Application of kinetic models of fixed bed for ion exchange process

为了掌握所选的Thomas模型,Yoon-Nelson模型和Adams-Bohart模型在固定床米格列醇离子交换过程中的应用情况,实验借助对不同质量浓度的米格列醇溶液在定量树脂和固定流速下研究其在固定床中离子交换过程,并通过对透过曲线实验数据分析来验证相关固定床动力学模型在此过程中的有效性.结果表明:固定床上样液质量浓度增大,达到平衡饱和点的时间将缩短,传质区长度增大,吸附率变小,上样液质量浓度在8 mg/mL时吸附量达到最大;用动力学模型拟合透过曲线的过程参数,结果表明Thomas模型和Yoon-Nelson模型具有较好的相关系数,Thomas模型的速率常数和最大吸附量值随着上样液质量浓度的降低而增大,Yoon-Nelson模型的速率常数随着上样液质量浓度的降低而减小,且在Yoon-Nelson模型中计算得到的透过曲线中出口质量浓度与上样质量浓度比值为1/2时所对应的计算值和实验值相差很小,Thomas模型和Yoon-Nelson模型可用于该过程的离子交换性研究.     

固定床动力学模型在离子交换过程中的应用

为了掌握所选的Thomas模型,Yoon-Nelson模型和Adams-Bohart模型在固定床米格列醇离子交换过程中的应用情况,实验借助对不同质量浓度的米格列醇溶液在定量树脂和固定流速下研究其在固定床中离子交换过程,并通过对透过曲线实验数据分析来验证相关固定床动力学模型在此过程中的有效性。结果表明:固定床上样液质量浓度增大,达到平衡饱和点的时间将缩短,传质区长度增大,吸附率变小,上样液质量浓度在8 mg/mL时吸附量达到最大;用动力学模型拟合透过曲线的过程参数,结果表明Thomas模型和Yoon-Nelson模型具有较好的相关系数,Thomas模型的速率常数和最大吸附量值随着上样液质量浓度的降低而增大,Yoon-Nelson模型的速率常数随着上样液质量浓度的降低而减小,且在Yoon-Nelson模型中计算得到的透过曲线中出口质量浓度与上样质量浓度比值为1/2时所对应的计算值和实验值相差很小,Thomas模型和Yoon-Nelson模型可用于该过程的离子交换性研究。     

米格列醇在大孔D001树脂上的离子交换性研究

为掌握米格列醇在离子交换树脂上的吸附行为,采用改变恒温振荡器的温度、震荡速率和溶液pH值来研究固定浓度的米格列醇溶液在定量树脂上的离子交换吸附行为,并结合热力学和动边界模型对交换过程进行分析.结果表明:吸附温度增大,分配系数KD变小,吉布斯函数值△G变大,不利于离子交换吸附,离子交换过程为放热过程;米格列醇溶液在中性条...     

固定床中米格列醇的离子交换洗脱规律性研究

为了探讨固定床中米格列醇的洗脱规律,在固定床D001树脂吸附米格列醇量给定下,实验通过洗脱剂种类、浓度和流速来分别考察其对米格列醇的洗脱影响,选择最佳洗脱条件,同时以此洗脱条件考察不同床层高度对米格列醇的洗脱影响。结果表明:氨水与盐酸和氯化钠相比,洗脱平衡时间最短,洗脱率最大,选择氨水为洗脱剂,且当氨水浓度为4 mol/L,流速为0.3 mL/min时米格列醇从固定床上的洗脱效果最好,洗脱率达到99.3%。以此选择的最佳洗脱条件对固定床不同床层高度下米格列醇洗脱率的影响研究结果表明:当床层堆积高度为2.8 cm时洗脱率相对较小,为1.5 cm时的洗脱率相对较大。     

