HPD-100树脂吸附小檗碱的热力学及动力学研究

研究了小檗碱在HPD-100树脂上的吸附热力学和动力学行为。考察了小檗碱在HPD-100树脂上的吸附等温曲线和吸附动力学曲线,确定了吸附过程的热力学及动力学参数。结果表明,HPD-100树脂对小檗碱的等温吸附可采用Langmuir方程描述、吸附为自发进行的放热型物理吸附过程;Dunwald–Wagnen内扩散方程能较好地拟合吸附动力学数据,吸附过程以颗粒内扩散为主要控制步骤,该吸附过程的表观活化能为29.11kJ/mol。本文为HPD-100树脂分离富集小檗碱类生物碱的实际应用提供基础数据及指导。     

SH15树脂吸附胞二磷胆碱的热力学及动力学研究

静态条件下,研究了SH15树脂吸附水溶液中胞二磷胆碱(CDPC)的热力学和动力学特性.测定了不同温度下,热力学性质的变化.实验结果表明,SH15树脂对CDPC吸附平衡数据符合Langmmuir吸附等温方程,吸附过程为自发的物理吸附过程.考察了温度、溶液浓度、树脂粒径和搅拌速率对吸附过程的影响.运用动边界模型(MBM)描述了SH15树脂吸附CDPC的动力学过程,确定在实验条件范围内,SH15树脂吸附CDPC的吸附速度受颗粒扩散控制,并计算出吸附过程的表观活化能为9.73kJ/mol,反应级数为0.47,速率常数为0.0744,并推导出CDPC:在SH15树脂上的动力学总方程.     

黄姜黄色素在大孔树脂上的吸附动力学研究

采用静态法考察了8种大孔吸附树脂对黄姜黄色素的吸附及解吸特性,筛选出LX-18G树脂具有较高的吸附选择性和良好的脱附性能.以LX-18G树脂对黄姜色素的吸附平衡和吸附动力学进行了深入探讨,测定了不同温度下黄姜色素在该树脂上的吸附等温线,以及不同温度,初始液浓度和转速下的吸附动力学曲线.结果表明,Langmuir方程可更好地描述黄姜色素在该树脂上的吸附平衡.吸附动力学规律可用二级速率方程表示,液膜扩散和颗粒内扩散分别是吸附初期和吸附后期的主要速率控制步骤,吸附活化能为5.37kJ/mol.     

201×7强碱性阴离子交换树脂吸附浓海水中溴的热力学研究

研究了201×7强碱性阴离子交换树脂吸附浓海水中溴的热力学行为,测定了不同温度下的吸附等温线,并计算出吸附过程的热力学参数ΔG、ΔH和ΔS。研究表明,该树脂对溴的吸附容量为2.489mg Br2/mL湿树脂,吸附率达到98%;吸附平衡数据符合Langmuir吸附等温方程;ΔG为负值,该吸附过程可自发进行;ΔH>0,且其绝对值小于40kJ/mol,表明该吸附过程吸热且属于物理吸附;ΔS>0,该吸附过程属于熵增过程。     

西藏雪莲总黄酮在大孔吸附树脂上的吸附动力学和热力学研究

研究大孔吸附树脂对西藏雪莲总黄酮的静态吸附动力学和热力学特性。静态吸附、解吸实验结果表明,在所选8种大孔吸附树脂中,XDA-8树脂对西藏雪莲总黄酮的吸附率和解吸率均最高。静态吸附动力学实验结果表明,303K、313K、323K时,XDA-8树脂对西藏雪莲总黄酮的吸附过程符合二级动力学方程,拟合值与实验值较接近,粒内扩散与膜扩散均影响吸附。热力学实验结果表明,XDA-8树脂对西藏雪莲总黄酮的吸附符合Freundlich模型,热力学参数ΔH0、ΔG0、ΔS0,由此可知,西藏雪莲总黄酮在XDA-8树脂上的吸附过程为吸热、熵增过程,可以自发进行,升高温度有利于吸附的进行。     

