Grafting polyelectrolytes onto polyacrylamide for flocculation 1. Polymer synthesis and characterization

Low-molecular-weight high-charge-density cationic diallyldimethylammonium chloride homopolymer (polyDADMAC) was grafted onto high-molecular-weight nonionic polyacrylamide (PAM) via a free radical mechanism using a gamma radiation technique. The graft copolymer systems were characterized in terms of viscosity, composition, gel content, degree of grafting and grafting efficiency. Degree of grafting was a strong function of radiation dose, dose rate and polyelectrolyte concentration. Gels were formed at high radiation doses and high PAM levels. Crosslinking between the electrolyte polymers was limited due to electrostatic repulsion. Gelation was mainly caused by coupling of PAM chains. High grafting efficiency was achieved: the lower the poly(DADMAC) concentration, the higher the grafting efficiency observed. The grafting mechanism and the effect of ion interactions on copolymer structural properties are also elucidated and discussed. Received: 6 April 1998 Accepted in revised form: 28 August 1998     

Ammonium persulfate-initiated polymerization of cationic starch-grafted-cationic polyacrylamide flocculant for the enhanced flocculation of oil sludge suspension

In this study, a novel, highly efficient and environmentally friendly flocculant, namely, cationic starch-grafted-cationic polyacrylamide (CS-g-CPAM), was synthesized by initiation polymerization of ammonium persulfate. First, CS-g-CPAM was polymerized with cationic starch(CS), acrylamide(AM) and diallyl dimethyl ammonium chloride (DMDAAC), and then the influence factors of graft polymerization were investigated, including total monomer concentration, initiator dosage, the monomer mass ratio of m_AM: m_CS: m_DMDAAC, post-polymerization temperature and post-polymerization time. And the intrinsic viscosity of the CS-g-CPAM was measured by the one point method accurately. The chemical structures and morphology of the samples were characterized by Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermo-gravimetric and differential scanning calorimetry (TG-DSC), and scanning electron microscope (SEM). The CS-g-CPAM was utilized to flocculate the oil sludge suspension, the effects of CS-g-CPAM dosage, temperature and pH value on the flocculation performance were investigated. The results show that CS-g-CPAM has outstanding flocculation effect.     

Ultrasonic characterisation of colloidal dispersions: detection of flocculation and adsorbed layers

A series of experiments to detect flocculation and the presence of adsorbed layers on polystyrene latices is presented. The system consisted of 504.1 nm diameter polystyrene latex at 4.39% w/w in the absence or presence of non-ionic surfactant, Triton (TX100) and hydroxyethylcellulose (HEC). Ultrasonic scattering calculations were performed on each system using the theory of Allegra and Hawley. Ultrasonic spectroscopy was carried out using the Institute of Food Research (IFR) discrete frequency spectrometer, accurate to 0.01% and 4% in velocity and attenuation, respectively. The instrumental precision was up to an order of magnitude better. There were marked increases in ultrasonic attenuation upon flocculation, whether by a bridging or a depletion mechanism. Small but significant increases in attenuation were observed in the presence of adsorbed layers of surfactant or HEC, compared with a model that assumed the solutes to be uniformly dispersed in the continuous phase.     

TiO2-SA纳米光催化材料接枝动力学、结构及性能

采用后处理表面改性法在纳米TiO₂表面接枝水杨酸(SA)(TiO₂-SA), 分别考察了超声搅拌、溶剂、物料比、pH值及温度等因素对接枝过程及光催化材料性能的影响, 并研究了接枝反应动力学. 通过傅里叶变换红外(FT-IR)光谱、X射线光电子能谱(XPS)、X射线衍射(XRD)等对TiO₂-SA纳米光催化材料进行了结构表征, 并提出了结构模型. 通过接触角测定、同步热分析(热重-差示扫描量热法(TG-DSC))、紫外-可见漫反射光谱(UV-VisDRS)、扫描电子显微镜(SEM)对光催化材料进行了性能表征. 结果表明, 水杨酸改性纳米TiO₂可以提高疏水性及分散性, 减缓在溶剂中的沉降速度, 并能稳定吸附在油-水界面, 实现了光谱响应范围向可见光的拓展. 在紫外光照射下, TiO₂-SA表现出优异的光催化降解硝基苯性能.     

