NaClO4 Solutions Research Articles

Spectrophotometric study of the uranyl monobenzoate complex at moderate ionic strength

The protonation of benzoate and the complexation of uranyl monobenzoate in NaClO4 solutions ranging from 0.1 to 0.5 M were quantitatively investigated by means of ultraviolet–visible (UV–Vis) spectrophotometry. The spectrophotometric study revealed that the uranyl monobenzoate species has a significantly enhanced absorption than that of free uranyl, especially in the UV region. The non-linear regression analysis of the UV–Vis absorption data was the first to calculate the protonation constant of benzoate and the stability constant of uranyl monobenzoate at moderate ionic strength. Based on the SIT (specific ion interaction theory), the protonation constants were extrapolated to the zero ionic strength as logβP° = 4.21 ± 0.01, and the ion interaction coefficient of the benzoate anion with the sodium cation was determined as ε(Ben-,Na+) = 0.17 ± 0.05 kg·mol−1. In the same manner, the stability constant of uranyl monobenzoate at zero ionic strength and the ion interaction coefficient of the uranyl monobenzoate cation with perchlorate anion were determined to be logβU° = 2.91 ± 0.01 and ε(UO2Ben+,ClO4-) = 0.22 ± 0.07 kg·mol−1, respectively.

Facile One-Step Electrodeposition Fabrication of Amorphous MoS2 Catalysts in Titanium for Hydrogen Evolution Reaction

Hydrogen is seen as a future energy carrier that will assist the global energy fuel demand. However, it is still necessary to study efficient and inexpensive catalysts that can be used on a large scale to make this technology practical. In this paper the electrodeposition of molybdenum disulfide (MoS2) film on titanium (Ti) substrate was performed by cyclic voltammetry and the film was evaluated for hydrogen evolution reaction (HER). The deposition optimized conditions was 25 cycles and 4 mmol L-1 (NH4)2[MoS4] in 0.1 mol L-1 NaClO4 solution. The film was characterized from X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and they showed an amorphous structure and high catalytic activity for HER. The Tafel slope was 85 mV dec-1 and overpotential at -10 mA cm-2 was -139 mV showing that Ti substrate compared with fluorine-tin doped oxide (FTO) substrate favored the HER and electroactivity of MoS2 films.

Stratification period, imbibition time in solutions of GA3, H2O and NaClO in the germination of yellow araçá tree

Para iniciar a insercao de uma nova cultura, como e o caso do aracazeiro, e necessario tecnicas eficientes para producao de mudas de qualidade. O objetivo deste estudo foi avaliar periodo de estratificacao, bem como a aplicacao do tipo de solucao composta por GA 3 ou NaClO com o tempo de imersao, na influencia da germinacao de sementes de aracazeiro amarelo. Foi realizado experimento em DIC no arranjo multifatorial triplo [periodo de estratificacao x tipo de solucao x tempo de imersao na solucao]. Cinco periodos de estratificacao (0, 5, 10, 15, 20 dias), cinco tipos de solucao de imersao (nenhuma, H 2 O, NaClO 5%, GA 3 100 mg L -1 , GA 3 300 mg L -1 ) e tres tempos de imersao em solucao (seis, 12 e 24 horas) com quatro repeticoes de 100 sementes. Avaliou-se a germinacao, o indice de velocidade de germinacao (IVG) e o tempo medio de germinacao (TMG). O GA 3 mostrou-se promotor eficiente para rapida germinacao de sementes de aracazeiro. A estratificacao so e recomendada para sementes de aracazeiro amarelo se nao associados ao uso do GA 3 . Os periodos de estratificacao podem ter o vigor das sementes afetados se aumentar os tempos de embebicao nas solucoes.

