Liquid Phase Oxidation Method Research Articles

Efficient Degradation of 2,4-Dichlorophenol on Activation of Peroxymonosulfate Mediated by MnO2.

Sulfate radical based-advanced oxidation process has received increasing interest in the remediation of wastewater and contaminated soil. In this study, degradation of 2, 4-dichlorophenol (2, 4-DCP) was investigated over peroxymonosulfate (PMS) activation by MnO2, which was prepared by liquid-phase oxidation method. The prepared MnO2 was characterized by transition electron microscopy, X-ray diffraction, N2 adsorption-desorption, and X-ray photoelectron spectroscopy. Characterization results showed that α-MnO2 exhibited the highest surface area and Mn (III) content. The PMS activation by MnO2 in 2, 4-DCP degradation followed the order of α-MnO2 > γ-MnO2 > β-MnO2, which is dependent on the properties of MnO2 including crystal structure, surface area and Mn (III) content. Influences of initial concentration of 2, 4-DCP, PMS and MnO2 dosage, pH and co-existing inorganic ions on the degradation were examined. Electron paramagnetic resonance (EPR) and quenching experiments with ethanol and tert-butanol suggested that sulfate radicals were the dominant radicals in the process. Findings in this study indicated that α-MnO2 was an attractive catalyst for activation of PMS to degrade 2, 4-DCP in aqueous solution.

Co-extraction of vanadium and chromium from high chromium containing vanadium slag by low-pressure liquid phase oxidation method

High chromium containing vanadium slag is refractory, and therefore cannot be processed efficiently by traditional roasting method. In this study, a low pressure leaching process using NaOH solution to co-extract both vanadium and chromium has been proposed. The effects of NaOH concentration, leaching temperature, oxygen pressure, and liquid-to-solid mass ratio on the vanadium and chromium leaching rate were discussed in detail. The results suggested that the NaOH concentration and leaching temperature were more influential factors for the extraction of vanadium and chromium. Under the optimal reaction conditions (temperature 200 °C, liquid-to-solid mass ratio of 6:1, NaOH mass concentration of 50%, agitation speed 700 rpm, pressure of 1 MPa, and reaction time 180 min), the recoveries of vanadium and chromium could reach up to 98.3% and 93.3%, respectively. The kinetics study indicated that the dissolution process of vanadium slag followed the shrinking core model, and the extraction of vanadium and chromium were both governed by the internal diffusion control. Furthermore, the apparent activation energies for the oxidation of vanadium and chromium were calculated to be 27.58 and 36.74 kJ/mol, respectively. The result from this study provides insights on effectively co-extracting V and Cr from high Cr-containing vanadium slag while minimizing the environmental contamination.

Fractal and spectroscopic analysis of soot from internal combustion engines

Today diesel engines are used worldwide for various applications and very importantly in transportation. Hydrocarbons are the most widespread precursors among carbon sources employed in the production of carbon nanotubes (CNTs). The aging of internal combustion engine is an important parameter in deciding the carbon emission and particulate matter due to incomplete combustion of fuel. In the present work, an attempt has been made for the effective utilization of the aged engines for potential applicationapplications in fuel cells and nanoelectronics. To analyze the impact of aging, the particulate matter rich in carbon content areis collected from diesel engines of different ages. The soot with CNTs is purified by the liquid phase oxidation method and analyzed by Field Emission Scanning Electron Microscopy, High-Resolution Transmission Electron Microscopy, Energy Dispersive Spectroscopy, UV-Visible spectroscopy, Raman spectroscopy and Thermogravimetric analysis. The SEM image contains self-similar patterns probing fractal analysis. The fractal dimensions of the samples are determined by the box counting method. We could find a greater amount of single-walled carbon nanotubes (SWCNTs) in the particulate matter emitted by aged diesel engines and thereby giving information about the combustion efficiency of the engine. The SWCNT rich sample finds a wide range of applicationapplications in nanoelectronics and thereby pointing a potential use of these aged engines.

