Low Acid Medium Research Articles

Mechanism and kinetics study of vanadium leaching from landfilled metallurgical residues by ultrasonic with ozonation enhancement in a low-acid medium

Landfilled metallurgical residues are valuable raw materials for the recovery of strategic vanadium resources. However, efficient separation of vanadium from these residues is challenging due to its strong oxidation resistance and coating within silicate inclusions. To address this issue, this study proposes an enhanced leaching process utilizing the synergistic effect of O3-catalyzed ultrasonic field in a low concentration sulfuric acid system. Results show that following a 10-minute O3 and ultrasonic treatment, the direct leaching rate of vanadium experienced a remarkable 46.7 % increase. Quenching experiments revealed a hierarchical order of active species within the reaction process:⋅OH >⋅O2−> H+, with⋅OH oxidation exhibiting the most pronounced capacity for disrupting the inclusion structure. Electron Paramagnetic Resonance analysis indicated that the highest⋅OH yield arose from the combined application of ultrasound and ozone. Kinetic investigations demonstrated that the vanadium leaching process is governed by interfacial chemical reactions. The activation energy of vanadium oxidation leaching under ultrasonic-O3 conditions was determined to be 40.41 kJ/mol, representing a 20.19 % reduction compared to ultrasonic conditions alone. Through the integration of analysis, characterization, and comparative evaluations, it was discerned that the synergistic impact of ultrasonic and ozone treatments significantly enhances the breakdown of silicate inclusions by low-concentration HF, particularly in the conversion of SiOSi bonds into SiOH bonds and SiF bonds. In summary, the refined leaching methodology incorporating ozone catalysis in conjunction with ultrasonic treatment provides a new idea for the separation and extraction of refractory residual vanadium.

Enhanced photoreduction efficiency of Cr(VI) driven by visible light in a new Zr-based metal-organic framework modified by hydroxyl groups.

While metal-organic framework (MOF) photocatalysts have demonstrated a unique Cr(VI) photoreduction capability in recent decades, their performance is still insufficient for practical applications because of their low Cr(VI) uptake and poor visible light response. To cope with these drawbacks, a new OH-modified Zr-based MOF, termed HCMUE-1, was successfully prepared via a solvothermal method in this work. The complete characterization of HCMUE-1 was performed through various techniques, including powder X-ray diffraction (PXRD), Raman spectroscopy, Fourier transform infrared (FT-IR), thermogravimetric analysis and differential scanning calorimetry (TGA-DSC), scanning electron microscopy combined with energy-dispersive X-ray (SEM-EDX), and X-ray photoelectron spectroscopy (XPS). The obtained data exhibited the excellent Cr(VI) photoreduction efficiency of HCMUE-1, reaching up to 98% after 90 min and almost 100% after 120 min under visible light illumination in a low acidic medium. Noteworthily, HCMUE-1 retained the same Cr(VI) removal rate for at least seven cycles without considerable loss. Further experimental investigations demonstrated that the structural stability and surface morphology of HCMUE-1 were retained after photoreduction. Moreover, the photocatalytic reduction mechanism of Cr(VI) to Cr(III) was interpreted through a series of systematic experimental measurements. These results indicate that HCMUE-1 possesses potential as an efficient photocatalyst for reducing toxic Cr(VI) species from wastewater in real-life conditions.

Highly selective separation of palladium from spent catalysts by ozonation with ultrasonic enhancement in a low-acid medium

It is of great significance to consider the recovery of palladium from spent catalyst in terms of resource reserve and environmental protection. However, the leaching percentage of palladium is limited by high oxidation potential and cladding layer. In order to solve this process problem, externalfield enhancementmethod with ultrasonic-assisted ozone is proposed for the recycling of palladium in this study. Mechanical and cavitation effects of ultrasonic can destroy cladding layer and promote solid–liquid interface reaction. The highly oxidizing free radicals generated by ultrasonic excitation of ozone can improve the oxidation of the reaction system and accelerate the oxidation rate of palladium. The leaching percentage of palladium is 93.7% under ultrasonic/ozone condition, which is 23.7% higher than that under conventional conditions. The leaching reaction kinetics shows that the reaction barrier is reduced and the apparent activation energy is reduced by 35.25 kJ/mol after introducing ultrasound and ozone. Additionally, mineralogical analysis is carried out to analyze the enhanced leaching mechanism of palladium. This work demonstrates the value of advanced oxidation process with ultrasonic-assisted ozone in efficient and green recovery of precious metals from secondary resources.

