Interaction Characteristics and Thermodynamic Behaviour of Gatifloxacin by Aluminium Hydroxide

ABSTRACT

The interaction pattern of gatifloxacin was temperature-dependent Langmuir isotherm, and the Langmuir coefficients increased as the temperature was raised. The perturbation experiment conducted on this system showed that the nature of interaction was irreversible. The enthalpy change is a positive value, indicating the existence of increased activation energy as the temperature is raised. The entropy value, 24.21 e.u. obtained in this system, indicated that the hydration shells of the ions were rather tightly bound. Intestinal permeation study also revealed the decreased bioavailability of gatifloxacin relatively to the presence of aluminium hydroxide. The strong adsorption of gatifloxacin by aluminium hydroxide is due to formation of complexes with cations of aluminium hydroxide through carboxyl and carbonyl groups of gatifloxacin.     

Carbothermal reduction and nitridation of aluminium hydroxide

Carbothermal reduction and nitridation of aluminium hydroxide was investigated by weight-loss measurement and X-ray diffraction. Experimental results indicated that aluminium hydroxide was first dehydrated to aluminium oxide and then reduced and nitrided to aluminium nitride. Aluminium oxynitride and Al₂O were found to be intermediate products. The reaction rate was found to be increased by increasing the nitrogen flow rate, the molar ratio of C/Al(OH)₃, or reaction temperature. The rate was also found to be increased by decreasing the sample size, the grain sizes of carbon or aluminium hydroxide or initial bulk density. Empirical rate expressions of the conversion of Al(OH)₃ and carbon, as well as the yield of AIN, were also determined.     

Equilibrium studies for trimethoprim adsorption on montmorillonite KSF

In this study, the adsorption of trimethoprim (TMP) on montmorillonite KSF was studied under different conditions (pH, ionic strength, temperature). The results indicate that a pH value of 5.04 is optimum value for the adsorption of TMP on KSF. The adsorption kinetics was interpreted using pseudo-first-order kinetic model, pseudo-second-order kinetic model and intraparticle diffusion model. The pseudo-second-order model provides the best correlation with the experimental data of KSF adsorption. The adsorption data could be fitted with Freundlich, Langmuir and Dubinin-Radushkevich equation to find the characteristic parameters of each model. It was found that linear form of Langmuir isotherm seems to produce a better model than linear form of Freundlich equation. From the Langmuir and Freundlich equation, the adsorption capacity values raised as the solution temperature decreased. From DR isotherm, it was also determined that the type of adsorption can be considered as ion-exchange mechanism. Determination of the thermodynamic parameters DeltaH(0), DeltaS(0) and DeltaG(0) showed that adsorption was spontaneous and exothermic in nature. It was also added that adsorption of TMP by KSF may involve physical adsorption.     

聚丙烯酰胺作分散剂从粉煤灰中制备纳米氢氧化铝

利用粉煤灰得到NaAlO2 溶液 ,以聚丙烯酰胺作分散剂 ,采用碳化法制备氢氧化铝粉体 ;研究了聚丙烯酰胺处理方式与用量、NaAlO2 浓度、碳化反应温度等因素的影响 ,得到纯度为 99 9% ,平均粒度为 6 0nm的氢氧化铝粉体     

Mullite and alumina composites preparation from cordierite and aluminium hydroxide

Densification and phase transformation of mullite and alumina composites prepared from cordierite and aluminium hydroxide mixture were investigated. X-ray diffraction revealed the presence of mullite since the early stage of aluminium hydroxide addition to the cordierite. Above 40 wt.% of aluminium hydroxide addition, the presence of spinel and mullite phases can be detected by X-ray diffraction and confirmed by X-ray photoelectron spectroscopy. The X-ray photoelectron spectroscopy analysis showed that the amounts of spinel as well as mullite present increased with increasing aluminium hydroxide concentration at the expense of cordierite. These analyses were completed by density measurements and scanning electron microscopy observation.     