Nghiên cứu nhân giống in vitro cây sâm bố chính (Hibiscus sagittifolius Kurz) thông qua nuôi cấy từ hạt và đốt thân

Hibiscus sagittifolius is not only a beautiful flower, but also species having high medicinal value. This study is aimed to complete the process of in vitro propagation of H.sagittifolius from seeds and nodes. The results show that the percentage of uninfected and survived samples was 71.99% when the seeds and nodes were sterilized with 15% NaClO solution for 15 min. The seed germination rate was improved when seed was pre-treated by immersion in 20 mg/L GA3 for 120 min before being sterilized. The MS medium supplemented with 2.0 mg/L BA, 30.0 g/L sucrose, 100.0 mL/L coconut water, pH 5.8 was suitable for multiplication of in vitro shoots. After 45 days of culture, the number of shoots obtained was 6.6 shoots per sample and the shoots’ average height was 3.28 cm. Afterwards, the in vitro shoots were inoculated on MS medium supplemented with 1 mg/L NAA for rooting. After 45 days of culture, the number of roots per shoot was 33.6 with an average length of 13 cm.

Preparation of poly(2,4,6‐triaminopyrimidine‐TMC)/P84 composite nanofiltration membrane with enhanced chlorine resistance and solvent resistance

AbstractBACKGROUNDNanofiltration membrane has attracted great study interest because of its high permselectivity and low operating cost. However, most commercial nanofiltration membranes are still not applicable for chemical separation processes due to their low resistance to organic solvent and chlorination.RESULTS2,4,6‐triaminopyrimidine (TAPI) was employed as an aqueous phase monomer to prepare poly (2,4,6‐triaminopyrimidine‐TMC) composite nanofiltration membrane with interfacial polymerization. Polyimide (P84) ultrafiltration (UF) membrane was crosslinked with TAPI and used as the supporting membrane. The composite membrane showed high rejection (91.4%) of Na2SO4 and a high flux (7.3 L m−2 h−1) at 0.3 MPa and ambient temperature. The membrane also showed high stability during 120 h immersion in N,N‐dimethylacetamide (DMAc) and acetone. The performance of membrane immersed in 200 ppm NaClO solution did not decline over 96 h.CONCLUSIONTAPI with reactive amino group can be used as aqueous phase monomer to prepare poly (2,4,6‐triaminopyrimidine‐TMC) composite nanofiltration membrane with high permselectivity. The pyrimidine ring of TAPI endows the functional layer with excellent chlorine resistance while the crosslinking of P84 membrane with TAPI significantly improves the solvent resistance. © 2018 Society of Chemical Industry

A Pitzer Model for Lead Oxide Solubilities in the Presence of Borate to High Ionic Strength

In this study, a hydrolysis model for lead, applicable to high ionic strength, is developed based on lead oxide solubilities as a function of ionic strength. Solubility measurements on lead oxide, α-PbO (tetragonal, red), mineral name litharge, as a function of ionic strength were conducted in NaClO4 solutions up to I = 0.45 mol·kg−1, in NaCl solutions up to I = 5.0 mol·kg−1, and in Na2SO4 solutions up to I = 5.4 mol·kg−1, at room temperature (22.5 ± 0.5 °C). The lead hydroxyl species considered in this work include the following, 1 $$ {\text{PbO}}\left( {\text{cr}} \right) \, + {\text{ 2H}}^{ + } \rightleftharpoons {\text{Pb}}^{ 2+ } + {\text{ H}}_{ 2} {\text{O}}\left( {\text{l}} \right) $$ 2 $$ {\text{Pb}}^{ 2+ } + {\text{ H}}_{ 2} {\text{O}}\left( {\text{l}} \right) \rightleftharpoons {\text{PbOH}}^{ + } + {\text{ H}}^{ + } $$ 3 $$ {\text{Pb}}^{ 2+ } + {\text{ 2H}}_{ 2} {\text{O}}\left( {\text{l}} \right) \rightleftharpoons {\text{Pb}}\left( {\text{OH}} \right)_{ 2} \left( {\text{aq}} \right) \, + {\text{ 2H}}^{ + } $$ 4 $$ {\text{Pb}}^{ 2+ } + {\text{ 3H}}_{ 2} {\text{O}}\left( {\text{l}} \right) \rightleftharpoons {\text{Pb(OH}})_{3}^{ - } + 3{\text{H}}^{ + } $$ The equilibrium constants for Reactions (1) and (2) were taken from literature. The equilibrium constants in base 10 logarithmic units for Reactions (3) and (4) are determined in this study as − 17.05 ± 0.10 (2σ) and − 27.99 ± 0.15 (2σ), respectively, with a set of Pitzer parameters describing the interactions with Na+, Cl−, and $$ {\text{SO}}_{4}^{2 - } .$$ In combination with the parameters from literature including those that have already been published by our group, the solution chemistry of lead in a number of media including NaCl, MgCl2, NaHCO3, Na2CO3, Na2SO4, NaClO4, and their mixtures, can be accurately described in a wide range of ionic strengths.

