Dissolution Phenomena Research Articles

The effect of microstructure on the leaching behaviour of electric arc furnace (EAF) carbon steel slag

Electric arc furnace (EAF) slag could be exploited in several fields of application, such as land filling, road constructions and concrete production, since their physical properties are similar, or even better, than natural materials like gravel. Environmental concerns related to pollutants leaching (Ba, V, Cr, chlorides, fluorides, cyanides, etc.), are the primary hindrance limiting the effective reuse of such material. Thus, chemical and structural stability are fundamental requirements to be fulfilled, especially when the slag comes in contact with water. The slag microstructure has a non-negligible influence on metals concentration in leachate, even if the phases that react with water have not yet been clearly identified. In this study, different classes of carbon steel EAF slag were investigated in order to correlate their leaching behaviour with microstructural and crystallographic features. Fine particles were chosen to enhance the dissolution rate of the phases involved in the leaching process and to quantify the effects of the fine fraction on leachate concentration with respect to the bulk material. Qualitative tests at different liquid-to-solid (L/S) ratios were also performed to detect dissolution of the phases, which would otherwise be non-appreciable in standard conditions. The analyses also allowed for the identification of the phases responsible for toxic metal leaching (Ba, Cr, V), as well as those that were not involved in dissolution phenomena, thereby consolidating the results proposed elsewhere on slag stabilization.

Chemical Dissolution Pathways of MoS2 Nanosheets in Biological and Environmental Media.

Material stability and dissolution in aqueous media are key issues to address in the development of a new nanomaterial intended for technological application. Dissolution phenomena affect biological and environmental persistence; fate, transport, and biokinetics; device and product stability; and toxicity pathways and mechanisms. This article shows that MoS2 nanosheets are thermodynamically and kinetically unstable to O2-oxidation under ambient conditions in a variety of aqueous media. The oxidation is accompanied by nanosheet degradation and release of soluble molybdenum and sulfur species, and generates protons that can colloidally destabilize the remaining sheets. The oxidation kinetics are pH-dependent, and a kinetic law is developed for use in biokinetic and environmental fate modeling. MoS2 nanosheets fabricated by chemical exfoliation with n-butyl-lithium are a mixture of 1T (primary) and 2H (secondary) phases and oxidize rapidly with a typical half-life of 1-30 days. Ultrasonically exfoliated sheets are in pure 2H phase, and oxidize much more slowly. Cytotoxicity experiments on MoS2 nanosheets and molybdate ion controls reveal the relative roles of the nanosheet and soluble fractions in the biological response. These results indicate that MoS2 nanosheets will not show long-term persistence in living systems and oxic natural waters, with important implications for biomedical applications and environmental risk.

Behavior of yttria-stabilized zirconia in the presence of molten salts: Part 1 - Dissolution and recrystallization phenomena

Yttria‐stabilized zirconia is supposed to be a promising candidate as anti‐corrosion coating on steel tubes in waste‐to‐energy (WTE) plants. Since the formation of low‐melting eutectic salt melts on the surface of those tubes is a common process within WTE plants, the performance of yttria‐stabilized zirconia under these conditions was evaluated. Beads of 5wt.‐% Y2O3 stabilized zirconia were embedded in an equimolar mixture of KCl-K2SO4-ZnCl2-ZnSO4. In a temperature range between 600 and 700°C under an atmosphere of N2—2.55vol.‐% HCl—0.45vol.‐% O2, a dissolution and recrystallization of the zirconia was observed. The driving force of this process is a changing electromotive force in combination with an increasing basicity of the melt, controlled by reactions between melt and atmosphere. With respect to an application as anti‐corrosion coating, the recrystallization process can enable the material to act as a self‐healing coating.

Micro-continuum Approach for Pore-Scale Simulation of Subsurface Processes

The enormous growth in computational capabilities of recent years has made Navier–Stokes-based simulation of flow and transport in natural porous media possible. Because of the complex multiscale nature of porous media, however, full Navier–Stokes representation of the physics everywhere in the domain is not always feasible. Here, we employ, a filtering—or micro-continuum—approach to model the smallest length scales. The Darcy–Brinkman–Stokes (DBS) equation offers an appealing framework for this hybrid modeling. A general modeling framework based on the DBS equation is proposed. The approach is then used to bridge the gap between scales for several challenging problems, including flow in fractured media, pore-scale simulation with immersed boundary conditions, modeling of dissolution phenomena, and thermal evolution of oil shale.

