Decomposition Of Aqueous Solutions Research Articles

Formulation Development and Evaluation of Highly Oxidative Degradative Drug Molecule Injectable Dosage form by Lyophilisation Techniques

Adrenaline (ADR) It is lifesaving and is the only first-line drug for the treatment of anaphylaxis. Adrenaline (ADR) is the endogenous catecholamine with potent alpha- and beta-adrenergic stimulating properties. Alpha-adrenergic action increases systemic and pulmonary vascular resistance, increasing both systolic and diastolic blood pressure. Adrenaline is released in the bloodstream, which increases heartbeat, muscle strength, blood pressure, and glucose metabolism. Oxidation degradation of the medicinal product is the main route of degradation. Affects chemical and physical changes in drugs during the formulation development process. Physicochemical changes in the product can affect both the safety and efficacy of the drug product. Main product development strategy to develop, a stable, freeze-dried product of epinephrine for injection. The stability of adrenaline injection is of paramount objective as it is classified as a catechol compound that is sensitive to oxidation to o-quinone and therefore can react further to form highly colored compounds. Adrenergic drugs further react to form adrenochrome, a highly colored indole derivative. The rate of this reaction increased with pH, temperature and presence of the metal ions. Aqueous solutions of adrenergic agonists decompose rapidly when exposed to air, light, or heat, turning pink due to oxidation to adrenochrome and brown due to melanin formation. Due to its strong oxidizing properties and easy decomposition in aqueous solutions. To achieve this, the aqueous solutions of adrenergic agonists decompose rapidly when exposed to air, light, or heat, turning pink due to oxidation to adrenochrome and brown due to melanin formation. Due to its strong oxidizing properties and easy decomposition in aqueous solutions.

Anion Exchanges of Water-Stable Perovskite Nanocrystals in the Pure Water Phase and Applications in Detecting Halide Ions via a Smartphone-Based Sensing Platform.

Recently, the newly emerging lead halide perovskite nanocrystals (PNCs) have been intensely researched in many fields, such as light-emitting diodes (LEDs), solar cells, lasers, and display devices. The extremely high fluorescence quantum yield (near 100%) of PNCs over classic fluorescent materials would enable good applications of PNCs in sensing. However, the study on PNCs for bio- and chemical sensing, especially for detecting targets that exist in aqueous medium, faces great challenges due to the well-known instability of PNCs in polar solvents, especially water. Although the encapsulation of polymers or inorganic materials can efficiently protect PNCs from decomposition in aqueous solution, the sensing based on the interaction between PNCs and targets is severely hindered by the compact protection coating at the surfaces of PNCs. In this work, novel water-dispersed PNCs (W-PNCs), i.e., CsPbBr3@CsPb2Br5 PNCs, with strong fluorescence and excellent water stability were synthesized from OAm-capped CsPbBr3 PNCs by a simple "oil-solid-water" phase transition. The W-PNCs without being encapsulated with compact polymers or inorganic materials can sensitively and stably sense targets in the pure water phase via direct chemical reactions. For the first time, ion exchanges between PNCs and halide ions and their effects on the fluorescence wavelength of PNCs were investigated in the pure water phase, on the basis of which a new, visualized, selective, and sensitive smartphone-based sensing platform for halide ions has been established by the integration of the conveniently prepared W-PNC nanoprobe and the portable mobile phone. It is envisioned that the uncoated but extremely water-stable and highly fluorescent W-PNCs have promising applications in chemical sensing, biosensing, and bioimaging of targets in aqueous medium.

Catalytic Decomposition of H2O2 in the Aqueous Dispersions of the Potassium Polytitanates Produced in Different Conditions of Molten Salt Synthesis.