Simultaneous extraction of vanadium and chromium from vanadium slag using low-pressure liquid phase oxidation method

A low-pressure liquid oxidation method was proposed and proven to be effective to extract vanadium and chromium simultaneously from the vanadium slag in concentrated NaOH aqueous solutions. The effect of temperature, NaOH mass concentration, liquid-to-solid mass ratio, stirring speed and pressure on the extraction of vanadium and chromium in NaOH aqueous solutions were systematically investigated. Under the optimal reaction conditions (temperature of 473 K, liquid-to-solid mass ratio of 6:1, stirring speed of 700 rpm, NaOH mass concentration of 50%, pressure of 1 MPa and reaction time of 180 min), the vanadium and chromium recovery reached 95% and 90%, respectively. It was found that the reaction temperature and NaOH concentration were important factors for the extraction of vanadium and chromium. The kinetics of the decomposition of vanadium slag in concentrated NaOH aqueous under low pressure was analyzed using the shrinking core model, and the results indicated that the extraction of vanadium and chromium were both governed by the internal diffusion step, with apparent activation energies calculated to be 26.22 and 32.79 kJ/mol, respectively.

Hydrogen adsorption of carbon nanotubes grown on different catalysts

Single wall carbon nanotubes (SWCNTs) were synthesized by catalytic chemical vapor deposition of C2H2 at 800 °C for 60 min. Catalysts were prepared by impregnation of transition metals (Fe, Co, Ni, V and bimetallic mixture of Fe–Co) on MgO powder substrate with a metal to MgO ratio of 5:100. After the synthesis, the samples were purified by liquid phase oxidation method with 1.5 M HNO3 for 30 min at 210 °C. The samples were characterized by thermal gravimetric analysis, scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The hydrogen storage capacities of purified SWCNTs were investigated by volumetric method. It was found that the hydrogen uptake was in the range of 2.76–5.25 wt% at cryogenic temperature and 100 bar pressure. The maximum capacity was obtained with purified SWCNTs produced on Fe catalyst whereas purified SWCNTs grown on Fe–Co catalyst had the minimum hydrogen uptake.

Study on Catalysis Properties of Graphene Catalyst Loading Iron Oxide

The graphite oxide was synthesized with Hummers liquid-phase oxidation method in experiment, and then was reduced to graphene by sodium borohydride, the iron oxide was loaded by dipping method. The catalyst that made reacted in SCR reaction unit in laboratory, the catalysis properties of catalyst was investigated. The experiment results showed that graphene was flake nanometer sheet and presented transparent fold shape, its crystal structure was in order arrangement; the nature of graphene was close to that of raw graphite; their surface function groups were similar; Fe/graphene SCR catalysts had certain catalytic ability in the reaction, the NO conversion rate of catalyst was about 50% while the temperature range was from 200°C to 300°C.

Hydrogen adsorption on carbon nanotubes purified by different methods

Hydrogen is considered to be a clean energy carrier. However, the most serious barrier to potential uses is the development of feasible hydrogen storage systems. The discovery of high hydrogen storage capacity of carbon nanotubes (CNTs) makes up alternatives for hydrogen storage systems. In this study, the hydrogen adsorption on carbon nanotubes was investigated. CNTs were firstly synthesized by chemical vapor deposition (CVD) of acetylene (C 2H 2) on a magnesium oxide (MgO) powder impregnated with an iron nitrate (Fe(NO 3) 3·9H 2O) solution. The synthesis parameters were selected as: the synthesis temperature of 800 °C, the iron content in the precursor of 5% and the synthesis time of 30 min. The liquid phase oxidation method was applied for the purification of the synthesized CNT materials. Three different chemicals—3 M HNO 3, H 2SO 4, and HCl–were used in the removal of the metal catalysts from the synthesized CNT material to investigate the possible effects of each acid solution to the purification step. Purification of the synthesized CNT material was carried out under the conditions of 75 °C for 15 h. A 30% H 2O 2:3 M HCl (1:1 v%) solution was also used in the purification step to remove both the metal catalysts and the amorphous carbon. The purification using this solution was performed at 75 °C for 8 h. The hydrogen storage capacities of the purified materials were measured using volumetric method. It was found that the hydrogen adsorption capacities of these materials were changed in the range of 0.60–4.86 wt% at the liquid nitrogen temperature and gas pressure up to 100 bar.

Study of Stability and Dispersibility of Oxidized Multiwall Carbon Nanotube and Characterization with Analytical Methods for Bioapplication

Nanotechnology is the study of manipulating matter on an atomic and molecular scale. Generally, nanotechnology deals with developing materials, devices, or other structures possessing at least one dimension size from 1 to 100 nanometers. Carbon nanotubes have great potentials for novel applications in industry, drug delivery system and many other uses. In this work after purification, multiwall carbon nanotube was functionalized in acids by liquid phase oxidation method for drug delivery system. The structural and chemical changes after carboxylation of MWNTs improved the solubility and dispersibility of the carboxylated MWNTs in water. Fourier transformed infrared spectroscopy, and transmission electron microscopies were carried out for characterization of these methods of MWCNTs functionalization.

