Molecular Dynamics Simulations Of Surfactant-influenced Wettability Alteration On Silica Dust

With the rapid development of industrialization and urbanization,air pollution caused by the industrial fine particles is becoming more and more serious.However,the conventional dust removal technology has low removal efficiency for submicron particles.In order to improve the removal efficiency of them,pretreatment technologies are usually used to promote the growth of fine particles.Among them,heterogeneous coagulation technology,which has a wide range of applications,creates a supersaturated vapor environment to promote heterogeneous condensation of vapor with fine particles as condensation nuclei,and the particles further collide and condense,which makes the size of the fine particles increase.However,the heterogeneous condensation process is difficult to occur on the surface of hydrophobic particles.In order to promote heterogeneous coagulation,surfactants are often added to water to improve the wettability of the particles.At present,researches on the role of surfactants in heterogeneous condensation process mostly focus on the improvement of macroscopic removal effect of fine particles,and the screening process of surfactants is complicated.Therefore,it is necessary to introduce a new research method to systematically study the micro-action process and reveal the mechanism of surfactant improving dust wettability.On this basis,an efficient screening method and screening principle of surfactants for different industrial dusts is explored,which can provide theoretical and technical support for the application of surfactants in heterogeneous coagulation.Based on the molecular dynamics method,this topic explores the microscopic process and action mechanism of surfactants to improve the wetting characteristics of silica dust with different surface groups.First of all,models are built to explore the correlation between contact angle,interaction energy and the wettability of solid surface,which proves that the wetting characteristics of solids can be characterized by solidliquid interaction.Secondly,based on the solid-liquid interface between silica and water,the effect of dust surface properties on the wettability is studied by the analysis of solidliquid interaction energy and other related parameters.Finally,the effect of surfactant type and concentration on wettability of silica are investigated by adding surfactants to the water phase,and the surfactants with the best effect of improving wettability are confirmed for silica dusts with different surface groups.The main research conclusions of this subject are as follows: 1.In the solid-liquid interface model,the greater the absolute value of the solid-liquid interaction energy,the stronger the wetting effect of the liquid on the solid surface.Therefore,it is reasonable to use the solid-liquid interaction energy to characterize the wettability of solid surface;2.The surface groups of silica dust are the fundamental reason that affects the wetting characteristics of silica dust.Surface groups mainly affect the wetting characteristics of dust from two aspects: polarity and electrical properties;3.For hydrophobic silica with non-polar methyl groups on the surface,OP10,with long hydrophobic chains,should be preferred when the surfactant is added to improve the wettability of silica surface due to the polarity of the dust.Besides,the concentration of OP10 should not exceed its critical micelle concentration;4.For hydrophilic silica with polar hydroxyl groups on the surface,due to the influence of the surface electrical properties of the dust,when adding surfactant to improve the wettability of silica surface,cationic surfactant CTAB should be the first choice and the concentration of CTAB should not exceed its critical micelle concentration.