ThepH buffering effect and charging behavior of oxides in aqueous solutio

A technique which measures the "equilibrium pH at high oxide loading" (EpHL) has been developed for the procurement of oxide PZC. This technique is an extension of the "mass titration" technique to very high oxide mass percent (the point of incipient wetness), where accuracy is highest. Measurement is made possible at this condition with a special semisolid pH probe. The advantages of EpHL over other techniques and its application in previously inaccessible pH ranges are demonstrated. A comprehensive model of oxide buffering reveals that the buffering effect is drastic not only at very high mass content but also for much lower levels of oxide area typical of laboratory scale "wet impregnation" experiments. The ramifications of these results on catalyst impregnation are discussed: pH shifts previously attributed to adsorption phenomenon can be accounted for solely by the buffering effect.;The procurement of the oxide acidity constant K$sb1$ and K$sb2$ has been accomplished by the fitting of mass titration data. This method appears to be more accurate than common "double extrapolation" techniques and less sensitive to experimental error than graphical interpolation methods. The goodness of fit of the simplest charging model is not much improved upon by invoking more complicated models. The simple model is thought suitable for describing the pH buffering effect and surface charging of common oxides, and can be employed within a larger model of metal adsorption.