Adsorption of Cu(II) in aqueous solution by sodium dodecyl benzene sulfonate-modified montmorillonite

The pristine montmorillonite (P-Mt) was modified with sodium dodecyl benzene sulfonate (SDBS) to form SDBS montmorillonite (SDBS-Mt) for the purpose of enhancing the removal performance of Cu(II) from aqueous solution. The materials were characterized by means of XRD, SEM-EDS, BET, and FTIR to analyze the surface morphology and structure. SDBS-Mt displayed a higher adsorption capacity than P-Mt. The adsorption kinetic model and the adsorption isotherm model are depicted by the pseudo-second-order kinetic equation and the Langmuir equation, respectively. The adsorption of Cu(II) on SDBS-Mt is a spontaneous and endothermic process. The order of influence of coexisting cations on the adsorption of Cu(II) is Ni(II) > Co(II) > Zn(II). In addition, the adsorbent has great regeneration performance after five cycles of regeneration. The main mechanisms of Cu(II) adsorption by SDBS-Mt may include electrostatic attraction, ion exchange, and complexation of sulfonate groups. In brief, SDBS-Mt may be a promising, simple, and low-cost adsorbent for the treatment of Cu(II) in aqueoussolutions.     

Entropic nature of the adsorption of sodium dodecylbenzenesulfonate on nanoparticles of aluminum and iron oxides in aqueous medium

The adsorption of anionic surfactant sodium dodecylbenzenesulfonate (SDBS) from aqueous solution on the hydrophilic surfaces of aluminum oxide and iron oxide nanoparticles is studied via UV spectrophotometry, electrophoretic light scattering, and isothermal microcalorimetry. It is shown that the isotherms of the adsorption of SDBS on the surfaces of both oxides in the area of concentrations up to 0.6 mmol/L is linear. It is found that the positive zeta potential of the surfaces of the particles falls to zero and shifts toward the range of negative values due to adsorption. The adsorption of SDBS is characterized by positive enthalpy values over the investigated range of concentrations, while the loss of energy during adsorption indicates it is of an entropic nature. It is concluded that the probable cause of the increase in entropy is the dehydration of SDBS molecules during on surface adsorption. The obtained results are discussed in terms of the formation of hemimicelles of surfactant on the hydrophilic surfaces of metal oxide nanoparticles in an aqueous medium.     

Application of hydrophobic silica based aerogels and xerogels for removal of toxic organic compounds from aqueous solutions

This work is devoted to the application of hydrophobic silica based aerogels and xerogels for the removal of three toxic organic compounds from aqueous solutions. These materials were tested and characterized regarding their morphology, particle size distribution, surface area and porous structure. The equilibrium tests were carried out at different adsorbate concentrations and the experimental data were correlated by means of Langmuir and Freundlich isotherms. The equilibrium data were well described by Langmuir and Freundlich in most cases. The maximum adsorption capacity by Langmuir model was observed for the adsorption of benzene onto aerogel (192.31 mg/g), though the most promising results were obtained for toluene adsorption due to the greater adsorption energy involved. Comparing these results with other reported results, the hydrophobic silica based aerogels/xerogels were found to exhibit a remarkable performance for the removal of benzene and toluene. In addition, the regeneration of previously saturated aerogel/toluene was also investigated by using an ozonation process. The adsorption/regeneration tests with ozone oxidation showed that the aerogel might be regenerated, nevertheless the materials lost their hydrophobicity and thus different methods should be evaluated in forthcoming investigations.     

Effect of SDBS on interfacial electron transfer at the liquid/liquid interface by thin layer method

The effect of an adsorbed anionic surfactant sodium dodecyl benzene sulfonate(SDBS) on electron transfer(ET) reaction between ferricyanide aqueous solution and decamethylferrocene(DMFc) located on the adjacent organic phase was investigated for the first time by thin layer method.The adsorption of SDBS at the interface resulted in a decay in the cathodic plateau current of bimolecular reaction with increasing concentrations of SDBS in aqueous phase.However,the rate constant of electron transfer(k_(et)) i...     

