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.     

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。     

Graphene oxide coated wad as a new sorbent in fixed bed column for the removal of crystal violet from contaminated water

An efficient method was developed to fabricate graphene oxide coated cotton wad (GO/W) using self-assembly technique. GO/W could be used as an adsorbent material in remediation of environmental pollutants in a continuous packed bed column. The efficiency of GO/W fixed bed column in the removal of crystal violet (CV) from an aquatic environment was studied. The experimental breakthrough data were modeled using Thomas, Adams-Bohart, and Yoon-Nelson models, and the column parameters for all these models were calculated. Increasing the effluent discharge rate and initial adsorbate concentration make the breakthrough and saturation points to be obtained faster and hence lower the adsorption capacity of column.     

Continuous cadmium removal from aqueous solutions by seaweed in a packed-bed column under consecutive sorption-desorption cycles

Packed-bed column process efficiency for cadmium adsorption from aqueous solution was investigated under different bed heights (2.6 to 7.5 cm) and feed flow rates (15 to 30 ml min^?1). The column was filled with brown seaweed, Sargassum angustifolium. Three simplified models, including Bed Depth Service Time, Thomas, and Yoon-Nelson were employed for describing the experimental breakthrough curves as well as achieving design parameters. Bed lifetime was also evaluated in several consecutive sorption-desorption cycles. Cadmium concentration of 0.005mg l^?1, as a standard limit for potable water, was considered as the breakthrough concentration. The maximum column performance was achieved 81% at 7.5 cm bed length and flow rate of 15 ml min^?1. Indeed, increasing the bed height increased the sorption performance and service time, while increasing the feed flow rate had a negative effect. Maximum sorption capacity value remained almost constant by the bed height changes; however, increase in the feed flow rate slightly decreased it. The modeling results revealed that the Yoon-Nelson model was more accurate than Thomas for describing the experimental breakthrough data, especially at low flow rates. Column service time predictions were surprisingly achieved using the Bed Depth Service Time model even at extrapolations. 20% reduction in column adsorption efficiency was observed at the end of four consecutive sorption-desorption cycles; however, desorption efficiencies were achieved more than 99% in each cycle.     

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。     

Influence of TiO2‐Layer Thickness of Spray‐Coated Glass Beads on Their Photocatalytic Performance

TiO₂ is a suitable catalyst for potential photocatalytic processes, e.g., in wastewater treatment. For a technical realization of such processes, the application of immobilized TiO₂ in a continuous process would be desirable. However, since UV radiation has a limited penetration depth into a packed bed of pure TiO₂, supporting it on UV‐transparent glass beads offers the possibility to implement continuous photocatalytic processes in a fixed‐bed reactor. Considering this fact, glass beads were coated with TiO₂ powder in a fluidized‐bed reactor. The coated glass beads with varying TiO₂ layer thickness were tested in the photocatalytic degradation of methylene blue, and the influence of an addition of methyl cellulose during the coating process on the photocatalytic performance was investigated.     

Effect of coating method on gas separation by PDMS/PES membrane

In this study, polydimethylsiloxane (PDMS)‐coated polyethersulfone (PES) composite membrane was prepared for gas separation. “Film casting” and “dip‐coating” techniques were used for producing selective PDMS layer on the surface of the PES support. The effects of coating technique and conditions including coating solution concentration and curing temperature on permselectivity of CO₂, CH₄, and N₂ were investigated. The prepared PES support did not provide any selectivity to the gases. When the concentration of PDMS coating solution was increased, initially permeability of CO₂ was rapidly dropped and then gradually reached to an almost constant value. The optimum concentration of coating solution was 5 wt%. Curing temperature showed no pronounced effect on the CO₂ permeability and selectivity. In “film casting” method, double coating showed superior permeability and selectivity. However, triple “dip‐coating” was promising. The selectivity of composite membrane prepared by “dip‐coating” was higher than “film casting” method. CO₂/N₂ and CO₂/CH₄ selectivity of five sequential dip‐coated composite membranes was 45.5 and 9.3, respectively. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers     

Kinetics and optimization of L-tryptophan separation with ion-exchange chromatography

Adsorption and desorption of L-tryptophan (L-trp) on strong acid cation exchange resin were investigated in a fixed-bed column. L-trp was effectively adsorbed onto the resin HZ-001, with the loading capacity and breakthrough time determined. Four kinetic models, including Adams-Bohard, Wolborska, Thomas, and Yoon-Nelson models, were adopted to determine the kinetic parameters of adsorption and to predict the breakthrough curves. The results showedthat the models used described the breakthrough well. Desorption of L-trp from the column bed was performed usingaqueous ammonia as the eluant. Optimum procedure was obtained with 2.0 M aqueous ammonia at the elution velocityof 6 BV/h. Five cycles of adsorption-elution-regeneration were conducted to evaluate the column reutilization.     

