天然斜发沸石粉对溶液中NH_4^+的吸附机理研究

Adsorption characteristics of ammonium ions by natural clinoptilolite powder

采用天然斜发沸石粉(平均粒径30μm)进行吸附溶液中NH4+的试验研究,并对系统中金属阳离子的液相和固相含量进行了全程跟踪测定.等温吸附试验、吸附动力学研究结果表明,天然斜发沸石对溶液中NH4+的吸附过程符合Freundlich线性模型(R2=0.996),该吸附过程属于优惠吸附;吸附动力学符合假二级方程(R2>0.99),且随着初始NH4+浓度的增加,吸附反应的优惠程度降低.沸石粉对NH4+的吸附过程中离子交换以Ca2+和Na+为主,Na+首先被交换出来,随着吸附过程进行,Ca2+交换量逐渐增加并超过Na+,两者交换当量分别占39%～60%和35%～57%.由于沸石粉粒径较小,其对NH4+的去除除了依靠离子交换作用外,物理吸附作用的贡献不容忽视.

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.