Adsorption characteristics of surfactants and phenol on modified zeolites from their aqueous solutions

Adsorption characteristics of anion-, cation- and nonion-type surfactants and phenol from their aqueous solution on Na-Y zeolites modified by SiCl₄ treatment and NA-ZSM-5 zeolites with several Si/Al ratios were measured. Surfactants used were sodium dodecylbenzenesulfonte (DBS), laurylpyridinium chloride (LPC), polyoxyethylenenonylphenylether (POENPE) and phenol.Adsorption of surfactants was enhanced by SiCl₄ treatment of Na-Y, which indicates an important role of the hydrophilic-hydrophobic character in the adsorption.Adsorption isotherms were in general of Langmuir type and adsorbed amount depended on the Al/(Si+Al) or Si/Al ratio of zeolite frameworks. In case of DBS adsorption of Na-ZSM-5 series, adsorption occurred only on the outer surface due to steric hindrance. LPC adsorption abilities were observed on even hydrophilic zeolites and were ascribed to ion exchange effect. In case of phenol adsorption on hydrophobic Na-Y, the adsorption isotherm was of Type V according to BDDT classification.     

Multi-modification of Na-Y zeolite with ZnO nanoparticles,amine, and mercapto functional groups for single and simultaneous heavy metal adsorption from water system

Research on Chemical Intermediates - A multi-functionalized Na-Y/ZnO/NH2/SH composite adsorbent was synthesized for Pb2+ and Ni2+ removal from single and binary aqueous systems. The prepared...     

Influence of NaCl on the behavior of PEO-PPO-PEO triblock copolymers in solution, at interfaces, and in asymmetric liquid films

The solution behavior of the polymeric surfactant Pluronic F127 (PEO(99)PPO(65)PEO(99)) and its adsorption behavior on aqueous-silica and aqueous-air interfaces, as well as the disjoining pressure isotherms of asymmetric films (silica/aqueous film/air) containing F127, are studied. The interfacial properties of adsorbed F127 layers (the adsorbed amount Gamma and the thickness h) as well as the aqueous wetting film properties [film thickness (h) and refractive indexes] were studied via ellipsometry. The solution properties of F127 were investigated using surface tensiometry and light scattering. The interactions between the air-water and silica-water interfaces were measured with a thin film pressure balance technique (TFB) and interpreted in terms of disjoining pressure as a function of the film thickness. The relations between the behaviors of the asymmetric films, adsorption at aqueous air, and aqueous silica interfaces and the solution behavior of the polymeric surfactant are discussed. Special attention is paid to the influence of the concentrations of F127 and NaCl. Addition of electrolyte lowers the critical micelle concentration, diminishes adsorption on silica, and increases the thickness of the asymmetric film.     

Adsorption behaviour of sugars versus their activity in single and multicomponent liquid solutions

In this work the activity of three carbohydrates (sucrose, glucose and fructose) in highly concentrated aqueous solutions was studied along with its effect on the adsorption behaviour of the investigated compounds. Activities of individual sugars in aqueous solutions of single solute as well as in binary mixtures were quantified on the basis of solubility properties. Solid–liquid equilibria of sugars were correlated with the NRTL (nonrandom, two liquid) model of activity coefficient formulation. Activities of individual sugars were incorporated into the single component adsorption isotherm model, which reproduced accurately the course of the adsorption equilibria of sugars in aqueous solutions obtained experimentally in previous work using an ion-exchange resin. Activities of sugars determined in binary solute systems along with the single component isotherms were used to predict competitive adsorption equilibria. To calculate adsorbed phase concentrations of individual sugars in binary mixtures the adsorbed solution theory was adopted. The isotherm shapes calculated were compared to the data of competitive adsorption from the former study and found to be able to describe these experimental results.     

Computer simulation of the adsorption of thiophene in all-silica Y and Na-Y

A grand canonical ensemble Monte Carlo simulation is performed to investigate the adsorption, heat of adsorption, and distributions of thiophene in all-silica Y and Na-Y zeolites. Biased particle insertions and deletions were implemented to allow the computation of equilibrium adsorption isotherms of such molecules. The calculated number of absorbed thiophene molecules in these zeolites is in good agreement with the experimental data. The calculated results show that the number absorbed of thiophene molecules in Na-Y is much greater than that in all-silica Y over the range of pressure. The calculated heat of adsorption is in good agreement with experimental results. The Na-Y zeolite, rather than all-silica Y, preferentially adsorbs the thiophene. A distribution analysis of the adsorbed phase structure reveals a different adsorption site in the zeolites.     

