木薯羧甲基淀粉对铜离子的吸附性能

采用搅拌球磨机对木薯淀粉进行机械活化,以活化60 min的木薯淀粉为原料,干法合成羧甲基淀粉吸附剂。考察羧甲基淀粉的取代度、溶液的pH值、Cu2+的初始浓度、吸附时间、羧甲基淀粉的投加量等因素对羧甲基淀粉吸附Cu2+性能的影响。结果表明,该羧甲基淀粉对Cu2+有很好的吸附作用;用取代度为0.841的羧甲基淀粉处理含Cu2+的废水,在pH=7.0、羧甲基淀粉的投加量50.00 mg/L、吸附时间15 min时,羧甲基淀粉对废水中Cu2+的吸附率高达98.80%,处理后的水质达到国家污水综合排放标准(GB8978-1996)中一级标准要求。     

The fluorination of titanium dioxide surfaces

Summary Gaseous hydrogen fluoride gave a bulk attack on titanium dioxide but dilute aqueous hydrofluoric acid gave a partial surface fluorination. A specific fluoride for chloride exchange reaction occurs on chloride containing titanium dioxide surfaces. A weak and a strong form of fluoride adsorption may be distinguished, the former being removed by prolonged treatment with water, the latter requiring steam at 1020 K for its complete removal. Some infra-red, electrophoretic and acidity studies on various fluorinated surfaces are reported.

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Zusammenfassung Eine verdünnte wäßrige Fluorwasserstoffsäure fluoriert Titandioxid teilweise an der Oberfläche, während Fluorwasserstoffgas auch das Kristallinnere angreift. Eine spezifische Austauschreaktion Fluorid gegen Chlorid tritt an chloridhaltigen Titandioxidoberflächen auf. Man kann zwischen einer schwachen und einer starken Fluoridadsorption unterscheiden. Die schwächer adsorbierten Fluoridionen werden durch längere Behandlung mit Wasser verdrängt, die stärker adsorbierten dagegen nur durch Dampf bei 1020 K. In der Arbeit wird außerdem über IR-Studien sowie über elektrophoretische Messungen und Aziditätsuntersuchungen an verschiedenen fluorierten Oberflächen berichtet.

     

Kinetics and adsorption behavior of carboxymethyl starch on alpha-alumina in aqueous medium

The adsorption of carboxymethyl starch (CMS) at the alpha-alumina/aqueous solution interface has been investigated through adsorption studies, electrokinetics mobility measurements, and FTIR spectroscopy. Zeta potential measurements show that the addition of CMS results in a more dramatic increase in the absolute zeta potential in the alkaline region, as well as a shift of the isoelectric point to lower values, indicating the adsorption of CMS from the aqueous solution onto the alumina surface. The positive hydrophilic surface sites of alumina are responsible for the adsorption of CMS molecules. The adsorption of CMS is possible after charge reversal by the addition of excess CMS. Nearly 30 min of contact time are found to be sufficient for the adsorption of CMS to reach equilibrium. CMS adsorption follows a Langmuir isotherm with adsorption capacities of 91.74 mg CMS per gram of alpha-alumina. For the adsorption of CMS, pseudo-second-order chemical reaction kinetics provides the best correlation with the experimental data. FTIR analysis indicated that CMS forms outer complexes with alumina surfaces depending on the shifting of the asymmetric and symmetric bands.     

XPS studies of amino acids adsorbed on titanium dioxide surfaces

Summary Adsorption of amino acids from aqueous solutions on TiO₂ surfaces as a function of pH is monitored quantitatively by X-ray photoelectron spectroscopy (XPS). Because of the amphoteric character of the TiO₂ and the zwitterionic behaviour of the amino acids the pH of adsorption indicates what chemical groups are involved in the adsorption reaction. The results confirm the ligand exchange model: in acidic milieu the carboxylic group replaces a basic surface hydroxyl group on a Ti site and binds to this Ti. For homocysteine the resulting position of the adsorbed molecule can also be concluded by comparing peak intensities.     