Control of mesoporous structure of aerogels derived from cresol-formaldehyde

Polycondensation of a cresol mixture (C(m)) with formaldehyde (F) in basic aqueous solutions leads to formation of highly cross-linked C(m)F aquagels that can be supercritically dried with carbon dioxide to form organic C(m)F aerogels. Aerogels synthesized with different catalyst contents and reactant concentrations are characterized by low-temperature nitrogen adsorption. The present experimental results suggest that the C(m)F aerogels are typical mesoporous materials and have almost no micropores in bulk. The microstructure of the organic C(m)F aerogels can be controlled and tailored effectively by varying synthesis conditions during the initial sol-gel process. C(m)F organic aerogels with specific surface area as high as 627 m(2)/g and corresponding pore volume 2.06 ml/g have been obtained with a dominant pore size of 30 nm. C(m)F organic aerogels with peaky pore size distributions concentrated at 11 nm have also been prepared.     

薄层法研究十二烷基苯磺酸钠对硝基苯/水界面电子转移的影响

用薄层法研究了阴离子表面活性剂十二烷基苯磺酸钠(SDBS)对硝基苯/水界面电子转移的影响. 实验结果表明, 随着水相中十二烷基苯磺酸钠浓度的增加, 有机相中十甲基二茂铁(DMFc)和水相中Fe(CN)₆^3-发生的界面双分子反应的阴极平台电流呈现递减趋势, 但是界面双分子反应速率常数却呈递增趋势. 这是由于阴离子表面活性剂十二烷基苯磺酸钠在硝基苯/水界面形成了修饰层, 影响了界面双电层结构. SDBS在液/液界面的吸附为Langmuir吸附.     

High surface area alumina-supported nickel (II) oxide aerogels using epoxide addition method

Nickel (II) oxide aerogels with an amorphous alumina support were synthesized by the expoxide addition method. The monoliths were obtained by adding propylene oxide to an alcoholic solution of hydrated metal nitrate salts. The wet gels were dried by supercritical extraction to produce porous monolithic aerogels. The as-synthesized aerogels were amorphous containing aluminum and nickel hydroxides. Annealing of the as-synthesized aerogels at 400 °C yields crystalline nickel oxide materials which retain the high surface areas (>160 m²/g) and porosities of the original aerogels. The resultant aerogel materials were characterized using powder X-ray diffraction, thermo-gravimetric analysis, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray analysis, and nitrogen adsorption/desorption analysis.     

BSA和SDBS在水溶液与空气界面的相互作用

表面活性剂与蛋白质在界面处的相互作用在许多应用里都会遇到．如去污、药品或生物制剂的制备和提纯、某些开科手术等等[1]这常常涉及到表面活性剂与蛋白质在界面的吸附，蛋白质大分子在界面吸附层的取向和构象．对于这两种物质在界面处可能发生的相互作用的性质，是表面活性剂     

Hydrophobic Silica Aerogels Strengthened with Nonwoven Fibers

Hydrophobic silica aerogels were prepared via a sol‐gel process by surface modification at ambient pressure. Nonwoven fibers were distributed inside the silica aerogels as a composite to act as a supporting skeleton which increased the mechanical property of the silica aerogels. The morphology and pore structure of the composites were characterized by scanning electron microscopy (SEM) and N₂ adsorption analyzer. The contact angle and the adsorption capacities of the composites were also determined. The results show that silica aerogels dispersed uniformly and maintained high porosity in the aerogel‐fiber composites. They have excellent hydrophobic properties and are excellent adsorptive materials.     

