Chem. J. Chinese Universities ›› 2022, Vol. 43 ›› Issue (4): 20210833.doi: 10.7503/cjcu20210833

• Physical Chemistry • Previous Articles     Next Articles

Points of Zero Charge and Surface Acid-base Reaction Equilibrium Constants of Mg-Al-Ti Layered Double Hydroxides

TIAN Zhen1, DU Na1, LI Haiping2, SONG Shue3, HOU Wanguo1,2()   

  1. 1.Key Laboratory of Colloid & Interface Chemistry,Ministry of Education
    2.National Engineering Technology Research Center of Colloidal Materials
    3.School of Chemistry and Chemical Engineering,Shandong University,Jinan 250100,China
  • Received:2021-12-15 Online:2022-04-10 Published:2022-02-12
  • Contact: HOU Wanguo
  • Supported by:
    the National Natural Science Foundation of China(21872082);the Natural Science Foundation of Shandong Province, China(ZR2019MB025)


Five Mg-Al-Ti-CO3 layered double hydroxides(LDHs) were synthesized using a coprecipitation method with a constant Mg2+/(Al3++Ti4+) molar ratio of 3.00 but varying Ti4+/(Al3++Ti4+) molar ratio(RTi, 0—0.40). Their structural charge density(σst), point of zero net charge(pHPZNC), and point of zero net proton charge(pHPZNPC) were determined using potentiometric, salt and potentiometric mass titrations, and their intrinsic equilibrium constants of surface acid-base reactions(pK, pKa1int and pKa2int) were estimated in turn based on the general 1-pK and 2-pK models. Special emphasis was placed on the effect of RTi on their crystal structure and interface electrochemical(IEC) properties. With an increase in RTi, the cell constants(ab and c) and d-spacing increase, arising from the strong electrostatic repulsion between Ti4+ ions. An increase tendency was also observed for pHPZNC, pHPZNPC, pK, pKa1int, and pKa2int with the increase of RTi, indicating a decrease in the deprotonation tendency of surface hydroxyl groups. In addition, it was observed that pHPZNPC is lower than pHPZNC and increases with increasing the electrolyte(NaNO3) concentration, arising from the effect of structural charges. This work provides a better understanding for the IEC properties of Ti4+-containing LDHs.

Key words: Layered double hydroxide, Points of zero charge, Interface acid-base reaction, Interface-charging mo-del, Acid-base titration

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