What Happens to LiMnPO4 upon Chemical Delithiation?

Olivine MnPO4 is the delithiated phase of the lithium-ion-battery cathode (positive electrode) material LiMnPO4, which is formed at the end of charge. This phase is metastable under ambient conditions and can only be produced by delithiation of LiMnPO4. We have revealed the manganese dissolution phenomenon during chemical delithiation of LiMnPO4, which causes amorphization of olivine MnPO4. The properties of crystalline MnPO4 obtained from carbon-coated LiMnPO4 and of the amorphous product resulting from delithiation of pure LiMnPO4 were studied and compared. The phosphorus-rich amorphous phases in the latter are considered to be MnHP2O7 and MnH2P2O7 from NMR, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy analysis. The thermal stability of MnPO4 is significantly higher under high vacuum than at ambient condition, which is shown to be related to surface water removal.

Investigating the Role of Transition Metal Deposition on Solid Electrolyte Interphase Formation and Growth Using Redox Shuttles

Transition metal based electrodes are attractive positive electrode materials for lithium ion-batteries due to their high energy densities and large capacities. However, these positive electrode materials are prone to dissolution of the transition metal structure into the electrolyte. The subsequent result of the dissolution is accelerated capacity and power fade. Investigation into the dissolution phenomena shows that after dissolution, the transition metals transport to the negative electrode. It is there where the metals ions deposit on the negative electrode surface, catalyzing solid electrolyte interphase (SEI) growth and blocking active sites for intercalation (1-3). In spite of these studies, much remains unclear about variations in the morphology and electronic passivity of the SEI due to transition metal deposition on the negative electrode surface. In this work, we investigate changes in the morphology and electronic passivity of the SEI using redox shuttles. We introduce manganese, nickel, and cobalt-based transition metal salts over a range of concentrations to the primary electrolyte. SEIs are formed on glassy-carbon electrodes by applying potentiostatic holds and cyclic voltammetry (CV). After formation, the SEI is probed using the ferrocenium-ferrocene redox shuttle. A mathematical model of the electrode-electrolyte interface is used to quantify the thickness and porosities of formed SEIs. Figure 1(a) shows the effectiveness of the redox shuttle in characterizing the magnitude of passivation on the working electrode surface. The working electrode is glassy carbon and primary electrolyte is (1:1 wt%) ethylene carbonate : diethyl carbonate with 1 M LiPF6 salt. CVs were measured at ν = 10 mV s-1 around the equilibrium redox potential, ~ 3.24 VLi/Li +. Increasing passivation time reduces redox peak currents, suggesting that surface passivation limits redox kinetics. Figure 1(b) shows experimentally obtained and simulated CVs, demonstrating that the system can be effectively modeled with an SEI.

A numerical study of isotropic and anisotropic ablation in MCCI by MPS method

Anisotropic and isotropic ablation in molten corium-concrete interaction (MCCI) phenomenon was studied with the Moving Particle Semi-implicit (MPS) method by carrying out numerical simulations of CCI-2 and 3 experiments. The interaction of the fully oxidized PWR core melts with specially-designed two-dimensional limestone and siliceous concrete test sections was analyzed, focusing on investigating the two-dimensional ablation behavior with both limestone and siliceous concrete. The phase transition of molten corium and concrete was modeled based on a phase transition model for mixture. Slag film model and crust dissolution models were incorporated in the current MPS code to simulate the effect of gas generation and crust dissolution phenomena in limestone concrete. The effects of gas generation and aggregates on the concrete ablation behavior were investigated by simulating different specially designed cases. The simulation results by MPS method reproduced the isotropic and anisotropic cavity ablation profile and the overall axial and lateral ablation rates agreed well with the experimental measures. The experimental and MPS results both indicate that the crust on the corium-concrete interface can play an important part in concrete ablation process. The simulation results by MPS method also provide evidence to support the theory that aggregates are part of the cause of anisotropic ablation profile in cavity with siliceous concrete because aggregates could delay the axial basemat ablation more significantly than the lateral one and influence the power split in the melt pool.