A combined DFT, Monte Carlo, and MD simulations of adsorption study of heavy metals on the carbon graphite (111) surface

This work investigated the adsorption mechanism of heavy metals: silver (Ag), mercury (Hg), cadmium (Cd), palladium (Pd), and zinc (Zn) on the carbon graphite (111) surface based on density functional theory (DFT), Metropolis Monte Carlo (MMC), and the molecular dynamics (MD) simulation methods. The obtained results from the adsorption of these species showed that the process is spontaneous and exothermic in nature. The maximum adsorption capacities were obtained in neutral to low acid medium, and the interaction between Hg-carbon graphite was more favored than other systems. These findings showed that carbon graphite was more efficient in the removal of the studied metals. Moreover, this study better explains the adsorption mechanism of heavy metals onto carbon graphite and gives a theoretical basis for the wider application of graphite adsorbent in the removal of heavy metals. This paper provides theoretical support for heavy metals removal in various mediums and also provides some new ideas for the secondary utilization of quantum chemical descriptors and molecular dynamics simulation methods.

One pot synthesis of chromium incorporated SBA-16 under acid medium-Application in the selective oxidation of benzyl alcohol derivatives

Cr-SBA-16 mesoporous silica heterogeneous catalysts (Si/Cr = 7, 14, and 28) were successfully synthesized by one-pot hydrothermal method at low acidic medium. The catalysts were characterized by means of X-ray diffraction (XRD), N 2 adsorption-desorption at 77 K, Fourier Transform Infrared (FTIR), X-ray photoelectron (XPS) and Diffuse Reflectance UV–Vis (DRS) Spectroscopies, Thermogravimetric analysis (TGA), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) techniques. Herein, Cr-SBA-16 catalysts are evaluated in the selective catalytic oxidation of benzyl alcohol derivatives using H 2 O 2 as oxidant. From XPS and UV–Vis (DRS) spectroscopies the molar ratios between Cr 6+ /Cr 3+ are found to increase versus chromium loading in the following order: Cr-SBA-16(28) < Cr-SBA-16(14) < Cr-SBA-16(7). Hence the highest Cr 6+ in tetrahedrally environment is observed for Si/Cr = 7. We demonstrated for the first time that the selective catalytic oxidation of benzyl alcohol (BzOH) using H 2 O 2 over Cr-SBA-16 occurs through noncompetitive adsorption mechanism and the reaction is pseudo-first order to BzOH. The activity of the reaction depends on the symmetry of chromium species, herein, high activity is observed for tetrahedral chromium species in Cr-SBA-16(7). The absence of any chromium ions in the filtrate shows no chromium leaching from the silica framework.

Fate of Neptunium in nuclear fuel cycle streams: state-of-the art on separation strategies

Abstract Neptunium, with a half life of 2.14 million years is one of the most notorious activation products in the nuclear fuel cycle. It has been more than 5 decades in the reprocessing of nuclear fuels by the well documented PUREX process, but the fate of Np in the PUREX cycle is still not well controlled. Although Np being stable in its pentavalent state in low acid media, its starts to undergo disproportionation at higher acidities. This disproportionation along with the oxidizing conditions of the HNO3 medium makes Np to exits as Np(IV), Np(V) and Np(VI) in the dissolver solution. The overall extractability of Np in the co-decontamination step of the PUREX cycle is dependent on its oxidation state in the medium as Np(VI) and Np(IV) being extractable while Np(V) being least extractable. The present review article discusses about the speciation of Np in HNO3 and its disproportionation. The variety of redox reagents are discussed for their effectiveness towards controlling Np redox behavior in the HNO3 media. The extraction of Np with the different class of extractant has also been discussed and the results are compared for better understanding. Solid phase extraction of Np using both commercially available resin and lab based synthesized resins were discussed. The anion exchange resins with the different cationic centers were shown to behave differently towards the uptake of Np form the acidic medium. The present review also highlight the chemical conditions required for controlling or minimizing the fate of Np in different process streams of the nuclear fuel cycle.

