Comparison of the influence of a kind of electrolyte and its ionic strength on the adsorption and electrokinetic properties of the interface: Polyacrylic acid/MnO2/electrolyte solution

The influence of a kind of electrolyte and its ionic strength on the adsorption of polyacrylic acid (PAA) 2000 and 60 000 on the surface of manganese dioxide (MnO2) was measured. As background electrolytes NaCl, KCl, CaCl2 and MgCl2 were used. It was proved that PAA adsorption amount is the highest in the presence of CaCl2 in comparison to PAA adsorption amount in the presence of other electrolytes. Polyacrylic acid adsorption amount increases with the increase of electrolyte ionic strength in all measured systems.The influence of a kind of electrolyte and its ionic strength on the zeta potential in the presence of polyacrylic acid of different concentrations was also measured. It was observed, that the zeta potential of MnO2 is higher when CaCl2 is used as a background electrolyte in comparison to the zeta potential of MnO2 in the presence of NaCl or KCl. What is more, the zeta potential of MnO2 increases with the increase of ionic strength for all measured systems.Potentiometric titrations of MnO2 suspensions in the presence of polymer and chosen electrolyte prove the large impact of polymer presence on MnO2 surface charge density. Other factors which also have the influence on the surface charge density are: a kind of used electrolyte and its ionic strength.Free energies of PAA adsorption in the presence of different electrolytes and ionic strengths were also calculated.