Phase-transfer catalysis and ultrasonic waves II: saponification of vegetable oil.

Saponification of oils which is a commercially important heterogeneous reaction, can be speeded up by the application of ultrasound in the presence of phase-transfer catalyst (PTC). This paper focuses on the ability of ultrasound to cause efficient mixing of this liquid-liquid heterogeneous reaction. Castor oil was taken as a model oil and the kinetic of the reaction was followed by the extent of saponification. The hydrolysis of castor oil was carried out with different PTC such as cetyl trimethyl ammonium bromide (CTAB), benzyl triethyl ammonium chloride (BTAC) and tetrabutyl ammonium bromide (TBAB) in aqueous alkaline solution. As hydroxyl anion moves very slowly from aqueous to oil phase, the presence of a PTC is of prime importance. For this purpose, cationic surfactants are selected. The sonication of biphasic system were performed by 20 kHz (simple horn and cup horn) and 900 kHz. It was found that CTAB was better than the two others and this could be related to the molecular structure of the PTCs. The effect of temperature was also studied on the saponification process. By increasing the temperature, the yield was also increased and this could be explained by intermolecular forces, interfacial tension and mass transfer. Saponification of three different vegetable oils shows that the almond oil is saponified easier than the two others and this could be related to their properties such as surface tension, viscosity and density.     

Ultrasonication assisted and surfactant mediated synergistic approach for synthesis of calcium sulfate nano-dendrites

Calcium sulfate (CaSO₄) nano-dendrimers were fabricated successfully via ultrasonic irradiation method using calcium chloride [CaCl₂] and ammonium per sulfate [(NH₄)₂SO₄] as precursors in aqueous solution by using cetyl trimethyl ammonium bromide (CTAB) as chemical surfactants. Diffusion-induced branching growth mechanism (DIBGM), influenced with the action of head-group and hydrocarbon chain effect of cationic surfactants, was the backbone in the formation of CaSO₄ nano-dendrites. Fourier Transform Infra-red Spectroscopy (FTIR), X-Ray powder Diffraction (XRD), Atomic Emission Spectroscopy (AES), Selected Area Electron Diffraction (SAED), Field-Emission Scanning Electron Microscopy (FE-SEM), Energy-Dispersive Spectroscopy (EDS), Dynamic Light Spectroscopy (DLS) and BET surface area analyzer were used to characterize the products. Results obtained were compared with conventional stirring method that proved the superiority of sonication method to obtain well-crystalline nanostructures. Also, surfactant concentration, sonication frequency and time were noticed as the critical factors to generate such absolute morphologies at nano-crystalline size.     

Adsorption of naphthalene onto sonicated talc from aqueous solutions

The adsorption behavior of naphthalene onto naturally hydrophobic talc from aqueous solution was investigated in this study. The natural talc was first pretreated by sonication to improve the surface characteristics and enhance the uptake capacity by increasing the specific surface area (SSA) of talc. The naphthalene uptake of talc was found as 276 mg g^?1 and increased to 359 mg g^?1 after the sonication. Adsorption studies also showed that the adsorption of naphthalene onto the sonicated talc was not affected by changes in pH suggesting that the main driving forces for naphthalene adsorption onto talc was hydrophobic bonding rather than electrostatic force. The pseudo-first and pseudo-second orders and intraparticle diffusion equation were used to evaluate the kinetic data and the constants were determined. Adsorption process of naphthalene onto talc followed the pseudo-second-order rate expression for different initial naphthalene concentrations. The Langmuir and Freundlich isotherm models were used to model the isotherm data for their applicability. The Freundlich isotherm best fitted for the adsorption of naphthalene onto talc.     