Investigations on the microstructures of sea urchin spines via selective dissolution

The sea urchin spines are composed of three-dimensionally bicontinuous porous magnesium-containing calcium carbonate embedded with a small amount of organic matrix. In this work, the selective dissolution process of transverse cross sections of sea urchin spines in aqueous solutions of Cu(NO3)2 was investigated to unravel their microstructures for the first time. A lot of concentric rings composed of microneedle arrays appeared on the transverse cross sections of sea urchin spines when they were kept in an aqueous solution of Cu(NO3)2 for a certain amount of time. Randomly arrayed microneedles instead of concentric rings were obtained on the annealed cross sections of sea urchin spines after a similar dissolution process. The unique phenomenon of selective dissolution might reveal a slightly heterogeneous distribution of occluded components such as the amorphous phase, Mg ions and biomolecules in the Mg-containing calcite mesocrystals of sea urchin spines, while the slight difference for the low amount of occluded components is hardly distinguished by using traditional elemental characterization techniques. These concentric rings were supposed to indicate the mineralization frontier of sea urchin spines.

Liquisolid Technology: A Review

Liquisolid system is a novel concept of drug delivery via oral route. Solubility is the phenomenon of dissolution of solid in liquid phase and is one of the important parameter to achieve desired concentration of drug in systemic circulation for pharmacological response. Poorly water soluble compound's oral administration often require high doses in order to reach therapeutic plasma concentrations because insufficient dissolution rate of the drug is the limiting factor in the oral bioavailability and one of the most challenging aspects of drug development. Design of this technique was according to new mathematical model proposed by Spireas et al. The drug is dissolved or dispersed in suitable non-volatile solvent and this liquid medication is converted to free flow powder by using carrier and coating material. To this suitable excipients were added and tabletting by direct compression. In this case, even though the drug is in a solid dosage form, it is held within the powder substrate in solution or, in a solubilized, almost molecularly dispersed state, which contributes to the enhanced drug dissolution properties. Large scale production of fabricated drug on commercial level. Succesful liquisolid tablet is a determination of optimal flowable liquid retention.

Investigating the Stratigraphy and the Gender of Nano-Fossils in the Lower Part of the Abtalkh Formation in Kopet Dagh Zone

A structural-sediment zone of Kopet Dagh is one of the geological units. The southern Kopet Dagh zone is limited to Binalood and the northern limit is with the Turan plateau fault and is created as sediment (Trough) in the late Triassic. The main fault zones are divided into two groups of foundation faults and overthrust. Kopet Dagh is a giant gas field between Turkmenistan, Iran and Afghanistan. Most areas of the region have a temperate climate so cold. From the middle Cambrian to the present, five phases of orogeny have occurred in the region. The geographic location of the study area is 37°43'03"N latitude and 55°35'47"E. In terms of stratigraphic formations in the Cretaceous period, Kopet Dagh area, respectively, is from old to new, including: Shurijeh, Zard, Tiregan, Sar Cheshmeh, Sanganeh, Aitamir, Abderaz, Abtalkh, Neyzar and Kalat. Abtalkh formation is one of the most important rock units in the late Cretaceous in the Kopet Dagh Basin. Abtalkh formation is 489 m and its stratigraphic units are 80 meters of dark grayshale, 20 km dark grayshale with calcareous layers with Inoseramus, 50 m gray marl tend to bluish with Siliceous limestone interlayers, 19 meters of gray-blueshale, 320 meters of light gray shale withthinlayer limestone interlayers. To take pictures of the samples, 100× objective lens and digital camera were used. In the course of this study, the lower part of Abtalkh formation was in Itamir cutting of the study and 9 genera were identified. Recognized calcareous Nannofossil had diversity and abundance. In general, in the greater thickness of the study, samples have moderate preservation. In some cases, the impact of dissolution phenomenon was so great that the main part of the species were corroded. Paying attention to the range of the rise and fall of index species and fossil assemblages, 4 biozones were identified for cutting according to the zones (CC18-CC21) of Sysyngzoning, 1977.