TiO2-SiO2复合气凝胶：常压干燥制备及性能表征

以廉价的四氯化钛和工业水玻璃为原料,通过溶胶-凝胶法制得TiO2-SiO2复合湿凝胶,用三甲基氯硅烷(TMCS)/乙醇(EtOH)/正己烷(Hexane)混合溶液对湿凝胶进行改性,常压干燥制备了TiO2-SiO2复合气凝胶.利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、红外光谱(FTIR)、X射线衍射(XRD)及N2吸附/脱附法对复合气凝胶的形貌和性质进行了分析.结果表明,TiO2-SiO2复合气凝胶具有连续多孔结构,150℃干燥后复合气凝胶的比表面积为1 076 m2·g-1,孔体积为4.96 cm3·g-1;经550 ℃热处理后,复合气凝胶仍然具有高的孔隙率,比表面积为856 m2·g-1,孔体积为3.46 cm3·g-1.吸附和光催化降解罗丹明B的结果表明,复合气凝胶同时具有较好的吸附和光催化性能,其吸附/光催化协同作用活性优于纯SiO2气凝胶和锐钛矿TiO2粉末;且重复利用四次降解率仍然可达到89%.     

Anionic surfactant adsorption on to asphalt-covered clays

Asphalt adsorption from from water-saturated tolene on Na⁻ kaolinite, Ca²⁻ kaolinite, Na⁻ illite and Ca²⁻ illite clays was investigated. It was found that the kaolinite surface adsorbed more asphalt than illite for both the Na⁻ -and the Ca²⁻ exchanged forms. Adsorption from aqueous solutions of sodium dodecylbenzenesulphonate (SDBS) and sodium dodecyl sulphate (SDS) on various asphalt-covered clays was also studied. The shape of the isotherms depended on the asphalt-clay substrate and showed a much lower adsorption of SDBS beyond the CMC. Desorption of asphalt from various clays with SDBS and SDS surfactants was measured spectrophotometrically. The percentage weight of asphalt desorbed with SDBS was twofold higher than that desorbed with SDS surfactant.     

Adsorption of sodium dodecylbenzenesulfonate on activated carbons: effects of solution chemistry and presence of bacteria

The objective of the present investigation was to determine the effectiveness of activated carbon in removing sodium dodecylbenzenesulfonate (SDBS) and to analyze the chemical and textural characteristics of the activated carbons that are involved in the adsorption process. Studies were also performed on the influence of operational variables (pH, ionic strength, and presence of microorganisms) and on the kinetics and interactions involved in the adsorption of this pollutant on activated carbon. The kinetics study of SDBS adsorption revealed no problems in its diffusion on any of the activated carbons studied, and Weisz-Prater coefficient (C WP) values were considerably lower than unity for all activated carbons studied. SDBS adsorption isotherms on these activated carbons showed that: (i) adsorption capacity of activated carbons was very high (260-470 mg/g) and increased with larger surface area; and (ii) dispersive interactions between SDBS and carbon surface were largely responsible for the adsorption of this pollutant. SDBS adsorption was not significantly affected by the solution pH, indicating that electrostatic adsorbent-adsorbate interactions do not play an important role in this process. The presence of electrolytes (NaCl) in the medium favors SDBS adsorption, accelerating the process and increasing adsorption capacity. Under the working conditions used, SDBS is not degraded by bacteria; however, the presence of bacteria during the process accelerates and increases SDBS adsorption on the activated carbon. Microorganism adsorption on the activated carbon surface increases its hydrophobicity, explaining the results observed.     

Equilibrium and kinetics of wetting hydrophobic microporous membrane in sodium dodecyl benzene sulphonate and diethanolamine aqueous solutions

Liquid penetrations into hydrophobic capillaries are controlled by the adsorption and diffusion of the solute in the vicinity of the moving meniscus. The wetting process of microporous hydrophobic polyvinylidenefluoride (PVDF) and polytetrafluoroethylene (PTFE) membrane was investigated in both sodium dodecyl benzene sulphonate (SDBS) and diethanolamine (DEA) aqueous solutions. The experimental results revealed that wetting both the PVDF and PTFE membranes in SDBS solutions at high concentrations proceeded in two stages: rapid wetting and slow wetting, but this transition in the wetting rate was not observed during the membrane wetting at low SDBS concentration and in DEA solutions. The membrane wetting process was accelerated by increasing the solution temperature.     