二氧化钛纳米管的制备与光催化活性

用阳极氧化法,室温条件下在含NH4F和H2O的电解液(丙三醇+NH4F+H2O;乙二醇+NH4F+H2O)中制备了TiO2纳米管阵列。用环境扫描电子显微镜(SEM)、X射线衍射仪(XRD)表征二氧化钛纳米管阵列的微观形貌和物相结构。在丙三醇电解液中,电压为60 V,65 V,70 V,75 V制备的纳米管直径依次为160、170、190、220 nm。对甲基橙(10 mg/L)降解测试TiO2纳米管阵列的光催化性能。研究结果表明:在100 V阳极电压制备经过500℃退火处理后的TiO2纳米管阵列的光催化效果最好,其光催化降解率在光照时间120 min时达到89.2%。     

In situ attenuated total reflection infrared (ATR-IR) study of the adsorption of NO2-, NH2OH, and NH4+ on Pd/Al2O3 and Pt/Al2O3

In relation to the heterogeneous hydrogenation of nitrite, adsorption of NO2-, NH4+, and NH2OH from the aqueous phase was examined on Pt/Al2O3, Pd/Al2O3, and Al2O3. None of the investigated inorganic nitrogen compounds adsorb on alumina at conditions presented in this study. NO2-(aq) and NH4+(aq) on the other hand show similar adsorption characteristics on both Pd/Al2O3 and Pt/Al2O3. The vibrational spectrum of the NO2- ion changed substantially upon adsorption, clearly indicating that NO2- chemisorbs onto the supported metal catalysts. On the contrary, adsorption of NH4+ does not lead to significant change in the vibrational spectrum of the ion, indicating that the NH4+ ion does not chemisorb on the noble metal but is stabilized via an electrostatic interaction. When comparing the adsorption of hydroxylamine (NH2OH(aq)) on Pd/Al2O3 and Pt/Al2O3, significant differences were observed. On Pd/Al2O3, hydroxylamine is converted into a stable NH2(ads) fragment, whereas on Pt/Al2O3 hydroxylamine is converted into NO, possibly via HNO(ads) as an intermediate.     

Counter ion effect on phase behavior in adsorbed film of fluoroalkanol and cationic surfactant mixture

The surface tension of the 1H,1H-heptafluoro-1-butanol (FC4OH)–dodecyltrimethylammonium chloride (DTAC) mixed aqueous solution was measured as a function of the total molality of the mixture and the composition of DTAC at 298.15 K under atmospheric pressure.The phase diagram of adsorption (PDA) that gives the composition relation between the aqueous solution and adsorbed film was constructed. It was suggested that the subtle balance between the attractive surfactant cation-OH dipole interaction and the weak dispersion interaction between C–H and C–F chains is crucial for the phase behavior. The phase diagram of adsorbed film (PDAF) showing the composition relation between the different state of adsorbed films demonstrated the phase behavior is significantly dependent on the degree of counter ion binding. Moreover, the possible surface structures at the azeotropes are suggested.     

Miscibility of sodium chloride and decyl methyl sulfoxide in the adsorbed film and micelle

The surface tension of aqueous solutions of a sodium chloride (NaCl)-decyl methyl sulfoxide (DeMS) mixture was measured as a function of the total molality of the mixture and the mole fraction of DeMS in the mixture at 298.15 K under atmospheric pressure. The total surface density of the mixture and the mole fraction of DeMS in the adsorbed film and micelle were numerically evaluated by applying the thermodynamic treatment of surfactant mixture to the NaCl-DeMS mixture. Miscibility of NaCl and DeMS in the adsorbed film and micelle was clarified by use of the phase diagram of adsorption and micelle formation. Positive adsorption of NaCl was observed in the presence of DeMS and attributed to attractive interaction between the polar head group of DeMS molecule and Na+ or Cl- ions in the adsorbed film and micelle. The results were compared with those of NaCl-octyl methyl sulfoxide and NaCl-decyldimethylphosphine oxide mixtures to elucidate the structure effect of nonionic surfactant on the miscibility.     

