Keren, R., Institute of Soil, Water and Environ. Sci., Volcani Center Agricultural Research Organization (ARO), P.O. Box 6, Bet Dagan 50250, Israel
Communar, G., Institute of Soil, Water and Environ. Sci., Volcani Center Agricultural Research Organization (ARO), P.O. Box 6, Bet Dagan 50250, Israel

Although it is well known that B interacts with organic matter, no information is available yet on B adsorption by dissolved organic matter (DOM) from treated sewage effluent. This study aimed to determine the effect of pH on B adsorption by DOM in sewage effluent, and to develop a B adsorption model for DOM as a function of pH. The DOM used in this study was separated from effluent from a municipal wastewater treatment plant. The B adsorption isotherms for the DOM were determined at various pH levels ranging from 5.1 to 10.9. Boron adsorption by DOM increased significandy as the pH increased from 5-8 to 9.25, and maximized at pH 9.3. The B adsorption values at any given constant pH, as calculated by using the Langmuir adsorption equation fitted every single adsorption isotherm well, but the adsorption parameters kB-DOM and bmDOM were both pH dependent. The competitive adsorption model simulated well B adsorption by DOM only at the high pH range, but failed at the lower range. The deviation between the predicted values and the experimental data in the low pH range is probably due to changes in DOM structure and acidic functional groups content. Good agreement between calculated and experimental results at the lower pH range was obtained by introducing a correction factor in the competitive adsorption model to account for these changes. © Soil Science Society of America.