Advanced Materials Research Vols. 233-235

Abstract: The MWNT-TiO₂ nanocomposite was synthesized via direct growth of TiO₂ nanoparticles on the surface of the functionalized MWNTs by the hydrothermal treatment and utilized as the photocatalyst in the carbaryl degradation under both visible light and UV light irradiation. Visible-light-driven activity and enhanced UV-light-driven activity are both achieved as the composite MWNTs with TiO₂ can efficiently enhance the light absorption and charge separation and then photocatalytic activity. The photodegradation efficiency of carbaryl was examined by HPLC and IC techniques, which demonstrates that carbaryl can be readily degraded under visible light irradiation. Based on the obtained experimental results, assisted with the computer simulation of carbaryl molecule on PM3 level, it is presumed that the degradation of carbaryl starts with the break of N21-C23 and C19-N21 bonds and ends in the generation of naphthalen-1-ol before the ring-opening reaction.

Abstract: The synthesis of dimethyl carbonate (DMC) from urea and methanol includes two main reactions: one amino of urea is substituted by methoxy to produce the intermediate methyl carbamate (MC) which further converts to DMC via reaction with methanol again. In a stainless steel autoclave, the kinetics of these reactions was separately investigated without catalyst and with Zn-containing catalyst. Without catalyst, for the first reaction, the reaction kinetics can be described as first order with respect to the concentrations of methanol and methyl carbamate (MC), respectively. For the second reaction, the results exhibit characteristics of zero-order reaction. Over Zn-containing catalyst, the first reaction is neglected in the kinetics model since its rate is much faster than second reaction. After the optimization of reaction condition, the macro-kinetic parameters of the second reaction are obtained by fitting the experimental data to a pseudo-homogenous model, in which a side reaction of DMC synthesis is incorporated since it decreases the yield of DMC drastically at high temperature. The activation energy of the reaction from MC to DMC is 104 KJ/mol while that of the side reaction of DMC is 135 KJ/mol.

Abstract: In this work, magnetic nanoscale Fe₃O₄ particles were synthesized through coprecipitation of Fe(II) and Fe(III) in alkaline media. The structure, composition and properties of the nanoparticles prepared were characterized by transmission electron microscope (TEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM). Catalytic efficiency of the Fe₃O₄ nanoparticles was tested in degradation of phenol solution. At pH 7, the chemical oxygen demand (COD) removal rate reached 70% in 3 hours. The heterogeneous catalyst exhibited efficient catalytic activity close to that of iron homogeneous catalyst but with less than 3% leaching of irons cation. Further, it performed well under much wider pH range (pH 3~7) compared to classic Fenton reagent, providing potential alternative as a novel heterogeneous Fenton catalyst for environmental remediation.

Abstract: There are many areas in the world where the ground water has been contaminated by arsenic. One process to purify the water is to use TiO₂ to adsorb the arsenic. As the TiO₂ surface can be cleaned and reused, it has a promising potential as a water purifier. In this paper, the plane-wave function method, based on the density functional theory, has been used to calculate the structures of arsenic(III) on a perfect TiO₂ anatase (1 0 1) surface. All the arsenic(III) solution species such as H₃AsO₃, H₂AsO₃^-1, HAsO₃^-2 and AsO₃^-3 are put onto the surface with many different possible structures to obtain the adsorption energy. Based on the adsorption energy, the bidentate binuclear (BB) adsorption configurations of arsenic(III) on the surface are more favorable at low concentrations, whereas BB form and monodentate mononuclear (MM) form may coexist at higher concentrations. The models and results fit well with published experimental results. The results and conclusions will be of benefit to further research on arsenite adsorption and its photocatalytic oxidation on a TiO₂ surface.

Abstract: There are many areas in the world where the ground water has been contaminated by arsenic. One process to purify the water is to use TiO₂ to adsorb the arsenic. As the TiO₂ surface can be cleaned and reused, it has a promising potential as a water purifier. In this paper, the plane-wave function method, based on the density functional theory, has been used to calculate the structures of arsenic(III) on a perfect TiO₂ anatase (1 0 1) surface. All the arsenic(III) solution species such as H₃AsO₃, H₂AsO₃^-1, HAsO₃^-2 and AsO₃^-3 are put onto the surface with many different possible structures to obtain the adsorption energy. Based on the adsorption energy, the bidentate binuclear (BB) adsorption configurations of arsenic(III) on the surface are more favorable at low concentrations, whereas BB form and monodentate mononuclear (MM) form may coexist at higher concentrations. The models and results fit well with published experimental results. The results and conclusions will be of benefit to further research on arsenite adsorption and its photocatalytic oxidation on a TiO₂ surface.

