Acid Solution Treatment Research Articles

Oxygen breaks into carbon nanotubes and abstracts hydrogen from propane

We have revealed that molecular oxygen breaks into carbon nanotubes forming active sites to abstract hydrogen from propane. Various carbonaceous species (carbon defects and debris) on carbon nanotubes were identified and their effects on the oxo-functionalization as well as the catalytic performance in the oxidative dehydrogenation of propane were thoroughly investigated. The results indicate that certain amount of accessible skeleton defects is beneficial to the selective introduction of ether and ketonic carbonyl groups. However, amorphous carbons are poorly selective during oxo-functionalization and the related functionalities decompose easily during the long-term catalytic test. The proportion of ether and ketonic carbonyl groups obtained from oxygen functionalization reaches to 93%, which is twice more than that obtained from acidic solution treatment. Turnover frequency of 1.5 h−1 in the oxidative dehydrogenation of propane is successfully correlated with ketonic carbonyl groups (CO), while there is no obvious correlation between the activity and the amount of ether groups (C–O–C).

High performance sponge-like cobalt sulfide/reduced graphene oxide hybrid counter electrode for dye-sensitized solar cells

A sponge-like cobalt sulfide/reduced graphene oxide (CoS/rGO) hybrid film is deposited on fluorine doped SnO2 (FTO) glass by electrophoretic deposition and ion exchange deposition, following by sodium borohydride and sulfuric acid solution treatment. The film is used as the counter electrode of dye-sensitized solar cells (DSSCs), and is characterized by field emission scanning electron microscopy, Raman spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy and Tafel measurements. The results show that the CoS counter electrode has a sponge structure with large specific surface area, small charge-transfer resistance at the electrode/electrolyte interface. The addition of rGO further improves the electrocatalytic activity for I3− reduction, which results in the better electrocatalytic property of CoS/rGO counter electrodes than that of Pt counter electrode. Using CoS/rGO0.2 as counter electrode, the DSSC achieves a power conversion efficiency of 9.39%; which is increased by 27.93% compared with the DSSC with Pt counter electrode (7.34%).

Topical tranexamic acid improves the permeability barrier in rosacea

To evaluate the influence of tranexamic acid on epidermal permeability barrier function in rosacea and its potential mechanisms. A randomized, vehicle controlled, split-face study was performed on 30 rosacea patients. This study involved 2 weeks of 3% tranexamic acid solution treatment and vehicle control treatment. Skin physiological parameters, including skin surface pH, stratum corneum hydration, and transepidermal water loss, were measured. The expression of protease-activated receptor 2 (PAR-2) in rosacea and normal skin samples was assessed with immunohistochemical staining. The expression of PAR-2 in HaCaT keratinocytes was determined using reverse transcription polymerase chain reaction after stimulation with tranexamic acid. Changes of intracellular calcium induced by PAR-2 activation were measured using Fluo-4 NW calcium assay. Individuals with rosacea expressed a higher baseline level of PAR-2 compared with normal skin. Tranexamic acid improved the permeability barrier function in rosacea patients and inhibited calcium mobilization in keratinocytes induced by PAR-2 activation. The PAR-2 expression was not altered by tranexamic acid stimulation. Topical tranexamic acid could improve the epidermal permeability barrier function and clinical signs of rosacea, likely resulting from inhibition of PAR-2 activation and consequent calcium influx. Thus, tranexamic acid could serve as an adjuvant therapy for rosacea.

Surface Characterization of Some Novel Bonded Phase Packing Materials for HPLC Columns Using MAS-NMR Spectroscopy

Information on the surface properties of three novel chemically bonded phase packing materials for High performance liquid chromatography (HPLC) were obtained using spectra obtained by solid state cross-polarization (CP) magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopic experiments for the 29Si, and 13C nuclei. These packing materials were: Cogent bidentate C18 bonded to type-C silica, hybrid packing materials XTerra MS C18, and XBridge Prep. C18. The spectra obtained using cross-polarization magic angle spinning (CP-MAS) on the Cogent bidentate C18 bonded to type-C silica show the surface to be densely populated with hydride groups (Si-H), with a relative surface coverage exceeding 80%. The hybrid packing materials XTerra and XBridge gave spectra that reveal the silicon atoms to be bonded to organic moieties embedded in the molecular structure of these materials with over 90% of the alkyl silicon atoms found within the completely condensed silicon environments. The hydrolytic stability of these materials were investigated in acidic aqueous solutions at pHs of 7.0 and 3.0, and it was found that while the samples of XTerra and XBridge were not affected by hydrolysis at this pH range, the sample of Cogent lost a significant proportion of its Si-H groups after five days of treatment in acidic aqueous solution.

