Study Of Calcium Carbonate Scaling Mechanism Based On Molecular Simulation

Scaling is a widespread problem in many areas of industrial production.The technical means to completely solve the problem of equipment scaling has not yet been developed.The solution of this problem relies on the correct understanding of the scaling mechanism in the complex physical and chemical environment of the scaling system.Most of the studies have been conducted from experiments,but their results of scaling mechanisms are often more controversial.As an atomic-level research method,molecular simulation can obtain microstructural information at the nanoscale and kinetic information at high temporal resolution,which provides microscopic theoretical support for mechanism explanation and has advantages that cannot be replaced by experiments.Therefore,this paper investigates the microscopic kinetic process of calcium carbonate scaling in aqueous solution and the microscopic interfacial properties after scaling based on molecular simulation to reveal the scaling mechanism from the microscopic point of view.The main findings and conclusions of the study are as follows.（1）The effects of temperature,ion concentration,and substrate material on the scaling of calcium carbonate aqueous solution were investigated in terms of particle motion characteristics,ion binding,and ion-surface interaction.It is also supplemented by density functional theory（DFT）calculations to study the adsorption behavior of ions on different surfaces.The results show that above the critical temperature,ions in aqueous solutions overcome the hindrance to their movement caused by the motion of water molecules and then interact strongly with the surface to scale.At higher ion concentrations,the highly agglomerated clusters formed by ions not only limit the diffusive motion of ions,but also weaken the interaction between remote ions and the surface,resulting in the interaction energy between the surface and the ion clusters first increasing and then decreasing with increasing concentration.Both molecular dynamics（MD）simulations of aqueous calcium carbonate solutions and DFT calculations of adsorbed scale-forming ions under solventized conditions show that the tendency of Fe（111）,Ni（111）,and Cu（111）surfaces to scale decreases sequentially.（2）The bulk phase,surface,and interfacial properties of Fe/CaCO₃,Cu/CaCO₃,Ni/CaCO₃and effect of CaCO₃ layer number on interfacial properties were investigated.The results show that the interfacial stability is related to the surface energy,and the interfacial energy of the interface formed by the low surface energy surface is more negative and the interface is more stable.When forming the interface with the charged CaCO₃（110）,the low surface energy metal surface will produce electrostatic response to make the formed interface more stable,but the high surface energy surface will not produce electrostatic response,so the formed interface is not stable.As the number of CaCO₃ layers increases,a stable CaCO₃ layer is formed on the substrate surface first,at which time the interface is stable and tightly bound.And then the CaCO₃ interlayer interaction inhibits the two-phase material interaction at the interface,which eventually leads to a decrease in interfacial stability and bond strength.