An investigation of gold adsorption from a binary mixture with selective mesoporous silica adsorbents

Gold-selective adsorbents were prepared from mesoporous MCM-41 silica by grafting organic amine groups (i.e., RNH2, R2NH, and R3N; R=propyl). NH2-MCM-41, NRH-MCM-41, and NR2-MCM-41 displayed strong affinity for gold and at 1 mmol/g loading adsorbed 0.40, 0.33, and 0.20 mmol/g of gold. Copper and nickel were not adsorbed on these adsorbents. Grafting surface chemical moieties introduces heterogeneity on an otherwise uniform MCM-41 pore surface and metal adsorption is best described by the Freundlich adsorption model. A series of binary adsorption equilibrium studies with NH2-MCM-41 containing 2.2 mmol RNH2/g shows that NH2-MCM-41 adsorbs only gold from solutions containing copper and nickel with an adsorption capacity of 0.6 mol of Au/mol of RNH2 (1.1 mmol of Au/g of NH2-MCM-41). Copper and nickel were not adsorbed by NH2-MCM-41 regardless of the solution concentration, composition, and pH (i.e., 2 to 4) in the presence of gold. The LeVan and Vermeulen adsorption model based on a single component Freundlich isotherm and corrected for the anion effect accurately predicted the binary adsorptions. The adsorbed gold was completely recovered by a simple acid wash and the recovered gold solution is 99% pure. The regenerated NH2-MCM-41 remained 100% selective for gold removal and exhibited the same adsorption capacity even after several uses.     

Cu-[M’]MOR和Ag-[M’]MOR (M’=B,Al, Ga,Fe)的酸性

采用Dmol3程序中基于密度泛函理论(DFT)的广义梯度方法(GGA)和BLYP方法以及DND基组, 研究了丝光沸石H-[M']MOR、Cu-[M']MOR和Ag-[M']MOR(M'=B, Al, Ga, Fe)结构及其对NH3分子的吸附, 获得了吸附平衡构型和吸附能. NH3分子在H-[M']MOR中的吸附主要是通过NH3分子中氮原子上的孤对电子与质子酸位作用, NH3分子在H-[Al]MOR、H-[Ga]MOR和H-[Fe]MOR上发生化学吸附, 而在H-[B]MOR上发生物理吸附, 这与文献结果相符. NH3分子与Cu-[M']MOR 和Ag-[M']MOR分子筛之间主要通过氮上的孤对电子和平衡离子(Cu+和Ag+)的s空轨道间配位作用而发生化学吸附. 吸附能数据表明, 在H-[M']MOR、Cu-[M']MOR 和Ag-[M']MOR中, A1原子进入骨架导致H-[A1]MOR、Cu-[A1]MOR和Ag-[A1]MOR的酸强度最强; 对于同一种原子取代的丝光沸石, 其酸强度次序为: Cu-[M']MOR > Ag-[M']MOR > H-[M']MOR. 此外, 还对吸附前后的沸石中平衡离子(H+、Cu+和Ag+)及NH3分子的Mulliken电荷集居数作了研究和分析.     

Adsorption of anionic and cationic dyes by activated carbons, PVA hydrogels, and PVA/AC composite

The textural and adsorption characteristics of a series of activated carbons (ACs), porous poly(vinyl alcohol) (PVA) gels, and PVA/AC composites were studied using scanning electron microscopy, mercury porosimetry, adsorption of nitrogen (at 77.4 K), cationic methylene blue (MB), anionic methyl orange (MO), and Congo red (CR) from the aqueous solutions. Dye-PVA-AC-water interactions were modeled using the semiempirical quantum chemical method PM6. The percentage of dye removed (C(rem)) by the ACs was close to 100% at an equilibrium concentration (C(eq)) of less than 0.1 mM but decreased with increasing dye concentration. This decrease was stronger at C(eq) of less than 1 mM, and C(rem) was less than 50% at a C(eq) of 10-20 mM. For PVA and the PVA/AC composite containing C-7, the C(rem) values were minimal (<75%). The free energy distribution functions (f(ΔG)) for dye adsorption include one to three peaks in the -ΔG range of 1-60 kJ/mol, depending on the dye concentration range used and the spatial, charge symmetry of the hydrated dye ions and the structural characteristics of the adsorbents. The f(ΔG) shape is most complex for MO with the most asymmetrical geometry and charge distribution and adsorbed at concentrations over a large C(eq) range. For symmetrical CR ions, adsorbed over a narrow C(eq) range, the f(ΔG) plot includes mainly one narrow peak. MB has a minimal molecular size at a planar geometry (especially important for effective adsorption in slit-shaped pores) which explains its greater adsorptive capacity over that of MO or CR. Dye adsorption was greatest for ACs with the largest surface area but as molecular size increases adsorption depends to a greater extent on the pore size distribution in addition to total and nanopore surface areas and pore volume.     

