Sorption and Desorption Characteristics of Ion Exchange Resins to Estimate Leaching Losses in the Field

Abstract

Laboratory experiments were conducted to determine sorption and desorption properties of ion exchange resins based on recovery rates. Dissolved nitrate (41.6 mM NO₃ ⁻ and 166.5 mM NO₃ ⁻), ammonium (63.9 mM NH₄ ⁺ and 256.1 mM NH₄ ⁺), phosphate (3.5 mM PO₄ ^3– and 13.9 mM PO₄ ^3–), and potassium (16.11 mM K⁺ and 63.94 mM K⁺) were factorially combined and added at flow rates of 5 L at 3 and 9 h to an exchange resin / sand mixture. Six extractions with 1 M sodium chloride (NaCl) desorbed >90% of the added ions. Apparent recovery rates for nitrate (NO₃-N) averaged 99% (±6), for ammonium (NH₄-N) averaged 100% (±8), and for phosphate (PO₄-P) averaged 109% (±6). Apparent recovery rates of potassium (K) were erroneously high (151% ± 12) and largely reflected analytical interference problems with the inductively coupled plasma (ICP) method. Concentrations of dissolved ions did not affect recovery rates of any studied ion.

Keywords:

• Ion recovery rate
• nutrient flows
• vertical flux rate

Acknowledgments

We are thankful to Eva Wiegard, Claudia Thieme, Gabriele Dormann, Anja Sawallisch, Anita Kriegel, and Christa Hake for technical help and to the Deutsche Forschungsgemeinschaft (DFG) for funding of this research within the Graduate Research Training Group 1397 “Regulation of Soil Organic Matter and Nutrient Turnover in Organic Agriculture” at the University of Kassel-Witzenhausen, Germany.