InAs Native Oxides Prepared by Liquid Phase Oxidation Method

Using liquid phase oxidation technique to prepare native oxides on InAs is demonstrated. In addition to scanning electron microscope, atomic force microscopy and X-ray photoelectron spectroscopy were used to analyze the surfaces and chemical compositions of the oxides. The chemical composition of the InAs native oxide is a mixture of indium oxide and arsenic oxide . The annealing effects on the oxide properties were also investigated.

The changes of morphology, structure and optical properties from carbon nanotubes treated by hydrogen plasma

In this paper, carbon nanotubes synthesized by floating catalyst method were purified by liquid-phase oxidation method and treated by hydrogen plasma with different time. The morphology and microstructure of carbon nanotubes were characterized by transmission electron microscope (TEM), high-resolution transmission electron microscope (HRTEM), selected area electron diffraction (SAED) and Raman spectroscope. The results showed that carbon nanotubes with bamboo-like structure changed solid and helical structure with the treatment of hydrogen plasma for 5 h and 10 h, and the intensity of D peak in Raman spectrum was larger and larger. The UV–vis absorption spectrum indicated that the absorption peak of treated carbon nanotubes was redshifted, stronger and narrower than that of untreated carbon nanotubes. However, the effect of hydrogen plasma treatment on the FT-IR spectrum of carbon nanotubes was slight. The results probably made carbon nanotubes have important applications in optical absorption material with controllable wavelength.

LIQUID PHASE OXIDATION GROWN MISM AND MISIM SWITCHES BY GaAs NATIVE OXIDES

Experimental predictions have been made for two-state bistable switching in both metal- GaAs native oxide-semiconductor-metal (MISM) and metal- GaAs native oxide-semiconductor- GaAs native oxide-metal (MISIM) structures for the first time, where the GaAs native oxides are formed by the liquid phase oxidation method. Bidirectional two-state switching (DIAC-like) and three-terminal operation are also shown in the photo-sensitive MISIM structure. Typical switching voltages for GaAs MISM and MISIM switches under 4 nm-thick native oxides are 7 V and 15 V, respectively. The corresponding voltage control efficiencies for MISM and MISIM switches are also as high as 3.944 and 7.04. The corresponding variation in voltage control efficiency, Δη=ΔVS/VH, is also as high as 2.5 at 150 nW incident light power.

Preparation of hydrophilic and acid-proof silicalite-1 zeolite membrane and its application to selective separation of water from water solutions of concentrated acetic acid by pervaporation

Abstract Hydrophilic and acid-proof silicalite-1 zeolite membrane was successfully prepared by repeating hydrothermal synthesis of silicalite-1 layer on an alumina ceramic filter (repeated batch synthesis) followed by a liquid phase oxidation method with H2O2 to remove template molecules. This prepared membrane has marked amount of silanol group both in the micro pores of silicalite-1 crystals and in the apertures among the crystals. Networks of water molecules are formed via hydrogen bond in silanol groups. These networks allow only water molecules to diffuse through the networks. Therefore, when this membrane was applied to the pervaporation of concentrated acetic acid (30–98 wt.%), only water molecules passed through the membrane. To examine the usefulness of the membrane, the pervaporation of two kinds of water solutions, acetone and ethanol, were conducted by this membrane. In both systems, only water was permeated, as well as the case of the water solution of acetic acid. The permeation rate at the pervaporation temperature was found to lie on a single line for acetone–water, ethanol–water and acetic acid–water systems. Thermogravimetric analysis of hydrophilic silicalite-1 powders indicated that dominant channels for the permeation of water molecules were apertures among fine silicalite-1 crystals of the membrane.

One step synthesis of mibk (methyl isobutyl ketone) from acetone over CaO-supported Ni catalyst

One step synthesis of MIBK from acetone over Ni/CaO catalysts was studied. 10 wt% Ni/CaO catalysts were prepared by conventional impregnation method (catalyst I), and liquid phase oxidation method using NaOCl as an oxidant (catalyst L). Catalyst L showed much higher activity than catalyst I because of recovered CaO pore structure and high BET surface area. Catalyst C, prepared by coprecipitation method, showed 60% of MIBK selectivity with a fairly high overall acetone conversion. Catalysts L and C had two CO2 desorption states (α, Β). Incorporated Ni enabled support precursor [Ca(CO)3] to decompose easily into CaO andCO2even at low temperature and generated weakCO2desorption state (α) which was from active state.