Adsorption of methylene blue onto sonicated sepiolite from aqueous solutions

The aim of the present study is to enhance the methylene blue (MB) adsorption of sepiolite by ultrasonic treatment. The natural sepiolite was pretreated by sonication to improve the surface characteristics and enhance the dye uptake capacity. Sonication process resulted in a significant increase in the specific surface area (SSA) of sepiolite. The FTIR spectrum of the sonicated sepiolite indicates that the tetrahedral sheet is probably distorted after sonication process. The effect of various parameters such as sonication, pH, initial dye concentration and temperature on dye adsorption has been investigated. The adsorbed amount of MB on sepiolite increased after sonication as well as with increasing pH and temperature. The experimental data were evaluated by applying the pseudo-first- and second-order, and the intraparticle diffusion adsorption kinetic models. Adsorption process of MB onto sepiolite followed the pseudo-second-order rate expression. The experimental data were analyzed by Langmuir and Freundlich isotherms, and found that the isotherm data were reasonably well correlated by Langmuir isotherm. Maximum monolayer adsorption capacity of sepiolite for MB increased from 79.37 to 128.21 mg/g after the sonication. Various thermodynamic parameters, such as ΔG⁰, ΔH⁰ and ΔS⁰ were calculated. The thermodynamics of MB/sepiolite system indicated spontaneous and endothermic nature of the process. Adsorption measurements showed that the process was very fast and physical in nature.     

Improved optical performance of CdO films prepared with CTAB as surfactant

The influence of surfactant cetyl trimethyl ammonium bromide (CTAB) on structural, morphological and optical properties of CdO films has been investigated. Five series of CdO films were successfully prepared by successive ionic layer adsorption and reaction method with the assistance of CTAB. These CdO films were characterized by X-ray diffraction, scanning electron microscopy and UV–vis spectroscopy. The CTAB caused in a decrease in crystallite size but an increase in the optical band gap of CdO films. From the optical investigations, it was observed that the transmittance of the pure film was about 2% and it increased dramatically to 37% for 2?M% CTAB added CdO films at the wavelength of 1100?nm. The results show that the amount of CTAB played an important role in determining the physical properties of the CdO nanostructures.     

Ultrasound assisted synthesis of polyacrylic acid–nanoclay nanocomposite and its application in sonosorption studies of malachite green dye

Synthesis of nanoclay nanocomposite has been undertaken by using polyacryalic acid (PAA) in aqueous medium and ultrasound environment and its application in dye removal has been investigated. The synthesized product was characterized by using FTIR and XRD techniques. The sonosorption capacity of the product namely PAA–nanoclay composite was determined by choosing malachite green (MG) dye as a model pollutant. The effects of various parameters such as nanocomposite loading, pH, various process conditions etc. have been studied. On comparing the results obtained with that of nanoclay as an adsorbent, it was found for an initial concentration of 500 mg/l, the PAA–nanoclay nanocomposite exhibited higher percentage of pollutant removal (68%) and for nanoclay it was 54%. The adsorption data has been correlated using Langmuir and Freundlich models. The fit of the Freundlich isotherm model was found to be good in the entire range of concentration for the experimental sorption data obtained on the nanoclay nanocomposite. A plausible reaction mechanism for use of PAA–nanoclay nanocomposite as an adsorbent is also proposed.     

Preparation and application of polymer-grafted magnetic nanoparticles for lipase immobilization

Functionalized superparamagnetic particles were prepared by graft polymerization of glycidyl methacrylate and methacryloxyethyl trimethyl ammonium chloride onto the surface of modified-Fe₃O₄ nanoparticles. The resultant particles were characterized by X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and vibrating sample magnetometry. The results indicate that the polymer chains had been effectively grafted onto the surface of Fe₃O₄ nanoparticles. The functionalized particles remained dispersive and superparamagnetic. Lipase was immobilized on the magnetic particles under mild conditions by electrostatic adsorption and covalent binding with the activity recovery up to 70.4%. The immobilized lipase had better thermal stability compared to free lipase.     

Stability and characterization of mesoporous molecular sieve using natural clay as a raw material obtained by microwave irradiation

Mesoporous molecular sieve was synthesized via microwave irradiation method, and using natural clay, sodium silicate and aluminum chloride as raw materials and cetyl trimethyl ammonium bromide (CTAB) as a template agent under alkaline condition. The samples were characterized by various analytic and spectroscopic tools such as XRD, FT-IR, TEM, TG-DSC and N₂ physical adsorption, respectively. The results show that the synthesized sample has typical mesoporous structure and exhibits good mesoporous ordering. On the other hand, the as synthesized sample after calcination at 550 °C for 10 h has a surface area of 576.0 m²/g and an average pore size of 4.83 nm. Furthermore, the synthesized mesoporous molecular sieve still exhibits good mesoporous ordering after calcination at 750 °C for 3 h or hydrothermal treatment at 100 °C for 10 days.     