It is shown that the potassium polytitanate powder (PPT) synthesized at 500 °C via the treatment of powdered TiO2 (rutile) in molten mixtures of KOH and KNO3 is a cheap and effective catalyst of H2O2 chemical decomposition in aqueous solutions. At the same time, the PPT catalytic activity strongly depends on the [TiO2]:[KOH]:[KNO3] weight ratio in the mixture used for the synthesis, increasing with [KNO3] in the order of PPT (30:30:40) < PPT (30:50:20) < PPT (30:70:0). The obtained results are explained by increased [Ti3+] in the PPT structure (XPS data), which is grown in this order from 0 to 4.0 and 21.9 at.%, respectively, due to the reduced oxidation activity of the melt used for PPT synthesis. The mechanism of the autocatalytic process taking place in the PPT-H2O2-H2O system is analyzed. Taking into account the data of FT-IR spectroscopy, it is assumed that the increased catalytic activity of the investigated materials is related to the increased surface concentration of the Ti4+-O(H)-Ti4+ groups, formed from the Ti3+-O(H3O+)-Ti4+ clusters and further transformed into Ti-O-O-H catalytic centers. Some possible applications of the PPT-H2O2-H2O catalytic system, including the oxidation processes of green chemistry and photo-catalysis, are discussed.

Gamma radiolytic decomposition of methylparaben for environmental protection purposes

The methyl ester of p-hydroxybenzoic acid (methylparaben, MP) is commonly used as a preservative in cosmetics, food and pharmaceuticals. Its widely examined interactions with aqueous system and human organisms prove a necessity of the monitoring of its release to natural environment and the efficiency of its removal from waters and wastewaters.In this work, the yield of MP decomposition in aqueous solutions by gamma-radiation was investigated under oxidative conditions. The LC/MS, GC/MS and ion-chromatography were employed for examination of the yield of MP decomposition in function of the absorbed dose of radiation and for identification of stable products derived from MP formed during radiolysis prior to its complete mineralization. The studies were carried out in aerated aqueous solutions and under conditions with the predominance of OH radicals. The mechanisms of radical reactions were proposed leading to formation of the identified stable products. The irradiation of aerated MP solutions was assumed as a more favorable condition in terms of the yield of MP decomposition and a lack of changes of cytotoxicity towards 3 human cell lines was found. Under such conditions a 90% decomposition of MP at initial concentration 0.5 mg L−1 was observed for 100 Gy absorbed dose, which for the employed 60Co γ -source took 3.3 min. This provides a much better efficiency of MP decomposition in comparison to most of developed AOPs for this purpose.

High energy radiation – Induced cooperative reductive/oxidative mechanism of perfluorooctanoate anion (PFOA) decomposition in aqueous solution

The mechanism of high-energy radiation induced degradation of perfluorooctanoate anion (PFOA, C7F15COO−) was investigated in aqueous solutions. Identification and quantification of transient species was performed by pulse radiolysis and of final products by gas and ion chromatography, electrochemical method using fluoride ion-selective electrode and ESI-MS after γ-radiolysis. Experimental data were further supported by kinetic simulations and quantum mechanical calculations. Radiation induced degradation of PFOA includes as a primary step one-electron reduction of PFOA by hydrated electrons (e−aq) resulting in formation of [C7F15COO−]●−. The rate constants of this reaction were found to be in the range 7.7 × 107−1.3 × 108 M−1s−1 for ionic strength of the solutions in the range 0.01–0.1 M and were independent of pH of the solutions. At pH > 11 [C7F15COO−]●− tends to defluorination whereas at lower pH undergoes protonation forming [C7F15COOH]•−. A sequence of consecutive reactions involving [C7F15COOH]•− leads to PFOA regeneration what explains a high radiation resistance of PFOA at moderately acidic solutions. A simultaneous presence of oxidizing transient species (●OH) in the irradiated system enhanced decomposition of (C7F14)·COO− as well as [C7F15COOH]•−. The key steps in this complex radical mechanism are the reactions of both these radical anions with ●OH leading to semi-stable products which further undergo consecutive thermal reactions. On the other hand, direct reactions of PFOA with ●OH and ●H were found to be relatively slow (7 × 103 and <4 × 107 M−1s−1, respectively) and do not play relevant role in PFOA degradation. Collected for the first time results, such as dependence of selected reaction rate constants and selected products radiation chemical yields on pH as well as finding of several semi-stable products, missing in previous studies, indicate incompleteness of published earlier reaction pathways of PFOA degradation. The presented overall mechanism explains experimental results and verifies previously suggested mechanisms found in the literature.

Catalytic oxygen evolution from hydrogen peroxide by trans-[Co(en)2Cl2]@InBTB metal-organic framework catalytic system.