Effect of crystal form and particle size of titanium dioxide on the photodegradation behaviour of ethylene-vinyl acetate copolymer/low density polyethylene composite

The photodegradation behaviour of ethylene-vinyl acetate copolymer (EVA)/low density polyethylene (LDPE) composite containing four different types of titanium dioxide (TiO₂) was investigated through colour difference, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and mechanical tests. The results showed that the performance losses of composites were qualitatively correlated with the degradation degree. The vinyl acetate (VA) groups in EVA were sensitive to UV light and the photodegradation mainly occurred in the amorphous region. The chain scission and annealing effect facilitated the secondary crystallization of composites. The heterogeneous nucleation effect of TiO₂ on the crystallization of composites was related to the particle size of TiO₂. The micro rutile TiO₂, micro anatase TiO₂ and their mixture (rutile/anatase = 13/87) exhibited a photo-stabilising effect, while the nano mixed crystals TiO₂ (rutile/anatase = 20/80) had an opposite effect.     

Synthesis of nanocomposites from cationic polyacrylamide and modified carbon black: Application as flocculants for oily sludge suspension

Carbon black was modified using various liquid‐phase oxidation methods (modified carbon black = m‐CB, m = (1, 2, 3): 1, sulfuric acid/potassium permanganate method; 2, nitric acid method; 3, hydrogen peroxide method). With acetone–ethylene glycol as initiator, dimethyldiallylammonium chloride (DMDAAC) and acrylamide (AM) as monomer, cationic polyacrylamide (CPAM) was prepared by UV excitation of the monomer. The m‐CB/CPAM nanocomposites were synthesized using a hydrothermal method. The factors that affected the molecular weight of CPAM were investigated, including the total monomer concentration, the dosage of the complex initiator, the mass ratio of m_AM:m_DMDAAC and the UV irradiation time. The chemical structures and morphologies of the samples were characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental composition, X‐ray diffraction and scanning electron microscopy. 1‐CB/CPAM was utilized to flocculate oil sludge suspension, and the effects of 1‐CB quality, 1‐CB/CPAM dosage, temperature and pH value on the flocculation performance of 1‐CB/CPAM were investigated. The flocculation mechanism of 1‐CB/CPAM was also analyzed. The results show that 1‐CB/CPAM has an outstanding flocculation effect, and it flocculates oil sludge particles by adsorption bridging and charge neutralization in acidic and alkaline conditions.     

CNT/Fe-Ni/TiO_2/ZnO阵列修饰Ni阳极的制备及光催化制氢性能

采用层层自组装方法在Ni片阳极上构建TiO2/Zn O纳米棒阵列,以二氧化钛前驱体溶胶中掺杂的铁和镍为催化剂,通过气相沉积法在TiO2/Zn O纳米棒阵列间原位生长碳纳米管(CNTs),得到CNT/Fe-Ni/TiO2/Zn O复合光催化剂修饰的光活性Ni片阳极.以碱性电解池为基础,用紫外线辐照修饰的Ni阳极实现光催化和电解水的有机耦合制氢过程.通过场发射扫描电子显微镜(FESEM)、透射电子显微镜(TEM)、拉曼光谱(Raman)和电化学阻抗谱(EIS)对CNT/Fe-Ni/TiO2/Zn O复合膜光催化剂的结构进行了表征,并测试了其光催化辅助电解水制氢(WEAP)活性.结果表明,生长了碳纳米管的光催化复合膜CNT/Fe-Ni/TiO2/Zn O修饰的Ni阳极的产氢速率分别比Fe-Ni/TiO2/Zn O修饰的Ni阳极和纯Ni片提高了93.7%和533.0%.     

