Thermodynamic And Electrochemical Research Of Additives Adsorption On Theβ-2CaO·SiO₂Interface

The mechanisms of surfactants were lack of intensive study, added into the dissolution system of clinker, which reduced the loss of alumina by the reason of secondary reaction. The adsorption behavior on β-2CaO·SiO2of Sodium polyacrylate (PAAS) and polyethylene glycol (PEG), available in industrial production, as well as the compound by the ratio of1:1, were studied in this text. And according to Gibbs formula, it was easy to obtain the influence of adsorption on interfacial tension. The mechanisms ware also analyzed by investigating the electrical properties, providing theoretical guidance of the screening of surfactants.The adsorption of PAAS was saturated on β-2CaO·SiO2, of which the adsorption isotherm of "L-type" coincided the Langmuir monolayer adsorption model owing to the decentralized structure in the molecule by the repulsion electrostatic between-COO groups; The the adsorption isotherm of PEG was in the typical type of "S" with multiple molecular layer saturated adsorption, described by Freundlich equation. The reason of adsorption was that the hydrogen bonding between the ether key (-O-) and the β-2CaO·SiO2particles and the hydrogen bond between molecules by the-OH in the end of the chain, which caused the sharp rise of adsorption capacity at High concentration by interaction. When PAAS and PEG were compounded by the ration of1:1, the isotherm and model were not changed. But the coordination key between PAAS and β-2CaO·SiO2enhanced the adsorption of PEG, which lead to the increase of Kf in Freundlich equation. At the same time, the molecules interactions made the isotherm narrow to the origin of the direction with characteristics of saturated adsorption.The relationship of π-σ by formula of Gibbs showed that surfactants could reduce interface tension of β-2CaO·SiO2, of which the trend corresponding to adsorption isotherms. When adsorption was saturated, the distance between molecules was obtained the biggest compression.The adsorption of PAAS on β-2CaO·SiO2caused the decrease of ζ potential and isoelectric point (pHIEP) of particles, relevant to-COOCa. Furthermore, the absolute value of energy change were more than the error analysis (±0.2eV) of Ca2p, Si2p and Ols of resolving mud by XPS, which showed the chemical adsorption and inner complex; while the adsorption of PEG had no effect on ζ potential and pHEIEP, equal to the no effect on β-2CaO·SiO2, and the atoms energy also occured basically unchanged by XPS. So the behavior of PEG adsorption was physical including hydrogen bonding and van der Waals force and absorption product was the outer complex.