The diethylammonium counter-cations of the [Et2NH2]3[In3(BTB)4] metal–organic framework (InBTB MOF, BTB = 1,3,5-benzenetribenzoate) with an anionic framework can be effectively exchanged with cationic trans-[Co(en)2Cl2]+ complex ions through a simple cation-exchange process. The heterogenized trans-[Co(en)2Cl2]+-encapsulated InBTB MOF (trans-[Co(en)2Cl2]@InBTB) catalytic system maintained the activity of the captured trans-[Co(en)2Cl2]+ complex ion for hydrogen peroxide decomposition in aqueous solution under mild reaction conditions. The captured trans-[Co(en)2Cl2]+ complex also exhibited trans–cis isomerization to produce either cis-[Co(en)2Cl2]@InBTB or cis-[Co(en)2(H2O)Cl]@InBTB based on IR spectroscopic investigation. The trans-[Co(en)2Cl2]@InBTB catalytic system showed high recyclability for oxygen evolution from hydrogen peroxide. The catalytic ability of trans-[Co(en)2Cl2]@InBTB was maintained up to seven times of recycling.

Photocatalytic Activity of Nanocoatings Based on Mixed Oxide V-TiO2 Nanoparticles with Controlled Composition and Size

V-TiO2 photocatalyst with 0 ≤ V ≤ 20 mol% was prepared via the sol–gel method based on mixed oxide titanium–vanadium nanoparticles with size and composition control. The mixed oxide vanadium–titanium oxo-alkoxy nanonoparticles were generated in a chemical micromixing reactor, coated on glass beads via liquid colloid deposition method and underwent to an appropriate thermal treatment forming crystallized nanocoatings. X-ray diffraction, Raman, thermogravimetric and differential thermal analyses confirmed anatase crystalline structure at vanadium content ≤ 10 mol%, with the cell parameters identical to those of pure TiO2. At a higher vanadium content of ~20 mol%, the material segregation began and orthorhombic phase of V2O5 appeared. The crystallization onset temperature of V-TiO2 smoothly changed with an increase in vanadium content. The best photocatalytic performance towards methylene blue decomposition in aqueous solutions under UVA and visible light illuminations was observed in V-TiO2 nanocoatings with, respectively, 2 mol% and 10 mol% vanadium.

Determination of Sodium Metamizole by High Performance Liquid Chromatography Taking into Account its Decomposition in Aqueous Solutions in the Study of Dissolution Profiles

A procedure for the quantitative HPLC determination of sodium metamizole is developed and validated to study dissolution profiles of the PENTALGIN IC® medicinal preparation, tablets, taking into account the decomposition of sodium metamizole in aqueous solutions. In the study of dissolution profiles, along with the release of sodium metamizole from the finished dosage form, its hydrolysis to the decomposition product, methylaminophenazone, occurs. The decomposition reaction is unimolecular; therefore, the chromatograms of the test and reference solutions have two peaks, corresponding to metamizole and methylaminophenazone. It is shown that, for the correct calculation of the amount of sodium metamizole passed to the solution from the tablet, one should determine it from the sum of areas of both peaks, taking into account detector response factors.

Highly effective photocatalyst of TiO2 nanoparticles dispersed on carbon nanotubes for methylene blue degradation in aqueous solution

AbstractIn the present study, titania nanoparticles are highly dispersed on carbon nanotubes via hydrolysis process of tetra‐isopropyl‐orthotitanate Ti[OCH(CH3)2]4 (TPOT). The obtained composite (TiO2/CNTs) is characterized by modern methods. The anatase‐TiO2 phase is realized based on X‐ray diffraction spectrum at different pHs of hydrolysis solution. The band gap of TiO2/CNTs (Eg) is calculated by Tauc method using diffuse reflectance spectroscopy (DRS). The TiO2/CNTs composite plays as an active photocatalyst for methylene blue (MB) decomposition in aqueous solution. The effect of time to photocatalytic ability of TiO2/CNTs composite is described using Langmuir‐Hinshelwood kinetic model. The values of enthalpy variation (ΔH), entropy change (ΔS) and Gibbs free energy variation (ΔG) of the decomposition of MB are determined from thermodynamic study. In the range temperature from 283 K to 323 K, the positive values of ΔH and negative value of ΔG confirms endothermic and spontaneous nature of MB degradation. With the increase of temperature, the reaction occurs more easily, which is proved by more negative values of Gibbs free energy calculated from Van't Hoff equation.

