Study On The Adsorption Thermodynamics And Kinetics Characteristics And Phase Transition Process Of Solid-gas Interface

Solid-gas interface adsorption is the relative aggregation process of gas molecules on the solid surface.It is a typical surface heat and mass transfer process,and it is also an important research topic in surface science.The research on the adsorption characteristics of the gas-solid interface in the equilibrium state has made fruitful research results,and the field of wetting has also made amazing achievements.However,the current research lacks a systematic study of the characteristics of the interface evolution from adsorption to phase change,and even wetting.The physical mechanism of the influence of the adsorption process at the gas-solid interface on the wetting transition process is still unclear.Therefore,this article takes the gas-solid two-phase interface adsorption,phase transition and wetting transition process as the research object.Based on Zeta isotherm adsorption theory,adsorption entropy theory,statistical rate theory,etc.,the physical meaning of isothermal parameters is analyzed to capture adsorbate molecular clusters.The formation and evolution of clusters determine the critical conditions for the occurrence of the adsorption phase change,and reveal the mechanism of the gas-solid interface from adsorption to phase change.First,the physical meaning of isothermal parametersαand c is discussed,and the influence of isothermal parametersαand c on the adsorption isotherm is analyzed.Among them,the parameterαcan characterize the degree of difficulty of the transition between adsorbate phases,and the size of the isothermal parameterαis equivalent to the size of the critical conditions required for the adsorption phase change.The parameter c can characterize the strength of the interaction between the adsorbate and the adsorbent,and mainly affects the value of the heat of adsorption and the type of isotherm.Based on the Zeta isotherm adsorption equation,the adsorption process of vapor on a uniform solid surface is theoretically analyzed and experimentally studied.The theoretical analysis results are in good agreement with the experimental results.The Zeta adsorption isotherm equation not only fully describes the adsorption isotherm in the range of the total pressure ratio,but also provides the evolution law of different types of molecular clusters at various partial pressure ratios,showing a wealth of interface adsorption characteristics.Secondly,the evolution of adsorbate molecular clusters with pressure ratio changes when water vapor is adsorbed on the surface of different adsorbents is analyzed.Combined with the statistical rate theory（SRT）,the adsorption kinetic curve of each partial pressure ratio interval was obtained,and the adsorption rate of different pressure ratios and the time required to reach adsorption equilibrium were analyzed.The results show that the medium pressure ratio is not much different in the adsorption rate,while the high pressure ratio interval rate is significantly greater,and it takes longer to reach equilibrium.The reason is that the high pressure ratio has a greater chemical potential difference between the gas and solid phases.There is a greater adsorption rate.On the other hand,the Zeta adsorption isotherm equation is extended to the near equilibrium region.Firstly,based on the theory of adsorption entropy,the critical conditions for the adsorption phase transition at the gas-solid interface are captured.The results show that when the pressure ratio reachesα^-1,the adsorption capacity increases sharply,and the adsorption capacity change rate increases to the maximum.At this time,the occurrence probability of various types of clusters at the interface is equal,with the largest cluster types and the largest disorder in the adsorption layer.The adsorption entropy reaches the maximum value,and the first-order phase transition occurs in the interface adsorption.Secondly,combined with the adsorption heat equation,the change of the isometric adsorption heat in the high pressure ratio zone and the near equilibrium zone is captured,and the change rule of molecular clusters is used as an analysis method to give the physical mechanism of the isometric adsorption heat curve changing with the pressure ratio.When the value of the heat of adsorption is close to the latent heat of the adsorbate,the adsorption interface forms a wetting transition and reaches the wetting state.Combining the Gibbs adsorption equation and Young’s equation,the variation of the gas-solid surface tension with the pressure ratio is captured,and the surface tension of the gas-solid interface under the condition of zero adsorption is obtained.This parameter belongs to the physical property constant of the material.When different vapors are adsorbed on the same adsorbent,this parameter can be used to predict the critical thermodynamic conditions required for the wetting transition.