DuoliteA-30树脂对5’-三磷酸尿苷的静态吸附热力学及动力学特征

研究了DuoloyeA-30树脂对水溶液中5'-三磷酸尿苷(UTP)的静态吸附热力学和动力学特征,测定了不同温度下吸附等温线热力学性能的变化,利用热力学函数关系计算了吸附焓、自由能和吸附熵,确定在实验范围内,DuoliteA-30树脂对UTP的吸附符合Langmuir吸附等温式,吸附过程为自发的吸热过程.考察了温度、浓度、粒径、溶液pH值和搅拌速度对交换过程的影响,运用动边界模型(MBM)描述交换过程的动力学,确定在实验范围内离子交换行为的速度控制步骤为颗粒扩散,并推算出了交换过程的表观活化能,反应级数以及速率常数,得到了UTP在DuoliteA-30树脂上的动力学总方程.     

氨基修饰聚苯乙烯树脂对酚酸物质的吸附性能

通过对XAD 4聚苯乙烯树脂的氨基修饰制备了一种亲水性的NDA 10 0树脂 .研究了NDA 10 0树脂对苯酚和对羟基苯甲酸等酚酸类物质的吸附动力学和热力学行为 .结果表明 ,NDA 10 0树脂对苯酚和对羟基苯甲酸具有良好的吸附性能 ,在研究的浓度范围内 ,吸附平衡数据符合Langmuir和Freundlich等温吸附方程 ,吸附为放热的物理吸附过程 .吸附动力学符合Lagergren准二级速率方程 ,颗粒内扩散为吸附速率的主要控制步骤 .     

大孔树脂吸附苯和甲苯的平衡及动力学研究

研究并比较了四种大孔吸附树脂对正庆烷中低浓度苯、甲苯的吸附平衡及动力学。Langmuir方程能够良好地描述吸附等温线,由单组分吸附平衡得到的参数;可以很好地预测双组分吸附平衡。动力学研究表明,内扩散过程是决速步,并估算出粒内扩散系数。     

疏水/亲水性聚二乙烯基苯/聚丙烯酸大孔互穿聚合物网络树脂对苯胺的吸附性能

采用分步悬浮聚合法制备了聚二乙烯基苯/聚丙烯酸甲酯（PDVB/PMA）大孔互穿聚合物网络,将其中的聚丙烯酸甲酯转化为聚丙烯酸,得到具有疏水/亲水性能的聚二乙烯基苯/聚丙烯酸（PDVB/PAA）大孔互穿聚合物网络（IPN）,研究了这类疏水/亲水大孔PDVB/PAA IPN对苯胺的吸附热力学和吸附动力学,测定了该树脂的孔结构、含水量、弱酸交换量和溶胀性能;测定了该树脂对苯胺在不同温度下的吸附等温线,利用热力学函数关系计算了吸附焓、自由能和熵。 红外光谱显示,成功合成了疏水/亲水PDVB/PAA IPN,与PDVB、PDVB/PMA IPN树脂相比,其BET表面积以及孔容均减小,含水量为62.73％,弱酸交换量为1.91 mmol/g;对苯胺的吸附为放热、自发的过程;溶胀实验、静态解吸实验表明,PDVB/PAA IPN树脂中疏水性的PDVB网具有疏水作用吸附能力,亲水性的PAA网具有氢键作用吸附能力。 对苯胺的吸附在90 min时即可达到吸附平衡,树脂吸附苯胺符合一级速率方程,吸附速率主要受颗粒内扩散的控制,同时还受液膜扩散的影响,吸附动力学可采用HSDM模型描述。     

D-101大孔吸附树脂对黄花蒿黄酮的吸附热力学和动力学研究

通过静态吸附实验,研究了D-101大孔吸附树脂对黄花蒿黄酮的吸附热力学和动力学过程。结果表明,当温度在298~318K和在实验研究浓度范围内,D-101大孔吸附树脂对黄花蒿黄酮的吸附符合Freundlich等温吸附方程;ΔG0,吸附过程能自发进行;ΔH0,为放热过程;ΔS0,D-101大孔吸附树脂吸附黄花蒿黄酮的作用大于水的解吸过程,导致熵减。分别采用准一级动力学方程、准二级动力学方程和粒内扩散动力学模型探讨其吸附特性,研究结果表明,吸附过程符合准二级动力学方程,粒内扩散与膜扩散交互控制黄花蒿黄酮在D-101大孔吸附树脂上的吸附。     