Kinetics of Alkaline Leaching of UO2 and FeS2 in Co-existing System

The dissolution of uranium dioxide under oxidative alkaline conditions is critically influenced by iron pyrite (FeS2), which is a gangue mineral commonly found in uranium ores. This paper makes an effort in understanding the kinetics of dissolution of UO2 in a co-existing system of UO2 and FeS2 under the lixiviant combination of Na2CO3 and NaHCO3–O2 at elevated temperature and pressure. Dissolution experiments were carried out in a laboratory batch autoclave reactor using synthetic mixtures of minerals consisting of UO2, FeS2 (reactive gangue—varied from 1 to 6 %), silica (inert gangue) and calcite (inert gangue). The kinetic profiles indicated that the rate of dissolution of UO2 increased with initial increase in FeS2 content in the feed and decreased when the FeS2 weight increased beyond 3 %. The dissolution phenomenon was analysed using scanning electron microscopy and X-ray diffraction studies.

P70] Diffusion study on Mg-based alloys: an experimental and modeling approach

Magnesium alloys are receiving global attention in transportation sectors thanks to their superior light weight capacity which allows the design of fuel efficient vehicles with lower CO2 emissions. To develop commercial Mg alloys and optimize their manufacturing processes, fundamental knowledge in thermodynamics and diffusion kinetics is indispensable. In these thermally activated processes, diffusion can play a key role in the optimization of process parameters. A good knowledge of diffusion is thus imperative to understand the relationships between the microstructure and the high temperature process parameters. In the present study, diffusion kinetics of Mg alloys was investigated by both experiments and simulations.Pure magnesium has an hcp crystal structure (c/a ratio = 1.6236) and as a result, self-diffusion of Mg shows anisotropic behavior. Anisotropic diffusion is also observed for various alloying elements such as Ag, Cd, In, Sb, and Sn in hcp Mg. Apart from Ag, the diffusion of solute elements and Mg itself along the a-axis of Mg is faster than along the c-axis. However, the anisotropic behavior of the most common alloying elements like Al and Zn has not been investigated so far. Moreover, no data are available for rare earth elements (REE) despite the fact that their importance is increasing in Mg alloys.In the present study, the anisotropic impurity diffusion coefficients of Al, Zn, Gd, and Y were found to follow the same trend as Mg-self diffusion. The diffusion coefficients along the a-axis is maximum and is about 1.3 times faster than along the c-axis in the conventional material processing temperature. In addition, the effect of the basal plane orientation of Mg on Al and Zn diffusion was investigated and it was found that the diffusion coefficients of Al and Zn in hcp Mg decrease linearly with an increase of the tilting angle of the basal plane. Interdiffusion coefficients and growth constants of all binary intermetallics in Mg-Al, -Zn, -Gd, and –Y systems were also obtained from diffusion couple experiments.The grain boundary diffusion of Al at high angle grain boundaries in polycrystalline Mg was also investigated with diffusion couple experiments. To obtain Al concentration profiles at the grain boundary, high resolution cold field emission-secondary electron microscope (CFE-SEM) energy dispersive spectroscopy (EDS) was used. Al diffusion at grain boundaries close to 75° misorientation is about two orders of magnitude higher than the one through for the bulk.In the present study, a multiphase diffusion couple simulation model was developed which can successfully explain the experimental results. A homogenization and dissolution model was also developed to explain the solution treatment process of Mg-Al and Mg-Zn alloys. The model was validated with the help of annealing experiments for the binary Mg-Al (3, 6 and 9 wt. % Al) and Mg-Zn (1.5, 4.0 and 5.5 wt. % Zn) alloys. The model was then extended to the ternary Mg-Al-Zn system to predict the homogenization and dissolution phenomenon for the AZ…

Surface Analysis of Ti/Sb-SnO2/PbO2 Electrode after Long Time Electrolysis

Abstract The surface morphology is significant on the stability of electrode. In this study, the surface morphology of a target electrode, Ti/Sb-SnO2/PbO2, was analyzed after long time electrolysis under constant current density conditions in Na2SO4 solution. SEM, EDS, XRD and ICP-OES were used to characterize the change of its surface morphology and the metal content in the electrolyte solution. The SEM images show that the dissolution and detachment phenomenon occur on the surface of Ti/Sb-SnO2/PbO2 electrode after long time electrolysis. Pb element is detected in the electrolytes after electrolysis, which uncovers the dissolution of PbO2. The XRD patterns indicate that the surface layer is still PbO2 but the intensity of diffraction peaks is decreased. It is speculated that the mechanisms of the Ti/Sb-SnO2/PbO2 electrode deactivation are the oxide layer dissolution, detachment and the substrate passivation.

