Liquid-phase Treatment Research Articles

Tapered Optical Fiber Sensor Coated with Single-Walled Carbon Nanotubes for Dye Sensing Application

The present study aimed to improve the optical sensing performance of tapered optical fiber sensors toward aqueous Rhodamine B solution of different concentrations by applying single-walled carbon nanotubes (SWCNTs). The functional coating was formed on the surface of the tapered optical fiber sensor using an aerosol layer-by-layer deposition method. Before deposition, the SWCNTs were processed with multistage liquid-phase treatment in order to form a stable dispersion. The effect of SWCNT treatment was investigated through Raman spectroscopy. The deposition of 220 layers caused a reduction of up to 60% of the initial optical power of radiation propagating through the optical fiber core. The optical fiber sensor coated with SWCNTs demonstrated significantly higher sensitivity compared to a non-coated sensor in the range of 2-32 mg/L of Rhodamine B concentration in an aqueous solution. The experimental results demonstrated that the sensitivity was increased 10 times from 32 (mg/L)-1, for the non-coated sensor, up to 317 (mg/L)-1 after SWCNT coating deposition. Moreover, the SWCNT-coated sensor demonstrated high repeatability that allowed for the evaluation of the concentration regardless of the previously analyzed dye concentration.

Aluminium alloy corrosion inhibition by a two-stage modified nanoporous zeolite

ABSTRACT A two-stage synthesis of anti-corrosion pigments based on synthetic zeolites was performed. New pigments retain the zeolite framework structure in the nanopores of which the amorphised phosphate phase is formed. The pigments effectively reduce the aluminium alloy corrosion in sodium chloride solution. The most effective pigment is obtained by mechanochemical modification of zeolite with calcium cations, followed by liquid-phase treatment with zinc nitrate and sodium phosphate. The pigments induce the formation of a protective film of zinc hydroxides on intermetallic inclusions of the alloy. The formation of phosphates is possible on the anode sections. The pigments can become promising inhibitory components of primer paints used for the protection of structures made from aluminium alloys.

A Blueprint for the Synthesis and Characterization of Thiolated Graphene.

Graphene derivatization to either engineer its physical and chemical properties or overcome the problem of the facile synthesis of nanographenes is a subject of significant attention in the nanomaterials research community. In this paper, we propose a facile and scalable method for the synthesis of thiolated graphene via a two-step liquid-phase treatment of graphene oxide (GO). Employing the core-level methods, the introduction of up to 5.1 at.% of thiols is indicated with the simultaneous rise of the C/O ratio to 16.8. The crumpling of the graphene layer upon thiolation without its perforation is pointed out by microscopic and Raman studies. The conductance of thiolated graphene is revealed to be driven by the Mott hopping mechanism with the sheet resistance values of 2.15 kΩ/sq and dependable on the environment. The preliminary results on the chemiresistive effect of these films upon exposure to ethanol vapors in the mix with dry and humid air are shown. Finally, the work function value and valence band structure of thiolated graphene are analyzed. Taken together, the developed method and findings of the morphology and physics of the thiolated graphene guide the further application of this derivative in energy storage, sensing devices, and smart materials.

Chemical recycling of waste Poly Vinyl Chloride (PVC) by the liquid-phase treatment

Liquid-phase treatment of waste Poly Vinyl Chloride (PVC) was performed. Chlorine change rate was high when using alcohol, cresol and terpene compared with that observed in the treatment without solvent, so the importance of solvent for dechlorination from PVC was confirmed. By the treatment in alcohol, generation of porous structure was confirmed, which were not observed in the treatment of PVC alone. We were able to propose a method of utilizing carbon resources after chlorine is removed from a different perspective than previous reports. The number of pores and pore size were controlled by adding CO2 gas and basic compound, especially Na2CO3 in 1-Butanol. It indicated that these elements were effective for the production of porous structure based on the liquid-phase treatment. On the other hand, solubilization rate reached near 90% by using terpene at 300 °C in air atmosphere. The most effective solvent for solubilization was o-Cresol and solubilization rate reached to 99.8% at 250 °C in air atmosphere. This result indicates that PVC can be completely decomposed by these solvents in the presence of oxygen. From this research, it is possible to utilize and decompose solid residue by selecting the conditions.