Langmuir aggregation of Nile blue and safranine T on sodium dodecylbenzenesulfonate surface and its application to quantitative determination of anionic detergent.

We studied the interaction of sodium dodecylbenzenesulfonate (SDBS) with Nile Blue (NB) and Safranine T (ST) by a spectral correction technique. The aggregations of NB and ST on an SDBS surface obeyed Langmuir isothermal adsorption. The adsorption ratios of NB and ST to SDBS were both 0.5, and the adsorption constants of the aggregates were 1.80 x 10(5) and 9.49 x 10(4). The aggregations were applied to the quantitative determination of anion detergent in samples; the recovery of SDBS was between 90.3 and 106% together with an RSD of 3.78%.     

Adsorption of supercritical CO2 in aerogels as studied by small-angle neutron scattering and neutron transmission techniques

Small-angle neutron scattering (SANS) has been used to study the adsorption behavior of supercritical carbon dioxide (CO2) in porous Vycor glass and silica aerogels. Measurements were performed along two isotherms (T=35 and 80 degrees C) as a function of pressure (P) ranging from atmospheric up to 25 MPa, which corresponds to the bulk fluid densities ranging from rho(CO2) approximately 0 to 0.9 gcm3. The intensity of scattering from CO2-saturated Vycor porous glass can be described by a two-phase model which suggests that CO2 does not adsorb on the pore walls and fills the pore space uniformly. In CO2-saturated aerogels an adsorbed phase is formed with a density substantially higher that of the bulk fluid, and neutron transmission data were used to monitor the excess adsorption at different pressures. The results indicate that adsorption of CO2 is significantly stronger in aerogels than in activated carbons, zeolites, and xerogels due to the extremely high porosity and optimum pore size of these materials. SANS data revealed the existence of a compressed adsorbed phase with the average density approximately 1.07 gcm3, close to the density corresponding to closely packed van der Waals volume of CO2. A three-phase model [W. L. Wu, Polymer 23, 1907 (1982)] was used to estimate the volume fraction phi3 of the adsorbed phase as a function of the fluid density, and gave phi3 approximately 0.78 in the maximum adsorption regime around rho(CO2) approximately 0.374 gcm3. The results presented in this work demonstrate the utility of SANS combined with the transmission measurements to study the adsorption of supercritical fluids in porous materials.     

Temperature-swing solid-phase extraction of heavy metals on a poly(N-isopropylacrylamide) hydrogel

The feasibility of temperature-swing adsorption of heavy metals on a thermosensitive N-isopropylacrylamide (NIPA) hydrogel was examined. We have proposed a novel temperature-swing solid-phase extraction (TS-SPE) technique. First, a metal ion in an aqueous solution is complexed with an extractant. Subsequently, the metal-extractant complexes (or micelles) are adsorbed onto the NIPA hydrogel through a hydrophobic interaction above the lower critical solution temperature (LCST). Finally, the metal-extractant complexes are desorbed from the NIPA hydrogel after it is cooled below the LCST. In a model system consisting of Cu(II) ions, sodium n-dodecylbenzenesulfonate (SDBS), and NIPA hydrogel, the proposed TS-SPE technique has been successfully conducted. The following observations can be made: the amount of adsorbed Cu(II) ions increases with the increase in temperature, the maximum adsorption is attained at a temperature above the LCST, and the hydrogel adsorbs and desorbs Cu(II) ions reversibly due to the temperature-swing between 10 and 40 degrees C. The LCSTs of poly(NIPA) in aqueous SDBS solutions with/without CuCl2 and the surface tensions of their solutions suggest that the hydrophobicity of the complex Cu(DBS)2 is greater than the hydrophobicities of SDBS and DBS. In addition to the separation of heavy metals, TS-SPE is potentially applicable to cases such as the separation of biological molecules by means of metal-ion affinity.     