A study of the electrochemical dissolution and passivation phenomenon of roasted gold ore in cyanide solutions

This study investigates the electrochemical interactions between gold and its associated oxide minerals either in one (OC) or two separate containers (TC) in the presence or absence of slurry. Magnetite showed negative effect on gold leaching, while maghemite and hematite demonstrated positive effect, relatively. The presence of slurry generally resulted in lower current densities. However, when the tailings of slurry was used again as a new feed in two separate containers (TC), the dissolution rate of gold was increased by 3 times (30 to 90μAcm−2), suggesting that the removal of detrimental ions in the first stage. Moreover, the current density of gold was enhanced up to 10 times by magnetic pre-treatment of roasted gold ore. It was found that in cyanide solutions saturated with atmospheric oxygen, cathodic Tafel slope only (8.60×10−7±4.56%molm−2s−1) provides close corrosion rates of gold to that in practical cyanidation (10.57×10−7±1.33%molm−2s−1), suggesting that cathodic polarization is the rate controlling one. Furthermore, a new electrode consisted of equal quantities of magnetite and hematite in one electrode was developed to examine the influence of these two major iron oxides on gold leaching, concurrently 0.04M NaCN at 100rpm agitation was found to be optimal. SEM analysis indicated the presence of Fe-oxide and Au–C compound products that could be responsible for partial passivation of gold surface.

