PREPARATION AND CHARACTERIZATION OF NOVEL CHITOSAN DERIVATIVES:ADSORPTION EQUILIBRIUM OF IRON(Ⅲ)ION

The adsorption of Fe(Ⅲ)ions from aqueous solution by chitosan alpha-ketoglutaric acid(KCTS)and hydroxamated chitosan alpha-ketoglutaric acid(HKCTS)was studied in a batch adsorption system.Experiments were carried out as function of pH,temperature,agitation rate and concentration of Fe(Ⅲ)ions.The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms and isotherm constants were determined.The Langmuir model agrees very well with experimental data.The pseudo-first-order and second-order kinetic models were used to describe the kinetic data and the rate constants were evaluated.The dynamical data fit well with the second-order kinetic model.The pseudo second-order kinetic model was indicated with the activation energy of 19.61 and 7.98 KJ/mol for KCTS and HKCTS,respectively.It is suggested that the overall rate of Fe(Ⅲ)adsorption is likely to be controlled by the chemical process.Results also showed that novel chitosan derivatives(KCTS and HKCTS)were favorable adsorbents.     

PREPARATION AND CHARACTERIZATION OF NOVEL CHITOSAN DERIVATIVES: ADSORPTION EQUILIBRIUM OF IRON(Ⅲ) ION

The adsorption of Fe(Ⅲ)ions from aqueous solution by chitosan alpha-ketoglutaric acid(KCTS)and hydroxamated chitosan alpha-ketoglutaric acid(HKCTS)was studied in a batch adsorption system.Experiments were carried out as function of pH,temperature,agitation rate and concentration of Fe(Ⅲ)ions.The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms and isotherm constants were determined.The Langmuir model agrees very well with experimental data.The pseudo-first-order and second-order kinetic models were used to describe the kinetic data and the rate constants were evaluated.The dynamical data fit well with the second-order kinetic model.The pseudo second-order kinetic model was indicated with the activation energy of 19.61 and 7.98 kJ/mol for KCTS and HKCTS,respectively.It is suggested that the overall rate of Fe(Ⅲ)adsorption is likely to be controlled by the chemical process.Results also showed that novel chitosan derivatives(KCTS and HKCTS)were favorable adsorbents.     

Excitation-emission-kinetic fluorescence coupled with third-order calibration for quantifying carbaryl and investigating the hydrolysis in effluent water

A novel method for determination of carbaryl in effluent was proposed in this study. The kinetic evolution of excitation-emission matrix fluorescence (EEM) for the pesticide were recorded and come into being a four-way data array. The four-way fluorescence data were analyzed using the parallel factor analysis (PARAFAC). The methodology exploits the second-order advantage of three-order calibration based on quadrilinear parallel factor analysis, allowing analyte concentrations to be estimated even in the presence of an uncalibrated fluorescent background. It gave the satisfactory results for determination of the carbaryl in effluent samples. In addition, the kinetic study of degradation of carbaryl was performed according to the kinetic profile provided by the calibration.     

过渡金属Schiff碱配合物的研究(Ⅱ)——N-水杨醛甘氨酸三吡啶合镍(Ⅱ)热分解非等温动力学的研究

对由水杨醛及其衍生物所形成的Schiff碱配合物的研究已有不少报道,其中一些配合物具有抑菌、抗癌和抗病毒活性,可作为生物氧载体的模型化合物.     

Isolation and partial characterization of a biosurfactant mixture produced by Sphingobacterium sp. isolated from soil

The concentration decay curves for the adsorption of phenol on organobentonite were obtained in an agitated tank batch adsorber. The experimental adsorption rate data were interpreted with diffusional models as well as first-order, second-order and Langmuir kinetic models. The surface diffusion model adjusted the data quite well, revealing that the overall rate of adsorption was controlled by surface diffusion. Furthermore, the surface diffusion coefficient increased raising the mass of phenol adsorbed at equilibrium and was independent of the particle diameter in the range 0.042-0.0126 cm. It was demonstrated that the overall rate of adsorption was essentially not affected by the external mass transfer. The second-order and the Langmuir kinetic models fitted the experimental data quite well; however, the kinetic constants of both models varied without any physical meaning while increasing the particle size and the mass of phenol adsorbed at equilibrium.     