水厂铝污泥对磷的动态吸附特性研究

对水厂铝污泥吸附柱去除水中磷的动态吸附特性进行了实验,利用BDST和THOMAS模型对吸附穿透曲线进行了数学模拟,预测不同吸附高度下出水含量随运行时间的变化关系。结果表明,铝污泥能够稳定有效地去除水中的磷,随着吸附柱高度的增加,吸附柱除磷穿透时间相应增大,在平均流速为2.0 m/d条件下吸附带高度约为0.18m。BDST和THOMAS模型能够准确地预测不同吸附柱高度下出水含量随运行时间的变化关系,BDST模型所预测的吸附柱耗竭时间与实际耗竭时间误差小于15%,THOMAS模型计算所得饱和吸附容量与实际吸附容量误差小于3%。可利用这2个模型对铝污泥吸附柱动态除磷的运行工况进行预测和模拟计算。     

铝基吸附剂固定床分离卤水锂资源过程研究

铝基锂吸附剂是一种非常适用于低锂品位、高镁锂比盐湖卤水提锂的吸附剂,具有无溶损、稳定性高等优点,也是目前唯一一种已投入工业化生产的吸附剂。使用自制的球形铝基锂吸附剂GLDH填充固定床,系统研究了吸附温度、进料流速、初始锂离子浓度和床层高度对GLDH固定床分离卤水锂资源过程中吸附穿透曲线的影响。结果表明：升高温度、增加床层高度、降低初始锂离子浓度和进料流速会导致穿透时间延长、穿透吸附容量升高。采用BDST、Clark、Thomas、Y-N和M-D-R 5种经验模型对锂吸附穿透曲线进行拟合,确定M-D-R模型能够较准确地描述固定床锂吸附过程。     

对二甲苯在活性炭固定床上的吸附动力学

研究了对二甲苯在活性炭固定床上的吸附动力学。考察了初始浓度、气体流量、床层长度等因素对吸附透过曲线的影响。同时,采用Yoon—Nelson模型对吸附透过曲线进行线性回归分析。实验结果表明,随着初始浓度的增大,透过时间缩短,吸附量增大：气体流最对透过曲线的形状影响不大：床层长度基本不影响透过曲线;Yoon-Nelson模型可以较好的模拟固定床吸附过程。     

混合离子交换树脂除盐的性能研究

研究了强酸型离子交换树脂D072和强碱型离子交换树脂D201混合吸附杂离子的性能。D072和D201的质量比为1∶2,考察其30℃时的吸附特性,结果表明,混合树脂符合兰格缪尔吸附模型,等温吸附平衡方程为q=7.55c/(0.97+c) (R2=0.9971)。此外,考察了树脂固定床的操作性能。进料流速与初始进料浓度对树脂固定床的穿透曲线影响显著,当液相初始进料浓度为800 mg/L、进料速度为3 min/L时,穿透时间为83 min,该操作条件大幅提高了离子交换树脂的吸附效率。     

阴离子树脂HZD-9对丁二酸吸附行为的研究

选用新型阴离子树脂HZD-9对丁二酸进行吸附分离,并运用吸附等温模型、动力学模型以及BDST模型来描述树脂对丁二酸的吸附行为。结果表明:在质量浓度为30 mg/m L、p H值为2.4的丁二酸溶液中HZD-9树脂具有稳定的吸附量,最大吸附量为545.8 mg/g,吸附量随温度的升高、p H值的升高而降低;在实验浓度范围内符合Langmuir吸附等温模型,相关系数R2为0.998 1,吸附为单分子层吸附,吸附行为符合拟二级动力学模型,扩散控制为颗粒扩散控制;BDST模型较好地描述了吸附床层高度和透过时间之间的关系,误差在5%以内;90℃的去离子水洗脱率为57%,0.1 mol/L的盐酸的洗脱率为90%。     

凹凸棒石粘土对Ni(Ⅱ)的动态吸附研究

研究了凹凸棒石粘土对水中Ni(Ⅱ)的动态吸附性能。探讨了Ni(Ⅱ)溶液初始浓度、流速、初始pH值及吸附床高度对穿透曲线的影响,同时采用BDST模型对动态实验数据进行了线性拟合分析,对新的操作条件下的穿透时间进行了预测。结果表明,凹凸棒石粘土能够有效地去除水中的Ni(Ⅱ),随着吸附床高度的增加,穿透时间延长;而随着Ni(...     