A Study of the Bubble Column Evaporator Method for Improved Ammonium Bicarbonate Decomposition in Aqueous Solutions: Desalination and Other Techniques

A bubble column was used to study the improved thermal decomposition of NH4HCO3 in aqueous solution using a continuous flow of hot gas bubbles of optimum sizes (1-3 mm) produced via controlled bubble coalescence to maintain bubble size. The rapid transfer of heat from small, hot (dry) gas bubbles to the surrounding water, i.e. into a transient hot surface layer, was used as an effective and energy efficient method of decomposing ammonium bicarbonate in aqueous solution. It is shown that the continuous flow of (dry) hot gases, even at 275°C, only heat the aqueous solution in the bubble column to about 57°C, at which it was also established that NH4HCO3 has a negligible decomposition rate even with long-term exposure to this solution temperature. Hence, the effects observed appeared to be caused entirely by the effective collisions between the hot gas bubbles and the solute. It was also established that the use of high gas inlet temperatures can reduce the thermal energy requirement to only about 50% (i.e. about 575 kJ/L) of that reported in previous studies and less than 25% of solution boiling.

Разработка и исследование плазмохимической технологии получения смешанных оксидов урана и плутония из растворов

This paper presents the results of work on the application of plasma-chemical technology for producing uranium and plutonium oxides and their homogeneous mixtures from nitrate solutions of a given composition for the purpose of manufacturing fuel element cores. The technology is based on the process of high-temperature decomposition of aqueous solutions of salts by spraying them into a flow of the heat-transfer gas (air) heated to 5000 – 6000 K in a plasma torch. It is a highly productive short-stage process. No reagents are required for salt precipitation; there are no filtration and high-temperature treatment precipitation operations; the resulting powders are chemically active. It was found that the transformation time of salt solution drops to oxides is 0.05 – 0.10 s for the length of 0.5 – 0.7 m. The temperature in the reactor varies in the range of 1200 – 1800 K; no sintering and fusion of particles occurs. The apparatus-technological scheme of the plant has been developed. The technological equipment is made in a nuclear-safe design and installed in the exhaust boxes. The scheme includes a high-frequency induction plasmatron (plasma torch) with coaxial gas inlet into the discharge chamber. The high-frequency induction discharge is excited by inserting a grounded ignition electrode into the plasmatron discharge chamber. The plasmatron design provides the possibility of long continuous operation at high plasma temperatures with the creation of intensive plasma-jet processes for processing radioactive solutions. The reactor provides ways to prevent product accumulation on the walls (gas curtain method, electric pulse cleaning of cylindrical surfaces, vortex tangential gas supply at the level of the outlet holes of the injectors). Equipment for the separation of nanodispersed oxide powders from high-temperature steam- and powder-gas flows (vortex precipitators, filters with a metal-woven partition) has been developed and applied. The degree of oxide recovery in vortex precipitators is 88 – 92 % per stage, in filters with a metal-cloth partition the degree of purification reaches 105 – 108. Plasma-chemical oxides are nanocrystalline and nanoscale materials represented by crystalline and amorphous structures. Mixed powders are a homogeneous mixture of oxides in the form of solid solutions. The particle size does not exceed 3 μm; the crystallite size is about 10 nm. Fuel elements were manufactured from mixed powders at FGUP “Mayak”, which passed successful tests in the “Bor-60” reactor. Seven industrial fuel elements were manufactured for the BN-600 reactor, six of which were loaded into the reactor.

Solid Acid Electrochemical Cell for the Production of Hydrogen from Ammonia

Summary Production of high-purity hydrogen by thermal-electrochemical decomposition of ammonia at an intermediate temperature of 250°C is demonstrated. The process is enabled by use of a solid-acid-based electrochemical cell (SAEC) in combination with a bilayered anode, comprising a thermal-cracking catalyst layer and a hydrogen electrooxidation catalyst layer. Cs-promoted Ru on carbon nanotubes (Ru/CNT) serves as the thermal decomposition catalyst, and Pt on carbon black mixed with CsH2PO4 is used to catalyze hydrogen electrooxidation. Cells were operated at 250°C with humidified dilute ammonia supplied to the anode and humidified hydrogen supplied to the counter electrode. A current density of 435 mA/cm2 was achieved at a potential of 0.4 V and ammonia flow rate of 30 sccm. With a demonstrated faradic efficiency for hydrogen production of 100%, the process yields hydrogen at a rate of 1.48 m o l H 2 / g c a t h .

