ISSN:
1435-1536
Schlagwort(e):
Anatase
;
radiofrequency electric field
;
surface charge
;
hydrous titanium dioxide
;
ion exchange
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
,
Maschinenbau
Notizen:
Abstract Potentiometric titrations of TiO2 (anatase) suspensions in solutions of 10−2, 10−3, and 10−4 M NaCl prior to treatment with a radiofrequency (RF) electric field gave values of pHpzc and pHiep of 5.75±0.1 and 5.85±0.1, respectively, within the range of literature values. Surface charge plots versus pH for untreated samples gave curves with a common intersection point, indicating that NaCl acts as an indifferent electrolyte. Identical suspensions of anatase were then exposed for 30 min to an RF electric field with a peak-to-peak, no-load amplitude of 34V and a frequency of 44 MHz. Portions of the treated suspension were titrated after different time periods following removal of the field (2, 15, 30, and 45 min). At 2 min, the pHpzc had shifted to 6.50±0.1, and at 15, 30 and 45 min, the curves for the three NaCl concentrations were found to lack a common intersection point, an effect which became more pronounced with time. It is proposed that RF treatment results in the formation of a porous gel layer of hydrous titanium dioxide on the surface of the anatase particles that subsequently undergoes a slow ion-exchange reaction involving ions of the supporting electrolyte.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00653088
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