Preparation of Polybenzimidazole Hollow-Fiber Membranes for Reverse Osmosis and Nanofiltration by Changing the Spinning Air Gap.

High-performance polybenzimidazole (PBI) hollow-fiber membranes (HFMs) were fabricated through a continuous dry-jet wet spinning process at SRI International. By adjusting the spinning air gap from 4″ (10.2 cm) to 0.5″ (1.3 cm), the HFM pore sizes were enlarged dramatically without any significant change of the fiber dimensional size and barrier layer thickness. When fabricated with an air gap of 2.5″ (6.4 cm) and a surface modified by NaClO solution, the PBI HFM performance was comparable to that of a commercial reverse osmosis (RO) HFM product from Toyobo in terms of salt (NaCl) rejection and water permeability. The PBI RO HFM was positively surface charged in acidic conditions (pH < 7), which enhanced salt rejection via the Donnan effect. With an air gap of 1.5″ (3.8 cm), the PBI HFM rejected MgSO4 and Na2SO4 above 95%, a result that compares favorably with that achieved by nanofiltration. In addition, the PBI HFM has a defect-free structure with an ultra-thin barrier layer and porous sublayer. We believe PBI HFMs are ideal for water purification and can be readily commercialized.

Impact of the electrolyte salt anion on the solid electrolyte interphase formation in sodium ion batteries

Aiming at a more comprehensive understanding of the solid electrolyte interphase (SEI) in sodium ion batteries (NIBs), a detailed X-ray photoelectron spectroscopy (XPS) investigation of the few-nanometer thick passivation film formed on hard carbon (HC) in contact with various Na+-ion conducting electrolytes is reported. The electrolytes investigated include 1 M solutions of NaPF6, NaClO4, NaTFSI, NaFSI, and NaFTFSI, all dissolved in a common mixture of ethylene carbonate (EC) and diethylene carbonate (DEC) (EC/DEC = 1/1 wt. ratio). For comparison, the study of analogous Li-based electrolytes containing LiPF6 and LiFSI as representative electrolyte salts is also reported. The anion and cation of the electrolyte salt appear to play a key role in determining the overall SEI layer composition, including its depth evolution and thickness. The SEI building species formed on hard carbon by solvent reduction upon sodiation are found to decrease with the various salts in the order: NaPF6 > NaClO4 ≈ NaTFSI > NaFTFSI > NaFSI. The comparison of lithiated and sodiated HC electrodes shows that the SEI layer is more homogeneous and richer in organic species upon the use of Na-based electrolytes. Surface and depth-profiling XPS analysis on HC electrodes charged in the various electrolyte formulations provides in-depth insights on the differences and similarities of the SEI (composition, thickness, depth evolution, etc.) evolving from the variation in the chemical structure of the cations and anions of the respective salts.