Fluorine-doped TiO2 powders prepared by spray pyrolysis and their improved photocatalytic activity for decomposition of gas-phase acetaldehyde

F-doped TiO₂ (FTO) powders were synthesized by spray pyrolysis (SP) from an aqueous solution of H₂TiF₆. The resulting FTO powders possessed spherical particles with a rough surface morphology and a strong surface acidity. The fluorine concentrations in the FTO powders calculated from XPS spectra significantly depended on SP temperature and ranged from 2.76 to 9.40 at.%. The FTO powder prepared at SP temperature of 1173 K demonstrated the highest photocatalytic activity for the decomposition of gas-phase acetaldehyde under both ultraviolet (UV) and visible light (vis) irradiations, and it was higher than that of commercial P 25. This high photocatalytic activity was ascribed to several beneficial effects produced by F-doping: enhancement of surface acidity, creation of oxygen vacancies, and increase of active sites. It was interesting to point out that the vis photocatalytic activity of FTO powders was achieved by the creation of surface oxygen vacancies rather than the improvement of optical absorption property of bulk TiO₂ in vis region.     

2-(p-toluidino)-6-naphthalene sulfonate as a fluorescent probe for flocculation studies of cationic potato amylopectin and nanosized silica particles 1. 2-p-(toluidino)-6-naphthalene sulfonate binding to cationic amylopectin

2-(p-toluidino)-6-naphthalene sulfonate (TNS) is a probe that fluoresces strongly when bound to certain proteins and polymers, but weakly in aqueous solution. Absorption and fluorescence spectroscopy were used to study the interaction of TNS with native amylopectin potato starch (NApS) and cationized amylopectin potato starch (CApS) in aqueous solution. The anionic TNS binds to CApS at a single type of binding site, with an affinity which has both electrostatic and nonelectrostatic contributions (including hydrogen bonding), whereas binding to NApS occurs at the same type of site but only by nonelectrostatic means. The affinity to CApS decreases strongly with increasing salt concentration, due to screening of the electrostatic attraction, whereas with NApS increasing salt concentration slightly enhances the binding affinity, most likely due to screening of a weak repulsive interaction between TNS and phosphate residues on NApS. The association constant for binding of TNS to CApS in 5 mM NaCl is 110 ± 20 M⁻¹. This comparatively weak binding makes TNS a useful probe in kinetic investigations of the flocculation of anionic silica particles by CApS. Received: 14 August 1998 Accepted in revised form: 4 December 1998     

表面修饰多壁碳纳米管负载二氧化钛的制备及催化碳酸二甲酯与苯酚酯交换反应的性能

制备了表面修饰多壁碳纳米管负载TiO₂的催化剂,并将其应用于碳酸二甲酯与苯酚的酯交换反应. 采用X射线电子能谱、透射电子显微镜、低温N₂吸附-脱附和X射线衍射等对催化剂进行了表征. 结果表明,以低浓度的氨水（0.4%）代替去离子水作为沉淀剂时,制备的催化剂显示出更好的催化活性、分离性与重复使用性. 考察了TiO₂负载量、催化剂用量及反应时间对反应性能的影响. 在最佳反应条件下,苯酚转化率为42.5%,碳酸甲苯酯与碳酸二苯酯的总选择性达到99.9%以上. 经过4次重复使用后,催化剂的活性略有下降.     

An expeditious method for determining particle size distribution by near infrared spectroscopy: Comparison of PLS2 and ANN models

The particle size distribution of a solid product can be crucial parameter considering its application to different kinds of processes. The influence of particle size on near infrared (NIR) spectra has been used to develop effective alternative methods to traditional ones in order to determine this parameter. In this work, we used the chemometrical techniques partial least squares 2 (PLS2) and artificial neural networks (ANNs) to simultaneously predict several variables to the rapid construction of particle size distribution curves. The PLS2 algorithm relies on linear relations between variables, while the ANN technique can model non-linear systems.Samples were passed through sieves of different sieve opening in order to separate several size fractions that were used to construct two types of particle size distribution curves. The samples were recorded by NIR and their spectra were used with PLS2 and ANN to develop two calibration models for each. The correlation coefficients and relative standard errors of prediction (RSEP) have been used to assess the goodness of fit and accuracy of the results.The four calibration models studied provided statistically identical results based on RSEP values. Therefore, the combined use of NIR spectroscopy and PLS2 or ANN calibration models allows determining the particle size distributions accurately. The results obtained by ANN or PLS2 are statistically similar.     

