%0 Journal Article
%A Tian, Rui
%A Yang, Gang
%A Zhu, Chang
%A Liu, Xinmin
%A Li, Hang
%D 2015
%T Specific
Anion Effects for Aggregation of Colloidal
Minerals: A Joint Experimental and Theoretical Study
%U https://acs.figshare.com/articles/journal_contribution/Specific_Anion_Effects_for_Aggregation_of_Colloidal_Minerals_A_Joint_Experimental_and_Theoretical_Study/2190097
%R 10.1021/jp512078v.s001
%2 https://acs.figshare.com/ndownloader/files/3824260
%K anion specificity
%K OH
%K aggregation kinetics
%K H 2PO
%K charge density measurements
%K Specific Anion Effects
%K HPO
%K mineral
%K surface charge densities
%X In
this work, dynamic light scattering experiments and density
functional calculations were combined to demonstrate the specific
anion effects for the aggregation of negatively charged colloidal
minerals. Although the aggregation kinetics is dominated by electrolyte
cations, anions also play a significant role. The critical coagulation
concentrations and activation energies indicated a clear Hofmeister
series for the various anions as H2PO4– < Cl– < NO3– < SO42– < HPO42– < PO43–. Moreover,
interaction energies of anions with cations and proton affinities
of anions were explored as the influencing factors for anion specificities,
which were corroborated by measurement of surface charge densities.
Owing to the largest interactions with cations, PO43– causes the most pronounced inhibition effect to the
aggregation kinetics and corresponds to the strongest anion specificity.
Proton exchange from H2PO4– reduces the negative charges of minerals and accelerates the aggregation
process, thus resulting in an inferior anion specificity than NO3–. Density functional calculations indicated
that proton transfer from minerals to OH– can occur
facilely and increase the negative charges of minerals, as confirmed
by charge density measurements and dilution experiments. This further
adds to the aggregation difficulty and causes OH– to show distinctly stronger anion specificity than other univalent
anions.
%I ACS Publications