两种大孔吸附树脂对麻黄碱和伪麻黄碱的吸附动力学和热力学研究

通过等温静态吸附实验研究大孔树脂AB-8和D101对麻黄碱及伪麻黄碱的等温吸附过程,根据Langmuir平衡吸附速率方程考察两种树脂对两种成分吸附的平衡速率常数,用Van’t Hoff公式计算各热力学参数(ΔHm,ΔGm及ΔSm)。结果表明麻黄碱、伪麻黄碱的吸附平衡数据符合Freundlich吸附等温方程和Langmuir平衡吸附速率方程,相关性良好。吸附的焓变(ΔHm)和熵变(ΔSm)均大于零,吉布斯自由能变(ΔGm)均小于零,表明麻黄碱及伪麻黄碱在树脂上的吸附属于自发的物理吸附过程。     

原位合成羟基磷灰石/壳聚糖复合吸附剂及除氟特性研究

利用原位共沉淀法合成了羟基磷灰石/壳聚糖复合吸附剂,通过扫描电镜、X射线粉末衍射、红外光谱和N2吸附-脱附曲线,研究复合前后羟基磷灰石的理化特征变化。实验结果表明与壳聚糖复合后羟基磷灰石的晶型并没有改变,只是结晶度有所降低,且复合后表面形成了不规则的凹凸结构,表面粗糙度增加。比表面积从106.75m2/g增加到127.58m2/g。复合吸附剂孔径大部分集中在10~50nm,属于介孔结构。利用Langmuir和Freundlich吸附等温方程对实验数据进行了拟合,对比相关系数R2值,Langmuir模型能更好地描述该吸附过程。复合吸附剂对氟离子的吸附符合拟二级反应动力学方程。计算了吸附热力学和动力学参数值,探讨了复合吸附剂对氟离子的吸附机理。ΔG0<0、ΔH0>0和ΔS0>0,说明复合吸附剂对氟离子的吸附是自发的、吸热的熵增过程,温度升高有利于吸附。吸附活化能(Ea)=15.03kJ·mol-1,迁移能(E)=7.639kJ·mol-1,说明该吸附过程以物理吸附为主。     

气体在固体表面吸附的热力学模型及吸附等温式

描述气体在固体表面吸附的两个著名吸附等温式Langmuir公式和Bronauer—Emmett—Teller(B·E·T)公式可以由动力学方法和统计热力学方法导出。但在导出过程中,都要引进一些基本假定之外的附加限制和近似. 根据经典热力学的唯象特点,能建立气体在固体表面吸附的吸附表面相热力学模型.从吸附平衡是一种热力学相平衡这一观点出发,可以由相平衡原理十分简洁地导出Langmuir吸附等温式和多层吸附的B·E·T吸附等温式.     

金属有机骨架材料MOF-5吸附苯并噻吩性能

苯并噻吩类硫化物的脱除是燃油实现深度脱硫的关键。实验研究了典型的金属有机骨架材料MOF-5吸附苯并噻吩性能。结果表明,MOF-5对模型油中苯并噻吩的吸附动力学过程满足拟二级动力学模型。Langmuir、Freundlich和Dubinin-Radushkevich (D-R) 三种等温吸附模型均可较好地描述MOF-5对苯并噻吩的等温吸附行为 (Freundlich>D-R>Langmuir)。热力学参数表明,MOF-5对苯并噻吩的吸附是自发的吸热吸附过程。     

固相萃取-衍生化气相色谱/质谱法测定制药厂污水中的环境雌激素

采用固相萃取-衍生化气相色谱/质谱法(GC/MS)测定某制药厂污水中的雌酮(E1)、雌二醇(E2)、雌三醇(E3)和乙炔基雌二醇(EE2)4种雌激素化合物。样品经固相萃取柱萃取富集及双(三甲基硅烷基)三氟乙酰胺(1%三甲基氯硅烷)（BSTFA(1%TMCS)）衍生化后进行GC/MS分析。该法对4种目标物的检出限为1.8～4.7 ng/L,相对标准偏差为2.3%～9.1%(n=8)。目标化合物的加标回收率为（94.0±2.9）%～（101±3.8）%,说明该方法能较好地应用于污水中雌激素化合物的定量检测。通过对某制药厂污水中的雌激素进行定量分析,发现污水中乙炔基雌二醇和雌酮质量浓度分别达396.6 和39.9 ng/L;经过传统的厌氧兼氧好氧生物处理后,污水中的环境雌激素的去除率仅为35%～40%,说明传统的污水处理工艺对去除污水中雌激素效果并不明显,需要改进。     