Characteristic and mechanism of Cr(Ⅵ) adsorption by ammonium sulfamate-bacterial cellulose in aqueous solutions

A new adsorbent, ammonium sulfamate-bacterial cellulose (ASBC), was prepared through chemical modifications of bacterial cellulose. The process of adsorbing Cr(Ⅵ) including its isotherm and kinetics, was measured and studied. The results showed that pH value was a very important parameter to the adsorbing efficiency. The adsorption kinetics can be described by a pseudo-second rate model and a particle diffusion equation. Both physical and chemical adsorptions existed in the adsorption process, but chemical adsorption was more dominatant. And particles internal diffusion was not the only rate controlling step. The adsorption equilibrium can be described by the Langmuir type, which indicated that a typical single-molecule layer adsorption of Cr(Ⅵ) by ASBC could be described. And the rate of adsorption followed the Slips model well, which indicated that ASBC had some multiphase and asymmetry. The coordination adsorption and ion exchange effect were the main mechanisms of chemical adsorption. The absorbed Cr(Ⅵ) can be desorbed effectively by 0.5 mol/L EDTA or HCl from the adsorbent, which could make it be reusable.     

Equilibrium and kinetics of water adsorption in carbon molecular sieve: theory and experiment

Measurements of water adsorption equilibrium and kinetics in Takeda carbon molecular sieve (CMS) were undertaken in an effort to characterize fundamental mechanisms of adsorption and transport. Adsorption equilibrium revealed a type III isotherm that was characterized by cooperative multimolecular sorption theory. Water adsorption was found to be reversible and did not display hysteresis upon desorption over the conditions studied. Adsorption kinetics measurements revealed that a Fickian diffusion mechanism governed the uptake of water and that the rate of adsorption decreased with increasing relative pressure. Previous investigations have attributed the observed decreasing trend in the rate of adsorption to blocking of micropores. Here, it is proposed that the decrease is attributed to the thermodynamic correction to Fick's law which is formulated on the basis of the chemical potential as the driving force for transport. The thermodynamically corrected formulation accounted for observations of transport of water and other molecules in CMS.     

Kinetic modeling of liquid-phase adsorption of reactive dyes on activated carbon

In this paper, adsorption equilibrium and kinetics of three reactive dyes from their single-component aqueous solutions onto activated carbon were studied in a batch reactor. Effects of the initial concentration and adsorbent particle size on adsorption rate were investigated Adsorption equilibrium data were then correlated with several well-known equilibrium isotherm models. The kinetic data were fitted using the pseudo-first-order equation, the pseudo-second-order equation, and the intraparticle diffusion model. The respective characteristic rate constants were presented. A new adsorption rate model based on the pseudo-first-order equation has been proposed to describe the experimental data over the whole adsorption process. The results show that the modified pseudo-first-order kinetic model generates the best agreement with the experimental data for the three single-component adsorption systems.     

Diffusion Mechanisms of Biosorption of Cr(VI) onto Powdered Cotton Stalk

The present study investigates biosorption diffusion mechanism for the removal of toxic hexavalent chromium from aqueous solution using powdered cotton stalk an agricultural waste biomass. The effects of pH, temperature, adsorption isotherms, adsorption kinetics, and thermodynamic on chromium biosorption were investigated. The results showed that a maximum removal efficiency of 95% was achieved at pH 2. The pH at zero point charge (pH_zpc) on biosorbent surface was 4.3. The adsorption kinetics showed that the pseudo-second order rate expression fitted well the biosrption process. The equilibrium isotherm was measured experimentally and results were analyzed by Langmuir, Freundlich, and Temkin isotherms using linearized correlation coefficients. The significant parameters for isotherms were determined. The Langmuir adsorption isotherm relative to two other isotherms was found to fit the equilibrium data best for chromium adsorption. Thermodynamic studies reveal that the biosorption of Cr(VI) on cotton stalk was endothermic, spontaneous and occurs with increase in disorder at solid-liquid interface. Adsorption diffusion kinetic was further analyzed and showed that biosorption mechanism was totally controlled by intraparticle diffusion mechanism.     