Investigation on slag fiber characteristics: Mechanical property and anti-corrosion performance

Inorganic fiber shows good insulation performance in civil construction and industry insulation. In the present paper, tensile strength of slag fiber produced with molten blast furnace slag was investigated systematically with the Weibull distribution theory in comparison with glass and basalt fibers. It was found that the mean tensile strength reached 2578.60MPa and the shape parameter m in Weibull distribution is 2.4494, which indicates a lower uniformity. Anti-corrosion performances were also studied by means of the mass and strength loss after acid and alkaline solution treatment. Furthermore, SEM and FTIR were used to analyze the structural characteristics of original and treated fibers. This work has proved that the H+ and OH− can both break the Si–O bond and then lead to the movement to high wavenumber for the bands of the symmetric stretching vibrations of [SiO4]-tetrahedra. The anti-corrosion results indicated that slag fibers could not be used in acid environment, while its anti-alkali performance is relatively excellent compared with glass and basalt fibers.

酸処理によるアモルファスおよびルチル型 TiO<sub>2</sub> 粒子の光触媒活性向上

To activate the photocatalytic behavior of predominantly amorphous TiO2 fine particles, the surfaces of the particles were modified by immersion in sulfuric acid aqueous solutions with different concentration, followed by heating at 525℃ for 1 h. The photocatalytic activity for acetaldehyde decomposition under UV irradiation increased on increasing the sulfuric acid concentration in the solutions used for immersion from 0.001 N to 1 N ; however, intermediate products, such as acetic acid, methanol and formic acid, were generated and remained in the case of immersion in 1 N sulfuric acid aqueous solution. The rate of decomposition of acetaldehyde remarkably increased, without generation of intermediate products, on using 0.001 N sulfuric acid for the immersion of amorphous TiO2 fine particles. Since only immersion in a sulfuric acid aqueous solution did not activate the photocatalytic behavior of rutile TiO2 particles, they were treated with a 3 mass％ aqueous solution of hydrogen peroxide, followed by immersion in a 1 N sulfuric acid solution and heat treatment. The rate of decomposition of acetaldehyde under UV irradiation using the surface treated rutile particles was increased about 10 times higher than that of the untreated rutile particles.

Pt-Based Catalytic Microcombustor for Micropower Generation

This paper presents the fabrication and characterization of platinum-based catalytic microcombustor. The platinum catalyst was deposited onto type-304 stainless steel using the wet impregnation method. The stainless steel undergoes controlled conversion coating treatment in sulfuric acid solution to increase the porosity of its surface before the deposition of the platinum catalyst. The scanning electron microscopy result showed that the porosity on the stainless steel surface will depend on the length of treatment time in the sulfuric acid solution. The surface porosity increased as the treatment time increases. The stainless steel surface morphology changed from smooth to ‘cracked-mud’ morphology after treatment in sulfuric acid solution. The treatment time also provide significant effect to the amount of platinum deposited on the stainless steel surface. The energy dispersive x-ray analysis showed that the amount of deposited platinum for 10 seconds of treatment time was 0.68 wt%, whereas those for 20 and 30 seconds were 0.87 wt% and 1.10 wt%, respectively. Liquefied petroleum gas-air combustion result showed that the flame completely submerged inside the microcombustor with a catalyst, whereas portions of flame can be observed at the exhaust for the microcombustor without a catalyst. The minimum air-to-fuel ratios before the combustion blow-out for 10, 20, and 30 seconds of treatment time was 0.5, 0.4, and 0.3 respectively.