Sonochemical preparation of high surface area MgAl2O4 spinel

High surface area MgAl(2)O(4) has been synthesised by a sonochemical method. Two kinds of precursors were used, alkoxides and nitrates/acetates and in both cases nanostructured MgAl(2)O(4) was obtained. The effect of the addition of a surfactant during the sonication, cetyl trimethyl ammonium bromide, was also investigated. In the case of alkoxides precursors the as-made product is a mixture of hydroxides of aluminium and magnesium, while with nitrates/acetates a gel is obtained after sonication, containing the metal hydroxides and ammonium nitrate. Heating at 500 degrees C transforms the as-made products into MgAl(2)O(4) spinel phase. The surface area is up to 267m(2)/g after treatment at 500 degrees C and 138m(2)/g at 800 degrees C.     

有机膨润土制备及性能表征

采用湿法工艺,分别用十六烷基三甲基氯化铵、十八烷基二甲基苄基氯化铵、十八烷基三甲基氯化铵与钠基膨润土,进行离子交换反应合成了有机膨润土。以红外光谱、X-ray衍射和差热分析等手段对改性膨润土进行了结构表征,讨论了不同的季铵盐对有机膨润土性能的影响。实验表明,表面活性剂离子进入膨润土晶片层间,使其晶片层间的亲水环境改变为疏水环境并增大晶片层间距离,为制备高聚物/膨润土纳米复合材料奠定基础。     

Preparation of activated carbon from Enteromorpha prolifera and its use on cationic red X-GRL removal

Enteromorpha prolifera was pyrolyzed to prepare activated carbon using chemical activation by zinc chloride. The effect of activation parameters such as activation temperature, weight ratio (Enteromorpha prolifera to ZnCl₂), and activation time was investigated. The BET results showed that the surface area and pore volume of activated carbons were achieved as high as 1722 m²/g and 1.11 cm³/g, respectively, in the optimal activation conditions. Batch adsorption studies were carried out to study the adsorption properties of cationic red X-GRL onto activated carbon by varying the parameters like initial solution pH, contact time, and temperature. The kinetic studies showed that the adsorption data followed a pseudo second-order model. The isotherm analysis indicated that the adsorption data could be represented by the Langmuir isotherm model. The Langmuir monolayer adsorption capacity of cationic red X-GRL was estimated as 263.16 mg/g at pH 6.0.     

纺锤形β-FeOOH的形成过程研究

应用透射电镜技术观察了FeCl3 水解形成纺锤形 β FeOOH过程中颗粒的形貌变化 ,发现纺锤形β FeOOH颗粒是由针形初级粒子沿长轴聚集长大形成的 .加入表面活性剂十六烷基三甲基溴化铵 (CTAB)后 ,β FeOOH 形成机制发生改变 ,β FeOOH晶核通过扩散过程而长成纺锤形颗粒 .CTAB的存在使 β FeOOH颗粒变小而且粒径更均匀 .改变反应条件包括起始FeCl3 的浓度、陈化温度 ,得到了纺锤形和针形、不同轴比的单分散β FeOOH .     

Adsorption behavior of a textile dye of Reactive Blue 19 from aqueous solutions onto modified bentonite

The aim of this study is to evaluate adsorption kinetics, isotherms and thermodynamic parameters of Reactive Blue 19 (RB19) onto modified bentonite from aqueous solutions. The effects of pH, contact time, initial dye concentration and temperature were investigated in the experimentally. Natural bentonite was modified by using 1,6-diamino hexane (DAH) as a modifying agent. The characterization of modified bentonite (DAH-bentonite) was accomplished by using FTIR, TGA, BET and elemental analysis techniques. The optimum pH value for the adsorption experiments was found to be 1.5 and all the experiments were carried out at this pH value. The pseudo-second-order kinetic model agrees very well with the experimental results. Equilibrium data were also fitted well to the Langmuir isotherm model in the studied concentration range of RB19 at 20 °C. The results indicate that DAH-modified bentonite is a suitable adsorbent for the adsorption of textile dyes.     