Dissolution of Germanium in Sulfuric Acid Based Solutions

Introduction The usage of germanium has recently been considered for the MOSFET channel in order to improve the performance of the integrated semiconductor devices. Since Ge is oxidized easily and dissolves in to the wet solution, much attention is required for wet cleaning process with minimal dissolution of Ge. The present study covers the mechanism of Ge dissolution in sulfuric acid based solution in view of different application as the selective NiPt-etch during germanidation and the IIPR strip from Ge. Experiments 80nm Ge layers were epitaxially grown on 300mm Si wafers. These wafers were cut into coupons for following tests to determine the Ge loss in sulfuric acid based solutions. All tests were performed in a beaker at 30 degrees C and the amount of each solution was 50ml. (1) Dissolution phenomenon Coupons were immersed in the sulfuric acid based solutions, 30 to 98 wt% sulfuric acid with and without 5g/L of an oxidizer. The oxidizer used in the study is peroxosulfuric acid generated by Electrolyzing Sulfuric Acid, and is referred hereinafter to ESA. The dissolution of the Ge in the sulfuric acid solution was assessed by ICP-MS (Inductively Coupled Plasma-Mass Spectrometry), and it allowed us to calculate the dissolved volume and dissolution rate. (2) Dissolution mechanism In order to study the dissolution mechanism in the sulfuric acid based solutions, the surface of the coupon was examined with XPS (X-ray Photoelectron Spectroscopy) before and after immersion to 30wt% sulfuric acid solution and 2wt% hydrogen peroxide solution. The solutions were subjected to ICP-MS after immersion and the results were compared with the XPS data. Results and discussion (1) Dissolution phenomenon Figure 1 shows the dissolution rate of Ge after immersing the different coupons in the sulfuric acid based solutions, 30 to 98 wt% sulfuric acid with and without 5g/L of an oxidizer. When no oxidizer is added, the Ge dissolution rate is less than 1nm/min regardless of sulfuric acid concentration. However, it can be observed that Ge dissolved in an inverse proportion to the sulfuric acid concentration when the oxidizer is existed in the solution. (2) Dissolution mechanism Results of XPS analysis conducted on the original surface before immersion as shown in Figure 2. Peaks for Ge, GeO and GeO2 are apparent. When the coupons were immersed in the sulfuric acid, the XPS determinate that no GeO2 is present and only Ge and GeO are remained. When immersed in the hydrogen peroxide solution, both Ge and GeO peaks are detected but GeO peak is much weaker than that with sulfuric acid. No GeO2 is present in either condition. Additionally, a significant increase in dissolution is observed when the Ge coupon was immersed in hydrogen peroxide solution. These results indicate that GeO2dissolves readily in all solutions tested, and that GeO does not serve as a strong passive film during dissolution, and that active dissolution of Ge requires both water and oxidizer. Proposed dissolution reaction is: GeO2 + H2O → HGeO3 -+ H+ GeO + 2H2O → HGeO3 -+ 3H+ + 2e- Ge + H2O → GeO + 2H++ 2e- Considering the peaks of the original surface and the effect of UPW and sulfuric acid above mentioned, the foremost surface is GeO2as shown in Figure 3. Conclusion Conclusions drawn from the present study are as follows; 1) Dissolution of Ge is inversely proportional to sulfuric acid concentration only when an oxidizer is present in its solution. 2) The surface of Ge consists of three layers, i.e. GeO2, GeO and and Ge with the foremost layer being GeO2. 3) Only GeO2 dissolves in solutions without oxidizer, but Ge readily dissolves only when it is present in the solution. The ultimate goal of the present study is to enable either the selective etch of the both NiPt-etch during germanidation or strip IIPR from Ge without germanide or Ge dissolution. When Ge is treated with sulfuric acid including an oxidizer, as shown Figure 1, the higher sulfuric acid concentration is, the less Ge dissolution rate is. This result indicates that it is important to keep sulfuric acid concentration as high as possible when sulfuric acid with oxidizer is applied for Ge wet cleaning process. SPM is difficult to apply for Ge wet cleaning process because it is a mixture of sulfuric acid and 30wt.% hydrogen peroxide in order to generate oxidizer. Since the water from 30wt.% hydrogen peroxide results the sulfuric acid concentration of SPM lower, SPM dissolves Ge easily. Figure 1

Investigation of Stability Reduction in PtCoMn Ternary Alloy Catalyst for PEFCs

Pt/C and PtCo/C electrocatalysts are well known as highly active cathode catalysts for PEFCs [1]. In the previous work, in order to exceed activity of the existing catalysts, we investigated oxygen reduction reaction (ORR) activity of PtCoX (X = Mn, Ni, Fe, Cr, Ti, Cu, Zn, Mo, V, Sn, In, Pd, Ir, Ru, Au) / high surface area carbon (HSAC, Surface area of carbon = ca. 800 m2/g) ternary alloy catalyst [2]. PtCoMn / HSAC showed the highest ORR activity in all of the catalysts evaluated. The ORR activity of PtCoMn / HSAC was two times higher than that of Pt / HSAC measured in MEA. Therefore, we focused on the development of PtCoMn / HSAC catalyst. In this study, we evaluated the stability of PtCoMn / HSAC in MEA by voltage cycling test (650 mV-1050 mV). In addition, the MEA were investigated by SEM / EDX and EPMA line analysis. To evaluate the stability of PtCoMn / HSAC, we utilized the voltage cycling test. Fig. 1 shows mass activities and electrochemical surface area (ECSA) of Pt, PtCo and PtCoMn catalysts before and after the voltage cycling test. As a result of this test, ORR activity and ECSA of PtCoMn catalyst decreased gradually in each test. It was found that the stability of PtCoMn / HSAC was not comparable to existing Pt and PtCo catalysts. To understand the mechanism of reducing ORR activity of PtCoMn / HSAC, we investigated MEA which was used in voltage cycling test by SEM / EDX. For comparison, MEA before testing was investigated in the same way. Fig. 2 shows SEM image of cross -section of the MEA which was used in the test. A lot of particles were found at the interface of the membrane and the cathode catalyst. On the other hand, there were no particles in the fresh MEA. To investigate the particles which are composed of any elements, we utilized EDX mapping analysis. Fig. 3 shows SEM / EDX mapping analysis of cross -section of the MEA which was used in the test. As a result of analysis the particles, Pt element was detected. On the other hand, Co and Mn elements were not found in the particle. It became clear that the particles are composed of Pt. These results suggest that Pt in the PtCoMn catalyst dissolved and turn to be Pt ions, and then they were re-deposited as Pt metal particles at the interface of the membrane and the cathode catalyst during the voltage cycling test. To understand the Pt dissolution phenomenon of PtCoMn / HSAC, we utilized cross-section of MEA by EPMA line analysis. Fig. 4 shows EPMA line analysis of cross -section of the MEA which was used to the test. As a result of analysis, Co and Mn elements were detected in the Nafion membrane. On the other hand, these transition metal elements did not observed in the fresh MEA. The intensity of Pt, Co and Mn elements decreased gradually in the interface of the membrane and PtCoMn cathode catalyst, and the intensity of Pt element increased significantly at the interface of the membrane and the cathode catalyst with the generation of particles. These results suggest that not only Pt but also Co and Mn in the PtCoMn catalyst dissolved during the voltage cycling test. And these results indicate that Pt, Co and Mn in the cathode catalyst dissolved from the near of the interface between the membrane and PtCoMn cathode catalyst. From the above results, it is considered that the stability of PtCoMn / HSAC would be improved by suppressing the dissolution of the metal in the PtCoMn / HSAC. [1] K. Matsutani, K. Hayakawa, T. Tada, Precious Metal Review, 54(4), 223-232 (2010). [2] M. Ishida, K. Matsutani, ECS Trans., 64(3), 107-112 (2014). Figure 1