Transparent and flame retardant cellulose/aluminum hydroxide nanocomposite aerogels

Cellulose-based nanocomposite aerogels were prepared by incorporation of aluminum hydroxide (AH) nanoparticles into cellulose gels via in-situ sol-gel synthesis and following supercritical CO₂ drying. The structure and properties of cellulose/AH nanocomposite aerogels were investigated by Fourier transform infrared spectroscopy, scanning electron microscopy, ultraviolet-visible spectrometry, N₂ adsorption, thermogravimetric analysis, and micro-scale combustion calorimetry. The results indicated that the AH nanoparticles were homogeneously distributed within matrix, and the presence of AH nanoparticles did not affect the homogeneous nanoporous structure and morphology of regenerated cellulose aerogels prepared from 1-allyl-3-methylimidazolium chloride solution. The resultant nanocomposite aerogels exhibited good transparency and excellent mechanical properties. Moreover, the incorporation of AH was found to significantly decrease the flammability of cellulose aerogels. Therefore, this work provides a facile method to prepare transparent and flame retardant cellulose-based nanocomposite aerogels, which may have great potential in the application of building materials.     

表面活性剂和聚乙烯吡咯烷酮在ZrO2上的吸附对其悬浮体稳定性的影响

研究了水溶液中十二烷基苯磺酸钠（ＳＤＢＳ）、溴代十四烷基吡啶（ＴＰＢ）和聚乙烯吡咯烷酮（ＰＶＰ）在ＺｒＯ２上的吸附及对ＺｒＯ２水悬浮体稳定性的影响。结果表明：ｐＨ＝２．４时ＳＤＢＳ在ＺｒＯ２上的吸附等湿线为ＬＳ型，ｐＨ＝７．０时ＴＰＢ的吸附等温线为Ｓ型，吸附等温线与ＺｒＯ２粒子ζ电势变化同线有大体一致的关系。在最大吸附量时ＺｒＯ２粒子ζ电势较大，且吸附的表面活性剂离子形成大部分亲水基朝向水相的表面     

Controlling the morphology of a zinc ferrite-based aerogel by choice of solvent

Zinc ferrite-based aerogels were prepared by the epoxide addition method. The effects of changing the reaction solvent were investigated. The porosity of the resultant materials was investigated by gas adsorption techniques while the microstructure of the aerogels was investigated by scanning electron microscopy and transmission electron microscopy. The solvent in which the gels were formed was found to have a profound impact on the surface morphology of the aerogels and the size of the nanoparticles therein. The aerogels were further analyzed by thermal gravimetric analysis and powder X-ray diffraction. After annealing at 350 °C, the porous material is found to maintain its nanocrystalline properties.     

Pyrolysis of N-doped organic aerogels with relation to sorption properties

Resorcinol–formaldehyde aerogels (five samples, three of them with addition of nitrogen containing precursors—3-hydroxypyridine, 3-aminophenol and melamine) have been prepared by sol–gel polycondensation, subcritical drying and pyrolysis. The pyrolysis of prepared organic aerogels has been studied by non-isothermal TG at constant heating rate. The process of pyrolysis has been found to consist of three steps with the total mass loss 40.2–61.7% (room temperature—1,000 °C). The resulted carbon aerogels have been tested as sorbents of Ni(II), Pb(II) and Cu(II) ions from aqueous solutions. Various relations have been found among the results obtained from the pyrolysis experiments and properties affecting adsorption. Besides the expected correlation between the mass loss gained from TG (isothermal step at 500 °C was applied) and from heating in the laboratory oven, the relationship between the mass loss during pyrolysis and sorption capacities for all three metal ions has been found. Other relations among pyrolysis behaviour, surface area and content of nitrogen have been also examined. Batch adsorption experiments show (with an exception of one sample) that N-doped samples have higher adsorption capacity for metal ions. In addition, changing of nitrogen functionalities during the pyrolysis has been considered and pyridinic-N (N-6) functionality has been contemplated as a suitable structure for the adsorption process.