A preliminary study of oxidant stimulation for enhancing coal seam permeability: Effects of sodium hypochlorite oxidation on subbituminous and bituminous Australian coals

Chemical oxidation is proposed as an effective means to react and dissolve small regions of coal in the near wellbore region, thereby raising permeability for gas flow. In this study, we investigated the effect of sodium hypochlorite (NaClO) treatment on the structure of bituminous coal (Coal B) and subbituminous coal (Coal S) separately from the Bowen and Surat basins in Queensland, Australia.Swelling and leaching tests showed that both coals swelled, dissolved and broke in 5%wt. aqueous solutions of NaClO. Coal S reacted more vigorously in 5% NaClO, with 49% mass loss and 3840 mg/L of dissolved organic carbon (DOC) measured in the oxidant filtrate, than Coal B. The Coal B mass loss in 5% NaClO was 4.5% with 430 mg/L DOC measured in the filtrate. After NaClO treatment the total accessible pore volume of Coal S particles increased from 4.6% to 6.1%, and the porosity of Coal B increased from 8.6% to 8.9%. Pore size distributions determined from mercury intrusion porosimetry (MIP) indicated that oxidation enlarged the pores in Coal S more significantly than Coal B. Scanning electron microscopy (SEM) confirmed oxygen generated large pores on the surface of Coal S particles, but there were no significant changes on Coal B.We used a microfluidic cleat flow cell (CFC) to inject NaClO into artificial channels scribed in polished samples of Coal S and Coal B, and measured an increase in the widths of the channels after NaClO treatment. The increase in channel width observed in the CFC indicated that coal solubilisation was a more dominant mechanism than coal swelling. Similarly, the channel aperture of Coal S increased more than Coal B. CFC results also showed that NaClO etched dull coal bands (inertinite-rich) more significantly than bright coal bands (vitrinite-rich), and we proposed this result was due to the greater porosity in semi-fusinite, which allowed greater penetration of NaClO in dull coal bands than in bright coal bands. The low coal rank sample (Coal S) with higher liptinite content and more oxygen content was more susceptible to oxidisation by NaClO than Coal B.

Selective Separation and Recovery of Pt(IV) from Pd(II) through an Imidazolium-ionic-liquid-based Supported Liquid Membrane.

A supported liquid membrane (SLM) system for the selective separation of platinum(IV) from palladium(II) has been developed. The SLM was prepared using imidazolium-based IL 1-octy-3-methylimidazolium bis(trifluoromethanesulfonyl)imide. The initial flux and separation factor of Pt(IV) from Pd(II) were found to significantly depend on the composition of the receiving solution. Based on the performance, a 0.1 mol dm-3 NaClO4 solution was selected as a suitable receiving solution. Membrane transport experiments showed that 93% of Pt(IV) can be selectively transported into the receiving solution, whereas most Pd(II) remains in the feed solution.

Novel Oxidized and UV‐Irradiated Araucaria angustifolia Pine Seed Starch for Enhanced Functional Properties

Starch is an important raw material for industrial processes. Therefore, an investigation of new sources of starch and starch modification methods is necessary. The dual oxidation effect on the properties of the native pine seed starch is investigated. Native starch is extracted from pine seeds and its proximate composition determined. The starch is then subjected to a dual oxidation process in standard NaClO or H2O2 solutions (0.2; 0.5; 0.8 mol L−1) and simultaneous exposure to ultraviolet light irradiation (UVC λ = 254 nm). Thermogravimetric (TG‐DTA) curves reveal enhanced stability to thermal degradation of the dual NaClO/UV process modified starch up to 20%. Differential scanning calorimetry (DSC) shows a strong decrease in gelatinization enthalpy due to the action of the UV‐rays coupled with the sodium hypochlorite (NaClO) solution. The H2O2/UV modified starch has a high final viscosity while the NaClO/UV starch pastes have a low tendency to recrystallize. Furthermore, structural analysis using an X‐ray diffractometer and scanning electron microscopy (SEM) show crystallinity patterns of type A starch and that the shape of the starch granules are unaltered following the modification processes. Color parameters show a strong increase in the L* value (for whiteness) for the NaClO/UV treated samples. The modified starches demonstrate improved physicochemical properties which are suitable for several industrial applications including as stabilizers for frozen bakery products, whitening agents for paper products, and tableting agents for cosmetic and pharmaceuticals products.