一步法制备聚脲多孔材料及其对染料的吸附

以甲苯二异氰酸酯为单体, 在水和丙酮混合溶剂中不用致孔剂且无需任何高分子改性一步法合成了聚脲多孔材料(PPU), 通过扫描电镜和BET氮气吸附法对其表面形貌和孔参数进行了表征. 以酸品红(AF)溶液模拟染料废水, 对其在PPU上的吸附进行了研究, 讨论了pH、 吸附时间、 AF初始浓度及吸附剂用量对吸附过程的影响, 优化了吸附条件. 结果表明, PPU对染料AF具有优异的吸附效果. PPU在30℃, pH=3时对AF的最大吸附量为44.60 mg/g. PPU对AF的吸附过程更接近于Langmuir等温吸附的单分子层吸附机理. PPU对水溶性染料刚果红(CR)也有很好的吸附能力. 使用水、 乙醇和水混合溶剂以及NaOH水溶液对染料吸附后的解吸附结果表明, 乙醇和水混合溶剂对吸附染料的解吸效率最高, 对2种染料的解吸附都达90%以上. 解吸后PPU的再吸附能力略有下降, 但第三次吸附量仍达到首次吸附的80%以上.     

不等链长的碳氟、碳氢正负离子表面活性剂混合体系的表面活性

研究了全氟辛酸钠与溴化十四烷基三甲铵混合水溶液的表面活性. 测定了不同比例混合物水溶液的表面张力-浓度曲线, 得出临界胶团浓度(cmc)及监 界胶团浓度时的溶液表面张力(γcmc)值. 应用Gibbs吸附公式及吸附层中两表面活性剂分子相互作用参数法求出表面总吸附量、吸附层组成及两表面活性剂分别吸附量等. 指示此吸附层具有多分子层性质. 这可能是碳氢、碳氟正负离子混合体系的特点.     

Cu(I), Ag(I)/分子筛化学吸附脱硫的π-络合机理

应用DFT 研究了一系列含硫的杂环化合物(噻吩、苯并噻吩、二苯并噻吩和4, 6-二甲基二苯并噻吩)以及苯分子在Cu(I)-Y、Ag(I)-Y 分子筛上的化学吸附. 计算采用16T 分子筛簇模型(H22Si15AlO22), 对过渡金属采用了赝势基组, 在BLYP/DNP水平上完成. 相互作用能的结果表明, 阳离子交换的分子筛对含硫杂环芳香族化合物吸附能力的顺序为Cu(I)-Y >Ag(I)-Y. 两种吸附剂对噻吩类分子的吸附能力大于苯分子. 噻吩衍生物的吸附能顺序依次为, 4, 6-二甲基二苯并噻吩<二苯并噻吩约噻吩<苯并噻吩, 与实验结果相近. 通过自然键轨道计算,研究了分子筛上担载的Cu(I)、Ag(I)金属离子与噻吩和苯分子之间的π-络合作用, 分析比较了自然键电子给体-受体之间的二阶微扰稳定化能, 并探索其络合机理.     