Adsorption of sulfur dioxide on hematite and goethite particle surfaces

The adsorption of sulfur dioxide (SO(2)) on iron oxide particle surfaces at 296 K has been investigated using X-ray photoelectron spectroscopy (XPS). A custom-designed XPS ultra-high vacuum chamber was coupled to an environmental reaction chamber so that the effects of adsorbed water and molecular oxygen on the reaction of SO(2) with iron oxide surfaces could be followed at atmospherically relevant pressures. In the absence of H(2)O and O(2), exposure of hematite (alpha-Fe(2)O(3)) and goethite (alpha-FeOOH) to SO(2) resulted predominantly in the formation of adsorbed sulfite (SO(3)(2-)), although evidence for adsorbed sulfate (SO(4)(2-)) was also found. At saturation, the coverage of adsorbed sulfur species was the same on both alpha-Fe(2)O(3) and alpha-FeOOH as determined from the S2p : Fe2p ratio. Equivalent saturation coverages and product ratios of sulfite to sulfate were observed on these oxide surfaces in the presence of water vapor at pressures between 6 and 18 Torr, corresponding to 28 to 85% relative humidity (RH), suggesting that water had no effect on the adsorption of SO(2). In contrast, molecular oxygen substantially influenced the interactions of SO(2) with iron oxide surfaces, albeit to a much larger extent on alpha-Fe(2)O(3) relative to alpha-FeOOH. For alpha-Fe(2)O(3), adsorption of SO(2) in the presence of molecular oxygen resulted in the quantitative formation of SO(4)(2-) with no detectable SO(3)(2-). Furthermore, molecular oxygen significantly enhanced the extent of SO(2) uptake on alpha-Fe(2)O(3), as indicated by the greater than two-fold increase in the S2p : Fe2p ratio. Although SO(2) uptake is still enhanced on alpha-Fe(2)O(3) in the presence of molecular oxygen and water, the enhancement factor decreases with increasing RH. In the case of alpha-FeOOH, there is an increase in the amount of SO(4)(2-) in the presence of molecular oxygen, however, the predominant surface species remained SO(3)(2-) and there is no enhancement in SO(2) uptake as measured by the S2p : Fe2p ratio. A mechanism involving molecular oxygen activation on oxygen vacancy sites is proposed as a possible explanation for the non-photochemical oxidation of sulfur dioxide on iron oxide surfaces. The concentration of these sites depends on the exact environmental conditions of RH.     

Adsorption studies for the acrylic polyester hyper-dispersant on titanium dioxide

A novel acrylic polyester hyper-dispersant was used to disperse titanium dioxide in different organic solvents. The adsorption behaviors were investigated in ethyl acetate, toluene, and isopropyl alcohol. Meanwhile, the data of adsorption isotherms were correlated using the Langmuir, Freundlich, Redlich–Peterson, Tempkin, and Fritz–Schlunder models. The results showed that the four-parameter Fritz–Schlunder isotherm equation was the best correlation. The mean free energy of sorption was calculated by Dubinin–Radushkevick equation using the adsorption data and its E value was 2.09–3.11 kJ mol^?1, this indicated the adsorption was a physical process in accordance with the FTIR test result.     

Adsorption of polymethacrylic acid from aqueous solutions on disperse titanium dioxide

The state of macromolecules of polymethacrylic acid adsorbed on the surface of disperse titanium dioxide was assessed using a combination of the differential concentration approach to the determination of adsorption and methods for determining the size of disperse adsorbents by dynamic light scattering and sedimentation analysis in the field of centrifugal forces. Three sections were found on the isotherm of adsorption: in the first, isolated islands of adsorbed macromolecules formed; in the second, layers of macromolecules with a different degree of deformation were observed; in the third, determining the adsorption of macromolecules is complicated by other accompanying processes, and assessing the state of macromolecules in the adsorption layer becomes difficult.     