Microstructural and electrochemical properties of TiAlN(Ag,Cu) nanocomposite coatings for medical applications deposited by dc magnetron sputtering

AISI 420 stainless steel is currently used in the manufacture of surgical and dental instrumentation due to its hardenability, acceptable biocompatibility and suitable resistance to corrosion in low acid or basic medium. However, it is necessary to increase the wear and corrosion resistance of this type of steel when it is used in certain biomedical applications. Therefore, multiple surface modification strategies have been used in order to overcome these drawbacks in the properties of this material. In this work, TiAlN coatings doped with Ag and Cu nanoparticles in four different quantities (11 at.% to 20 at.%) were deposited onto 420 steel by DC magnetron sputtering technique. The microstructure, and chemical and phase composition, were analyzed by scanning and transmission electron microscopy (SEM/TEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction, while roughness was determined using atomic force microscopy (AFM). The electrochemical behavior of the coatings was evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. A reduction in the corrosion current density of the steel substrate was evident once it was superficially modified with the TiAlN matrix coating, which formed a protective barrier to the corrosive medium. The TiAlN(Ag,Cu) coatings developed superior electrochemical activity to the TiAlN matrix, and consequently exhibited higher corrosion current densities. This behavior was accentuated with increased Ag/Cu content in the coating, and it was correlated mainly with the increase in the dissolution rates of silver and copper to the surrounding medium. This suggests a potential bactericidal effect of this kind of coating, which might be considered for potential application in surgical and dental instrumentation.

Honeycomb structured activated carbon synthesized from Pinus roxburghii cone as effective bioadsorbent for toxic malachite green dye

Herein, we have demonstrated the designing of activated carbon from Pinus roxburghii cone (PRCAC) by facile carbonization method. The synthesized PRCAC was utilized for the removal of malachite green (MG), a basic dye from aqueous medium. The surface properties of PRCAC were elucidated by N2 adsorption- desorption and point zero charge studies. Quite attractive adsorption results were obtained by PRCAC due to it’s high surface area (202 m2/g). Influence of numerous elements; concentration of MG, pH, time, adsorbent dose and temperature were studied in detail. Low acidic medium found to be preferential for the adsorption process. The adsorption isotherm studies were also carried out and results showed that the data fitted well to Langmuir isotherm. Maximum adsorption capacity of PRCAC was found to be 250 mg/g. Different kinetic model were also studied for the undertaken adsorption reaction.

Solvent extraction of zinc from chloride solutions using dialkyl derivatives of 2,2′-bibenzimidazole as extractants

Four new 1,1′-dialkyl-2,2′-bibenzimidazoles were used to extract zinc(II) from acid chloride solutions at various concentrations of chloride and hydrogen ions. In low acidity media (pH > 2), the maximum zinc(II) extraction with the compounds is observed at chloride concentrations in the range 0.7–1.8 M. Zinc(II) ions are extracted as neutral (ZnCl2)mLn complexes (L = extractant) in which the m:n ratio varies from 1:2 to 3:3, depending on the metal-to-extractant molar ratio in the extraction media. In strongly acidic systems, anionic zinc(II) chloro-complexes may be extracted from aqueous solutions by protonated bibenzimidazoles as (LH+)2(ZnCl42−) or/and (LH+)(ZnCl3−) ion pairs. In weakly acidic media, at [Cl−] < 2 M, Zn(II) can be separated from Cd(II), Cu(II), and Ni(II) by 1,1′-didecyl-2,2′-bibenzimidazole, the best extractant from the tested dialkyl derivatives of 2,2′-bibenzimidazole. From the feed containing 26 g/L Zn(II), over 80% of zinc(II) ions is selectively separated after four extraction stages. 1,1′-Didecyl-2,2′-bibenzimidazole can be used for the selective separation of pure Fe(III) and Zn(II) from acidic chloride solutions. At a high chloride concentration (6 M) and at 0.5–0.8 M HCl in the aqueous feed, Fe(III) is efficiently transferred into the organic phase in the presence of Zn(II) and is then easily stripped off with water. Zn(II) can be completely removed from the iron-free raffinate after this aqueous solution is acidified to 1.5 M HCl.