Symmetric electrochemical supercapacitor performance evaluation of N-doped graphene prepared via supercritical fluid processing

Here, the fast and shorter duration synthesis route was proposed for the production of N-doped graphene by supercritical fluid method involving ammonium oxalate as a source of nitrogen. Within the different proportions of graphene oxide and nitrogen source, the nitrogen-doped graphene formed from ammonium oxalate having nitrogen content of 3.3 wt% showed an enriched specific capacitance of 274 Fg−1 at 1 A/g in 20% KOH electrolyte. The long-term stability results obtained from galvanostatic charge-discharge in ammonium oxalate-based N-doped graphene revealed that 90% specific capacitance retention was achieved up to 10,000 cycles at 10 A/g. To examine the device proficiency, a full cell was fabricated and the performance was evaluated in two different approaches. Among the different media in aqueous electrolytes, the fabricated symmetric supercapacitor has achieved a maximum specific capacitance value of 160 F/g at 1 A/g in alkaline medium (20% KOH solution). Between 20% KOH solution and 1 M NaClO4 solution in acetonitrile, the fabricated symmetric supercapacitor exhibits an energy density of 26.5 Wh/kg as well as 5.5 Wh/kg in 1 M sodium perchlorate in acetonitrile solution and 20% KOH solution, respectively.

Improved permselectivity of forward osmosis membranes for efficient concentration of pretreated rice straw and bioethanol production

The hydrothermal pretreatment of rice straw generates a liquid fraction that contains low concentrations of sugars, as well as fermentation inhibitors which are not favourable for efficient bioethanol production. For the development of a forward osmosis (FO) process to concentrate sugars and remove fermentation inhibitors, we fabricated polyamide-polysulfone (PA-PSf) membranes treated with NaClO solution. The NaClO treatment improved the water permeability (A value) and the permselectivity of fermentation inhibitors against sugars. Maximum separation of xylose from furfural and acetic acid was achieved when the treated membranes had A values of 5.5–7 L m−2 h−1 bar−1. Using an optimized membrane with A value of approximately 6 L m−2 h−1 bar−1, a liquid fraction from hydrothermally pretreated rice straw was concentrated in a one-step FO process to increase sugar concentrations and decrease fermentation inhibitor concentrations. The ethanol concentration and yield (ethanol/total sugar) by xylose-utilizing Saccharomyces cerevisiae reached 18.0 g/L and 0.40, respectively, which were much higher than those obtained with commercial FO membranes. These results clearly indicate the possibility of introducing a simple and low-cost FO process into bioethanol production from lignocellulosic biomass by incorporating NaClO treatment to FO membrane.

Layered LiNi0.80Co0.15Al0.05O2 as cathode material for hybrid Li+/Na+ batteries

LiNi0.80Co0.15Al0.05O2 (NCA) is explored to be applied in a hybrid Li+/Na+ battery for the first time. The cell is constructed with NCA as the positive electrode, sodium metal as the negative electrode, and 1 M NaClO4 solution as the electrolyte. It is found that during electrochemical cycling both Na+ and Li+ ions are reversibly intercalated into/de-intercalated from NCA crystal lattice. The detailed electrochemical process is systematically investigated by inductively coupled plasma-optical emission spectrometry, ex situ X-ray diffraction, scanning electron microscopy, cyclic voltammetry, galvanostatic cycling, and electrochemical impedance spectroscopy. The NCA cathode can deliver initially a high capacity up to 174 mAh g−1 and 95% coulombic efficiency under 0.1 C (1 C = 120 mA g−1) current rate between 1.5–4.1 V. It also shows excellent rate capability that reaches 92 mAh g−1 at 10 C. Furthermore, this hybrid battery displays superior long-term cycle life with a capacity retention of 81% after 300 cycles in the voltage range from 2.0 to 4.0 V, offering a promising application in energy storage.

Proton-Rocking-Chair-Type Redox Capacitors Based on Indium Tin Oxide Electrodes with Multilayer Films Containing Ru Complexes.