Adsorption of carboxymethyl cellulose on polymer surfaces: evidence of a specific interaction with cellulose

The adsorption of carboxymethyl cellulose (CMC), one of the most important cellulose derivatives, is crucial for many scientific investigations and industrial applications. Especially for surface modifications and functionalization of materials, the polymer is of interest. The adsorption properties of CMC are dependent not only on the solutions state, which can be influenced by the pH, temperature, and electrolyte concentration, but also on the chemical composition of the adsorbents. We therefore performed basic investigation studies on the interaction of CMC with a variety of polymer films. Thin films of cellulose, cellulose acetate, deacetylated cellulose acetate, polyethylene terephthalate, and cyclo olefin polymer were therefore prepared on sensors of a QCM-D (quartz crystal microbalance) and on silicon substrates. The films were characterized with respect to the thickness, wettability, and chemical composition. Subsequently, the interaction and deposition of CMC in a range of pH values without additional electrolyte were measured with the QCM-D method. A comparison of the QCM-D results showed that CMC is favorably deposited on pure cellulose films and deacetylated cellulose acetate at low pH values. Other hydrophilic surfaces such as silicon dioxide or polyvinyl alcohol coated surfaces did not adsorb CMC to a significant extent. Atomic force microcopy confirmed that the morphology of the adsorbed CMC layers differed depending on the substrate. On hydrophobic polymer films, CMC was deposited in the form of larger particles in lower amounts whereas hydrophilic cellulose substrates were to a high extent uniformly covered by adsorbed CMC. The chemical similarity of the CMC backbone seems to favor the irreversible adsorption of CMC when the molecule is almost uncharged at low pH values. A selectivity of the cellulose CMC interaction can therefore be assumed. All CMC treated polymer films exhibited an increased hydrophilicity, which confirmed their modification with the functional molecule.     

Adsorption of cadmium(II) on humic acid coated titanium dioxide

The rapid increase in nanotechnology has led to growing concerns on environmental effects and health risks of nanoparticles (NPs). Many studies investigated the adsorption of toxic pollutants on NPs; however, the interaction between heavy metals and natural organic matter (NOM) coated metal oxide NPs was scarcely studied. In this study, using humic acid (HA) as model NOM, the adsorption of Cd(II) on humic acid coated titanium dioxide (HA-TiO(2)) NPs was investigated. Solution parameters such as pH and salinity were investigated to exploit the mechanisms. Our results demonstrated that the adsorption isotherms of Cd(II) to both TiO(2) and HA-TiO(2) complied well with Freundlich model. q(e) values increased with pH increase, mainly due to electrostatic attraction, whereas q(e) values increased initially and then decreased at 100 mmol L(-1) with salinity increase, mainly due to complexation and electrostatic effects. It is noteworthy that an overall trend of higher Cd(II) adsorption was observed on HA-TiO(2) compared to that on TiO(2), implying that HA coating might modify bioavailability of heavy metals in aquatic environment. The possible adsorption mechanisms in views of electrostatic interactions and covalent effects were interpreted, and the X-ray photoelectron spectroscopy (XPS) results also verified the possible mechanisms.     

纳米TiO-2对模型病毒-f2噬菌体的吸附特性

为了提高饮用水处理系统对病毒的去除效果,本研究采用静态实验,研究纳米TiO2对模型病毒—f2噬菌体的吸附去除特性,系统考察TiO2投加浓度、病毒浓度、温度及pH值等因素对吸附效果的影响.实验结果表明：f2噬菌体在纳米TiO2表面的吸附符合准二级吸附动力学模型,遵循化学吸附机理,颗粒内扩散为该吸附过程中的速率控制步骤,但不是唯一控制步骤;纳米TiO2对f2噬菌体的吸附符合Freundlich等温吸附模型（qe=27.4Ce1.24）,属于多层吸附类型;在20~40℃范围内,温度对纳米TiO2的吸附性能影响不大,而酸性条件下更有利于纳米TiO2对f2噬菌体的吸附.     

SECM characterization of immobilised enzymes by self-assembled monolayers on titanium dioxide surfaces

SECM in generator-collector mode was used to detect the presence of immobilised enzymes on titanium dioxide layers which were chemically or electrochemically generated with possible application as chemical sensors and biosensors. Glucose oxidase (GOx) and horseradish peroxidase (HRP) were immobilised by SAM generation using aminopropyltriethoxysilane (APTES) and ascorbic acid. The enzymes were successfully immobilised on two different TiO(2) surfaces. A simple test of durability of the system was made and a model of SAM organisation is presented.     

