Effect of the Occurrence State of Dodecylamine on the Adsorption Behavior of Calcium Sulfate Dihydrate and Silica

In this work, the effects of dodecylamine storage state on the adsorption behavior of calcium sulfate dihydrate and silica were systematically investigated by using Raman detection, solution equilibrium calculation, and calculation based on density functional theory. The results show that the selective adsorption behavior of dodecylamine with calcium sulfate dihydrate and silica is closely related to its occurrence state. The adsorption of dodecylamine in the ionic state with calcium sulfate dihydrate and silica is dominated by the strong electrostatic adsorption between the H-O atoms under acidic conditions, while that of dodecylamine in the molecular state is dominated by the weak electrostatic adsorption between the Ca-N or Si-N atoms under alkaline conditions. Finally, by comparing the distribution coefficients and adsorption energies of the ionic/molecular states of dodecylamine with the change in pH, the reason why dodecylamine adsorbs calcium sulfate dihydrate more readily under acidic conditions was explained at the atomic level.