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Kinetics of Ion Removal from an Iron-Rich Industrial Coproduct: I. Chloride

Soil Reclamation Dep., Keren Kayemeth LeIsrael, P.O. Box 45, 26103 K. Hayim, Israel;

Donald L. Sparks^*, Masoud Ghodrati and Gerald J. Hendricks

Dep. of Plant and Soil Sci., Univ. of Delaware, Newark, DE 19717-1303.

^* Corresponding author (dlsparks{at}brahms.udel.edu).

ABSTRACT

An industrial TiO₂ extraction process results in a Fe-rich material (IRM) that contains substantial chlorides. Recent investigations showed that washed IRM may serve as a soil amendment for agricultural use. Yet, washing processes at the industrial production facility are currently problematic and costly, and it is essential to devise effective procedures for Cl removal. This study was conducted to determine the mechanism of Cl retention, and to ascertain whether the rate of Cl removal was governed by time-dependent surface-chemical kinetics or diffusion (transport)-controlled kinetics. The IRM samples we used throughout the study were homogenous. It was physicochemically characterized and concentrations of heavy metals were determined. The IRM batch studies revealed negative Cl adsorption, even though its point of zero charge was 8.3. Column studies showed that 92% of the Cl was removed with the first pore volume. Additionally, the salt removal decreased the electrolyte concentration, caused dispersion, and, ultimately, lowered the hydraulic conductivity. Stirred-flow kinetic studies established that Cl leaching was a function only of the total volume that flowed through the chamber, and that no chemical kinetics were involved.