Synthesis of Alpha Alumina Using Microwave Energy

This work investigated the synthesis of α-alumina using dissolution and re-precipitation of aluminum nitrate and microwave heating. The synthesized powders were characterized by X-ray diffraction, thermal analysis (TGA and DTA) and surface are by BET. The dissolution process was carried out using acid solution and heat treatment. Results depicted the efficiency of the process to accelerating the synthesis of alpha alumina. The results showed that the powders have the microwave structure of α-alumina with specific areas ranging between 3 and 15m2/g and pore diameters between 190 to 485nm.

The effect of chemical treatment on the strength and transmittance of soda-lime cover glass for mobile

Most cracks in sheet glasses originate in edges and are a major cause of decreasing strength. Glass covers are being adopted in more mobile devices, especially smart phones, and are required to enhance reliability. In this study, micro-cracks in the chamfered edge of soda-lime cover glasses were eliminated by chemical polishing process with several etchants, and their mechanical properties and transmittance were measured. After ammonium fluoride and organic acid solution treatment, the transmittance of glass was not degraded and the strength was increased up to 20%. However, in the case of HF-based solutions, the strength of soda lime glasses increased but its transmittance decreased.

Electroreduced Tantalum Pentaoxide for Hydrogen Evolution Reaction

Abstract A novel technique to activate tantalum pentaoxide is introduced. An electrochemical reductive treatment in acidic solution is found to be an effective method for transforming the Ta5+ in Ta2O5 to Ta<5+, in such a way that it is active for hydrogen evolution. This opens a new route to the development of metal oxide-based catalysts.

Preparation and application of monodispersed mesoporous submicron carbon particles as a drug carrier

Monodispersed mesoporous carbon (MMPC) submicron carbon particles have been fabricated by co-spray drying of SBA-15 submicron particles and sucrose, followed by carbonization in a nitrogen environment and removal of the hard SBA-15 template in NaOH solution. The ratio of sucrose/SBA-15 used for the co-spray drying affected the integration and dispersibility of the obtained mesoporous carbon particles and sucrose/SBA-15 ratios at 1.0–1.5 resulted in monodispersed mesoporous carbon submicron particles. The surface properties of MMPC could be modified by treatment in nitric acid solution to create oxygen groups and thus increase wettability of MMPC powder. MMPC particles were used as drug carrier to enhance the dissolution rate of a poorly soluble drug, indomethacin (IDMC) via co-spray drying. The morphology of MMPC was not changed after drug loading as most IDMC molecules were encapsulated into its pore channels in amorphous state, which was characterized by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). Due to the ordered mesoporous structure, the pore walls separate the IDMC particles and prevent recrystallization from happening. The amorphous IDMC/MMPC solid dispersion exhibited excellent stability under stress storage conditions of 40°C/75% RH for six months. The amorphous formulation contributed to the significantly enhanced dissolution rate of IDMC from solid dispersion.

Determination of Moxifloxacin and its Oxidation Products with Kinetic Evaluation Under Potassium Permanganate Treatment in Acidic Solution by Ultra-Performance Liquid Chromatography/Tandem Mass Spectrometry

A simple, sensitive, and reproducible ultra-performance LC method for the determination of moxifloxacin (MOXI) oxidation stability under permanganate treatment in acidic conditions (pH 3.0-6.0) was developed. Besides the MOXI peak [retention time (RT) = 2.58], four additional products (RT = 0.86, 0.91, 1.42, and 1.89) were observed in all conditions tested. The oxidation process followed second-order reaction kinetics and depended upon solution acidity. The highest reaction rate constant was observed at pH 3.0, and this value decreased as the pH was increased to 6.0. The oxidation products were characterized, and their fragmentation pathways, derived from MS/MS data, were proposed. Two of these products were identified as hydroxyl derivatives of MOXI and two others as their oxidation product analogs with molecular ions of 418.4 and 416.4 m/z, respectively.