Simultaneous Delamination and Rutile Formation on the Surface of Ti3C2Tx MXene for Copper Adsorption

In this work, we studied the formation of the rutile phase of titanium dioxide (TiO₂) on delaminated MXene (d‐Ti₃C₂T_x) flakes by the reaction of Ti₃C₂T_x with amino acids in water. Three types of amino acids with varied side‐chain polarity were used to delaminate Ti₃C₂T_x. d‐Ti₃C₂T_x flakes formed stable colloidal solutions due to the negative surface charges of chemisorbed amino acids on the d‐Ti₃C₂T_x. Rutile formed on d‐Ti₃C₂T_x at room temperature upon the intercalation of aromatic amino acids and subsequent sonication of the solution, while flakes intercalated with aliphatic amino acids did not oxidize. X‐Ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy revealed the nanosize rutile formation on the surface of Ti₃C₂T_x flakes. The XPS results indicated the surface functionalization of histidine on d‐Ti₃C₂T_x flakes. As‐synthesized histidine functionalized rutile TiO₂@d‐Ti₃C₂T_x hybrid was used for adsorption of Cu²⁺ ions from aqueous solution with a maximum uptake of 95 mg g^?1.     

CO2 utilization as gas antisolvent for the pharmaceutical micro and nanoparticle production: A review

A reduction in particle size improves the solubility and bioavailability of pharmaceuticals. The traditional methods utilized in this regard are associated with problems so the use of supercritical fluid has been highlighted in recent decades. To prepare nanoparticles by employing the gas antisolvent (GAS) technique, a specific amount of solution (solute dissolved in organic solvent) was loaded into a cell in the oven. The supercritical carbon dioxide was injected and dissolved into the organic solvent. Therefore, volume expansion occurred and the solute was precipitated with a new particle size distribution on the filter at the end of the cell. This technique exhibits advantages such as particle size control, solvent-free product, and low-temperature process. Many experimental and modeling research has been conducted to synthesize nano- and microparticles based on the GAS process. The present study seeks to review the effective factors and literature on the GAS technique. All parameters affecting the GAS process including pressure, temperature, antisolvent addition rate, initial soluble concentration, and solvent were investigated. Volume expansion, thermodynamic modeling, and kinetic modeling of the GAS process were reviewed. A comparison was conducted between the advantages and disadvantages of this method with other methods of producing nanoparticles with supercritical fluid.     

TiO2‐modified Carbon Paste Electrode as a Sensor for the Assay of Weak Organic Acids/Bases and Complex Matrix Samples

The construction, general performance characteristics and analytical application of a titanium dioxide–modified carbon paste electrode sensitive to hydrogen ions, based on incorporation of titanium dioxide in a carbon paste matrix, is described. The proposed electrochemical sensor exhibits a linear response in the pH range from 2 to 10, at 25 °C, with a sub‐Nernstian slope. The value of a slope is in a direct correlation with the electrode composition – the optimum content of a titanium dioxide in carbon paste is 30 %. Titanium dioxide‐modified carbon paste electrode shows fast response time and reproducibility, confirmed by different compounds determination in both, individual and complex material, namely, in synthetic and real samples. Besides, the electrode shows high selectivity in the presence of the alkali and the alkaline earth ions as Na⁺, K⁺, Ca²⁺ or Mg²⁺. The standard deviation of the investigated acids (acetic, oxalic, 5‐sulfosalicylic, p‐toluensulfonic acid, and amino acid‐glycine) and bases (N,N′‐diphenylguanidine and collidine) is less than 1.3 %. The obtained data are compared with those obtained by using a conventional glass pH‐electrode under the same experimental conditions and indicate a high correlation between them.     