Surface characteristics, corrosion and bioactivity of chemically treated biomedical grade NiTi alloy.

The surface of NiTi alloy was chemically modified using acidified ferric chloride solution and the characteristics of the alloy surface were studied from the view point of application as a bioimplant. Chemically treated NiTi was also subjected to post treatments by annealing at 400°C and passivation in nitric acid. The surface of NiTi alloy after chemical treatment developed a nanogrid structure with a combination of one dimensional channel and two dimensional network-like patterns. From SEM studies, it was found that the undulations formed after chemical treatment remained unaffected after annealing, while after passivation process the undulated surface was filled with oxides of titanium. XPS analysis revealed that the surface of passivated sample was enriched with oxides of titanium, predominantly TiO2. The influence of post treatment on the corrosion resistance of chemically treated NiTi alloy was monitored using Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy (EIS) in Phosphate Buffered Saline (PBS) solution. In the chemically treated condition, NiTi alloy exhibited poor corrosion resistance due to the instability of the surface. On the other hand, the breakdown potential (0.8V) obtained was highest for the passivated samples compared to other surface treated samples. During anodic polarization, chemically treated samples displayed dissolution phenomenon which was predominantly activation controlled. But after annealing and passivation processes, the behavior of anodic polarization was typical of a diffusion controlled process which confirmed the enhanced passivity of the post treated surfaces. The total resistance, including the porous and barrier layer, was in the range of mega ohms for passivated surfaces, which could be attributed to the decrease in surface nickel content and formation of compact titanium oxide. The passivated sample displayed good bioactivity in terms of hydroxyapatite growth, noticed after 14days immersion in Hanks' solution.

Hydrogeochemical controls on mobilization of arsenic in groundwater of a part of Brahmaputra river floodplain, India

Abstract Study region Arsenic enriched groundwater regime within low-industrialized Brahmaputra floodplains in Assam, NE India. Study focus We examined the origin, distribution and processes of As release by investigating the salient groundwater chemistry and subsurface sedimentological characteristics. Besides collection of groundwater samples from domestic and public water supply wells, sediment samples from boreholes were investigated for textural and colour linkages. New hydrological insights for the region Arsenic concentrations above the WHO guideline value of 10 μg/L were present in 33 wells and above the previous Indian national drinking standard of 50 μg/L were present in 15 wells. The green-olive colour sediments were more likely to yield As-enriched groundwater. The supersaturation of groundwater with respect to Fe(II) minerals, such as siderite and vivianite, explained the poor correlation between dissolved As and Fe. The result reinforced the phenomenon of reductive dissolution of Fe(III) oxyhydroxides releasing As to groundwater. This study throws light on the processes and mechanisms involved with As release in groundwater. The homogenous floodplain terrain makes the hydrological As imprint unambiguous and the hydrogeological signatures untarnished. Considering the absence of anthropogenic sources in the study area, the conclusions on the nature and causes for As release to groundwater looked dependable although the final contamination at specific subsurface sites would be influenced by advection–dispersion of groundwater flow accompanied by retardation, ion exchange, surface complexation and possible biodegradation.