Enhancement of saccharin removal from aqueous solution by activated carbon adsorption with ultrasonic treatment

This study investigates the use of ultrasonication as a pretreatment process and its effect on the adsorption characteristics of saccharin onto activated carbon (AC). Ultrasonic decomposition of saccharin was performed at a frequency of 500 kHz under argon and O2/N2 (20/80 vol%) atmospheres. Adsorption was carried out using a commercial activated carbon. The behavior of total organic carbon (TOC) during ultrasonication was investigated. Saccharin removal after 180 min of ultrasonication under Ar and O2/N2 atmospheres are 38% and 26%, respectively, while the amount of saccharin removed by activated carbon adsorption without US pretreatment is 40% after 16 h. After 16 h of AC adsorption with 180 min of ultrasonic pretreatment under Ar and O2/N2 atmospheres, both removal ratios increased to 75%. These results indicated that the pretreatment of sonication under O2/N2 leads to the increase in the amount of saccharin adsorbed on AC. On the other hand, the TOC removal by decomposition by ultrasound is not more than 5% in both Ar and O2/N2 atmospheres after 180 min ultrasonication. However, the TOC removal increased to 54% and 69% after 16 h of adsorption of saccharin pretreated by ultrasonication for 180 min under Ar and O2/N2 atmospheres, respectively. About 13% and 16% TOC removal in Ar and in O2/N2, respectively, were achieved due to adsorption of the by-products. It is considered that the improvement in TOC removal is also brought about by the formation of the by-products that were adsorbed onto AC.     

Kinetics, thermodynamics and surface heterogeneity assessment of uranium(VI) adsorption onto cation exchange resin derived from a lignocellulosic residue

A new cation exchange resin (PGTFS-COOH) having a carboxylate functional group at the chain end was prepared by grafting poly(hydroxyethylmethacrylate) onto tamarind fruit shell, TFS (a lignocellulosic residue) using potassium peroxydisulphate-sodium thiosulphate redox initiator, and in the presence of N,N′-methylenebisacrylamide (MBA) as a crosslinking agent, followed by functionalisation. The adsorbent was characterized with the help of FTIR, XRD, scanning electron micrographs (SEM), and potentiometric titrations. The kinetic and isotherm data, obtained at optimum pH value 6.0 at different temperatures could be fitted with pseudo-second-order equation and Sips isotherm model, respectively. An increase in temperature induces positive effect on the adsorption process. The calculated activation energy of adsorption (E_a, 18.67 kJ/mol) indicates that U(VI) adsorption was largely due to diffusion-controlled process. The values of adsorption enthalpy, Gibbs free energy, and entropy were calculated using thermodynamic function relationships. The decrease in adsorption enthalpy with increasing U(VI) uploading on the adsorbent, reflects the surface energetic heterogeneity of the adsorbent. The isosteric heat of adsorption was quantitatively correlated with the fractional loading for the U(VI) ions adsorption onto PGTFS-COOH. The results showed that the PGTFS-COOH possessed heterogeneous surface with sorption sites having different activities.     

Synthesis of Hydrophobic Cationic Chitosan Flocculant and Its Sludge Dewatering Property

The hydrophobic cationic chitosan (HTCC) flocculant was synthesized by reacting chitosan with epoxy propyl trimethyl ammonium chloride (EPTAC) and (2,3-epoxy propyl) dodecyl dimethyl ammonium chloride (EDC), to improve its waste sludge dewaterability. By FTIR and ¹H NMR analysis, EPTAC and EDC were confirmed to be grafted onto the molecular chains of chitosan (CTS) successfully. With the increase of EDC content, G′ of HTCC aqueous solution with 1:1.5:1.5 mole ratio of CTS:EPTAC:EDC consistently showed higher values than G″ over the entire frequency range explored, indicating the formation of a physically cross-linked network. The crystallization ability of HTCC decreased compared with pristine CTS. The long alkyl chains on the EDC molecules enhanced the hydrophobicity of HTCC, and better dewaterability of the waste sludge was achieved through the promoted bridging action of HTCC.     

