HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Kuo, S. Articles by Lotse, E. G. Search for Related Content PubMed Articles by Kuo, S. Articles by Lotse, E. G. Agricola Articles by Kuo, S. Articles by Lotse, E. G.

Kinetics of Phosphate Adsorption by Calcium Carbonate and Ca-Kaolinite¹

ABSTRACT

The objective of the present investigation was to elucidate the time-dependence of phosphate adsorption by calcium carbonate and Ca-kaolinite and to suggest a mechanism of adsorption. The phosphate adsorption by calcium carbonate and Ca-kaolinite at low phosphate concentrations in solution could be described by Langmuir adsorption isotherms, indicating that a monolayer of phosphate is formed on the surface. The calculated maximum surface saturation was 25µg/g for calcium carbonate and 187µg/g for Ca-kaolinite. A second-order kinetic equation was developed which considers both the change in phosphate concentration in solution and the surface saturation of the adsorbent during the adsorption process. The rate constant of phosphate adsorption was about 30,000 times greater for calcium carbonate than for Ca-kaolinite. About 80% of the phosphate adsorption by calcium carbonate was completed within 10 sec. The variation of the second-order rate constant with phosphate concentration was different in the two systems. The rate constant decreased in the calcium carbonate-phosphate system and increased in the Ca-kaolinite-phosphate system with increasing phosphate concentration. It was suggested that phosphate ions are adsorbed by displacing coordinated water molecules and/or coordinated anions.

Contribution from the Dep. of Plant and Soil Sci., Univ. of Maine, Orono, Maine 04473. Supported in part by a grant from the Office of Water Resour. Res. Dep. of the Interior under the Public Law 88–379 program, project no. A-016-ME. The work published is being done as part of the senior author's thesis requirements for the doctor's degree at the Univ. of Maine.

² Graduate Research Assistant and Associate Professor of Soil Chemistry, respectively.

Received for publication November 30, 1971. Accepted for publication April 24, 1972.

This article has been cited by other articles:

				S. Hunger, J. T. Sims, and D. L. Sparks How Accurate Is the Assessment of Phosphorus Pools in Poultry Litter by Sequential Extraction? J. Environ. Qual., January 1, 2005; 34(1): 382 - 389. [Abstract] [Full Text] [PDF]