In vitro dissolution methodology, mini-Gastrointestinal Simulator (mGIS), predicts better in vivo dissolution of a weak base drug, dasatinib

USP apparatus I and II are gold standard methodologies for determining the in vitro dissolution profiles of test drugs. However, it is difficult to use in vitro dissolution results to predict in vivo dissolution, particularly the pH-dependent solubility of weak acid and base drugs, because the USP apparatus contains one vessel with a fixed pH for the test drug, limiting insight into in vivo drug dissolution of weak acid and weak base drugs. This discrepancy underscores the need to develop new in vitro dissolution methodology that better predicts in vivo response to assure the therapeutic efficacy and safety of oral drug products. Thus, the development of the in vivo predictive dissolution (IPD) methodology is necessitated. The major goals of in vitro dissolution are to ensure the performance of oral drug products and the support of drug formulation design, including bioequivalence (BE).Orally administered anticancer drugs, such as dasatinib and erlotinib (tyrosine kinase inhibitors), are used to treat various types of cancer. These drugs are weak bases that exhibit pH-dependent and high solubility in the acidic stomach and low solubility in the small intestine (>pH 6.0). Therefore, these drugs supersaturate and/or precipitate when they move from the stomach to the small intestine. Also of importance, gastric acidity for cancer patients may be altered with aging (reduction of gastric fluid secretion) and/or co-administration of acid-reducing agents. These may result in changes to the dissolution profiles of weak base and the reduction of drug absorption and efficacy. In vitro dissolution methodologies that assess the impact of these physiological changes in the GI condition are expected to better predict in vivo dissolution of oral medications for patients and, hence, better assess efficacy, toxicity and safety concerns. The objective of this present study is to determine the initial conditions for a mini-Gastrointestinal Simulator (mGIS) to assess in vivo dissolution of BCS class IIb drugs, dasatinib as a model drug, including the different gastric condition.The maximum dissolution of dasatinib with USP dissolution apparatus II was less than 1% in pH 6.5 SIF, while the one with mGIS (pH 1.2 SGF/pH 6.5 SIF) reached almost 100%. The supersaturation and precipitation of dasatinib were observed in the in vitro dissolution studies with mGIS but not with USP apparatus II. Additionally, dasatinib dissolution with mGIS was reduced to less than 10% when the gastric pH was elevated, suggesting the co-administration of acid reducing agents will decrease the oral bioavailability of dasatinib.Accurate prediction of in vivo drug dissolution would be beneficial for assuring product safety and efficacy for patients. To this end, we have created a new in vitro dissolution system, mGIS, to predict the in vivo dissolution phenomena of a weak base drug, dasatinib. The experimental results when combined with in silico simulation suggest that the mGIS predicted the in vivo dissolution well due to the elevation of gastric pH. Thus, mGIS might be suitable to predict in vivo dissolution of weak basic drugs. This mGIS methodology is expected to significantly advance the prediction of in vivo drug dissolution. It is also expected to assist in optimizing product development and drug formulation design in support of Quality by Design (QbD) initiatives.

Chemical prosperity of various chemical gypsums from viewpoint of particle morphology

Dissolution rate of various chemical gypsums in the water was investigated by using batch experiment. The rate of the dissolution of the gypsum had good agreement for explanation of dissolution of plate particle. The rate constants of the experimental formula were different with particle morphology of the gypsums. When morphology of the particle was sheet-liked, the dissolution rate was 10 timed large than it of block-shaped particle. From result of observation of dissolution phenomena of the in the water, it was find that dissolution of the gypsum was preceded on long axis. From these results, particle morphology is seems to be important parameter for using chemical gypsums.