Highly efficient titanosilicate catalyst Ti-MCM-68 prepared using a liquid-phase titanium source for the phenol oxidation.

A highly efficient Ti-MCM-68 catalyst for phenol oxidation with H2O2 was prepared by a mild liquid-phase treatment for the first time. The key preparation procedures to excellent catalytic activity and high para-selectivity were the use of aqueous solutions of the Ti source and calcination at 650 °C prior to catalytic use.

Study of the Performance of a Composite Bioreactor on Removal of High Concentrations of Formaldehyde

Controlling high concentrations of industrial formaldehyde pollution has become a hot issue in recent years. This problem needs to be solved, where formaldehyde, which is highly soluble in water, in biofilm packed towers led to the reduction of removal performance of the packed towers. This paper presented a new method which is based on the biofilm packed tower, a liquid-phase treatment device consisting of an aeration tank and a sedimentation tank that was added to construct a composite bioreactor system. Moreover, this study investigated the effects of the composite bioreactor on the removal of formaldehyde under different operation conditions and the structural succession characteristics of the dominant bacterial communities in the composite biological system. The results indicated that even if the operating conditions including meteorological formaldehyde concentrations at the inlet, gas flow, and circulating liquid flow were changed, the B (amount of biochemically degraded formaldehyde in waste gas per unit time in a unit volume) in the composite bioreactor was also higher than that of the blank biofilm packed tower. Also, at the genus level, the microbial community structures of the two systems were not the same, where the dominant genera of the biofilm packed tower (blank group) included Pseudomonas, Methyloversatilis, Cupriavidus, and Hyphomicrobium. After the addition of the liquid-phase treatment device, the composite bioreactor promoted three aerobic bacteria including Ensife, Acidimicrobiales_norank, and Anaerolineaceae_norank to become the dominant genera. In the two systems, the relative abundances of the formaldehyde-degrading bacteria including Pseudomonas, Methyloversatilis, Methylophilus, and Methylobacterium increased with time and gradually became stabilized.

Generation of paramagnetic centers in carboxylated materials via coordination attachment of diamagnetic tetraazamacrocyclic complexes of nickel(II)

Coordination bonding of Ni(II) tetraazamacrocyclic (TAMC) complexes to carboxylic groups of organic polymers and graphene oxide paper (GOP) is proposed for a facile generation of paramagnetic centers by combining two diamagnetic components. The coordination functionalization occurs under basic conditions in water solution at room temperature. The coordination configuration of central Ni(II) changes from tetracoordinated square-planar to hexacoordinated pseudooctahedral, which implies the conversion from low-spin to high-spin nickel centers. In the case of organic polymers, the coordination bonding of Ni(II) macrocycles gives rise to characteristic changes in coloration (from yellow-orange to violet-blue), as well as clearly manifests itself in UV–visible, FTIR and EPR spectra. In the case of GOP, in addition to evident changes in FTIR spectra, morphological alterations in the mat surface and an increase in the mat thickness are observed in SEM images, which can be explained by an intercalating effect of voluminous macrocyclic cations, as well as by partial disintegration of GOP structure due to the liquid-phase treatment. The effective magnetic moments of tetraazamacrocycles attached to organic polymers vary from 0.88 to 1.47 BM, whereas for GOP considerably higher values of 2.10 and 2.87 BM were obtained.