Hierarchically 1D CdS decorated on 2D perovskite-type La2Ti2O7 nanosheet hybrids with enhanced photocatalytic performance

In this paper, a heterojunction of hierarchically one-dimensional (1D) cadmium sulfide (CdS) nanowires decorated on the two-dimensional (2D) La2Ti2O7 (LTO) has been fabricated by a simple two-step hydrothermal process. The structure, morphology and surface chemical composition of CdS/LTO were studied by a variety of characterizations, in which the X-ray photoelectron spectroscopy (XPS) results showed a strong interaction between CdS and LTO through S–O bonds. The type II band alignment of CdS/LTO for favorable electron transfer from CdS to LTO and hole transfer from LTO to CdS was clarified by ultraviolet–visible (UV–Vis) diffuse reflectance spectroscopy and Mott–Schottky (M–S) plot measurements. In the absence of any co-catalyst, H2 production from water splitting and Rhodamine B (RhB) decomposition in aqueous solution were carried out to evaluate the photocatalytic activities, showing that the photocatalytic performance of CdS/LTO was superior to that of pure LTO and CdS under visible light and simulated sunlight. The optimal CdS content in the CdS/LTO system was determined to be 7.5 wt%. The present results show an effective pathway to design a 1D/2D heterojunction photocatalyst in the face of overwhelming problems of energy crisis and environmental pollution.

Chemical actinometry and paraben decomposition in aqueous solution utilizing ultraviolet radiation combined with hydrogen peroxide

In this paper, ultraviolet radiation combined with hydrogen peroxide is presented to investigate the degradation of methyl, ethyl, and propyl parabens. The proposed kinetic model incorporates photochemical, chemical reactions, and reaction-rate constants to formulate the overall kinetic rate expressions, which are integrated into MATLAB. Thus, the chemical actinometry has been investigated to identify the incident ultraviolet-light intensity (1.59 × 10−6 Einstein.cm−1 s−1) and the optical path-length (5.83 cm) of the new reactor. Based on the optimal parameters of the previous study, an experimental campaign was performed at fixed hydrogen peroxide concentration to compare the half-life of the decomposition of these parabens and to determine the evolution of the pH and the pseudo-first-order rate constant. Accordingly, the study provides a comparison between numerical results and experimental data. The use of hydrogen peroxide at 25 µM resulted in 80% removal of propyl paraben (10 mg/L) within 90 min reaction time, while 50% of methyl and ethyl was oxidized. The performed model had a satisfactory predictive performance of paraben removal during the reaction, and the numerical pseudo-first-order rate constant was in agreement with the experimental value. Although the proposed model slightly overestimates the decrease of experimental pH, it provides insight into the evolution of hydroxide, superoxide, and hydroperoxyl ions. Finally, this paper proposes a discussion on the limitations of the study and suggests future work concerning the effects of water matrix, carbonate species, paraben mixture, and cytotoxicity of degradation by-products.

High dispersity, stability and bioaccessibility of curcumin by assembling with deamidated zein peptide

Many liposoluble nutrients are restricted for applications in foods due to their poor water solubility, stability and bioavailability. Here, a deamidated zein peptide with a broad molecular weight distribution and high carboxyl and hydrophobic residue contents was used to solubilize curcumin. The complex nanoparticles of curcumin and the peptide were produced through self-assembly in aqueous solutions. Fluorescence and infrared spectra revealed that hydrogen bonding and hydrophobic interactions actuated the assembly. The complex nanoparticles had a curcumin loading capacity of 31.9% and completely inhibited curcumin crystallization. The peptide effectively protected curcumin from decomposition in aqueous solutions by inhibiting the reaction between dissolved oxygen and curcumin. The nanoparticles presented excellent freeze-drying/re-dispersion stability without any lyoprotectant. The curcumin bioaccessibility of the nanoparticles was 75% and the nanoparticles exerted a significant antioxidant effect after oral administration in mice. This study indicates that the nanoparticles are potentially useful as an antioxidant additive in foods.