A rechargeable proton-rocking-chair-type redox capacitor was fabricated using scalable layer-by-layer-(LbL)-assembled films composed of two dinuclear Ru complexes that exhibit proton-coupled electron-transfer (PCET) reactions with different Ru(II/III) redox potentials (RuNH-OH and RuCH-OH). RuNH-OH and RuCH-OH contain different coordination environments that involve two phosphonate linker ligands at both ends and bridging 2,6,2',6'-tetrakis(benzimidazol-2-yl)-4,4'-bipyridine or 1,3,1',3'-tetrakis(benzimidazol-2-yl)-5,5'-biphenyl ligands, respectively. The molecular units were assembled onto indium tin oxide (ITO) electrodes by complexation between the phosphonate groups and zirconium(IV) ions. The LbL growing process of these multilayer films was monitored by electrochemical or UV-vis spectroscopic measurements. The thus obtained LbL films on the ITO electrodes showed PCET reactions at different potentials, depending on the bridging ligands. The introduction of cyclometalated Ru-C bonds in the bridging ligand of RuCH-OH led to the stabilization of the ruthenium(III) oxidation state, and therefore, RuCH-OH exhibited lower p Ka values for the imino N-H protons in the bridging benzimidazole groups compared to those of the corresponding RuNH-OH complex. The proton movements that accompany the redox reaction in the Ru multilayer films on the ITO electrode were confirmed using a pH indicator probe. For the performance test of a proton-rocking-chair-type redox capacitor, a two-electrode system composed of RuNH-OH and RuCH-OH multilayer films on ITO electrodes was examined in an aqueous solution of NaClO4. Under galvanostatic conditions, stable, reversible, and repeatable charging/discharging processes occurred. The capacitance increased with an increasing number of LbL layers. For comparison, a similar redox capacitor composed of two RuNMe-OH and RuCMe-OH analogues, in which all four imino N-H protons on the benzimidazole moieties are protected by N-Me groups, was constructed and examined. In these complexes, the capacitance decreased by 77% compared to the PCET-type capacitor composed of a cell containing RuNH-OH and RuCH-OH; this result strongly suggests that the proton movement plays a more important role for the charge storage than the anion movement. In such LbL films composed of Ru complexes that exhibit PCET-type redox reactions, the capacitance is drastically improved with an increasing number of layers and using protons as charge carriers.

Quantitative analysis of the polarization behavior of iron in an aerated acidic solution using SECM

The apparent corrosion current of pure iron in aerated 5 mM HClO4 + 0.1 M NaClO4 solution was separated into Fe oxidation, proton reduction and oxygen reduction currents using SECM in a modified tip generation/substrate collection (TG/SC) mode. The oxidation current density of Fe was 1.11 × 10−3 A/cm2, equal to the sum of proton reduction and oxygen reduction current density, around 5.26 × 10−4 and 5.84 × 10−4 A/cm2, respectively, implying that oxygen reduction and proton reduction are equally important at open circuit potential (OCP). Moreover, oxygen reduction was suppressed on the Fe electrode in the potential range between −0.7 and −1.1 V vs Ag/AgCl because of the inhibitory effect of the proton reduction reaction and a potential-dependent surface effect, then the suppression is weakened and oxygen reduction is enhanced. Finally, the Fe corrosion current was dominated by oxygen reduction and Fe oxidation at potentials more positive than −0.6 V.

Photodegradation of Natural Wood Veneer and Studies on Its Color Stabilization for Automotive Interior Materials

The aim of this study was to investigate the color and chemical changes of natural wood veneers after ultraviolet (UV) exposure for automotive interior materials. To control the photodegradation, chemical treatments with hydrogen peroxide (H2O2) and sodium hypochlorite (NaClO) solution were applied to the veneer under different concentration conditions. The veneers treated with H2O2 showed strong color changes on the surface after the UV test. On the other hand, the veneers treated with NaClO solution (2–3% concentration) showed excellent color stability compared to the untreated veneer because NaClO partially removed lignin compounds on the veneer surface. NaClO can improve the color stability by destroying the lignin structures. However, 3% NaClO condition was seen to cause surface damage although this treatment condition had the best effect on photoprotection. Therefore, treatment with 2% NaClO was the best condition in this study for against color change and photodegradation caused by UV light.