Remediation of phosphate-contaminated water by electrocoagulation with aluminium, aluminium alloy and mild steel anodes

The present study provides an electrocoagulation process for the remediation of phosphate-contaminated water using aluminium, aluminium alloy and mild steel as the anodes and stainless steel as the cathode. The various parameters like effect of anode materials, effect of pH, concentration of phosphate, current density, temperature and co-existing ions, and so forth, and the adsorption capacity was evaluated using both Freundlich and Langmuir isotherm models. The adsorption of phosphate preferably fitting the Langmuir adsorption isotherm suggests monolayer coverage of adsorbed molecules. The results showed that the maximum removal efficiency of 99% was achieved with aluminium alloy anode at a current density of 0.2 A dm(-2), at a pH of 7.0. The adsorption process follows second-order kinetics.     

Effect of binder type and content on physical and mechanical properties of geopolymers

In this study, the physical and mechanical behaviors of geopolymers prepared by using different amounts of silica fume and calcium hydroxide as binding materials, acidic pumice as fine aggregate and waste aluminium particles as air-entraining agent were investigated. Test results showed that binder types, amount of binders and alkali activator (sodium hydroxide) significantly affected the physical and mechanical behavior of geopolymer specimens. Bulk density, compressive and flexural strength decreased with the higher alkali activator content. Addition of waste aluminium particles led to decrease in bulk density and strength due to the some extent of entrained air. In the case of same alkali activator content, compressive and flexural strength increased with increase in silica fume and calcium hydroxide up to a certain level.     

Kinetic and equilibrium study for the sorption of cadmium(II) ions from aqueous phase by eucalyptus bark

The efficiency of eucalyptus bark as a low cost sorbent for removing cadmium ions from aqueous solution has been investigated in batch mode. The equilibrium data could be well described by the Langmuir isotherm but a worse fit was obtained by the Freundlich model. The five linearized forms of the Langmuir equation as well as the non-linear curve fitting analysis method were discussed. Results show that the non-linear method may be a better way to obtain the Langmuir parameters. Maximum cadmium uptake obtained at a temperature of 20 degrees C was 14.53mgg(-1). The influence of temperature on the sorption isotherms of cadmium has been also studied. The monolayer sorption capacity increased from 14.53 to 16.47 when the temperature was raised from 20 to 50 degrees C. The DeltaG degrees values were negative, which indicates that the sorption was spontaneous in nature. The effect of experimental parameters such as contact time, cadmium initial concentration, sorbent dose, temperature, solution initial pH, agitation speed, and ionic strength on the sorption kinetics of cadmium was investigated. Pseudo-second-order model was evaluated using the six linear forms as well as the non-linear curve fitting analysis method. Modeling of kinetic results shows that sorption process is best described by the pseudo-second-order model using the non-linear method. The pseudo-second-order model parameters were function of the initial concentration, the sorbent dose, the solution pH, the agitation speed, the temperature, and the ionic strength.     

Thermal stability and decomposition kinetics of Li2Al4CO3(OH)12·3H2O

The thermal stability of lithium containing hydrotalcite, a material that has potential application for providing atmospheric corrosion protection to aluminium alloys, was investigated. Lithium aluminium carbonate hydroxide hydrate (Li₂Al₄CO₃(OH)₁₂·3H₂O) coatings were prepared by immersion of an 1100 aluminium alloy into a lithium carbonate-lithium hydroxide solution, and the bulk material was prepared by precipitation in the same solution. Thermal stability of the coatings and the bulk material existed to around 150 °C. Above this temperature, interlayer water was expelled, followed by loss of structural water and carbon dioxide. The kinetic parameters for interlayer water loss have been determined, and water loss can be described by a Johnson-Mehl-Avrami rate equation.     

Microstructural transitions in an RS Al-4La alloy

The use of rapid solidification (RS) techniques to increase the thermal stability of aluminium and aluminium alloys is considered a promising processing route. The Al-La equilibrium binary system tends to form a high melting temperature intermetallic compound on the aluminium rich side. The limited solid solubility of solute, high solubility in the liquid and the relatively low solid state diffusivity, in general, of rare earth (RE) elements in aluminium suggests this system (as well as other Al-RE systems) as a suitable lightweight, dispersion-strengthened alloy candidate for elevated homological temperature applications. RS processing promotes the formation of a relatively finer microstructure in an Al-4La alloy, as well as the formation of a finely dispersed metastable phase. This metastable phase, is fairly stable up to 400° C. Lanthanum concentration in the ribbon bulk matrix, is considerably increased via RS process ing, and the formation of a heavy eutectic is suppressed.     