纳米二氧化钛对痕量铅的吸附性能研究

提出了纳米TiO2分离富集, 火焰原子吸收光谱法测定水样中痕量铅的新方法.考察了铅在纳米TiO2上的吸附动力学、最佳酸度和吸附容量.实验结果表明：在最佳实验条件下,纳米TiO2能定量、快速地吸附水中的痕量Pb^2＋,其静态吸附容量为17.90 mg/g.吸附在纳米TiO2上的Pb^2＋可用0.1 mol/L HNO3＋0.1 mol/L CH3COOH完全洗脱.对Pb2＋的检出限为2.57 ng/mL, 相对标准偏差为2.5% （n=11, ρ=0.10 μg/mL）,加标回收率在94.5%～102.5%之间.可用于实际水样中铅的测定.     

Adsorption behavior of DNA-wrapped carbon nanotubes on self-assembled monolayer surfaces

We have examined the adsorption of DNA-wrapped single-walled carbon nanotubes (DNA-SWNTs) on hydrophobic, hydrophilic, and charged surfaces of alkylthiol self-assembled monolayers (SAMs) on gold. Our goal is to understand how DNA-SWNTs interact with surfaces of varying chemical functionality. These samples were characterized using reflection absorption FTIR (RAIRS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. We have found that DNA-SWNTs preferentially adsorb to positively charged amine-terminated SAMs and to bare gold surfaces versus hydrophobic methyl-terminated or negatively charged carboxylic acid-terminated SAMs. Examination of the adsorption on gold of single-strand DNA (ssDNA) of the same sequence used to wrap the SWNTs suggests that the DNA wrapping plays a role in the adsorption behavior of DNA-SWNTs.     

Adsorption behavior of noble metal ions (Au, Ag, Pd) on nanometer-size titanium dioxide with ICP-AES.

The adsorption behavior of gold (Au), silver (Ag) and palladium (Pd) on nanometer-size titanium dioxide (NSTD) at low concentrations was studied using inductively coupled plasma atomic emission spectrometry (ICP-AES). A preconcentration procedure of the analytes was carried out using NSTD as a solid-phase extractant before their determination by ICP-AES. The optimum conditions for adsorption were studied in detail, and under the condition that Au, Ag and Pd ions could be adsorbed and recovered quantitatively. The static adsorption capacities of Au, Ag and Pd on NSTD were 22.63, 14.06 and 11.82 mg/g, respectively. For the elution of gold, silver and palladium, a mixture of 5% thiourea solution and 3 mol L(-1) HNO3 was used. The parameters tested included: pH conditions, contact time of the analytes with NSTD, flow rate, adsorption capacity and sorption kinetics. According to the definition of IUPAC, the detection limits (3sigma) of this method for Au, Ag and Pd with an enrichment factor of 50 were (0.016), (0.006) and (0.012) microg mL(-1), respectively, the relative standard deviations (RSD) were 8.7%, 4.5% and 7.4%, respectively (n = 6). Some geological samples were determined with satisfactory results.     

Photochronocoulometric measurement of the coverage of surface-bound dyes on titanium dioxide crystal surfaces

Atomically flat terraced single-crystal anatase and rutile surfaces can be prepared allowing for the reproducible adsorption of covalently attached sensitizing dyes. Once reproducible surfaces and dye coverages are achieved, a photochronocoulometric technique is developed to measure the surface coverage of the dyes, an important parameter in determining the efficiency of sensitization. The surface-bound dyes are irreversibly oxidized by exposure to a light pulse with the n-type oxide semiconductor electrode held in depletion. A double-exponential decay of the subsequent photocurrent is then measured, where the integration of the faster decay is associated with the adsorbed dye coverage and the second much slower decay is attributed to trace regenerators, including water, in the nonaqueous electrolyte. The ruthenium-based N3 dye shows the expected linear dependence of the rate constant on light intensity whereas a dicarboxylated thiacyanine dye shows a square root dependence of its photooxidation rate on light intensity. The sublinear response of the thiacyanine dye is discussed in terms of the more complex surface chemistry that is known for this family of sensitizing dyes.     