The morphology control on the preparation of silver nanotriangles

A seed-mediated growth method was commonly applied to prepare one-dimension nanomaterials. However, some associated particles were unavoidable in the formation of target nanoparticles. Herein, we reported a modified method to prepare silver nanotriangles with higher uniform shape and particle size. The size and morphology of the formed nanoparticles could be controlled by regulating reaction conditions. The results showed that cetyl trimethyl ammonium bromide (CTAB) concentration and seed concentration were related with both the morphology and the particle size. The NaOH concentration, AgNO₃ concentration, and the mole ratio of V_c/Ag⁺ mainly affected the particle size of the formed nanotriangles. The formation of silver nanotriangles may be due to the selective stacking of the new tiny nanoparticles and the oriented growth of silver seed crystals. The oxidizing action of Br⁻/O₂ existing in the CTAB system should be responsible for the final morphology of truncated triangular silver nanoplates.     

Effect of surfactants on the degradation of perfluorooctanoic acid (PFOA) by ultrasonic (US) treatment

Perfluorooctanoic acid (C₇F₁₅COOH, PFOA) is an aqueous anionic surfactant and a persistent organic pollutant. It can be easily adsorbed onto the bubble-water interface and both mineralized and degraded by ultrasonic (US) cavitation at room temperature. The aim of this study is to investigate whether the effect of US on the degradation of PFOA in solution can be enhanced by the addition of surfactant. To achieve this aim, we first investigated the addition of a cationic (hexadecyl trimethyl ammonium bromide, CTAB), a nonionic (octyl phenol ethoxylate, TritonX-100), and an anionic (sodium dodecyl sulfate, SDS) surfactant. We found the addition of CTAB to have increased the degradation rate the most, followed by TritonX-100. SDS inhibited the degradation rate. We then conducted further experiments characterizing the removal efficiency of CTAB at varying surfactant concentrations and solution pHs. The removal efficiency of PFOA increased with CTAB concentration, with the efficiency reaching 79% after 120 min at 25 °C with a 0.12 mM CTAB dose.     

SiO2微球表面吸附PDADMAC的研究

研究了SiO2 微球表面吸附聚阳离子电解质聚二烯丙基二甲基氯化铵PDADMAC的吸附等温线分别随溶液NaCl浓度、pH值和温度的变化趋势 ,以及不同 pH值下的Zeta电位 .测试结果表明 ,聚电解质在SiO2 微球表面的吸附分别随盐浓度和pH值的增加而增加 ,该吸附属于Langmuir型 .随着PDADMAC吸附量的增加 ,SiO2微球的等电点逐渐向碱性范围移动 .在碱性条件下 ,吸附PDADMAC的SiO2 微球显示良好的分散稳定性 .XPS分析显示 ,SiO2 微球表面吸附PDADMAC后含氮 ,其N1s结合能为 4 0 1.7eV .O1s谱含两个峰 ,分别对应低结合能的SiO2 结构氧和高结合能的吸附氧 .当SiO2 微球表面吸附PDADMAC后吸附氧部分的O1s峰增加 .     

Adsorption of nicotine from aqueous solution onto hydrophobic zeolite type USY

The isothermal adsorption of nicotine from an aqueous solution onto zeolite type USY was investigated. The adsorption isotherms of nicotine onto the zeolite at different temperatures ranging from 298 to 322 K were determined. It was found that the adsorption isotherms can be described by the model of Freundlich adsorption isotherm. Based on the adsorption isotherms the changes of adsorption heat, free energy and entropy with adsorption degree were determined. The determined decrease of adsorption heat with adsorption degree can be explained by the presence of the adsorption centers of different energy and concentration on interface of zeolite-nicotine solution. It was found that the probability function of density distribution of the heat of adsorption (DDF) has exponential form. It was concluded that the possibility of fitting the adsorption isotherms of nicotine onto the zeolite by Freundlich adsorption isotherm was a direct consequence of that. The determined increase in entropy with the increase in adsorption degree can be explained with the change of phase state of adsorbed nicotine.