The physical/chemical properties and electrode performance variations of SWNT films in consequence of solution based surfactant elimination processes

The effects of the surfactant elimination from single wall carbon tube (SWNT) films on the physical/electrical properties of SWNT films are concretely studied. The surfactant, which helps to disperse the SWNTs in polar solvent without damage, completely wraps SWNT in film as well as in solution condition and therefore, it still critically precludes from showing up the original characteristics of SWNT material. However, after the stepwise dipping processes in deionized water and acid solution, the properties of SWNT film become close to the SWNT characteristics according to the surfactant elimination. Compared to as-deposited SWNT film, the optical transmittance, surface roughness and resistivity noticeably increase after surfactant elimination processes and besides, the acid solution treatment generates the partially functionalization (–OH or –COOH group introduction) of SWNTs. Because the functionalization of SWNT increases the work function as well as number of catalytic, those have highly positive influences on the performances of electrodes for organic devices. Actually, compared to as-deposited or deionized water treated SWNT film, the HNO3 treated SWNT film shows higher performance as source/drain electrode in organic thin film transistor and catalytic cathode electrode in dye sensitized solar cell.

Adsorptive removal of humic acid on activated carbon prepared from almond shell: approach for the treatment of industrial phosphoric acid solution

ABSTRACTAlmond shell was used as a precursor to prepare activated carbon, using carbon dioxide as a physical activation agent. Its ability to remove the humic acid was evaluated. The surface area of almond shell activated carbon was found to be 1,310 m2/g. The effects of experimental parameters such as pH, initial humic acid concentration, contact time, adsorbent dosage, and solution temperature on the adsorption were investigated. To describe the equilibrium isotherms the experimental data were analyzed by the Langmuir, Freundlich, and Temkin isotherm models. Pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models were used to find out the kinetic parameters and mechanism of adsorption process. The thermodynamic parameters such as ΔG°, ΔH°, and ΔS° were calculated for predicting the nature of adsorption. For an approach to an industrial application, activated carbon prepared from almond shell seems to be an effective, low-cost, and good adsorbent precursor for the removal of hu...

Porous silicon/NaOH texturization surface treatment of crystalline silicon for solar cells

Crystalline silicon surface texturing is one of the important issues of modern silicon solar cells efficiency improvement. In this work an attempt has been made to obtain a well-textured multicrystalline silicon and monocrystalline silicon surface through two different approaches. The first with standard alkaline (NaOH) solution, the second is based on a combination of formed structures obtained in NaOH and stain etching treatment in acid (HF/HNO3/H2O) solution. effect of texturisation based on these two methods on the surface morphology of Si wafers as well as on the optical and optoelectronic properties are presented in this paper. Extensively study of the surface morphologies evolution of Si wafer has been carried out and correlate to the reflectance, the effective lifetime, the internal quantum efficiency (IQE) maps and current–voltage (I–V) characteristics change before and after surface treatment.

Hierarchical nanotubular clay materials derived from natural cellulose substance

Versatile hierarchical nanotubular clay materials were fabricated by using natural cellulose substance as template. Cellulose nanofibers were pre-coated with ultrathin titania gel films employing the surface sol–gel process, followed by layer-by-layer self-assembly of poly(diallyldimethylammonium chloride) and the specific clay nanosheets (kunipia-F, montmorillonite-K10 and sumecton-SA) through electrostatic interactions. The as-deposited cellulose/titania/polymer/clay composite sheets were calcined to remove the organic components, resulting in bulk hierarchical nanotubular titania/clay hybrid materials. Further sulfuric acid solution treatment of the resultant titania/kunipia-F hybrid sheet led to the pure nanotubular structured kunipia-F material. Low-temperature sodium hydroxide/urea solution treatment of the as-prepared cellulose/titania/polymer/kunipia-F composite sheet formed nanotubular titania/polymer/kunipia-F hybrid. Iron nanoparticles were immobilized onto the as-prepared cellulose/titania/polymer/kunipia-F composite sheet as the substrate, resulting in a new composite material showing high efficiency of decoloration of aqueous methylene blue.

