A study of sodium oleate adsorption on Ca²⁺ activated quartz surface using quartz crystal microbalance with dissipation
Date
2016
Authors
Kou, J.
Xu, S.
Sun, T.
Sun, C.
Guo, Y.
Wang, C.
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International Journal of Mineral Processing, 2016; 154:24-34
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The adsorption kinetics, density and structural property of sodium oleate on Ca2²⁺ activated quartz surface have been studied using the techniques of quartz crystal microbalance with dissipation (QCM-D) and atomic force microscope (AFM). The real-time measurements of frequency (Δf) and dissipation shifts (ΔD) with SiO₂ coated sensor have revealed the changes in surface property of the quartz during the entire activation and adsorption process at different Ca²⁺ concentrations and pH's. An activation layer with an adsorption density of 89 ng/cm2 was observed at pH=12.0. Since pseudo-first-order model fitted well with adsorption process of sodium oleate,the mass transfer (diffusion-controlled) was the rate determining step at pH 12.0. Therefore, the reactions of RCOO−/(RCOO)²₂− and Ca(OH)+/Ca²⁺ is considered to be the dominant process in the solution at pH 12.0 which generated (RCOO)₂Ca precipitation and formed poorly-organized dissipative adsorption layer on activated quartz surface. Two distinct adsorption stages were identified from the different slopes K₂ N K₃ and K₃ ≤ 0.2 of ΔD − Δf plots which demonstrated the existence of conformational changes in the adsorption layer.
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Copyright 2016 Elsevier