铝掺杂针铁矿的制备、表征及吸附氟的特性

水热条件下制备了针铁矿(Goe)和几种铝掺杂针铁矿(Goe-Al_(0.1),Goe-Al_(0.2)和Goe-Al_(0.4)),用X射线衍射(XRD)、扫描电镜(SEM)、氮气物理性吸附、酸碱滴定等手段对样品进行了表征,并研究了它们对氟离子的吸附特性。结果表明,随着铝掺杂量的增加,铝掺杂针铁矿的结晶度不断减弱、颗粒的长度不断减小。4种样品的微孔表面积、孔体积和表面分形度都表现为GoeGoeAl0.1Goe-Al_(0.2)Goe-Al_(0.4),而孔径分布表现为相反的顺序。Goe、Goe-Al_(0.1)、Goe-Al_(0.2)和Goe-Al_(0.4)的电荷零点(PZC)分别为8.2、8.3、8.5和8.7,pH=5.0时它们的表面电荷量分别为0.66、0.83、1.03和1.19 mmol·g~(-1)。准二级动力学模型适合描述4种样品对氟的吸附动力学过程,表明化学吸附是主要作用机制。一位Langmuir模型可较好的拟合等温吸附数据(R2为0.967~0.981),二位Langmuir模型对等温吸附数据的拟合度更高(R2为0.982~0.995),而Freundlich模型的拟合度较低(R2为0.877~0.912)。初始pH=5.0时,Goe、Goe-Al_(0.1)、Goe-Al_(0.2)和Goe-Al_(0.4)对氟的最大吸附容量分别为8.83、10.24、11.72和12.86 mg·g~(-1)。可见,铝掺杂针铁矿对土-水环境中氟的吸附容量高于纯针铁矿。     

一种钌(Ⅱ)聚吡啶化合物的电化学行为及其对亚硝酸根的催化作用

讨论了钌(Ⅱ)聚吡啶化合物[Ru(bipy)2dppz]2+(bipy=2,2-联吡啶;dppz=吡啶并[3,2-a2′,3′-c]吩嗪)的电化学行为.在盐酸溶液中,化合物在-0.11 V和-0.08 V (vs.SCE)出现一对峰,它在玻碳电极和碳糊电极上均表现出吸附特性.在玻碳电极上的最大吸附量Γmax为2.37×10-11 mol/cm2,吸附系数β0为4.89×105 L/mol,在电极上的吸附行为符合Langmuir吸附等温式.实验中发现该化合物能对亚硝酸根的还原起催化作用.     

纳米TiO_2粒径、孔径对酸性紫43吸附动力学与热力学行为的影响

探究锐钛型纳米TiO2粒径(5-10、25、40、60、100nm)及孔径(96,120,134,143,52)对染料废水(酸性紫43)吸附动力学与热力学行为的影响。假二级方程和准一级方程分别能准确描述TiO2粒径≤100nm吸附动力学过程。经Weber-Morris和Dumwald-Wagner扩散模型分析,吸附速率由膜扩散和内扩散共同控制并受粒径影响。吸附热力学符合Langmuir等温吸附方程,最大吸附量(Qmax)与孔径正相关,与粒径无关,60nm TiO2孔径最大,吸附效果最好,Qm可达104.17mg/g;参数40kJ/mol△H0,吉布斯自由能△G0,受温度影响不大,说明吸附过程是自发的吸热反应,以物理吸附为主。     

阴离子树脂D02吸附2-酮基-L-古龙酸的热力学和动力学研究

应用一种新型的阴离子树脂D02直接吸附发酵液中的2-酮基-L-古龙酸.研究了D02树脂对水溶液中2-酮基-L-古龙酸的吸附热力学和吸附动力学特性.热力学研究表明,2-酮基-L-古龙酸在D02树脂上的吸附平衡数据遵循Langmuir吸附等温方程.吸附过程△G＜0,△S＞0,△H＞0,表明此吸附过程吸热,升高温度有利于吸附反应的发生.动力学研究显示,D02树脂对2-酮基-L-古龙酸的吸附过程主要受内扩散控制.     

