【作者】 秦承欢；

【导师】 马伟；

【作者基本信息】 大连理工大学 ， 无机化学， 2009， 硕士

【摘要】 在海水淡化应用越来越多的同时,浓海水的处理问题也凸现出来,浓海水中存在着大量的钙离子,由于钙离子极易形成碳酸钙等使设备结垢,影响到浓海水的处理,因此浓海水中钙离子的去除,对浓海水综合利用起着十分重要的作用。吸附法可以去除浓海水中的钙离子,沸石因其具有吸附量大,选择性好的的特点,也受到越来越多的关注。本文用水热法合成钙选择性沸石并对其用SEM,XRD和FT-IR进行表征,然后研究钙选择性沸石对钙离子的吸附能力,主要通过震荡实验研究钙选择性沸石吸附剂对钙离子吸附参数,并通过数学模型模拟其吸附行为。主要用到吸附等温模型有Langmuir,Freundlich,主要用到的动力学模型有一级反应动力学,二级反应动力学和扩散方程,此外考虑到H~+竞争的模型也被用于对实验数据进行拟合,并通过对pH变化进行追踪从而探讨不同pH下的吸附机理。在震荡试验中,通过主要参数的变化(初始浓度200～1000mg/L,吸附剂投加量0.1～0.7g,pH 2～12.5,吸附时间0～100min,温度298K～318K),得到了吸附量随着浓度的升高而升高,随着吸附剂投加量的增加而降低,随温度的升高而升高,钙的吸附最佳pH值为12.5,吸附平衡时间约为70min,最佳条件时钙的最大吸附量为105mg/g的结论。在等温吸附模型中,在固定pH值的条件下,钙离子的吸附更加符合Langmuir等温吸附模型。动力学实验则满足二级动力学方程。在H~+竞争吸附模型中,不考虑钙离子价态对吸附影响的模型,能够更好的描述实验数据。热力学计算显示钙选择性沸石对钙离子的吸附行为是吸热、熵增、自发进行的过程。通过讨论离子强度对钙选择性沸石吸附钙离子的影响以及在模拟海水中对钙离子的吸附可以看出,钙离子吸附量随离子强度增加而降低,但仍能体现出较高的吸附量,用钙选择性沸石在浓海水中吸附钙离子是可行的。更多还原

【Abstract】 With the development of seawater desalination technologies,how to deal with the brine is becoming more and more important.A lot of calcium ion was in brine.The high calcium concentrations are problematic,because they result in clogging of pipelines and heat exchangers through scaling as the form of carbonate precipitates et al.Therefore the removal of calcium plays a very important role in utilization of brine.Zeolite is getting more and more attention because its adsorption capacity and the characteristics of good selectivity.Ca-Selectivity zeolite sample was prepared.The structure morphology,the physical and chemical performances were characterized by SEM,XRD and FT-IR.The adsorptive experiments were carried out in batch systems.The models were adopted to evaluate the experimental data.The Langmuir,Freundlich isotherms were adopted to evaluate the experimental data in fixed-pH.Three different kinetic models including pseudo-first-order model,pseudo-second-order model and intra-particle diffusion model were used to evaluate the adsorption kinetics and the competitive adsorption models were fitted to data in the condition which the pH values are without any control during adsorption process,time dependence study and mechanism was studied at different pH.Within the test range(initial concentration 200～1000 mg/L,sorption dose 0.1～0.7 g,pH 2～12.5,contact time 0～100min,tempreture 298K～318K),sorption performance for calcium ions showed an increase metal uptake capacity with an increasing in initial ions concentration and an increasing in tempreture but an decreasing in sorbent dose.The optimized condition of pH value for calcium is 12.5,while contact time is about 70 min.At equilibrium, the maximum total uptake by Ca-Selectivity zeolite was 105 mg/g.The results for calcium fit well to the Langmuir.Pseudo-second-order model described the sorption kinetic of calcium well.The Model assumes direct competition between metal and H~+ ions for binding sites and has been shown to fit the experimental data well.It is an endothermic process accompaning the increase of disorder of the system and can be occured spontaneously.From the effect of ionic strength and the sorption in simulated sea water,it can be seen that the adsorption amount of calcium decreased with the increase of TDS,but the Ca-Selectivity zeolite still exhibited high calcium ion exchange capability,we can conclude that the Ca-Selectivity zeolite was a potential adsorbent for calcium removal from brine.更多还原