Journal
ADVANCES IN COLLOID AND INTERFACE SCIENCE
Volume 103, Issue 1, Pages 57-76Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/S0001-8686(02)00083-0
Keywords
point of zero charge; adsorption; isoelectric point; goethite; hematite; Mossbauer spectroscopy; X-ray diffraction
Categories
Ask authors/readers for more resources
Aging of synthetic goethite at 140 degreesC overnight leads to a composite material in which hematite is detectable by Mossbauer spectroscopy, but X-ray diffraction does not reveal any hematite peaks. The pristine point of zero charge (PZC) of synthetic goethite was found at pH 9.4 as the common intersection point of potentiometric titration curves at different ionic strengths and the isoelectric point (IEP). For the goethite-hematite composite, the common intersection point (pH 9.4), and the IEP (pH 8.8) do not match. The electrokinetic potential of goethite at ionic strengths up to 1 mol dm(-3) was determined. Unlike metal oxides, for which the electrokinetic potential is reversed to positive over the entire pH range at sufficiently high ionic strength, the IEP of goethite is rather insensitive to the ionic strength. A literature survey of published PZC/IEP values of iron oxides and hydroxides indicated that the average PZC/IEP does not depend on the degree of hydration (oxide or hydroxide). Our material showed a higher PZC and IEP than most published results. The present results confirm the allegation that electroacoustic measurements produce a higher IEP than the average IEP obtained by means of classical electrokinetic methods. (C) 2003 Elsevier Science B.V. All rights reserved.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available