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。     

Sulfate adsorption and surface precipitation on a volcanic ash soil (allophanic andisol)

Sulfate strongly adsorbs on metal oxides and soils with variable charges. However, its surface precipitation has not been clearly evaluated and its adsorption mechanism has been in dispute. In the present study, an allophanic andisol, a typical volcanic ash soil having both negative and positive variable charges, was used to identify the adsorption mechanism of sulfate. Sulfate adsorption isotherms were obtained by a batch method at pH values of 4, 5, 6, and 7 in a wide range of concentrations in an Na-H-SO(4)-OH system. Theoretical isotherms were applied to the measured values for the evaluation. The surface precipitation was detected by the measured adsorption isotherms, and the BET isotherm confirmed the presence of multilayer adsorption. Stronger and weaker adsorption sites were suggested by using the Langmuir isotherm for the monolayer adsorption. The adsorption energies obtained from the Langmuir equation and recent spectroscopic analysis suggested that the stronger adsorption corresponded to an inner-sphere surface complex and that the weaker adsorption corresponded to outer-sphere surface complexation. The BET and Langmuir equations showed three types of adsorption mechanisms for the sulfate adsorption on the soil.     

Adsorption characteristics of poly(styrene-co-divinylbenzene) resin functionalized with methoxy and phenoxy groups for phenol

Two macroporous crosslinked poly(styrene-co-divinylbenzene) resins functionalized with methoxy and phenoxy groups, PVBME and PVBPE were prepared and their adsorption characteristics for phenol were studied in hexane as well as in aqueous solution. It was shown that the equilibrium adsorption capacity of phenol onto PVBPE was a little larger than that onto PVBME at the same temperature and equilibrium concentration. The adsorption onto PVBME in hexane can be correlated to Langmuir isotherm model, whereas the semi-empirical Freundlich isotherm model characterized the adsorption onto PVBPE better. The adsorption thermodynamic parameters were calculated and it was found that the adsorption enthalpy, adsorption free energy, and adsorption entropy were all negative, and the adsorption thermodynamic parameters onto PVBPE were more negative than the corresponding ones onto PVBME. The relationship of the adsorption capacity with the equilibrium concentration was linear in aqueous solution. The adsorption was hypersensitive to the solution pH in aqueous solution, and the optimum pH was determined to be 6.0. The adsorption dynamics of phenol onto PVBPE in aqueous solution was investigated and it was seen that the adsorption can be well fitted by the pseudo-first-order rate equation.     

介孔碳CMK-3对苯酚的吸附动力学和热力学研究

研究了介孔碳CMK-3对苯酚的吸附性能, 与传统商用活性碳(CAC)进行了比较, 结果表明, CMK-3比CAC的吸附量大、吸附速率快、达到平衡时间短, 是一种较好的吸附剂. 同时探讨了介孔碳CMK-3对苯酚的吸附热力学和动力学特征. CMK-3对苯酚的吸附行为可用Langmuir和Freundlich等温式进行描述, 相关性都较好, 但更符合Freundlich经验公式. 分别采用模拟一阶反应和二阶反应模型考察了吸附动力学, 并计算了这些动力学模型的速率常数. 模拟二级反应模型和实验数据之间有较好的相关性. 分别计算了热力学参数ΔG0, ΔS0和ΔH0, 结果表明, CMK-3对苯酚的吸附过程是吸热和自发的.     