New Seaweeds Coagulant Aids on Coagulation Performance and Floc Characteristics of Ferric Chloride Coagulant in Kaolin-Humic Acid Solution Treatment

Using coagulant aid to increase the organics removal is one of the main methods to improve the coagulation effect. The development of new coagulant aids has vital significance to water supply and sewage treatment. This paper develops two kinds of new seaweeds coagulant aids- Enteromorpha extract (EE) and sodium alginate (SA), and then the two coagulant aids were used together with ferric chloride (FC) in humic acid - kaolin water sample. The coagulation aid effect of EE and SA were studied through the comparation of coagulation effects before and after the application of them. Meanwhile, the growth, breakage and regrowth of flocs were investigated by use of a laser diffraction particle sizing device. The experimental results showed that Ee had significant coagulant aid effect while the aid role of SA was not obvious, but when used together with FC, flocs showed larger particle sizes and growth rates no matter which coagulant aid was selected. Meanwhile the strength and recovery ability of flocs showed a corresponding increase.

Adsorption of arsenic on pre-treated zeolite at different pH levels

Natural zeolites are widely used to minimise the impact of some pollutants in the environment, such as the removal of metals in various water sources as well as effluents used in the mining and metallurgical industry and in the treatment of mining acid solutions. The most common varieties of zeolites are analcime, chabazite, clinoptilolite, heroinite, ferrierite, mordenite. Researchers have studied for decades their synthesis, structure and proprieties, and as a result a large number of patents have been obtained on the preparation of different types of zeolite in conjunction with metals or metal compounds as selective adsorbents for anions and cations of water solutions. For example, iron, zirconium and magnesium hydroxide show selectivity in the adsorption of arsenic among other industrial applications of great interest.This study shows the importance of using natural pre-treated zeolites in the adsorption of arsenic in water due to the adsorption percentages that are higher than 90%, controlling the pH in the pre-treatment. Samples were treated at different pH levels, getting a better adjustment of isotherms of adsorption at pH = 9 with ZP-9.

Aspects of Surface Conditioning for High-Efficient Hetero-Junction Silicon Solar Cells

As a high-efficiency silicon solar cell concept amorphous silicon/crystalline silicon (a-Si:H(n,p)/c-Si (p,n)) hetero-junction solar cells are of great scientific interest [1, . The a-Si:H emitter is deposited by plasma-enhanced chemical vapor deposition (PECVD). The biggest challenge is to avoid recombination at the a-Si:H(i)/c-Si interface where the p-n junction is located. A clean, smooth, hydrogen terminated c-Si surface is supposed to be mandatory for a high passivation quality of the deposited layer [3, 4]. It is well established that treatment in dilute hydrofluoric acid (dHF) solution (1-10%) produces a hydrogen-terminated, clean Si surface [e.g. 5, 6, 7]. H-termination is supposed to rise with increasing etch time [8]. Whereas prolonged rinsing after the etch step leads to a formation of OH-groups at the surface [8]. Because of the high sensitivity of the a-Si:H(i)/c-Si interface the influence of prolonged etching in dHF (1%) as well as prolonged rinsing in deionized water (DI water) on the passivation quality of the deposited a-Si:H(i) layer has to be carefully studied. Also the possibility of decreased hydrophobicity and a possible iron recontamination from the HF has been taken into account.

Influence of a new coagulant aid-Enteromorpha extract on coagulation performance and floc characteristics of aluminum sulfate coagulant in kaolin–humic acid solution treatment

A new coagulant aid, Enteromorpha extract (Ee), was studied to enhance the coagulation performance when it was used together with aluminum sulfate (AS). The dual-coagulant, aluminum sulfate–Enteromorpha extract (AS–Ee), was achieved by dosing Ee 30s after AS was dosed. AS–Ee and AS were comparatively evaluated regarding their coagulation performance. The results showed that Ee played an important assistant part in the coagulation process. The coagulation effect of AS–Ee was about 10% higher than that of AS with respect to the removal of turbidity, UV254 and DOC. Floc characteristics were also investigated in terms of floc size, strength and recovery ability, with the results indicating that the strength of flocs produced by two coagulants were both enhanced with Al dosage increasing, while the floc recoverability was decreased. Floc produced by AS–Ee had bigger size and faster growth rate than that by AS. Meanwhile, the former was also stronger and had a better recoverability than the latter. The charge neutralization was the dominant mechanism of AS, and Ee had good adsorption bridging effect. Due to the combination of two advantages, coagulation efficiency of the dual-coagulant could be enhanced significantly.