A Gompertz Model Approach to Microbial Inactivation Kinetics by High-Pressure Processing Incorporating the Initial Counts, Microbial Quantification Limit, and Come-Up Time Effects

During come-up time (CUT), the time to reach a desired processing pressure, isobaric-isothermal conditions cannot be assumed in the estimation of kinetic parameters for the design of commercial high-pressure processing (HPP) treatments. Since CUT effects on microbial population, enzyme activity, and chemical concentration are often ignored, kinetic models incorporating the non-isobaric and non-isothermal conditions prevailing during CUT were the objective of this work. The analysis of peer-reviewed data on the HPP inactivation of bacteria (counts observations n = 919, 60 survival curves) and bacterial spores (n = 273, 12 curves) showed that a Gompertz model (GMPZ) approach is an effective alternative. The GMPZ parameter A was fixed as the difference between the initial population (log10No) and the lower quantification limit of microbial counts (log10Nlim), while exponential equations were used to describe pressure effects on the lag time (λ) and the maximum inactivation rate (μmax). In low-acid media (pH > 4.5), λ decreased exponentially with pressure, allowing the identification of a theoretical pressure level (Pλ) sufficient to initiate microbial inactivation during CUT. The parameter μmax exponentially increased with pressure for all evaluated datasets. Dynamic pressure effects during CUT were simplified by assuming isobaric conditions during CUT (tCUT), allowing to obtain GMPZ parameter estimates using only nonlinear regression (R2 ∼ 0.938, σ2 = 0.030–0.604). The proposed approach is a simpler, promising tool for a more informative analysis of the kinetics of microbial inactivation by HPP and should be further validated with additional experimental data.

Semi-empirical chemical model for indirect advanced oxidation of Acid Orange 7 using an unmodified carbon fabric cathode for H2O2 production in an electrochemical reactor

A commercial Unidirectional Carbon Fabric piece was used to design an electrode for the cathodic O2 reduction reaction in a divided (by a Nafion® 117 membrane) parallel plate reactor. The anode was a commercial stainless steel mesh. Under this approach it is feasible to produce H2O2 at low energy (2.08 kWh kg−1 H2O2) in low ionic acidic medium. In the catholyte side the H2O2 can be activated with Fe2+ to develop the Fenton reagent. It was found that Acid Orange 7 (AO7) indirect oxidation (in the concentration range of 0.12–0.24 mM) by Fenton chemistry follows a first order kinetic equation. The energy required for 0.24 mM AO7 degradation is 1.04 kWhm−3. From each experimental AO7 oxidation the main parameters (a, mM and k, min−1) of the first order kinetic equation are obtained. These parameters can be correlated with AO7 concentration in the concentration range studied. Based on this method a semi-empirical chemical model was developed to predict the AO7 abatement, by means of Fenton chemistry. Good AO7 oxidation predictions can be made in the concentration range studied. A detailed discussion of the energy required for oxidizing AO7 and the accuracy of the chemical model to predict its oxidation is included in this paper.