Preparation of degradable polypropylene by an addition of poly(ethylene oxide) microcapsule containing TiO2 part II. Modification of calcium phosphate on the TiO2 surface and its effect

To prepare a novel photo-degradable polypropylene (PP) with a higher degradation rate, a PP composite containing a poly(ethylene oxide) (PEO)/modified TiO₂ microcapsule was prepared. The modification of the TiO₂ was performed by the synthesis of octacalcium phosphate intercalated with succinic acid ion (OCPC) under various Ca/P molar ratio conditions. It was found that the synthesis conditions of the Ca/P = 3.5 and 3.6 M ratios were suitable to prepare the OCPC. However, the microscopic composition on the TiO₂ surface was different between these Ca/P conditions and affected the PP photo-degradation rate in the PP/PEO/modified TiO₂ composite. It was found from the Fourier Transform Infrared (IR) and the tensile testing measurements that the existence of the OCPC covering material on the TiO₂ surface brought about the higher PP photo-degradation rate. The facilitation behavior of the degradation was due to the release of the acid species (succinic acid ion) from the OCPC in the degradation process. In addition, the higher coverage of the OCPC on the TiO₂ surface brought about an induction period for the degradation.     

Hydrothermal synthesis of TiO2 nanorods: formation chemistry,growth mechanism,and tailoring of surface properties for photocatalytic activities

Titanium dioxide (TiO₂) is one of the best semiconductor photocatalysts with optical band gap of 3.2 eV. The optical band gap and photocatalytic properties could be further tuned by tailoring shape, size, composition, and morphology of the nanostructures. Hydrothermal synthesis methods have been applied to produce well-controlled nanostructured TiO₂ materials with different morphologies and improved optoelectronic properties. Among various morphologies, one-dimensional (1D) TiO₂ nanostructures are of great importance in the field of energy, environmental, and biomedical because of the directional transmission properties resulting from their 1D geometry. Particularly, TiO₂ nanorods (NRs) have gained special attention because of their densely packed structure, quantum confinement effect, high aspect ratio, and large specific surface area that could specially improve the directional charge transmission efficiency. This results in the effective photogenerated charge separation and light absorption, which are really important for potential applications of TiO₂-based materials for photocatalytic and other important applications. In this review, hydrothermal syntheses of TiO₂ NRs including the formation chemistry and the growth mechanism of NRs under different chemical environments and effects of various synthesis parameters (pH, reaction temperature, reaction time, precursors, solvents etc.) on morphology and optoelectronic properties have been discussed. Recent developments in the hydrothermal synthesis of TiO₂ NRs and tailoring of their surface properties through various modification strategies such as defect creation, doping, sensitization, surface coating, and heterojunction formation with various functional nanomaterials (plasmonic, oxide, quantum dots, graphene-based nanomaterials, etc.) have been reported to improve the photocatalytic activities. Furthermore, applications of TiO₂ NRs/tailored TiO₂ NRs as superior photocatalysts in degradation of organic pollutants and bacterial disinfection have been discussed with emphasis on mechanisms of action and recent advances in the fields.     

Electrochemically induced anatase inhibits bacterial colonization on Titanium Grade 2 and Ti6Al4V alloy for dental and orthopedic devices

Bacterial contamination of implanted devices is a common cause of their failure. The aim of the present study was to assess the capability of electrochemical procedures to: (a) promote the formation of anatase on the surface of commercially pure Grade 2 Ti and Ti Grade 5 (Ti6Al4V) alloy; (b) inhibit in vitro biofilm formation of Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus mutans and Porphyromonas gingivalis and oral plaque in vivo, (c) preserve favorable response of osteoblasts and fibroblasts to materials surfaces. Ti Grade 2 and Ti Grade 5 were respectively anodized at two different voltages: 90 and 130V for pure titanium; 100 and 120V for Ti6Al4V alloy. Surface characterization was performed by scanning electron microscopy (SEM) equipped with EDS probe, laser profilometry and X-ray diffractometry. Bacterial adhesion characterization was performed either in vitro and in vivo in patients. Osteoblast and fibroblast response was evaluated by metabolic activity assessment. The higher voltage applied in the anodization treatment of pure titanium (130V) and Ti6Al4V alloy (120V) surfaces, compared to the untreated pure titanium and Ti6Al4V and to lower voltage treatments, resulted in a greater decrease in bacterial attachment and biofilm formation in both in vitro and in vivo experiments. In contrast, the high voltage treatments were found to promote osteoblasts and fibroblasts proliferation. The observations indicated that the experimented high voltage anodization treatments may contribute to preserve the tissue integration and reduce bacteria colonization of titanium and titanium alloy for implantable applications.     

