Electrokinetics at high ionic strengths: Alumina

Mixed electrolytes producing very weak electroacoustic signal

“…The IEP of alumina at low ionic strengths is consistent with the IEP reported for AKP-30 in other studies [8], with the PZC of AKP-30 obtained by titration [7] and with results reported for other aluminas [8].…”

“…In the acidic range (pH about 4) the ζ potentials in 1 M electrolyte solution were in the range of about 20 mV. Such results were obtained from ESA measurements [3] and by electrophoresis [7]. On the other hand, the values obtained from CVI (colloid vibration current) measurements were substantially lower [3].…”

“…[9] are very consistent. Electrophoresis [7] produced systematically lower ζ potentials of AKP-30 at high ionic strengths than ESA. The discrepancies became more significant as the ionic strength increased, and in 1 M alkali nitrates the ζ potentials obtained by electrophoresis [7] were lower by a factor of 2 than those obtained by ESA (this study and Ref.…”

“…We believe that the former two values are close to the actual IEP, and the later value is overestimated, because alumina was brought too fast from low pH to pH about 9, and it did not have sufficient time to equilibrate. Hysteresis is commonplace in automatic titrations in flowthrough systems [7].…”

Electrokinetic studies of metal oxides in the presence of alkali trichloroacetates, trifluoroacetates, and trifluoromethanesulfonates

“…AKP-30 alumina from Sumitomo (7 m 2 /g, particle diameter 300 nm [16]) was used as obtained as a model oxide. Anatase from Aldrich (9 m 2 /g, particle diameter 300 nm [17]) was purified according to the procedure described elsewhere [17].…”