Contribution of concentration-dependent surface diffusion in ternary adsorption kinetics of ethane, propane and n-butane in activated carbon

The role of concentration-dependent surface diffusion in the adsorption kinetics of a multicomponent system is investigated in this paper. Ethane, propane and n-butane are selected as the model adsorbates and Ajax activated carbon as the model adsorbent. Adsorption equilibrium isotherm and dynamic parameters extracted from single-component systems are used to predict the ternary adsorption equilibria and kinetics. The effect of concentration-dependent surface diffusion on the adsorption kinetics predictions is studied by comparing the results of two mathematical models with the experimental data. Three diffusion mechanisms, macropore, surface and micropore diffusions are incorporated in both models. The distinction between these two models is the use of the chemical potential gradient as the driving force for the diffusion of the adsorbed species in one model and the concentration gradient in the other. It was found that the model using the chemical potential gradient provides a better prediction of the ternary adsorption kinetics data, suggesting the importance of the concentration dependency of the surface diffusion, which is implicitly reflected in the chemical potential gradient. The kinetic model predictions are also affected by the way how single-component adsorption equilibrium isotherm data are fitted.     

烷基聚葡糖苷溶液的表面吸附平衡与动力学

用吊片法和气泡最大压力法分别测定了烷基聚葡糖苷(APG)C₉.₆G_1.3水溶液的平衡和动态表面张力,研究了APG水溶液表面的吸附平衡、动力学及其影响因素.测得其cmc(临界胶束浓度)为0.032g/L.吸附过程由初始的扩散控制转变到势垒控制,吸附势垒为4～7kJ/mol.温度升高,平衡和动态表面张力均减小,吸附量增加;加入无机盐,平衡和动态表面张力增大,吸附量亦增加;醇类的吸附使动态表面张力下降速率加快,表明APG与醇分子间有协同吸附作用.     

Retention equilibrium and mass transfer characteristics in reversed-phase liquid chromatography using methanol-water mixtures

Pulse response experiments (i.e., elution chromatography) were made in reversed-phase liquid chromatography (RPLC) using a C18 silica gel column and methanol-water mixtures of different compositions (phi). The moment analysis of the elution peak profiles measured in the RPLC system provided some items of information about four parameters characterizing the retention equilibrium and the mass transfer kinetics in the column, i.e., adsorption equilibrium constant, isosteric heat of adsorption, surface diffusion coefficient and activation energy of surface diffusion. Characteristics of the chromatographic behavior were studied by analyzing the dependence of the four parameters on phi and the correlation between them. It was found that surface diffusion was one of the important processes of molecular migration having a significant contribution to the mass transfer kinetics in the column. Both the adsorption equilibrium constant and the surface diffusion coefficient varied depending on phi. The direction of their changes was approximately opposite, suggesting that the mass transfer in the manner of surface diffusion was restricted owing to the retention of the sample molecules on the stationary phase.     

一种球形木质素吸附剂对L-天门冬氨酸的吸附行为研究

以硫酸盐木质素为原料,利用反相悬浮技术制备出球形木质素吸附剂.通过静态吸附试验,研究了球形木质素吸附剂对L-天门冬氨酸的吸附动力学和热力学特性,探讨了pH对吸附过程的影响.结果表明,当溶液pH值为3.0时,SLA的平衡吸附容量为518.0mg/g,球形木质素吸附剂对L-天门冬氨酸的吸附速率同时受液膜扩散和颗粒内扩散过程控制.吸附符合Langmuir和Freundlich等温吸附方程.且焓△H-16.81kJ/mol,表明该吸附反应是以吸热的化学吸附过程为主,活化能Ea=3.3406kJ/mol,说明球形木质素吸附剂的吸附过程是以颗粒内扩散为主.     

大孔吸附树脂对邻甲酚的吸附行为研究

研究了大孔吸附树脂NDA—909吸附水溶液中邻甲酚的热力学特征，并与Amberlite XAD—4树脂进行了比较．通过吸附动力学实验，初步探讨了初始温度对吸附过程的影响。结果表明，NDA—909对邻甲酚的吸附符合Freundlich经验公式，表现为放热的物理吸附过程．此外吸附速率受颗粒内扩散和其它类型扩散的共同控制。