D301树脂动态吸附溴离子过程探究及模型拟合

研究了用D301树脂吸附岩盐矿提钾母液中溴离子的可能性，考察了吸附柱动态吸附过程中原料液溴离子初始浓度、床层高度及进料流速等因素的影响。结果表明，增加原料液溴离子初始浓度或降低进料流速能提高树脂单位饱和吸附量。当原料液溴离子初始浓度从1000 mg/L升至4000 mg/L时，树脂单位饱和吸附量从1.8 mg/L增至6.4 mg/mL。增加床层高度或降低进料流速会延长动态吸附突破时间及饱和时间，而原料液溴离子初始浓度对其没有影响。应用了Bed Depth Service Time(BDST), Thomas, Yoon-Nelson, Wolborska及Modified dose response(MDR)等五种吸附模型对动态吸附过程进行拟合，其中MDR模型的拟合效果最佳。D301树脂可用于从含有高浓度氯离子的提钾母液中提取溴离子。     

Adsorption of Carbamazepine in Fixed Bed Columns: Experimental and Modeling Studies

The adsorption of carbamazepine was evaluated on activated carbon in fixed bed columns. The effect of various parameters on breakthrough curves like carbamazepine initial concentrations (1.2, 1.6, and 2.5 mg/L), bed depths (0.4, 0.6, and 0.8 cm) and volumetric flow rates (1.0, 2.0, and 3.0 mL/min) was investigated. The breakthrough time increased with increase of bed depth, and decreased with increase of initial concentration and volumetric flow rate. In order to predict the theoretical breakthrough curves and to determine model parameters, BDST, Thomas, Yoon-Nelson and Clark models were applied to the experimental adsorption processes under the operational conditions described above. The Thomas and Yoon-Nelson models were in good agreement with the experimental data.     

Fixed-bed column study on removal of Mn(II), Ni(II) and Cu(II) from aqueous solution by surfactant bilayer supported alumina

In the present work, the potential of modified alumina for the removal of heavy metals such as Mn(II), Ni(II) and Cu(II) was evaluated in a fixed-bed column operation. The effects of bed depth, flow rate and initial concentration on the removal of Mn(II), Ni(II) and Cu(II) were investigated at the optimum pH. The modified alumina was found to be very efficient for the removal of such heavy metals from water environment. Bed depth service time (BDST) model was best fitted to adsorption data. The theoretical and experimental breakthrough curves were comparable for all heavy metals.     

锰氧化物负载沸石固定床离子交换柱去除铀(VI)的研究

The adsorption of uranium (VI) on the manganese oxide coated zeolite (MOCZ) from aqueous solution was investigated in a fixed-bed column. The experiments were conducted to investigate the effects of bed height, flow rate, particle size, initial concentration of uranium (VI), initial pH, presence of salt and competitive ions. The U-uptake by MOCZ increased with initial uranium (VI) concentration and bed height, but decreased as the flow rate and particle size increased. In the presence of salt and competitive ions, the breakthrough time was shorter. The ad-sorption capacity reached a maximum at pH of 6.3. The Thomas model was applied to the experimental data to de-termine the characteristic parameters of the column for process design using linear regression. The breakthrough curves calculated from the model were in good agreement with the experimental data. The BDST model was used to study the influence of bed height on the adsorption of uranium (VI). Desorption of uranium (VI) in the MOCZ column was investigated. The column could be used for at least four adsorption-desorption cycles using 0.1 mol•L－1 NaHCO3 solution as the elution. After desorption and regeneration with deionized water, MOCZ could be reused to adsorb uranium (VI) at a comparable capacity. Compared to raw zeolite, MOCZ showed better capacity for uranium (VI) removal.     