富锂锂锰氧化物的制备及其在溶液中的抽Li+/吸Li+性能

采用柠檬酸配合法合成了系列尖晶石富锂锂锰氧化物Li2O.nMnO2(n=1.75,2.0,2.25,2.5,3.0)。通过X射线衍射(XRD)和酸浸实验发现,350℃合成的Li2O.2.25MnO2具有纯相尖晶石锂锰氧化物结构,且在弱酸性介质中具有较高的锂溶出率和较低的锰溶损率。Li2O.2.25MnO2在酸浸之后转型为锂离子筛。XRD和扫描电子显微镜(SEM)分析发现锂离子筛能够保持尖晶石锂锰氧化物的结构和形貌。吸附实验表明,该锂离子筛在碱性含锂溶液中对Li+具有吸附性能,且吸附容量随着溶液温度和pH值的升高而增大,最高能达到40.14 mg.g-1。通过傅立叶红外光谱(FTIR)研究了锂离子筛的吸附机理,并用Langmuir模型描述了其在LiCl+LiOH溶液中的吸附行为。     

STUDY ON THE ADSORPTION OF PHENOL BY CHITOSAN FROM AQUEOUS SOLUTION

The effects of pH, initial concentration and temperature on the adsorption of phenol by chitosan were investigated in this paper. The isothermal data was applied to Langmuir linear and the Freundlich linear isotherm equation, and the thermodynamic parameters （AH, AG, AS） were calculated according to the values of binding Langmuir constant, KL. Results indicated that the adsorption between chitosan and phenol was significantly physical in nature, the negative ΔH constant at lower temperature confirmed that more phenol was adsorbed by chitosan at lower temperature. The kinetics of the sorption process of phenol on chitosan was investigated using the pseudo-first order and pseudo-second order kinetics, and results showed that the second order equation model provided the best correlation with the experimental results.     

Decontamination of bisphenol A from aqueous solution by graphene adsorption

The decontamination of bisphenol A (BPA) from aqueous solution by graphene adsorption was investigated. The maximum adsorption capacity (q(m)) of graphene for BPA obtained from a Langmuir isotherm was 182 mg/g at 302.15 K, which was among the highest values of BPA adsorption compared with other carbonaceous adsorbents according to the literature. Both π-π interactions and hydrogen bonds might be responsible for the adsorption of BPA on graphene, and the excellent adsorption capacity of graphene was due to its unique sp(2)-hybridized single-atom-layer structure. Therefore, graphene could be regarded as a promising adsorbent for BPA removal in water treatment. The kinetics and isotherm data can be well described by the pseudo-second-order kinetic model and the Langmuir isotherm, respectively. The thermodynamic studies indicated that the adsorption reaction was a spontaneous and exothermic process. Besides, the presence of NaCl in the solution could facilitate the adsorption process, whereas the alkaline pH range and higher temperature of the solution were unfavorable.     

Kinetics and thermodynamics of the adsorption of some dyestuffs and p-nitrophenol by chitosan and MCM-chitosan from aqueous solution

The effect of initial concentration, temperature, and shaking rate on the adsorption of three dyestuffs [orange II (O-II), crystal violet (CV), and reactive blue 5 (RB5)] and an ideal adsorbate, p-nitrophenol (PNP), by chitosan (Sigma C-3646) and the effect of temperature on the adsorption of O-II and CV by monocarboxymethylated chitosan (MCM-chitosan) were investigated. Kinetic data obtained for the adsorption of each dyestuff and PNP by chitosan and of O-II and CV by MCM-chitosan at different temperatures were applied to the Lagergren equation, and adsorption rate constants (k(ads)) at these temperatures were determined. These rate constants related to the adsorption of O-II and RB5 by chitosan and of O-II by MCM-chitosan were applied to the Arrhenius equation, and activation energies (E(a)) were determined. In addition, the isotherms for adsorption, at different temperatures, of each dyestuff and PNP by chitosan and of O-II and CV by MCM-chitosan were also determined. These isothermal data were applied to linear forms of isotherm equations that they fit, and isotherm constants were calculated. Because the isotherm curves obtained for the adsorption of O-II and CV by chitosan and of CV by MCM-chitosan fit the Langmuir adsorption isotherm, b constants were applied to thermodynamic equations, and thermodynamic parameters (delta G, delta H, and delta S) were calculated. Lastly, chitosan and MCM-chitosan were compared with respect to the ability to take up the dyestuffs and PNP.     