固定化脲酶催化作用下双醛纤维素对尿素氮的吸附平衡和动力学

研究了在固定化脲酶催化作用下双醛纤维素对尿素氮的吸附平衡和动力学. 吸附过程符合Langmuir方程, 为单分子层化学吸附. 考察了双醛纤维素的氧化度、初始尿素氮浓度、双醛纤维素与固定化脲酶的质量比和温度等对双醛纤维素吸附尿素氮的影响, 结果表明上述因素对尿素氮的吸附均有较显著的影响. 实验数据能很好地拟合准二级吸附速率方程, 说明该吸附过程遵从二级动力学模型. 当氧化度为88%的双醛纤维素与固定化脲酶的质量比为10∶1, 尿素氮浓度为638.3 mg•L^－1时, 由Arrhenius方程求得表观吸附活化能为6.0 kJ•mol^－1, 该吸附过程为吸热反应.     

胺基化壳聚糖微球上染料的吸附平衡和动力学

采用胺基化壳聚糖微球作为吸附剂,对三种阴离子偶氮染料——甲基橙MO[MethylOrange],活性艳红RR2[ReactiveRed2]和直接黑DB19[DirectBlack19]进行吸附,对此过程的吸附平衡和吸附动力学进行了研究。结果表明,三种染料的吸附体系是以物理吸附为主,兼有化学吸附,属多层吸附;二级速率方程描述三种染料在胺基化壳聚糖微球上的吸附行为比较贴切。     

Multistep adsorption of anionic dyes on silica/chitosan hybrid. 1. Comparative kinetic data from liquid- and solid-phase models

In this work, a hybrid silica/chitosan was synthesized and characterized by nitrogen elemental analysis and thermal analysis (TG, DTG, DTA, and DSC) and BET surface area. The hybrid was used in adsorption studies of two anionic dyes from aqueous solutions. A rise of temperature accelerates mass transfer of dyes into the hybrid. However, the maximum adsorption capacities reach similar values from 25 to 55 degrees C. The kinetic data were first evaluated in relation to the decrease of the time-related residual concentration of the dyes in solution, where the second-order model has presented the best fitting. The solid-phase interaction of dye data presents a rough fitting to the traditional first-order Lagergren kinetic model. However, a modified Avrami kinetic equation was successfully fitted to the kinetic quantities, where from five to seven kinetic regions were found. A pore-diffusion model has also demonstrated that the diffusion is the rate-controlling interaction mechanism. However, the experimental-calculated comparative values are the best way to evaluate a specific aqueous- or solid-phase kinetic model.     

Kinetics of enzymatic reactions in the production of fish protein hydrolysates

The kinetic laws of enzyme hydrolysis of waste products (heads, fins, bones, and muscle tissue) of the Atlantic cod Gadus morhua have been investigated. An enzyme specimen hepatopancreatine was used for the hydrolysis reaction (proteolysis). A kinetic model describing the mechanism of enzyme hydrolysis of fish proteins as a second-order reaction was developed. The proteolysis model was based on the existence of easily hydrolysed and hydrolysis-resistant protein fractions. Autolysis of the enzyme was also taken into consideration. In the context of the developed kinetic model, the second-order rate constants of the intermediate stages of proteolysis were calculated.     

Synthesis and characterization of epoxy-modified cement slurries--kinetic data at hardened slurries/HCl interfaces

In this study, two new epoxy-modified oilwell cement slurries were synthesized. All characterization measurements were performed and compared in relation to a standard cement slurry, which was synthesized using only cement and water. The XRD patterns, as well as TG/DTG and DSC analyses have suggested that portlandite (Ca(OH)2) and carbonate phases were not present in detectable amounts in the new cement slurries. The isothermal kinetic data of the interaction of HCl with the epoxy-modified cement were obtained using the batch mode from 25 to 55 degrees C. The kinetic data were best fitted to the second-order and the Avrami kinetic models, since differences between experimental and calculated values were lower for these models. The intraparticle diffusion model has pointed out that the new slurries present positive values for the parameter "C," which is related to higher boundary layer resistance to HCl diffusion into the internal parts of the slurries, in relation to the standard slurry. The characterization and the HCl interaction kinetic studies have suggested that the new cement slurries present good potential, from the chemical viewpoint, to be used in oilwell operations.     