Stabilization of Ni(I)(1,4,8,11‐tetraazacyclotetradecane)+ in a Sol‐Gel Matrix: It's Plausible Use in Catalytic Processes

AbstractMonovalent nickel is used as a catalyst in a diversity of important chemical systems due to its properties as a strong reducing agent. However, monovalent nickel is unstable in homogeneous systems; its lifetime is very short, and therefore, its efficiency as a catalyst is quite limited. In this article, we demonstrate the catalytic capabilities of Ni(I)(1,4,8,11‐tetraazacyclotetradecane)+ as a reducing and catalytic agent by its entrapment in the silica sol gel matrix. The EPR results indicate that the sol‐gel matrix plays two roles: it inhibits the common mechanism of Ni(I)L+ decomposition in aqueous solutions, and it also facilitates its functionality as a heterogeneous catalyst, by stabilizing it for at least several hours. The activity of Ni(I)L+ which is entrapped within the matrix, was studied by reducing 2,2‐Bis(bromomethyl)‐1,3‐Propanediol and I3−. The results indicate that Ni(I)L+/Ni(III)L−H2+ acts as a good reducing agent. These results have important implications for a variety of essential catalytic reactions by shedding light on a new feature of sol‐gel matrices and their use as active species stabilizers.

Application of ionizing radiation in decomposition of perfluorooctane sulfonate (PFOS) in aqueous solutions

The radiolytic methods of PFOS decomposition in aqueous solutions investigated in this work for potential environmental applications are based on the use of gamma rays or a beam of accelerated electrons (EB) under different chemical conditions in irradiated solutions. The most active reagents in the employed conditions are hydrated electrons from water radiolysis. There are also OH and H radicals which take part in the occurring reactions. In the presence of formate and 2-propanol in irradiated solutions, the reductive radicals derived from them (CO2−, (CH2)2C-OH) are able to induce reductive decomposition of PFOS. In turn, in the presence of tert-butanol, the radicals derived from the alcohol and PFOS dimerize forming alkyl-substituted derivatives. The most favorable conditions for irradiation were achieved in neutral deaerated solutions and aerated solutions containing 10 mM 2-propanol. In γ-irradiation processes the pseudo-first order rate-constants of PFOS decomposition are 0.0197 min−1 (0.310 kGy−1), and 0.0060 min−1 (0.0947 kGy−1), respectively, under both conditions. Due to a big difference in the dose-rate between the two employed types of radiation (gamma and EB), the values of pseudo-first order rate constants of PFOS decomposition are different, namely 0.0197 min−1 (0.310 kGy−1) and 0.368 s−1 (0.0184 kGy−1), respectively, for γ and EB radiation used for decomposition of 0.1 mg L−1 PFOS in neutral, deaerated solution. The EB-irradiation processes for PFOS decomposition are much more efficient than any other AO/RPs reported so far and can be easily employed at a technological scale for very large volumes of treated solutions. The gamma irradiation-based PFOS decomposition requires smaller absorbed doses and it does not require any external energy input because of the use of the isotope source of radiation.

Chemical and Electrochemical Regeneration of InP after GD-OES/XPS Profiling Experiments

