Backtitration Technique for Proton Isotherm Modeling of Oxide Surfaces

Batch potentiometric titration analyses were made on a 7-Al,O, colloidal suspension and interpreted in terms of the electroneutrality principle. Three titration methods involving a singular reference curve were compared. The first reference used was theoretical, the latter two were representative supernatant curves: an electrolyte solution, and an aliquot of the zero point of titration (ZPT) supernatant. All three methods resulted in similar charge isotherms and a zero point of charge (ZPC) = 8.60. A fourth titration method was developed involving each supernatant of the batch titration sample to act as a unique reference. This latter method is a backtitration technique which accounts for all sources that also consume H ions, leaving the difference to be the adsorbed proton concentration only. The NaClOj electrolyte solution used is postulated to be adsorbed with competitive cation and anion exchange mechanisms with a point of zero salt effect (PZSE) = 7.50. Additional Index Words: electroneutrality, proton isotherm, ZPC,