Adsorption characteristics of ammonium ions by natural clinoptilolite powder

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 (R20.99).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.