Cycling Performance of Sodium Ion Battery Comprised of Naphthalene Based Polyimide/MWCNT Composite Cathode and Highly Porous Polyvinylidene Fluoride Separator Membrane

Naphthalene based polyimide (PI)/multi-walled carbon nanotube (MWCNT) composite was prepared from naphthalene tetracarboxylic dianhydride and ethylene diamine with MWCNT by a two-step reaction. Chemical structure of PI/MWCNT composite was confirmed with Fourier Transform Infrared (FTIR) spectroscopy and studied its electrochemical behavior as a cathode active material for sodium ion battery (NIB). The presence of MWCNT help to increase the ease of electron transfer between the low conducting PI chains. PI/MWCNT composite cathode was prepared and fabricated NIB in combination with a highly porous polyvinylidene fluoride (PVdF) membrane separator containing 1 M NaClO4 solution in ethylene carbonate (EC)/propylene carbonate (PC)/dimethyl ether (DME) in 1:1:1 volume ratio. The combination of highly porous membrane with PI/MWCNT cathode exhibit good electrochemistry with high and stable cycle performance.

CuAg nanoparticles formed in situ on electrochemically pre‐anodized screen‐printed carbon electrodes for the detection of nitrate and nitrite anions

CuAg nanoparticles (CuAgNPs) were electrochemically formed in situ on pre‐anodized, screen‐printed carbon electrodes (SPCEs) that possessed many oxygen‐containing functional groups capable of adsorbing metal ions, namely Cu2+ and Ag+. Pre‐anodization was achieved using continuous cyclic voltammetry in the range of potential 0.3–2.0 V under a scan rate of 50 mV/s. Cu2+ and Ag+ ions were adsorbed on the pre‐anodized SPCE by immersing the electrode in solutions containing both metal ions, and then CuAgNPs were formed in situ via electrochemical reduction in a deaerated, neat NaClO4 solution after the electrode was ultrasonicated to remove physically adsorbed metal ions. Although CuNPs showed higher activity than AgNPs toward both nitrate (NO3−) and nitrite (NO2−) ions, the instability of CuNPs hindered the application, so CuAgNPs were employed to achieve a compromise between sensitivity and stability. The SPCE/anodized/CuAgNP electrodes showed activity toward the electrochemical reduction of NO3− and NO2−, respectively, with the limit of detection (LOD) of 15.6 μM (0.97 ppm) and 11.1 μM (0.51 ppm), which is sufficient to fit the allowed values (50 and 3 ppm, respectively) in drinking water as suggested by the World Health Organization (WHO).

자외선 노출에 의한 Walnut 베니어의 광 변색 방지 연구

The purpose of this study was to evaluate the effect of several chemical treatments to prevent photodegradation of wood veneer by external UV (Ultraviolet) light. Of woods, walnut veneer is selected as a raw material for this study since it is known as a luxurious wood with dark color giving an esthetic effect. Alcohol-benzene, hydrogen peroxide (H2O2) and sodium hypochlorite (NaClO) solution were used for investigate the effect on color stabilization. Despite the removal of the extractive compounds, which is known as a discoloration component, a significant color change of walnut wood veneer was observed. Meanwhile, the veneers treated by 20 and 30% H2O2 solution at 75°C for 1 h also showed the no positive effect of color stability exposed to UV light although they have a bleaching effect on wood veneer. Besides, it was difficult to maintain the original color of walnut veneer due to the elution of the extractive compounds. On the other hands, the veneer treated by NaClO solution indicated the good performance on color stability despite of the intensive UV light test. However, when the concentration exceeds 3%, surface roughness and fiber damage occurred simultaneously. Therefore, the walnut species should be treated with proper concentration when sodium hypochlorite is applied to the veneer.