晶种对氢氧化铝转相和热压烧结氧化铝晶形变化的影响

以氢氧化铝为初始原料,通过球磨过程中高纯氧化铝磨介的磨屑作为晶种引入氢氧化铝中.引入的α-Al₂O₃品种使氢氧化铝于1100℃×2h的条件下转变为α相氧化铝.而且随着α-Al₂O₃品种引入量的增加,煅烧后氧化铝颗粒的平均粒径减小,颗粒尺寸分布均匀.煅烧得到的氧化铝超细粉经热压烧结后,Al₂O₃晶粒形貌随品种的引入量的不同而发生变化.未引入α-Al₂O₃品种的条件下,晶粒形状主要为等轴状;晶种引入后,晶粒发育成六角片状;而且随着晶种引入量进一步增加时,六角片状晶粒尺寸减小,当晶种数量增加到20wt％以上时,晶粒发育生长为长柱状.     

Wood–plastics composites with better fire retardancy and durability performance

This study concerns the preparation and study of wood–plastic composites (WPCs). The matrix used was high density polyethylene. Results showed that the addition of wood fibres increased mechanical properties (tensile, flexural and compression) of the neat plastic remarkably. Additives such as fire retardants and light stabilizers were added to improve properties like fire retardancy and durability performance. The addition of fire retardants could lead to auto-extinguishing materials when ammonium polyphosphate or aluminium hydroxide were used. Outdoor durability depended on both the light stabilizer and the fire retardant added to the formulation. The fire retardant worsened the outdoor durability. However, stabilized fire retarded-WPCs showed much lower fading than non-stabilized non-fire retarded composites and several industrial samples. Stabilized composites with aluminium hydroxide as fire retardant showed the best overall results with a fading degree even lower than the stabilized non-fire retarded composite.     

Intergranular Fatigue Cracking Behaviour in Aluminium

In order to understand the basic mechanismof intergranular cracking in pure metals duringfatigue, stress-controlled push-pull fatiguetests were carried out with high purity aluminium.Tests were interrupted frequently so as to studythe grain boundary (GB) cracking behaviour bythe surface observation. The results show thatcrack initiation at GB was a process controlledby multi-factors, such as boundary structure,GB-slip interaction, GB sliding and so on. Ifthese factors are varied so that the incompati-bility at a GB increased, the possibility ofcyacking at the boundary will be raised. Someinteygranular cracking phenomena are not ableto be explained by the GB stepping mechanism.     

介孔氧化铝的可控制备及优异除氟性能

以偏铝酸钠(NaAlO_2)和氯化铝(AlCl_3·6H_2O)为铝源,葡萄糖(C_6H_(12)O_6·H_2O)为模板剂,采用水热及高温焙烧技术制备了不同晶型的氧化铝。用X射线衍射(XRD)、扫描电镜(SEM)、N2吸附脱附(BET)对制备产物的晶型、形貌及孔结构进行了表征。研究了不同晶型氧化铝对F-的吸附性能,结果表明550℃条件下的煅烧产物γ-Al_2O_3对F-的吸附效果最佳。吸附等温线结果表明介孔γ-Al_2O_3吸附F-为单层吸附,其Langmuir最大吸附容量为5.96mg/g。吸附动力学试验表明,介孔γ-Al_2O_3在5min内已吸附超过90%的F-,且吸附过程与准二级动力学模型相吻合。介孔γ-Al_2O_3吸附F-的机理涉及OH-与F-的离子交换。     

镨砷铁三元系高温产物及相互作用机理研究

研究将镨、砷按不同原子比密封在工业纯铁缸体内,按一定升温程序升温到1273 K并保温20 h。再通过光学显微镜、X射线衍射仪、扫描电镜能谱分析等手段,探究Pr-As-Fe在高温的相互作用。结果表明:二元化合物PrAs和Fe2As以及饱和砷的α-Fe固溶体为Pr-As-Fe高温相互作用的主要生成物,同时伴有少量Fe17Pr2化合物的生成。增加原子比,PrAs量随着减少,Fe2As和饱和砷的α-Fe固溶体量增加。Pr-As-Fe三元高温体系中,砷原子的量影响铁原子的扩散,铁原子的扩散量随着比例的增加而增加。     