Au/TiO2催化剂上非催化CO氧化反应中活性氧物种的生成和消除

在定量的瞬时产物分析(TAP)反应器中,于80 oC下采用CO脉冲和O2脉冲补充等方法,研究了高温(400 oC)焙烧的Au/TiO2催化剂上活性氧物种的移除反应活性,特别是活性氧物种的性质。以往的研究大多关注的是CO催化氧化反应中活性氧物种及其性质,在典型的反应条件下该物种的形成和消除是可逆的;而本研究表明,催化剂直接焙烧后就存在额外的氧物种;该物种对CO氧化反应也具有活性,但其在典型的反应条件下不生成或生成很少。基于此,讨论了Au/TiO2催化剂上CO氧化反应的机理,特别是不同活性氧物种的作用。     

Synthesis of mesoporous TiO2 with colloidal gas aphrons,colloidal liquid aphrons,and colloidal emulsion aphrons for dye-sensitized solar cells

High surface area mesoporous titanium dioxide (TiO₂) particles have been prepared by three different kinds of colloidal aphrons: colloidal gas aphrons, colloidal liquid aphrons, and colloidal emulsion aphrons (CEAs). The precipitate of amorphous TiO₂ was prepared by hydrolysis, condensation, and polycondensation reaction of the precursor. The reaction took place under the effect of coulombic repulsion and electrostatic layers of multilayer surfactant molecules. TiO₂ particles with various sizes were prepared with different molar ratio of titanium ion to surfactants, which were sodium lauryl sulfate (SDS), cetyltrimetyhlammonium bromide, triblock copolymer Pluronic P123, and triblock copolymer Pluronic F127. The synthesized samples were characterized by X-ray diffraction, Brunauer-Emmett-Teller analysis, N₂ adsorption/desorption, and transmission electron microscopy. The mesoporous TiO₂ prepared by CEAs method showed a high specific surface area of 224 m²/g with the total pore volume of 0.7751 cm³/g by using SDS as the membrane phase surfactant due to electrostatic attraction favors of anionic surfactant. The solar conversion efficiency of the cell made from TiO₂ increases with the combination of increased surface area and total pore volume for higher amount of dye wetting and loading.     

Metal-organic frameworks MOF-808-X as highly efficient catalysts for direct synthesis of dimethyl carbonate from CO2 and methanol

A series of metal-organic frameworks MOF-808-X (6-connected) were synthesized by regulating the ZrOCl₂·8H₂O/1,3,5-benzenetricarboxylic acid (BTC) molar ratio (X) and tested for the direct synthesis of dimethyl carbonate (DMC) from CO₂ and CH₃OH with 1,1,1-trimethoxymethane (TMM) as a dehydrating agent. The effect of the ZrOCl₂·8H₂O/BTC molar ratio on the physicochemical properties and catalytic performance of MOF-808-X was investigated. Results showed that a proper ZrOCl₂·8H₂O/BTC molar ratio during MOF-808-X synthesis was fairly important to reduce the redundant BTC or zirconium clusters trapped in the micropores of MOF-808-X. MOF-808-4, with almost no redundant BTC or zirconium clusters trapped in the micropores, exhibited the largest surface area, micropore size, and the number of acidic-basic sites, and consequently showed the best activity among all MOF-808-X, with the highest DMC yield of 21.5% under the optimal reaction conditions. Moreover, benefiting from the larger micropore size, MOF-808-4 outperformed our previously reported UiO-66-24 (12-connected), which had even more acidic-basic sites and larger surface area than MOF-808-4, mainly because the larger micropore size of MOF-808-4 provided higher accessibility for the reactant to the active sites located in the micropores. Furthermore, a possible reaction mechanism over MOF-808-4 was proposed based on the in situ FT-IR results. The effects of different reaction parameters on DMC formation and the reusability of MOF-808-X were also studied.