Adsorption of a polymeric siloxane surfactant on carbon black particles dispersed in mixtures of water with polar organic solvents

The adsorption of a rake-type polymeric siloxane surfactant (polydimethylsiloxane-graft-polyether copolymer) on carbon black (CB) particles dispersed in mixtures of water with polar organic solvents (ethanol, formamide, or glycerol) has been investigated. The adsorption obeys the Langmuir isotherm at low surfactant concentrations (below the critical micelle concentration, CMC). At these conditions, the average surface area occupied by one siloxane surfactant follows the sequence water+glycerol mixture >plain water >water+ethanol mixture. At higher surfactant concentrations in the solution in contact with the particles, a sharp increase in the adsorbed amount is observed. The adsorbed layer thickness has been determined by dynamic light scattering. Below the CMC the adsorbed layer thickness is less than 10 nm. Above the CMC, the adsorbed layer thickness increases to 20-30 nm, a length scale comparable to the diameter of the siloxane surfactant micelles in aqueous solution. This fact, together with SANS data that we have obtained in the absence of added polar organic solvent, indicates that the structure of the adsorbed layer is similar to that of micelles. The findings presented here are relevant to waterborne coatings and ink formulations, where polymeric surfactants are used in conjunction with polar organic solvents.     

CO氢化合成乙醇反应的过渡应答研究——改性Rh/Al2O3催化剂的吸附特性

本文以四极质谱作为过渡应答测量中的分析手段, 连续快速跟踪和分析被测物种, 测量了H_2和CO在改性Rh/Al_2O_3催化剂上的吸附和脱附性能。结果发现, 507 K时H_2或CO的吸附中存在着部份不可逆吸附。CO和H_2吸附在相同的活性位上, 存在竞争吸附。CO的吸附作用略强於H_2。钾元素的改性使催化剂对H_2或CO的吸附量均减少, 然而相对于H_2而言, CO的吸附作用更强了。     

甘氨酸在高岭土表面的吸附和热缩合反应

采用TG/DTA、FT-IR和in situ DRIFT等技术对甘氨酸在高岭土表面的吸附和热缩合反应进行了表征, 考察了甘氨酸平衡浓度和溶液pH值对吸附行为的影响, 同时探讨了原位条件下甘氨酸的缩合反应历程. 结果表明, 溶液呈弱酸性时, 甘氨酸在高岭土上的吸附量最大, 但吸附等温线不符合Langmuir模型. 在强酸性、弱酸性和碱性溶液中, 吸附态的甘氨酸分别主要以阳离子、两性离子和阴离子形式存在. 弱酸性溶液中, 甘氨酸的—NH3+基团与高岭土表面的≡S—O−(S为Si或Al)基团之间的氢键作用是吸附的主要驱动力, 而强酸性溶液中, ≡S—O−基团的质子化, 以及碱性溶液中—NH3+向—NH2的转化, 是导致吸附量下降的主要原因. In situ DRIFT结果表明, 在110−160 ℃温区, 有明显的线式二肽形成; 随着温度升高至210 ℃时, 二肽进一步脱水, 形成环化缩合产物哌嗪二酮(DKP). 没有检测到硅酯类或铝酯类中间体的特征峰, 反应可能按氢键促进下的自缩合机理进行, 高岭土的存在使缩合反应温度有明显降低.     

Enhanced adsorption of alkyl glucosides on the silica/water interface by addition of amine oxides

The effect of adding a small amount of dodecyl dimethylamine oxide (DDAO) on adsorption on silica from an aqueous solution of dodecyl maltoside (C12G2) has been investigated. The C12G2 itself does not adsorb significantly on silica at any concentration. DDAO on the other hand readily adsorbs in a bilayer-like structure at concentrations approaching the critical micelle concentration (cmc), but the adsorbed amount at the concentrations it has been applied in these mixtures is small. In contrast, by combination of the two surfactants, significant adsorption is observed at concentrations where the adsorption of the pure DDAO, as well as pure C12G2, is very low. We thus see a strong enhancement of the adsorption from the mixed system. The adsorption is suggested to be a two-step process, where individual DDAO molecules first adsorb to the silica surface through electrostatic interactions, and then C12G2 adsorbs at the hydrophobic sites the DDAO tails constitute through hydrophobic bonding. A minimum concentration of DDAO is required to induce adsorption from a solution with constant C12G2 concentration. This concentration is lower for C12G2 solutions below and equal to cmcC12G2 than above cmcC12G2. In addition, the total adsorbed amount shows a maximum around cmcC12G2 of the mixture for a solution with low DDAO contents. Both these effects are explained by incorporation of DDAO in the mixed micelles above cmc(mix), which leads to a desorption of DDAO from the surface.