Solvation and electrochemical analyses of neodymium complexes in TFSA-based ionic liquids dissolving the nitrates synthesized from spent Nd–Fe–B magnets

In this study, rare earth (RE) nitrates, M(NO3)3·xH2O, were synthesized from Nd–Fe–B magnets in order to apply nitric acid as a low cost acid medium. The synthesized RE nitrates were identified by ICP-AES, XRD and TG-DTA. These results revealed that the RE nitrates were mainly composed of Nd(NO3)3·6H2O.In addition, the solubility of the RE nitrates in n-hexyl-trimethyl-ammonium bis(trifluoromethyl-sulfonyl)amide, [N1116][TFSA], ionic liquids (ILs) was investigated by UV–Vis–NIR and Raman spectra. According to the hypersensitive peak (4I9/2→2G7/2) of Nd3+, the solubility of the RE nitrates in [N1116][TFSA] was estimated to be 0.05moldm−3. The solvation of the neodymium complex in [N1116][TFSA] dissolved RE nitrates was also researched by UV–Vis–NIR spectra. The molar extinction coefficients and the peak wavenumbers of the neodymium complex in ILs differed from related complexes such as [Nd(TFSA)5]2−, [Nd(H2O)9]3+ and [Nd(NO3)5]2−. This result suggested that the solvated structure was [Nd(NO3)a(TFSA)5−a]2− and the bond strength between the central Nd3+ ion and the surrounding ligands was expressed in the following order: [NO3−]<[TFSA−]<H2O. However, the significant peak at 750cm−1 did not appeared in Raman spectrum of [Nd(NO3)a(TFSA)5−a]2− in [N1116][TFSA]. This result revealed that the [TFSA−] anion bound to the central Nd3+ ion in the complex: [Nd(NO3)a(TFSA)5−a]2− was unstable in [N1116][TFSA]. Therefore, the spectrochemical series would be applicable for limited conditions of [NO3−] in TFSA-based ILs.Furthermore, the electrochemical behavior of the [Nd(NO3)a(TFSA)5−a]2− complex in [N1116][TFSA] was investigated by cyclic voltammetry. A cathodic current peak for [Nd(NO3)a(TFSA)5−a]2−/Nd(0) was observed at −3.0V and this reduction potential was shifted to the more positive side compared to [Nd(TFSA)5]2−/Nd(0), so that the interaction between the central Nd3+ ion and the ligand of [Nd(NO3)a(TFSA)5−a]2− would be weaker than that of [Nd(TFSA)5]2−. The diffusion coefficient of [Nd(NO3)a(TFSA)5−a]2− in [N1116][TFSA] was calculated to be 3.5×10−13m2s−1, which is almost the same as that for [Nd(TFSA)5]2−. The series of results enabled us to demonstrate that direct dissolution from RE nitrates and the electrodeposition in a TFSA-based ILs system could be applied for the recovery process of Nd metal.

Validation of spectrophotometric method for Se(IV) determination: analytical applications

As selenium is an important part of the antioxidant enzymes and also because there are several studies suggesting a possible link between cancer and selenium deficiency, this paper presents a spectrophotometric method for the assay of Se(IV), using N,N-diethyl-p-phenylenediamine monohydrochloride as reagent. The proposed method is based on the reaction between the selenium and potassium iodide in low acidic medium, when iodine is released. This last product will further oxidise the new reagent. The final obtained product is strongly coloured in red and has an absorption maximum at 552 nm and molar extinction coefficient (ε) of 6.1 × 10(4) L mol(-1) cm(-1). The optimum working conditions were established, and the developed method was validated, being characterised by a good linearity (in the range of 0.5-3.0 μg/mL), a limit of detection (0.0573 μg/mL) and a limit of quantification (0.1737 μg/mL). At the same time, the repeatability, the precision of the method and the accuracy were established. The proposed and validated method was applied with good results for the determination of Se(IV) in spring and bottled water from Iasi and also in pharmaceutical and cosmetic products.

