn this study, the surface of calcium oxide (CaO) was modified with n-octadecyltrichlorosilane [CH3(CH2)16CH2SiCl3] to obtain modified calcium oxide (CaO-M). CaO and CaO-M were melt-blended with polylactic acid (PLA) to prepare PLA/CaO and PLA/CaO-M, respectively. Moisture absorption measurement showed that the surface of modified CaO was changed from hydrophilic to hydrophobic. CaO and PLA had a tendency to agglomerate after blending, whereas the blend of CaO-M and PLA showed no signs of agglomeration, and the distribution of CaO-M in PLA was homogeneous. In addition, CaO-M had a heterogeneous nucleation effect on PLA, which effectively inhibited cold crystallization and promoted crystallization of PLA. In conclusion, CaO-M can be used as a nucleating agent of PLA.

Theoretical evaluation on selective adsorption characteristics of alkali metal-based sorbents for gaseous oxidized mercury

Alkali metal-based sorbents are potential for oxidized mercury (Hg2+) selective adsorption but show hardly effect to elemental mercury (Hg0) in flue gas. Density functional theory (DFT) was employed to investigate the Hg0 and HgCl2 adsorption mechanism over alkali metal-based sorbents, including calcium oxide (CaO), magnesium oxide (MgO), potassium chloride (KCl) and sodium chloride (NaCl). Hg0 was found to weakly interact with CaO (001), MgO (001), KCl (001) and NaCl (001) surfaces while HgCl2 was effectively adsorbed on top-O and top-Cl sites. Charge transfer and bond population were calculated to discuss the covalency and ionicity of HgCl2 bonding with the adsorption sites. The partial density of states (PDOS) analysis manifests that HgCl2 strongly interacts with surface sites through the orbital hybridizations between Hg and top O or Cl. Frontier molecular orbital (FMO) energy and Mulliken electronegativity are introduced as the quantitative criteria to evaluate the reactivity of mercury species and alkali metal-based sorbents. HgCl2 is identified as a Lewis acid and more reactive than Hg0. The Lewis basicity of the four alkali metal-based sorbents is predicted as the increasing order: NaCl < MgO < KCl < CaO, in consistence with the trend of HgCl2 adsorption energies.