Sorption behavior of germanium(IV) on titanium dioxide nanoparticles

Titanium dioxide nanoparticles were employed for the sorption of Ge(IV) ions from aqueous solution. The process was studied in detail by varying the sorption time, pH, and temperature. The sorption process was found to be fast, equilibrium was reached within 3 min. A maximum sorption could be achieved from solution when the pH ranges between 4.0 and 11.0. Sorbed Ge(IV) ions can be completely desorbed with 2 mL of 0.3 mol L⁻¹ K₃PO₄-1.0 mol L⁻¹ H₂SO₄ mixture solution. The kinetic experimental data properly correlate with the second-order kinetic model (k ₂ = 0.88 g mg⁻¹ min⁻¹ (25°C)), Reichenberg equation and Morris-Weber model. The estimated E _a for Ge(IV) adsorption on nano-TiO₂ was 19.66 kJ mol⁻¹. The overall rate process appears to be influenced by intra-particle diffusion. The sorption data could be well interpreted with the Langmuir and Dubinin-Radushkevich (D-R) type sorption isotherms. The D-R parameters were calculated to be K = −0.00321 mol₂ kJ⁻², q _m = 0.59 mmol g⁻¹ and E = 12.48 kJ mol⁻¹ at room temperature. Furthermore, the thermodynamic parameters were also determined, and the ΔH ⁰ and ΔG ⁰ values indicated a spontaneous exothermic behavior.     

Adsorption of tricarboxylic acid biosurfactant derived from spiculisporic acid on titanium dioxide surface

In the present study, adsorption isotherms of a polycarboxylic-acid-type biosurfantant, the sodium salt of (2-(2-carboxyethyl)-3-decyl maleic anhydride) (DCMA-3Na), on TiO₂, zeta potential, and changes in particle aggregate size as a function of biosurfactant concentration, solid-liquid ratio and pH were systematically investigated. The adsorption of DCMA-3Na on the surface of TiO₂ shows a relatively weak dependence on pH, unlike the adsorption behavior of chemically-synthesized surfactants. Adsorption of DCMA-3Na still occurs at pH above the isoelectric points of TiO₂ due to the buffering capacity, which is due to three carboxylate functional groups in the hydrophilic moiety of DCMA-3Na. Since DCMA-3Na has three anionic head groups, the zeta potential of TiO₂ at pH 3 decreases very steeply from positive to negative values as the surface charges are neutralized by the adsorption of biosurfactants. Trends in zeta potentials as a function of equilibrium DCMA-3Na concentration are quite closely related to the changes in flocculation of individual TiO₂ particles.     

Adsorption and inactivation behavior of horseradish peroxidase on cellulosic fiber surfaces

The physical immobilization behavior of horseradish peroxidase (HRP) on cellulosic fiber surfaces was characterized using adsorption and inactivation isotherms measured by the depletion method followed by fitting of Langmuir’s and Freundlich’s models to the experimental data. The adsorption and inactivation behavior of simpler and relatively non-porous high and low crystalline cellulosic substrates (microcrystalline cellulose and regenerated cellulose) as well as more complex and porous cellulosic pulp fibers (bleached kraft softwood fibers) were investigated. The effect of the sorbent surface energy on HRP adsorption was demonstrated by increasing the hydrophobicity of the cellulosic fibers using an internal sizing agent. The influence of the fiber surface charge density on HRP adsorption was studied via modification of the cellulosic fibers using TEMPO (2,2,6,6-tetramethyl-1-piperidiniloxy radical)-mediated oxidation methods. Results showed that hydrophobic interactions had a much larger effect on HRP adsorption than electrostatic interactions. More hydrophobic fiber surfaces (lower polar surface energy) result in larger enzyme-fiber binding affinity constants and higher binding heterogeneity. It was also found that oxidation of the cellulosic fiber substrate reduces enzyme adsorption affinity but significantly increases the loading capacity per unit weight of the surface.     

Graft copolymerization of acrylamide onto carboxymethyl starch

Water absorption resins of carboxymethyl starch graft acrylamide (CMS-g-AM) were synthesized by copolymerization based on a free radical reaction. At first, CMS was prepared with starch and chloroacetic acid in an alkali-methanol media. Then, AM was grafted onto CMS by using ceric ammonium nitrate as an initiator. The resulting graft products were identified by infrared spectra. The effects of the preparation conditions on the substituent degree (SD) of starch and the water absorption capacities of CMS-g-AM were investigated. The results showed that SD of starch first increased remarkably and then decreased gradually with increased addition of sodium hydroxide, and the water absorption capacity of CMS-g-AM depended greatly on the SD of CMS and its maximum with 0.75 of SD of starch was 350 g/g.