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| Adsorption characteristics of ammonium ions by natural clinoptilolite powder |
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Abstract Natural clinoptilolite powder, with an average particle size of 30μm, was selected as experimental material. The adsorption characteristics of the clinoptilolite on NH4+ in solution were studied, with the monitoring of metal elements concentration in liquid-phase and solid-phase. The isothermal adsorption experiment, adsorption kinetics experiment were conducted. The results showed that the ammonium adsorption by the natural clinoptilolite was fitted well with Freundlich adsorption isotherm (R2=0.996) and the pseudo second-order kinetics (R2>0.99). The adsorption process was less favorable with the increase of initial NH4+ concentration. Na+, Ca2+ occupied the major part of the exchange amount in this process. Na+ was exchanged into liquid-phase first. Then exchange amount of Ca2+ increased gradually and exceeded Na+ finally. The exchange amount of Na+ and Ca2+ occupied 39%~60% and 35%~57% in the adsorption process, respectively. For the clinoptilolite with fine particle size, besides ion exchange, the contribution of physical adsorption should not be neglected in nitrogen removal process.
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Received: 20 October 2009
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