Fluidized Bed Generation of Stable Silica Nanoparticle Aerosols

A long-lasting generator of continuous silica nanoparticle aerosols based in a fluidized bed of glass beads coated with nanosized silica has been developed. The attrition resulting from the bubbling fluidized bed regime progressively detaches the silica coating from the glass beads, giving rise to a steady production of silica nanosized aerosols with median diameters from 100 to 250 nm depending on the initial size of the coating nanoparticles. Continuous aerosol production could be maintained for more than 12 h, and the nanoparticle concentration can be easily tuned in the range of 2000 to 14,000 #/cm³ by adjusting the fluidization and/or dilution flow rates.

Copyright 2013 American Association for Aerosol Research     

低浓度甲苯和对二甲苯在微纤包覆活性炭结构化固定床上的竞争吸附

通过湿法造纸技术制备了微纤包覆活性炭复合材料,研究了甲苯和对二甲苯在基于微纤复合材料结构化固定床上的吸附透过行为. 结果表明,颗粒活性炭被很好地包覆在烧结锁定的三维网络中,活性炭包覆前后的比表面积分别为976和955 m2/g,微孔体积分别为0.261和0.247 cm3/g;甲苯和对二甲苯在单一颗粒碳固定床和结构化固定床上的吸附均展示出竞争吸附特性,在两床层中均是甲苯先透过. 在5%透过浓度下,甲苯和对二甲苯在结构化固定床上的透过时间较在颗粒碳固定床上分别延长了20和30 min,甲苯和对二甲苯分离时间增加了10 min. 采用Yoon-Nelson模型对透过曲线进行拟合,相关系数R2>0.98,甲苯和对二甲苯在结构化固定床上的吸附速率常数分别为颗粒碳固定床的3和1.6倍.     

Preparation and photocatalytic performance of nano-TiO2-coated beads for methylene blue decomposition

Fluidized bed chemical vapor deposition (FB-CVD) method using tetra iso-propoxide as a precursor of TiO₂ was applied to achieve TiO₂ coating onto various types of beads. The substrates of the beads included alumina, silica-gel, and glass, and these beads were of small diameter (ca. 1–2 mm). From our investigation of TiO₂-coated surfaces of these beads, we observed formation of TiO₂ coating down to ～35 nm in thickness. In addition, we found that both the type of the substrate and condition of coating process had effect on the surface morphology of coated beads. From combined studies of the surface morphology and the photocatalytic decomposition of methylene blue, we detected characteristic features of coated surface which were associated with high photocatalytic performance. Provided are the explanations to account for the high photocatalytic performance found for TiO₂-coated beads of silica-gel substrate.     

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.     

石墨烯基铁氧化物对水体中草甘膦的动态吸附性能及模型

采用热沉积法制备出石墨烯/四氧化三铁（RGO-Fe₃O₄）复合材料,针对草甘膦（GLY）污染水体,开展该吸附材料对GLY的动态柱实验,通过考察污染物浓度、pH、流速、柱高等因素对穿透过程的影响,研究复合材料对GLY的动态吸附性能,并结合扫描电子显微镜（SEM-EDS）、X射线光电子能谱仪（XPS）、全自动比表面和孔隙分析仪（BET）等表征手段和Thomas、Yoon-Nelson和Yan等吸附模型分析吸附机理。实验结果表明：随着柱高增加,穿透时间延长,吸附柱对GLY的吸附总量增大;随着GLY初始浓度的升高,穿透时间缩短,吸附柱对GLY的吸附总量增大;随着流速和pH的升高,穿透时间缩短,吸附柱对GLY的吸附总量减小。此外,Thomas、Yoon-Nelson和Yan模型拟合得到的R²均大于0.9,且理论单位吸附量均与实际值相差不大,即3种模型均可较好地描述石墨烯复合材料对GLY的动态吸附过程。本实验的研究对石墨烯材料的推广应用及实际GLY污染水体的修复具有重要意义。     

Chromatographic Fractionation of Polymers: The Effect of Column Length

Abstract

Two amorphous polymers, polystyrene and polyisobutene, have been fractionated in an attempt to optimize performance in column fractionation of polymers. We have studied the elution of the polymer from the glass beads on which the polymer is initially coated prior to passage through the column, and also varied the column length, i. e., the depth of the bed of uncoated glass beads in the column. The results that great care must be taken in this initial coating step, and that the length of column through which the polymer is eluted after this step is not of significant importance in achieving sharp fractions.     

Preparation of Microfibrous Entrapped Activated Carbon Composites and its Application for Benzene Adsorption

Microfibrous composites consisting of 150-200 μm activated carbon particles entrapped in 6.5 μm stainless steel fibers were prepared by wet layup papermaking and sintering process. The effects of a variety of operation parameters on the properties of microfibrous composites were investigated. The composite bed with microfibrous entrapped activated carbon was developed to purify air contaminated with benzene. The experimental results showed that the microfibrous composite with a ratio of 13:6 (W/W, carbon/ fibers) was of a relatively higher carbon entrapment ratio under the conditions of adding 2 L water, stirring at 50 Hz for 10 min, and then sintering at 1050^°C for 20 min. The breakthrough time of 5.0 cm composite bed increased by 28 min compared with that of a 5.0 cm individual GACs bed, and bed utilization increased 18.4% at 1% breakthrough concentration. The Bohart-Adams and Yoon-Nelson models were applied to analyze the experimental data of composite bed. The Bohart-Adams model fitted well with the experimental data for the C/C₀ region up to 0.5 but showed large discrepancies above this value. The Yoon-Nelson model predicted values were in very good agreement with the experimental results in the C/C₀ region above 0.05.     

