The Canadian Society for Bioengineering

This work studied simultaneous removal of ammonium and potassium ions by ion exchange with the natural zeolite clinoptilolite. Synthetic and real RO permeate used in experiments contained approximately 250 mg NH4/L and 200 mg K/L. The real RO permeate was obtained from membrane treatment of anaerobically digested cattle manure effluents. Batch experiments were conducted to determine ammonium and potassium ion uptake capacities, exchange kinetics, and pH effects. The experimental isotherm data were fitted well with the Langmuir equation. The equilibrium uptake capacity was 1.14 and 0.88 meq/g for ammonium and potassium, respectively. The simultaneous uptake of both ammonium and potassium was rapid but the potassium uptake was faster than that of ammonium. The uptake of both NH4 and K was independent of pH in the range of pH 4 – 8.5. With further pH increase over 9, the NH4 uptake capacity significantly decreased while the K uptake capacity slightly increased. The column flowthrough ion exchange tests with on-column regeneration were also conducted to determine the breakthrough curves and regeneration efficiencies. Both batch and column tests confirmed a higher selectivity for potassium than for ammonium on clinoptilolite. It was also confirmed that ammonium can be efficiently removed by clinoptilolite under the condition of simultaneous uptake of potassium.