Wien effect determination of binding and adsorption energies between positively charged nano-particles and anions

Abstract

The energy relationships between nano-particles and ions are the best measure characterizing the interactions of ions with nano-particles. The energy relationships, which include mean free binding and adsorption energies, can be easily determined via the measurements of Wien effect in suspensions. The hematite and γ-Al2O3 particles, which carried only the positive charge, were used as the testing samples in this work. The mean free binding and adsorption energies of F– , Cl–, and NO 3 – to hematite and γ-Al2O3 particles determined by means of the suspension Wien effect, measured with the homemade apparatus of SHP-2, are presented. The mean Gibbs free binding energies of the three anions to hematite and γ-Al2O3 particles diminished all in the order F– > Cl– > NO 3 – , but the binding energies of the anions to hematite particles, which was 5.99, 3.91, and 2.80 kJ mol–1 for F–, Cl–, and NO 3 – , respectively, were lower than those to γ-Al2O3 particles, which was 8.12, 7.96, and7.70 kJ mol–1, respectively. The changes in the mean free adsorption energies of the three anions to hematite particles were of the order F– > Cl– > NO 3 – at the field strengths more than 70 kV cm–1, while the mean free adsorption energies of the Cl– and NO 3 – to γ-Al2O3 particles nearly approached, but those for F– in the range of tested field strengths were all negative, which could suggest that the interaction of F– with γ-Al2O3 particles differed to some extent from that with hematite particles. The mean free binding energies of the three anions to hematite and γ-Al2O3 particles diminished all in the order F– > Cl– > NO 3 – , but the binding energies of the anions to hematite particles were lower than those to γ-Al2O3 particles. The changes in the mean free adsorption energies of the three anions to hematite particles were of the order F– > Cl– > NO 3 – at the field strengths more than 70 kV cm–1, while the mean free adsorption energies of the Cl– and NO 3 – to γ-Al2O3 particles nearly approached.