Band splitting in overloaded isocratic elution chromatography II. New competitive adsorption isotherms

The equations of two new binary competitive isotherms models are derived. The first of these models assumes that the isotherms of the two pure, single compounds have distinct monolayer capacities. Its derivation is based on kinetic arguments. The ideal adsorbed solution (IAS) framework was applied to derive the second model that is a thermodynamically consistent competitive isotherm. This second model predicts the competitive adsorption isotherm behavior of a mixture of two compounds that have single-component adsorption behavior following a BET and/or a Langmuir isotherms. Both models apply well to the binary adsorption of ethylbenzoate and 4-tert.-butylphenol on a Kromasil-C18 column (with methanol-water, 62:38, v/v, as the mobile phase). The best single-solute adsorption isotherms of these two compounds are the liquid-solid extended multilayer BET and the Langmuir isotherms, respectively. The kinetic and thermodynamic new competitive models were compared, regarding the accuracy of their prediction of the elution band profiles of mixtures of these two compounds. A better agreement between experimental and calculated profiles was observed with the kinetic model. The IAS model failed because the behavior of the ethylbenzoate/4-tert.-butylphenol adsorbed phase mixture is probably non-ideal. The most striking result is the qualitative prediction by these models of the peak splitting of 4-tert.-butylphenol during its elution in presence of ethylbenzoate.     

Adsorption of polyvinylimidazole onto kaolinite

The adsorption of polyvinylimidazole (PVI) onto kaolinite from aqueous solutions has been investigated systematically as a function of parameters such as calcination temperature of kaolinite, pH, ionic strength, and temperature. According to the experimental results, the adsorption of PVI increases with pH from 8.50 to 11.50, temperature from 25 to 55 degrees C, and ionic strength from 0 to 0.1 mol L(-1). The kaolinite sample calcined at 600 degrees C has a maximum adsorption capacity. Adsorption isotherms of PVI onto kaolinite have been determined and correlated with common isotherm equations such as Langmuir and Freundlich isotherm models. The Langmuir isotherm model appeared to fit the isotherm data better than the Freundlich isotherm model. The physical properties of this adsorbent are consistent with the parameters obtained from the isotherm equations. Furthermore, the zeta potentials of kaolinite suspensions have been measured in aqueous solutions of different PVI concentrations and pH. From the experimental results, (i) pH strongly alters the zeta potential of kaolinite; (ii) kaolinite has an isoelectric point at about pH 2.35 in water and about pH 8.75 in 249.9 ppm PVI concentration; (iii) PVI changes the interface charge from negative to positive for kaolinite. The study of temperature effect has been quantified by calculating various thermodynamic parameters such as Gibbs free energy, enthalpy, and entropy changes. The dimensionless separation factor (RL) has shown that kaolinite can be used for adsorption of PVI from aqueous solutions.     

Adsorption of crystal violet dye from aqueous solution using mesoporous materials synthesized at room temperature

In this work, batch adsorption experiments are carried out for crystal violet dye using mesoporous MCM-41 synthesized at room temperature and sulfate modified MCM-41 prepared by impregnation method using H₂SO₄ as sulfatising agent. The surface characteristics, pore structure, bonding behavior and thermal degradation of both the MCM-41 samples are characterized by nitrogen adsorption/desorption isotherms, X-ray diffraction (XRD) patterns, Fourier transform infrared (FT-IR) spectroscopy and thermo gravimetric analysis (TGA). The adsorption isotherm, kinetics and thermodynamic parameters are investigated for crystal violet (CV) dye using the calcined and sulfated MCM-41. Results are analysed using Langmuir, Freundlich and Redlich-Peterson isotherm models. It is found that the Freundlich model is an appropriate model to explain the adsorption isotherm. The highest adsorption capacity achieved is found to be 3.4×10⁻⁴ mol g⁻¹ for the sulfated MCM-41. The percentage removal of crystal violet dye increases with increase in the pH for both the MCM-41 adsorbents. Kinetics of adsorption is found to follow the second-order rate equation. From the thermodynamic investigation, it is evident that the adsorption is exothermic in nature.