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。     

Influence of Polymeric Suspension Characteristics on the Particle Coating in a Spouted Bed

Abstract

The influence of the coating suspensions and particle properties on the coating process in a conventional spouted bed is presented. Glass beads were coated at fixed operating conditions with different formulations of aqueous polymeric coating suspensions in a spouted bed of laboratory scale. The wettability of the solids by the liquid was quantified by the contact angle and surface tension of the coating suspensions. The coating efficiency and particle growth were correlated with the adhesion of the coating suspension to the solid particle, which is a function of the solids and liquid characteristics. The physical properties of the coated particles—particle mean diameter, sphericity, bulk, absolute and apparent densities, porosity and flow velocity—were determined and compared to the properties of uncoated particles.     

Column breakthrough studies for the removal and recovery of phosphate by lime-iron sludge: Modeling and optimization using artificial neural network and adaptive neuro-fuzzy inference system

Increases in the treatment of water to meet the growing water demand ultimately result in unmanageable quantities of residuals, the handling, and disposal of which is a major environmental issue. Consequently, research into beneficial reuse of water treatment residuals continues unabated. This study investigated the applicability of lime-iron sludge for phosphate adsorption by fixed-bed column adsorption. Laboratory-scale experiments were conducted at varying flow rates and bed depths. Fundamental and empirical models(Thomas, Yan,Bohart-Adams, Yoon-Nelson, and Wolboroska) as well as artificial intelligence techniques(Artificial neural network(ANN) and Adaptive neuro-fuzzy inference system(ANFIS)) were used to simulate experimental breakthrough curves and predict column dynamics. Increase in flow rate resulted in reduced adsorption capacity.However, adsorption capacity was not affected by bed depth. ANN was superior in predicting breakthrough curves and predicted breakthrough times with high accuracy(R~20.9962). Na OH(0.5 mol·L~(-1)) was successfully used to regenerate the adsorption bed. After nine cyclic adsorption/desorption runs, only a marginal decrease in adsorption and desorption efficiencies of 10% and 8% respectively was observed. The same regenerate Na OH solution was reused for all desorption cycles. After nine cycles the eluent desorbed a total of 1550 mg phosphate exhibiting potential for further reuse.     

Preparation and evaluation of chitosan‐coated polyphosphazene hydrogel beads for drug controlled release

Chitosan‐coated polyphosphazene‐Ca²⁺ hydrogel beads were fabricated by dropping polyphosphazene into CaCl₂/chitosan gelling solution. Polyphosphazene used here was a water‐soluble degradable polyanion (PCPAP), which carried almost two carboxylatophenamino groups on each phosphorus atom of the polymer backbone. Two kinds of turbidimetric titration were applied in this study to reveal the interaction between PCPAP and chitosan within the pH range of 4.57≈7.14. The effect of gelling solution pH on the properties of chitosan‐coated PCPAP beads was especially emphasized. It was found that the PCPAP/chitosan complex prepared at relatively high pH (pH 6.5) dissociated most slowly in pH 7.4 phosphate‐buffered solution (PBS). The erosion of chitosan‐coated beads and the release of model drug (Coomassie brilliant blue and myoglobin) in PBS were both obviously prolonged with the increase of gelling solution pH, exhibiting perfect accordance with the behavior of complex dissociation. In addition, the coating of PCPAP/chitosan complex on the bead surface facilitated the improvement of drug loading efficiency. The higher the gelling solution pH, the more the drug loading efficiency improved. At pH 6.5 (PCPAP 5%, CaCl₂ 7%, chitosan 0.3%), the loading efficiency of myoglobin in beads reached as high as 93.2%. These results indicate that the chitosan‐coated polyphosphazene‐ Ca²⁺ bead is a potential formulation for drug controlled release. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1993–1999, 2004     

Fixed‐Bed Adsorption of Allura Red Dye on Chitosan/Polyurethane Foam

The potential of a chitosan/polyurethane foam (CTS/PU) fixed‐bed column for the removal of Allura Red dye (AR) from aqueous solutions was evaluated. Breakthrough curves were constructed under different conditions and optimized using response surface methodology (RSM). The empirical models Thomas, Yoon‐Nelson, and Bed Depth Service Time (BDST) were fitted to the experimental data. The dynamic models of Yoon‐Nelson and BDST accurately fitted the experimental data. As a result, CTS/PU can be successfully applied in a fixed‐bed adsorption operation to remove AR dye.