Abstract: Advances of application of ionic liquids as solvents and catalysts in the catalytic oxidation reaction are summarized in this paper. Ionic liquids, as solvent, can provide an environment which is different from the traditional organic solvents for the chemical reactions, and make the catalytic activity and stability better, conversion and selectivity higher; Ionic liquids, as catalyst, not only play the function of promoting reaction, but also play a solvent/catalyst dual functions more directly. Currently ionic liquids in catalytic oxidation reaction are mostly used as solvent, Especially used widely in organic synthesis. The designability of ionic liquids provides a broad space for ionic liquids as catalyst.

Abstract: In order to study the fume suppressive effect of SBS and nano calcium carbonate， this paper studied the fume suppression laws of SBS and nano calcium carbonate， and carried out ratio test of SBS and nano calcium carbonate, and got the conclusions that: With the increasing adding level of SBS and nano calcium carbonate, the asphalt fume productive rate will reduce gradually and will reach a condition of stability. The adding level of 4% of SBS is a turning point. When less than 4%, the asphalt fume production rate decreased rapidly; and more than 4%, the asphalt fume production rate decreased slowly; when adding nano calcium carbonate at the level of 5%, the asphalt fume won’t decrease. The best ratio of SBS and nano calcium carbonate is 6% of SBS and 6% of nano calcium carbonate, with which asphalt fume reductive rate was up to 30%.

Abstract: Solid superacid sulfated titania (SO₄^2-/TiO₂) was prepared by impregnation of titanium hydroxide with an aqueous solution of (NH₄)₂SO₄, and then calcined at different temperatures. The structural properties of these samples were investigated using XRD, BET, and DSC. Surface acidity of the catalysts were tested by FT-IR, XPS, and NH₃-TPD. The SO₄^2-/TiO₂ calcined at 340 °C showed the strongest acid strength. The catalytic activity of the catalysts was evaluated in the depolymerization of polythene terephthalate (PET) with ethylene glycol (EG) by varying different parameters. Experimental results were correlated to the textural properties and surface acidity. The catalyst SO₄^2-/TiO₂ calcined at 340 °C exhibited maximum catalytic activity, with the conversion of PET as high as 72.9%, which may be due to the amorphous phase and the strongest acid strength. When the reaction temperature was at 194 °C, the conversion of PET was 100%, and the yield of the bis-2-hydroxyethyl terephthalate (BHET) monomer was 61.7%.

Abstract: Boron doping titanium pillared montmorillonite (B-Ti-mont) were prepared by the sol-gel technique using sodic montmorillonite (Na-mont) as a substrate. Several technics such as XRD, SEM, UV-vis diffuse reflection spectra were used to characterize the samples. The results showed that all of the samples were of anatase, the absorption in the visible light region was strengthened after doped with boron. The basic skeleton of montmorillonite did not change after doping. The photocatalyst with the boron mole content of 5% displayed the best photocatalytic performance.

Abstract: A new inorganic-organic composite dual-coagulant (PAFC-CPAM) was prepared by polyaluminum ferric chloride (PAFC) and cationic polyacrylamide (CPAM) and its treatment efficiency for oily wastewater was evaluated by coagulation jar tests. PAFC-CPAM dual-coagulants were characterized by FT-infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The FTIR spectra illustrated that there were some chemical reactions between PAFC and CPAM in PAFC-CPAM. SEM micrographs testified that PAFC-CPAM formed compact net structure which is different from PAFC and CPAM, resulting to its outstanding coagulation performance other than monomeric coagulant in treating oily wastewater. Coagulation jar tests presented that PAFC-CPAM improved 1.14% and 0.38% of oil removal rate and reduced 0.35NTU and 0.06NTU of residual turbidity than PAFC and CPAM respectively at the optimal dosage of 120mg/L. PAFC-CPAM enhanced 4.56% and 2.12% of oil removal efficiency and decreased 0.27NTU and 0.01NTU of residual turbidity on average in comparison with PAFC and CPAM respectively in the pH range of 4.0-8.0. All of above-mentioned experiment results demonstrated that PAFC-CPAM behaved superior coagulation performance than PAFC and CPAM.