Loss of TSC2 confers resistance to ceramide and nutrient deprivation

Nutrient stress that produces quiescence and catabolism in normal cells is lethal to cancer cells, because oncogenic mutations constitutively drive anabolism. One driver of biosynthesis in cancer cells is the mammalian target of rapamycin complex 1 (mTORC1) signaling complex. Activating mTORC1 by deleting its negative regulator tuberous sclerosis complex 2 (TSC2) leads to hypersensitivity to glucose deprivation. We have previously shown that ceramide kills cells in part by triggering nutrient transporter loss and restricting access to extracellular amino acids and glucose, suggesting that TSC2-deficient cells would be hypersensitive to ceramide. However, murine embryonic fibroblasts (MEFs) lacking TSC2 were highly resistant to ceramide-induced death. Consistent with the observation that ceramide limits access to both amino acids and glucose, TSC2(-/-) MEFs also had a survival advantage when extracellular amino acids and glucose were both reduced. As TSC2(-/-) MEFs were resistant to nutrient stress despite sustained mTORC1 activity, we assessed whether mTORC1 signaling might be beneficial under these conditions. In low amino acid and glucose medium, and following ceramide-induced nutrient transporter loss, elevated mTORC1 activity significantly enhanced the adaptive upregulation of new transporter proteins for amino acids and glucose. Strikingly, the introduction of oncogenic Ras abrogated the survival advantage of TSC2(-/-) MEFs upon ceramide treatment most likely by increasing nutrient demand. These results suggest that, in the absence of oncogene-driven biosynthetic demand, mTORC1-dependent translation facilitates the adaptive cellular response to nutrient stress.

Aniline-1,4-benzoquinone as a model system for the characterization of products from aniline oligomerization in low acidic media

Increase in the pH medium of aniline polymerization is used for giving products of different morphologies, which are often wrongly attributed to PANI chains. Infrared and Raman spectroscopic data, supported by quantum chemical calculations, show that aniline-1,4-benzoquinone (AnBzq) is a model system for the characterization of the products of aniline oligomerization in low acidic media. The Raman spectra excited at different laser lines reveal the bichromophoric nature of AnBzq, whose absorption bands at 550nm and 440nm can be attributed to π–π∗ transitions of the delocalized benzoquinone and amino-phenyl moieties, respectively.

Brazilian research on extremophiles in the context of astrobiology

AbstractExtremophiles are organisms adapted to grow at extreme ranges of environmental variables, such as high or low temperatures, acid or alkaline medium, high salt concentration, high pressures and so forth. Most extremophiles are micro-organisms that belong to the Archaea and Bacteria domains, and are widely spread across the world, which include the polar regions, volcanoes, deserts, deep oceanic sediments, hydrothermal vents, hypersaline lakes, acid and alkaline water bodies, and other extreme environments considered hostile to human life. Despite the tropical climate, Brazil has a wide range of ecosystems which include some permanent or seasonally extreme environments. For example, the Cerrado is a biome with very low soil pH with high Al+3concentration, the mangroves in the Brazilian coast are anaerobic and saline, Pantanal has thousands of alkaline–saline lakes, the Caatinga arid and hot soils and the deep sea sediments in the Brazilian ocean shelf. These environments harbour extremophilic organisms that, coupled with the high natural biodiversity in Brazil, could be explored for different purposes. However, only a few projects in Brazil intended to study the extremophiles. In the frame of astrobiology, for example, these organisms could provide important models for defining the limits of life and hypothesize about life outside Earth. Brazilian microbiologists have, however, studied the extremophilic micro-organisms inhabiting non-Brazilian environments, such as the Antarctic continent. The experience and previous results obtained from the Brazilian Antarctic Program (PROANTAR) provide important results that are directly related to astrobiology. This article is a brief synopsis of the Brazilian experience in researching extremophiles, indicating the most important results related to astrobiology and some future perspectives in this area.