The interest in III-V materials for photovoltaic applications has grown with the development of tandem or multi-junction solar cells. However, with the devices architecture getting more and more complex, the multiple processing steps have to be characterized by means of adapted characterization strategies. Indeed, the better efficiencies can be obtained once the entire solar cell is widely known and optimized. In this purpose, the best way would be a combination of electrical properties measurements, chemical and optical characterizations of all the layers and interfaces in the final cell stack. The present study focuses on physico-chemical characterizations from the surface to the different interfaces of interest, to help in determining optimal experimental conditions during the whole cell fabrication. To this end, we developed and implemented a new and specific approach combining two analytical techniques. To access the different buried interfaces, a fine quantitative chemical profiling through each layer is performed thanks to a combination of Glow Discharge – Optical Emission Spectroscopy (GD-OES), with its new Differential Interferometry Profiling (DiP) module, and X-ray Photoelectron Spectroscopy (XPS). The advantage of coupling these techniques is to combine the high etching rate of GD-OES and the XPS surface chemical (composition and chemical environment) diagnostic. In particular, specific in-depth location can be precisely reached by live GD-OES intensity profile monitoring, while XPS analyses (400 µm spot size) can be directly performed inside the GD-OES crater (4mm diameter) in order to obtain the detailed chemical composition. The proof of concept has been established [1], however, previous studies have demonstrated that, stopping the GD-OES profiling, and so the dynamic of the plasma sputtering, leads to possible degradation of the material and re-deposition processes. Therefore, a dedicated study of the degradation nature and perturbed depth dimension has to be performed to adopt the best strategy to regenerate the initial chemical and structural information and ensure the reliability of the analyses implemented inside the crater. For our purpose, this point is critical to certify that surface XPS analyses inside the crater bring representative information about the chemistry. Different regeneration solutions can be employed to eliminate the damaged surface [2] and we specifically investigate the capabilities of surface wet chemical engineering, by soaking, or physical removal by Ar+ or Arn + sputtering. This issue will be illustrated on the practical case of InP. First, the evaluation of the degradation of InP due to the GD-OES stopping for a better XPS exploitation of the GD crater will be presented. To obtain an overall characterization complementary analyses techniques were employed. Crater imaging and global chemical and microstructural analyses were achieved by scanning electron microscopy (SEM), Electron dispersive spectrometry (EDS) and electron BackScattered Diffraction (EBSD). Surface analyses were performed ex-situ by XPS and, at local scale (12 nm spot size) by nano-Auger) and in-situ by electrochemistry. Optical properties were obtained by ellipsometry (Fig. 1). From this work, a superficial In enrichment inside the GD-OES crater (Fig. 2), very close to the one obtained by the cathodic decomposition in aqueous solution, was shown. In addition, electrochemistry and XPS measurements displayed that this enrichment was attributed to the presence of metallic In. Then, a comparative study of the InP GD-OES crater evolution after different regeneration options, including wet chemical nano-engineering, electrochemistry and physical treatments, will be detailed.

Application of X-ray diffractometry and scanning electron microscopy to study the transformation of carnallite and thenardite to schoenite at 25 °C

An experimental study was carried out on the preparation of schoenite from carnallite and thenardite by the double-decomposition method. According to the metastable phase diagram for the quinary system, Na+, K+, Mg2+//Cl–, and SO42−-H2O at 25 °C, three theoretical models were established for the double-decomposition processes. The mineralogy and morphology of schoenite, sylvite, epsomite/hexahydrite, and halite were studied by X-ray powder diffractometry and scanning electron microscopy during the double-decomposition processes. It is confirmed the preparation of schoenite via carnallite and thenardite is feasible. The double-decomposition reactions processes were described by three model equations. First, sylvite was obtained by carnallite decomposition in aqueous solution; second, epsomite/hexahydrite was obtained by a conversion reaction via thenardite and an MgCl2-rich mother liquor; third, schoenite was obtained via sylvite and epsomite/hexahydrite. The results suggest that (1) sylvite exists in the primary reaction time, epsomite/hexahydrite form simultaneously, and their contents decrease as the reaction time increase. (2) The terminal product of the double-decomposition is schoenite, and its formation results from conversion via sylvite and epsomite/hexahydrite. (3) A tendency for the X-ray diffraction intensity of sylvite and epsomite/hexahydrite to weaken increases visibly with reaction time, and its change agrees well with the third model. (4) Scanning electron microscopy images of the halite, sylvite, epsomite/hexahydrite, and schoenite are clear and integrated, and their formation results from the precipitation of the three model conversion reactions. Results showed that a good agreement exists between the experimental and theoretical models.

Experimental and numerical study of methylparaben decomposition in aqueous solution using the UV/H2O2 process

The present paper aims at presenting a kinetic model that is supposed to result in the decomposition of methylparaben in completely mixed batch reactor (CMBR) using the UV/H2O2 process. The proposed model incorporates photochemical, chemical reactions and their constant rates to formulate the overall kinetic rate expressions which are integrated into MATLAB. Thus, the changes in pH values during the process of oxidation are taken into consideration. In addition, the effects of hydrogen peroxide (HP) dosage, as well as the concentration of hydroxyl radicals, are examined. Accordingly, the pseudo-first-order rate constant, its variation as functions of HP concentration, incident UV-light intensity and the limitations of the adopted approach are discussed. In line with that, the authors provided evidence of the validity of the kinetic model through the exposure of previous experimental studies as reported in the literature review then through the evidence of the present experimental data.