INFLUENCE OF LIQUID-PHASE OXIDATIVE TREATMENTS ON STRUCTURE AND HYDROPHILITY OF CARBON NANOTUBES

Carbon nanotubes (CNTs) were synthesized by gas phase chemical deposition (CVD) using methane as a hydrocarbon reagent and using a catalyst of iron oxide deposited on fine aluminum oxide, as well as the same catalyst with the addition of molybdenum oxide deposited on fine magnesium oxide. The synthesized materials were treated with concentrated nitric acid (HNO3) or a mixture of concentrated nitric and sulfuric acids (HNO3 / H2SO4) in a volume ratio of 2: 1, at a temperature of 110-120 ° C for 1 h. Some of them were subjected to peroxide action (H2O2) before oxidative acid treatments for 1-2 h at a temperature of 100-110 ° C. Structural features, elemental compositions of synthesized CNTs were investigated before and after liquid-phase oxidative treatments by methods such as transmission electron microscopy, Raman spectroscopy, X-ray energy dispersive spectroscopy, X-ray phase analysis. In this work, the ability of CNTs that were undergone treatment in various oxidizing environments to form stable concentrated aqueous suspensions was studied. It was established that the initial defectity of the CNT molecules significantly affects the hydrophilic properties of oxidized CNT modifications. This causes their different ability to form concentrated, stable aqueous suspensions, predetermines the choice of combinations of oxidizing liquid-phase treatments that most contributing to this. It was revealed that HNO3 and HNO3 / H2SO4 mixture at the used temperature conditions of treatments and their duration do not have a strong destructive effect on the structure of CNT. The oxidative effect of these reagents on the molecules of this material is manifested mainly in defective places. The cleaning of the catalytic components of the synthesis from the catalytic components contributes to the more efficient purification of HNO3 / H2SO4 with the formation of stable aqueous suspensions from the molecules of this material, and this does not depend on the characteristics of the synthesis of the CNTs.

Physicochemical properties of new cellulose-TiO2 composites for the removal of water pollutants: Developing specific interactions and performances by cellulose functionalization

Cellulose-TiO2 composites are developed using microcrystalline cellulose (MCC). The closed MCC structure was solubilized by liquid-phase treatments with nitric (HNO3) or phosphoric acids (H3PO4) to improve the TiO2-dispersion. These pretreatments simultaneously generate different types of oxygen and phosphorus functionalities on the cellulose chains that determine the interactions with Ti-alkoxide precursor during impregnation, leading to composite materials with different Ti-loadings and physicochemical characteristics. The morphological, textural, chemical and crystalline properties of both cellulose derivatives and cellulose-TiO2 composites were studied by complementary techniques. Microporous composites with round-shaped anatase TiO2 microcrystals were obtained by using HNO3 treatments, while H3PO4 favours the formation of mesoporous composites with flat and non-crystalline TiO2 particles. The photocatalytic efficiency of the obtained cellulose-TiO2 composites always improve the results obtained with the commercial TiO2-photocatalysts used as reference materials; this behaviour was analysed taking into account the physicochemical characteristics of the samples.

Assessing the environmental impact of energy production from hydrochar generated via hydrothermal carbonization of food wastes

Although there are numerous studies suggesting hydrothermal carbonization is an environmentally advantageous process for transformation of wastes to value-added products, a systems level evaluation of the environmental impacts associated with hydrothermal carbonization and subsequent hydrochar combustion has not been conducted. The specific objectives of this work are to use a life cycle assessment approach to evaluate the environmental impacts associated with the HTC of food wastes and the subsequent combustion of the generated solid product (hydrochar) for energy production, and to understand how parameters and/or components associated with food waste carbonization and subsequent hydrochar combustion influence system environmental impact. Results from this analysis indicate that HTC process water emissions and hydrochar combustion most significantly influence system environmental impact, with a net negative GWP impact resulting for all evaluated substituted energy-sources except biomass. These results illustrate the importance of electricity production from hydrochar particularly when it is used to offset coal-based energy sources. HTC process water emissions result in a net impact to the environment, indicating a need for developing appropriate management strategies. Results from this analysis also highlight a need for additional exploration of liquid and gas-phase composition, a better understanding of how changes in carbonization conditions (e.g., reaction time and temperature) influence metal and nutrient fate, and the exploration of liquid-phase treatment.

Effect of the initial state of carbon nanotubes on their ability to be dispersed in polar solvents upon liquid-phase oxidative treatments

Effect of the structural defectiveness of carbon nanotubes on the influence exerted on these nanotubes by their liquid-phase treatments with oxidizing agents (hydrogen peroxide, concentrated nitric acid, and its mixture with sulfuric acid) was studied. It was found that this factor affects changes in the structure of oxidized carbon nanotubes, their hydrophilicity, high-quality arrays of these tubes, and their ability to form stable dispersions in water, ethanol, isopropanol, and acetone.