Adsorption of chlorinated organic compounds from water with cerium oxide-activated carbon composite

Adsorptive removal of dichloromethane, chloroform, and carbon tetrachloride from aqueous solutions at 25 °C by activated carbon (AC) that was loaded with cerium oxide nanoparticles (CeO₂-NP/AC) was investigated. The developed adsorbent was characterized by scanning electron microscope (SEM), FTIR spectrophotometer, X-ray diffraction (XRD), and thermal gravimetric analysis (TGA). The effect of contact time, initial concentration, and the adsorbent dosage were also studied. The equilibrium and kinetics of adsorption were studied in a batch-type adsorption system, and the equilibrium experimental data were analyzed using Langmuir, Freundlich, and Temkin isotherm models. Freundlich adsorption isotherm showed the best fit for the equilibrium adsorption data. Three adsorption kinetic models, pseudo first- and second-order, and intraparticle diffusion models were applied to test the kinetic data. Kinetic characterization of the adsorption process onto CeO₂-NP/AC is well-described by the pseudo second-order model, and the adsorption best-fit by the intraparticle diffusion model. Our study shows that at optimum conditions, 82.72%, 99.40% and 89.42% of dichloromethane, chloroform, and tetrachloride, respectively, were removed by CeO₂-NP/AC, at concentration between 0.25 and 5.00 g/L.     

The Adsorption Effect of Quaternized Chitosan Derivatives on Bile Acid

Chitosan, which is easily derived from chitin by N-deacetylation. It is well known that hypercholesterolemia has been identified as a major risk factor in the development of atherosclerosis and its clinical sequelae like coronary heart disease and myocard…     

Modeling adsorption rate of organic micropollutants present in landfill leachates onto granular activated carbon

The overall adsorption rate of single micropollutants present in landfill leachates such as phthalic acid (PA), bisphenol A (BPA), diphenolic acid (DPA), 2,4-dichlorophenoxy-acetic acid (2,4-D), and 4-chloro-2-methylphenoxyacetic acid (MCPA) on two commercial activated carbons was studied. The experimental data obtained were interpreted by using a diffusional model (PVSDM) that considers external mass transport, intraparticle diffusion, and adsorption on an active site. Furthermore, the concentration decay data were interpreted by using kinetics models. Results revealed that PVSDM model satisfactorily fitted the experimental data of adsorption rate on activated carbon. The tortuosity factor of the activated carbons used ranged from 2 to 4. The contribution of pore volume diffusion represented more than 92% of intraparticle diffusion confirming that pore volume diffusion is the controlling mechanism of the overall rate of adsorption and surface diffusion can be neglected. The experimental data were satisfactorily fitted the kinetic models. The second-order kinetic model was better fitted the experimental adsorption data than the first-order model.     

Kinetics of free-radical decay reactions in polymeric solids

Kinetic equations for the decay of the free radicals in polymeric solids are given for the following assumptions on which they are based: (1) two simultaneous first-order but physically separated decay reactions; (2) two simultaneous noninteracting second-order decay reactions; (3) combined simultaneous but intermingled first- and second-order decay reactions; (4) the same but for independent, i.e., not intermingled, first- and second-order decay reactions; (5) a second-order decay reaction in the presence of some free radicals that do not decay; and (6) a first-order decay reaction in the presence of some free radicals that do not decay. In all of the above physical systems the total concentration only can be measured. Hence the above kinetic equations refer to the change of the total concentration with time. It is found that the data for the decay of the free radicals in irradiated isotactic polypropylene and 61% styrene-39% butadiene block copolymer agree best with the equations for the second-order decay in the presence of a fraction of nondecaying free radicals.     

Second-order advantage in determining Co (II) in real samples using kinetic-spectrophotometric data matrices and multivariate curve resolution-alternating least square approach

In the present study, multivariate curve resolution coupled to alternating least-squares (MCR-ALS) was used to analyze kinetic-spectroscopic second-order data. The purpose of the study was to achieve important second-order advantage under the conditions of extreme spectral overlapping among sample components. The obtained experimental data indicated that MCR-ALS, unlike other second-order multivariate calibration algorithms, can conveniently handle the investigated analytical problem provided that matrix augmentation is implemented in the spectral mode instead of the usual kinetic mode. In this work, row-wise augmentation was used to break rank deficiency under conditions of extreme spectral overlapping among sample components. The approach was applied to determine Cobalt (II) based on its oxidation reaction with Fe (III) and 1, 10-phenantroline in micellar media. The results indicated good analytical performance toward the analyte despite the intense spectral overlapping and the presence of unexpected constituents in the test samples. The maximum and minimum band boundaries of feasible solutions corresponding to the species profiles were estimated by multivariate curve resolution. The results of the study indicated that unique solution can be practically obtained using MCR-ALS under the selection of suitable constraints such as trilinearity.     