Biosorption of methylene blue from aqueous solution by fallen phoenix tree's leaves

A new adsorbent, the fallen phoenix tree's leaf, has been investigated in order to remove methylene blue (MB) from aqueous solutions. Variables of the system, including contact time, leaf dose, solution pH, salt concentration and initial MB concentration, were adopted to study their effects on MB biosorption. The results showed that as the dose of leaf increased, the percentage of MB sorption increased accordingly. There was no significant difference about the quantity of MB adsorbed onto leaf as the pH was within the range 4.5-10.0. The salt concentration has negative effect on MB removal. The equilibrium data were analyzed using the Langmuir and the Freundlich isotherms. The results of non-linear regressive analysis are that the Langmuir isotherm is better fit than the Freundlich isotherm at different temperature according to the values of determined coefficients (R(2)) and chi(2)-statistic (SS). The Langmuir monolayer saturation capacities of MB adsorbed onto leaf are 80.9, 83.8, 89.7mgg(-1) at 295, 309 and 323K, respectively. Using the equilibrium concentration contents obtained at different temperatures, various thermodynamic parameters, such as DeltaG degrees , DeltaH degrees and DeltaS degrees , have been calculated. The thermodynamics parameters of MB/leaf system indicate spontaneous and endothermic process. It was concluded that an increase in temperature be advantage to adsorb MB onto leaf.     

Low temperature synthesis of aluminium titanate by an aqueous sol-gel route

Formation of aluminium titanate (AT) has been achieved at low temperature through sol-gel process using boehmite and titanium hydroxide as precursors by controlling the particle size at nanoscale followed by in-situ peptisation. The formations of AT phase, particle size distributions, sintering and thermal expansion characteristics, and microstructural features have been reported. DTA and XRD analysis have been performed to confirm the formation of AT. A 94% relative density was obtained for aluminium titanate sintered at 1550 °C with controlled grain size in the range of 2-3 μm.     

Studies on sorption of Cd(II) on Tata chromite mine overburden

Chromite mine overburden containing iron as oxide/hydroxide, a waste material generated in chromite mines was used as sorbent for cadmium. The iron content of material was 43.75% with a specific surface area of 50.8m(2)/g. Batch experiments were conducted to study the sorption behavior of Cd(II) on this material. The variable experimental parameters were: time, pH, temperature, Cd(II) and sample concentration. The point of zero charge (PZC) of the overburden sample was experimentally determined as 6.48 which shifted to a pH of 7.8 when the sample was equilibrated with 100 mg/L Cd(II) solution. Maximum loading capacity of the overburden sample was found to be approximately 19 mg Cd/g of material. It was observed that within 30 min the sorption attains equilibrium. Hence, the sorption data generated at 30 min with various initial Cd(II) concentrations and temperatures were taken to evaluate the thermodynamic parameters, i.e., DeltaG degrees , DeltaH degrees and DeltaS degrees . The DeltaG degrees values reflect the feasibility of the metal removal from aqueous solution. The negative values of DeltaH degrees confirmed the exothermic sorption of cadmium and the positive DeltaS degrees values suggested the increased randomness at the solid-solution interface. The sorption data fitted well to both the Langmuir and Freundlich isotherm models indicating a monolayer sorption. The value of Freundlich parameter 'n' (n is indicative of sorption intensity) lying between 1.46 and 1.59 shows that the surface of the sorbent is heterogeneous in nature.     

Alumina ceramics by sol-gel technique

The processing of alumina ceramics using the sol-gel technique was investigated. Alumina sols were prepared by precipitation-peptization of aluminium hydroxide obtained from aluminium nitrate and aluminium oxyhydroxide obtained from aluminium isopropoxide. Sols cast on Teflon substrate were gelled by controlled dehydration at near-ambient temperature. Gels were converted to ceramics through processes of drying, calcination and sintering in the temperature range 773–1473 K. Ceramics derived from both the sols retained a porosity of 35–45% even after sintering at 1273 K. However, at 1473 K densification was drastically enhanced and bodies could be sintered to about 90–93% of theoretical density (TD) and was accompanied by theϑ-to-α transformation. The progress of the reactions occurring at various stages of the process was studied using pycnometry, TG-DSC, XRD, SEM, MIP and TEM techniques.