Effect of Heating Temperature and Modification of Al – 27% Cu – 6% Si Melt on the Structure and Phase Composition of Crystallized Specimens

The effect of liquid-phase treatment of Al – 27 wt.% Cu – 6 wt.% Si melt used for making A34 solder on the structure and phase composition of crystallized specimens is studied. Pioneer data are obtained on the changes in the microstructure of the alloy due to its direct heating on the specimen stage of an NTEGRA Therma scanning probe microscope at 150 and 300°C.

Development of a PIGE-Detection System for in-situ Inspection and Quality Assurance in the Evolution of Fast Rotating Parts in High Temperature Environment Manufactured from TiAl

Intermetallic γ-titanium aluminides are a promising material in high temperature technologies. Their high specific strength at temperatures above 700°C offers the possibility for their use as components of aerospace and automotive industries. With a specific weight of 50% of that of the widely used Ni-based superalloys TiAl is very suitable as material for fast rotating parts like turbine blades in aircraft engines and land based power stations or turbocharger rotors. Thus lower mechanical stresses and a reduced fuel consumption and CO 2 -emission are expected. To overcome the insufficient oxidation protection the halogen effect offers an innovative way. After surface doping using F-implantation or liquid phase-treatment with an F-containing solution and subsequent oxidation at high temperatures the formation of a protective alumina scale can be achieved. By using non-destructive ion beam analyses (PIGE, RBS) F was found at the metal/oxide interface. For analysis of large scale components a new vacuum chamber at the IKF was installed and became operative. With this prototype of in-situ quality assurance system for the F-doping of manufactured parts from TiAl some performance test measurements were done and presented in this paper. Received: 01 March 2013; Revised: 24 April 2013; Accepted: 25 April 2013

Gas phase oxidation as a tool to introduce oxygen containing groups on metal-loaded carbon nanofibers

Oxygen containing groups were introduced, onto carbon nanofibers (CNFs) that were previously loaded with palladium, using HNO3 vapor. Using traditional liquid-phase oxidations this is not possible due to severe metal leaching. For the samples oxidized using HNO3 vapor temperature programmed desorption and X-ray photoelectron spectroscopy revealed the presence of two major classes of oxygen containing groups, i.e. carboxylic acid groups which are thermally stable up to 300°C and less acidic (e.g. phenol) and basic groups which were stable up to 700°C. The amount of acidic oxygen containing groups introduced by this gas-phase treatment ranged from 0.1 to 0.3mmol/g, as determined by titration. The latter amount is comparable to that introduced by traditional liquid-phase treatment in 65% HNO3 on bare CNFs. Transmission electron microscopy and H2-chemisorption measurements show a gradual increase of the average metal particle size from 2.1nm for the starting Pd/CNF to 4.5nm for Pd/CNF treated for 75h in HNO3 vapor indicating that the extent of sintering with gas-phase treatment is limited. Elemental analysis showed that no leaching occurred upon gas-phase oxidation, whereas 90% of the metal was lost with a liquid-phase reflux HNO3 treatment.

Investigation on the surface characteristics of GaAs after sulfuric-vapor treatment

The chemical bonding state and surface morphology of sulfuric-vapor treated GaAs surface were investigated using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The sulfuric vapor was obtained through the heating of (NH4)2Sx solution at 60°C. At the initial state of the treatment, the decrease of elemental As and the generation of As–S bonds were observed. Even after all of the elemental As converted into As–S bonds, peak area of the As–S bond increased until 5 min exposure. Unlike the liquid-phase treatment, the dissolution of the elemental As did not happen during the treatment and the formation of As-polysulfides was observed. Through the surface treatment of the GaAs using sulfuric vapor, small particles were formed and increased with treatment time. After 5 min exposure, they were linked to form a large agglomerate. This corresponds to a deposit of polysulfides containing hydrogen. To evaluate the effectiveness of the sulfuric vapor-treatment against oxidation in air, the treated GaAs was exposed to air and compared with the GaAs treated using a (NH4)2Sx solution. The As-polysulfides and polysulfides containing hydrogen were revealed to be easily decomposed by exposure to air. The character of S bond with GaAs was revealed to be the most important to obtain a passivation effect.