纳米γ-Al_2O_3吸附Ge(Ⅳ)的机理及性能

研究了纳米γ-Al2O3吸附剂对Ge(Ⅳ)的吸附行为,考察了吸附平衡时间、温度和溶液的pH值等因素对吸附过程的影响.结果表明,纳米Al2O3对Ge(Ⅳ)的吸附在2min时基本达到平衡,在pH=4～11范围内,Ge(Ⅳ)可以被纳米Al2O3定量富集,吸附率大于95%;吸附于纳米Al2O3上的Ge(Ⅳ)可以用0.3mol/LK3PO4和1mol/LH2SO4混合溶液洗脱,5min后基本达到解析平衡,解析率能达到97%;该吸附过程符合准二级反应动力学模型,计算了不同温度下的吸附速率常数,并求得纳米Al2O3对Ge(Ⅳ)的吸附活化能(Ea)为11.63kJ/mol;该体系的吸附过程符合Freundlich等温式,由D-R等温式求得常温下纳米Al2O3对Ge(Ⅳ)的平均吸附能为10.87kJ/mol.Ge(Ⅳ)吸附反应的ΔG0为负值,焓变ΔH0为正值,说明该吸附过程是自发的吸热反应.     

明胶层中的扩散和反应的动力学研究——(Ⅲ)水溶性成色剂的偶合反应动力学

利用流动动力学装置跟踪测量技术和数值模拟技术研究了明胶层中水溶性成色剂的偶合反应动力学过程。通过实验结果与反应物在明胶层中边扩散边发生化学反应动力学过程的数值模型计算结果的吻合表明:在明胶层中,当pH不变时,水溶性成色剂的偶合反应是二级反应,并且它虽然带有—C₁₈H₃₇基团,但在明胶中不会形成胶束。本文还分别测定了彩色显影剂CD-2和CD-4的氧化产物在明胶层中的扩散系数以及它们分别与水溶性成色剂WC-1的偶合反应的速率常数。     

The water exchange process of tetraaquaplatinum(II): density-functional theory and ab initio computational study

The water exchange process of square planar tetraaquaplatinum(II) was computationally investigated at the Hartree-Fock, density-functional theory (B3LYP, PW91PW91, and mPW1PW91) and the second-order Moller-Plesset perturbation theory of levels of calculation. The stationary points on the gas phase and on the reaction field potential-energy surface were fully optimized and characterized. The self-consistent reaction field (SCRF) methods were also applied on the same system. The structures and energetic processes of all the species involved were investigated. The kinetic and thermodynamic properties for the gas phase and SCRF model data were compared with the available experimental data. The rate constants in MP2 level of theory and B3LYP isodensity polarized continuum model reaction field are in good agreement with the experimental data.     

Equilibria and kinetics for pH-dependent axial ligation of ethylester and methylester(aquo)cobaloximes with aromatic and aliphatic N-donor ligands and a molecular mechanistic study of the Co-C bond

Equilibrium constants are determined for the reaction of ethylester and methyl ester (aquo) cobaloximes with histamine, histidine, glycine and ethyl glycine ester as a function of pH at 25°C, using spectrophotometric technique. The functional dependence of pK _a on the substitution rate of H₂O varies with the pK _a of the incoming ligand, establishing the existence of nucleophilic participation of the ligand in the transition state. This data is interpreted with the help of kinetic data where dissociation kinetic reactions were also studied as a function of pH. Binding and kinetic data were correlated based on the basicity, steric hindrance of the entering ligand and HSAB principle. To compare the rate constants of the entering ligands pH-independent second-order rate constants were calculated. The effect of incoming ligand on Co-C bond is studied using molecular mechanics     

Kinetic parameters of a cyanate ester resin catalyzed with different proportions of nonylphenol and cobalt acetylacetonate catalyst

The isothermal cure of a dicyanate ester monomer has been investigated by differential scanning calorimetry (DSC) in the presence of different quantities of a catalyst system formed by nonylphenol (NP) and cobalt (II) acetylacetonate (Co(AcAc)₂). Two sets of experiences were studied. Firstly, the NP composition was varied from 0 to 10 per hundred resin (phr) and secondly, the Co(AcAc)₂ loadings were changed at 2 phr of NP. It has been observed that the cyanate conversion increases significantly after the first addition of the metal catalyst and, also, at the same time the thermal stability improves. Moreover, the kinetic data have been fitted with a second-order equation respect to the cyanate conversion in the kinetically conversion regime. Also, both the activation energies and the kinetic order respect to the NP and the Co(AcAc)₂ have been determined.