IMPACT OF pH AND CHELATORS ON FE(III) HYDROXIDE SOLUBILITY IN SEAWATER

Lee, Bong-Hun; Park, Heung-Jai

Environmental Engineering Research 2001;6(2): 91-98.

¹Department of Chemistry, Pusan National University, Pusan 609-735, Korea
²Department of Environmental Science, Inje University, Kimhae 621-749, Korea

Corresponding Author: Heung-Jai Park ,Tel: +82-55-320-3418, Fax: +82-55-320-3418, Email: envphj@ijnc.inje.ac.kr

Received: December 8, 2000; Accepted: May 6, 2001.

ABSTRACT

In seawaters and in the UV-irradiated seawaters of Pusan, Korea, iron solubilities of Fe(lII) hydroxide over a pH range of 5.51—8.15 at 20°C were determined. At pH range of 5.51—7.33, only the Fe(OH)₂⁺ ion was important species. The calculated solubility products, log Ks, for seawaters were 4.2—4.5. The solubilities within the pH range of 7.51—8.15 were relatively independent of pH and aging time. UV irradiation reduced the solubility to <0.1 nM. The vertical profiles of ambient Fe(III) solubility in seawaters had the following features in common; solubility in the surface mixed layer was high and variable (0.35 — 0.48 nM); solubility minima (0.19 — 0.30 nM) occurred at a depth of 100 — 500 m. These results suggested that natural organic Fe(IIl) chelators existed in high concentration and controlled the dissolved iron concentration in seawaters.

Keywords: chelators | Fe(III) hydroxide | seawater | solubility