Separation of Europium from Cobalt Using Antimony Silicates in Sulfate Acidic Media

The ores of rare earth elements (REEs) are usually digested in concentrated sulfuric acid media, which dissolve the REEs as main product with heavy metals as byproduct. In the present work, inorganic ion exchangers based on silico-antimonates (SiSb) were synthesized and characterized. SiSb mixed with metal oxides were prepared in molar ratio 2:1 with different aging time. In batch experiments, radionuclides Eu-152 and Co-57 were taken to represent the lanthanides and heavy metals, respectively. The sorption behavior was examined and distribution coefficients were evaluated for different effective conditions such as sulfuric acid concentration, pH, shaking time, metal ion concentration, and aging time. The new inorganic SiSb materials are characterized by rapid kinetics for Eu(III) and high adsorption selectivity for Co(II). The results showed that the SiSb are acidic in character and that their cation-exchange properties are better in low acidic media. Sorption efficiency is highly correlated with the structural framework, which depends on exchangeable water content. Various chelating agents were tested for desorption of the retained Eu(III) and Co(II). Maximum separation factors were obtained with SiSb materials after 2 or 3 days aging, providing efficient exchangers for the separation of economically valuable REEs from heavy metals.

Comparative Study of Corrosion Behaviour of Nickel and Gold Plated Carbon Steels Used as Ornamentals in Saline Environment

This study investigated the corrosion resistance of plated and unplated steels useful as ornamentals in saline environment. Nickel plating of carbon steel was done in watts solution for 25minutes with a current density of 3 Adm -3 at 60 o C. The nickel plated carbon steel was later gold plated for 20 minutes with a current density of 0.2 Adm -3 at 50 o C. The plated and unplated carbon steels were immersed in saline environment for 360 hours. Weight loss was taken every 24 hours in order to evaluate corrosion penetration rate (CPR). The results obtained showed that plated carbon steel generally offers a better corrosion resistance than the unplated one. Corrosion of ornamentals is equally gaining importance especially coated ornamentals. The use of nickel for ornamentals is gaining more prominence over silver rising due to its shiny surface and its cost. The use of nickel plated ornamentals just as gold plated ornamentals are being patronized will surely become common place due to affordability for the generality of people. However, the effects of everyday corrosive fluids from kitchen salt and low acidic media on the durability of the coatings need to be established. Carbon steel is the natural substrate used in orna- mental coatings .The results also showed that a small thickness of gold plated carbon steel exhibited better corrosion resis- tance in saline environment. More also, gold plated carbon steel is found to be more suitable and reliable candidate material than nickel plated carbon steel in this environment although with higher costs.

Constructions of polyaniline nanofiber-based electrochemical sensor for specific detection of nitrite and sensitive monitoring of ascorbic acid scavenging nitrite

A novel polyaniline nanofiber (PANI-NF)-based electrochemical sensor was constructed for specific detection of nitrite and sensitive monitoring of ascorbic acid scavenging nitrite. The electrochemical behaviors of PANI-NF were studied by cyclic voltammetry and amperometry in the presence of nitrite. Results showed that nitrite reduction was enhanced by the nanostructure of PANI-NF film. Under low potential difference and acid medium, PANI-NF catalyzed the conversion of nitrite ion to nitric oxide, and then realized the reduction of nitrite ion. Under optimal experimental conditions, PANI-NF-based sensor demonstrated a fast response time of 5s and a detection limit of 0.05μM nitrite (signal-to-noise ratio, S/N=3), a linear range from 0.2μM to 35mM. This electrochemical sensor has been successfully applied to sensitively monitor ascorbic acid scavenging nitrite, and it has the potential of being used in nitrite detection.

Synthesis, characterization and catalytic activity of acid–base bifunctional materials through protection of amino groups

Acid–base bifunctional mesoporous material SO3H-SBA-15-NH2 was successfully synthesized under low acidic medium through protection of amino groups. X-ray diffraction (XRD), N2 adsorption–desorption, transmission electron micrographs (TEM), back titration, 13C magic-angle spinning (MAS) NMR and 29Si magic-angle spinning (MAS) NMR were employed to characterize the synthesized materials. The obtained bifunctional material was tested for aldol condensation reaction between acetone and 4-nitrobenzaldehyde. Compared with monofunctional catalysts of SO3H-SBA-15 and SBA-15-NH2, the bifunctional sample of SO3H-SBA-15-NH2 containing amine and sulfonic acid groups exhibited excellent acid–basic properties, which make it possess high activity for the aldol condensation.