POTENTIOMETRIC TITRATION OF SULFATE LIGNIN

The dependences of adsorption of OH- and H+ ions (DELTA-GAMMA) on the pH and concentration of electrolytes were obtained from data on the potentiometric titration of sulfate lignin in solutions of NaNO3, NaCl, Na2SO4, Ca(NO3)2, and CaCl2, and they demonstrate the significant specific adsorption of Cl-, SO4(2-), and Ca2+ ions on the sulfate lignin. Hypotheses were advanced concerning the presence of two types of sites on sulfate lignin responsible for specific adsorption of cations and anions, respectively. The ions are in the following orders with respect to the adsorption power: Cl- > SO42- > NO3-; Ca2+ > Na+.