Adsorption Of Amphiphilic Alginate Derivatives On The Surface Of Nanoparticles

This paper studied the adsorption behavior of amphiphilic alginate derivatives that was a green polymeric surfactant by the hydrophobic modification of sodium alginate on the surface of solid particles. There were investigated properties of before and after adsorption such as particle size, surface electric property, particle morphology, surface tension, rheological property and stability by means of FTIR, DLS, TEM, Surface tensiometer, Rheometer and Turbidity instrument. At the same time the adsorption kinetics and thermodynamics of amphiphilic sodium alginate derivatives on the surface of particles not only were studied by using high performance liquid chromatography?HPLC?, but also its mechanism of adsorption stability was explored, which provided a certain theoretical basis for the dispersion stability of solid particles in the aqueous solution.Stable dispersion system of TiO₂ nanoparticles was made by dodecyl sodium alginate ?NaAlg-Dode? adsorbing on the TiO₂ nanoparticles. Results showed that NaAlg-Dode was conducive to the stability of TiO₂ nanoparticles dispersion system within the scope of pH=4-8. The average size of TiO₂ particles decreased to 500nm from 2.5 ?m and the surface Zeta potential of particles reduced to-40mV from 0 mV at pH=6.3. At the same time the shear stress of TiO₂ nanoparticles dispersion system increased gradually with the addition of NaAlg-Dode, which suggested that the interaction between particles enhanced. Therefore, the mechanism that NaAlg-Dode improved the stability of TiO₂ nanoparticles dispersion system was inferred: NaAlg-Dode molecules were able to reduce the particles aggregation via changing the zeta potential and space steric of TiO₂ by electrostatic interactions, hydrogen bonding and hydrophobic function.There was studied the adsorption behavior of amphiphilic sodium alginate ?NaAlg-Ugi? modifying by Ugi reaction on the surface of the TiO₂ particles and its influence on particles aggregation behavior in aqueous solution. Results show that NaAlg-Ugi can adsorb on the surface of TiO₂ particles by electrostatic interaction, hydrogen bonding and hydrophobic function in the condition of different pH. The average size of TiO₂ particles appeared significantly reduced and the surface Zeta potential of particles reduced to-45mV from 0 mV at pH=6.3. The shear stress of TiO₂ particles dispersion system increased gradually and showed better stability under high frequency with the addition of NaAlg-Ugi, which suggested that the interaction between particles enhanced. TEM and Stability tests showed that NaAlg-Ugi have a significant effect for stable dispersion of TiO₂ particles. Adsorption kinetics results show that the adsorption process of NaAlg-Ugi on the surface of TiO₂ particles in accorded with the Langmuir rate equation. Equilibrium adsorption capacity of NaAlg-Ugi increased to 0.193 mg/g from 0.128 mg/g, the adsorption time reduced to 1.3h from 2.5h and the adsorption rate constant increased to 0.6015 h'1 from 0.4873 h"1 with the increased of temperature. Thermodynamic results show that the adsorption isotherm of NaAlg-Ugi on the surface of TiO₂ particles followed the Langmuir isotherm equation. Its adsorption capacity and equilibrium constant increased with temperature rising, which suggested the raising temperature is advantageous to the adsorption.There was discussed the adsorption behavior of amphiphilic sodium alginate ?NaAlg-Ugi? modifying by Ugi reaction on the surface of the SiO₂ particles and its influence on particles aggregation behavior in aqueous solution. Results showed that NaAlg-Ugi can adsorb on the surface of SiO₂ particles by hydrogen bonding and hydrophobic function that diminished gradually with the pH increasing. NaAlg-Ugi had a dispersion effect on SiO₂ particles in the condition of low pH. Adsorption kinetics results show that the adsorption process of NaAlg-Ugi on the surface of SiO₂ particles in accorded with the Langmuir rate equation. Equilibrium adsorption capacity of NaAlg-Ugi increased to 0.138 mg/g from 0.162 mg/g, the adsorption time reduced to 1.3h from 3h and the adsorption rate constant increased to 1.0142 h'1 from 0.4646 h-1 with the increased of temperature. Thermodynamic results show that the adsorption isotherm of NaAlg-Ugi on the surface of TiO₂ particles followed the Langmuir and Freundlich isotherm equation, the correlation coefficient of the former was higher. Its adsorption capacity and equilibrium constant increased with temperature rising, which suggested the raising temperature is advantageous to the adsorption.