Experimental study and modelling of an azo colourant dynamic adsorption onto functional cross-linked chitosan/ceramic particles in a fixed bed column

The use of azo dyes in industrial activities generates a large volume of contaminated wastewater; these pollutants in water bodies affect aquatic biota and human health. A functional biocomposite sorbent material was synthesized using cross-linked chitosan with oxalic acid that forms a coating on alumina ceramic particles (AOCh). The removal of Reactive Red 195, a reactive azo dye, using a fixed-bed adsorption column filled with this material was tested. AOCh was physico-chemically characterized by Fourier transform infrared spectroscopy–total attenuated reflection (FTIR-ATR), scanning electron microscopy–energy dispersion spectrometry X-ray (SEM-EDS), X-ray diffraction (XDR), thermo-gravimetric analysis (TGA), and Z-potential. The dynamic adsorption performance was analyzed from experimental breakthrough curves obtained in fixed-bed columns by modifying different operating conditions (bed depth, volumetric flow rate, and dye inlet concentration). Equilibrium adsorption isotherms were determined under dynamic conditions and compared with batch results. The maximum adsorption capacity of the dynamic equilibrium isotherm obtained from the continuous assays was 331 mg/g; this value was the highest in comparison to other tested materials reported in the literature. Different dynamic adsorption models were applied to fit experimental data, including Thomas, Bohart–Admas, Yoon–Nelson, logistic general model, bed depth surface time (BDST), and modified dose response (Yan) models. A critical analysis of these equations was presented, showing the equivalences and the relationship among the coefficients. The Yan model achieved the highest level of agreement between the experimental and predicted values of the breakthrough curves. The use of this model enables scaling-up the industrial process for dye removal. The present work proposed a novel biosorbent material and contributes to the analysis of industrial dye removal under dynamic conditions.     

Simplified fixed bed column model for adsorption of organic pollutants using tapered activated carbon columns

The dynamic adsorption of organic pollutants (an acid dye and para-chlorophenol) has been investigated via tapered column adsorbers using activated carbon. Equilibrium sorption isotherm experiments were determined to provide a crucial parameter, the saturation capacity (q_e) of each pollutant by F 400 carbon, for operating continuous adsorption columns. The Redlich–Peterson isotherm gave the best fit model to describe the sorption process of these organic pollutants onto F 400 carbon. Adsorption studies of organic pollutants have been carried out in novel tapered fixed bed columns using activated carbon. A series of columns with different tapered angles, from one to five degrees, have been used. Experimental data obtained from the breakthrough curves have been analysed using the Bed Depth Service Time (BDST) model in this paper. However, the conventional BDST model has not been applied to tapered beds before, as the linear velocity of adsorbate is changing along the column. Therefore, some modifications have been developed to the original model. The extended-modified BDST model has proved to be successful in correlating the bed height and service time for tapered column adsorption.     

The Effect of Zeolite Fixed Bed Depth on Lead Removal from Aqueous Solutions

Abstract

The effect of zeolite bed depth on lead removal from aqueous solutions by the column method has been examined. The results indicate that the increase of bed depth delays the breakthrough point and exhaustion point, and increases the contact time of the zeolite – lead solution, and the height of the mass transfer zone, h_z. The increase of the bed depth lowers the effect of axial dispersion on the mass transfer process. In order to predict the time necessary for exceeding the defined effluent concentration for a constant bed depth, the bed depth service time (BDST) approach has been used. Experimentally obtained breakthrough curves for the flow rate of 1 ml/min were used to derive the BDST approach equations. These equations were successfully used for modelling of the system for flow rates of 2 and 3 ml/min. The BDST equations have yielded modelled linear equations used for calculation of h_z. The increase of the flow rate increases h_z, which indicates that the zeolite–solution contact time is not sufficient. This may be attributed to the affect of axial dispersion on mass transfer on the solid-liquid interface.