Work Functions and Surface Functional Groups of Multiwall Carbon Nanotubes

We have studied the work function and density of states (DOS) of multiwall carbon nanotubes (MWNTs) using ultraviolet photoelectron spectroscopy (UPS). Raw MWNTs were purified by successive sonication, centrifugation, sedimentation, and filtration processes with the aid of a nonionic surfactant. The purified MWNTs showed a slightly lower work function (4.3 eV) than that of highly oriented pyrolytic graphite (4.4 eV). Effects of three different oxidative treatments, air-, oxygen plasma-, and acid-oxidation, have also been studied. It was found that oxidative treatments affect the DOS of valence bands and increase the work function. X-ray photoelectron spectroscopy (XPS) measurements have suggested that gas-phase treatment preferentially forms hydroxyl and carbonyl groups, while liquid-phase treatment forms carboxylic acid groups on the surface of MWNTs. These surface chemical groups disrupt the π-conjugation and introduce surface dipole moments, leading to higher work functions up to 5.1 eV. We expect the ...

ATGA investigation of hydrated monoclinic zirconia

Thermogravimetric analysis (TGA) was used to monitor the surface hydroxyl and carbonate concentrations on porous zirconia after various vapor- and liquid-phase treatments. After equilibration with humid nitrogen, each of the surface zirconium atoms bears a single hydroxyl group and all surface oxygen atoms are present as bridged hydroxyl groups. Hydrochloric acid and sodium hydroxide treatments further increase the surface hydroxyl group concentration. In the presence of sufficient water, carbon dioxide chemisorption is inhibited. Once adsorbed, however, surface carbonates and bicarbonates are not removed by hydrochloric acid, sodium hydroxide or sodium fluoride washings.

Surface structure of finely dispersed iron powders III. Structure of a γ-aminopropyltriethoxysilane-modified coating

The surface structure of a γ-aminopropyltriethoxysilane-modified finely dispersed iron powder coating has been studied by X-ray photoelectron and infrared spectroscopy. It is shown that a gas-phase modification of finely dispersed iron powders leads to the formation of a dense γ-aminopropyltriethoxysilane monolayer, whereas a liquid-phase treatment yields a thicker polymer coating. The chemisorption of γ-aminopropyltriethoxysilane molecules on the surface of stabilized finely dispersed iron powders involves amino groups, in contrast to that occurring on the surface of metal oxides to give a SiOMe bond.

Aerobic treatment of swine manure: Physico-chemical aspects

Aerobic, liquid-phase treatment of 1000 litres of swine manure (44·0 g per litre of COD and 30·14 g per litre of TSS) in a bioreactor at ambient temperature led, after 168 h, to a 71% decrease in COD and about 40% in the TSS in the supernatant fraction. Presence of a microbial attachment support with the same treatment led to a 98% decrease in COD and 93% in TSS in the supernatant fraction; it also enhanced the diminution of the C/N ratio and the substrate. Bacterial growth was proven to be facilitated by maintaining the pH near 7·0. The final effluent had NNH 4 +, NNO 3 −, PPO 4 −3, TSS concentrations and COD suitable for microalgal cultivation.

Enhanced sintering treatments for ferrous powders

Powder metallurgy (P/M) constitutes a growing metal-forming technology with many favourable attributes. Ferrous materials provide the largest class of P/M alloys. The sintering of iron is examined in this review to establish the fundamental behaviour and to determine possible successes through enhanced sintering treatments. Within the scope of enhanced sintering, both activated and liquid-phase treatments are considered. The available data are collected to determine the effects of various additions on the sintering of iron. It is believed that small additions of elements like phosphorus, boron, carbon, and nitrogen provide for rapid densification and strengthening. However, the benefits are often offset by degradation of other properties such as ductility. These effects, as well as dimensional changes, are documented for several systems. Emphasis is given to describing the atomic processes responsible for the observed changes. There is considerable room for further progress in this area, including fundamental understanding and property optimization.