Effect Of Various Anions Research Articles

Investigating Anion Effects on Metal Ion Binding Interactions With Amyloid β Peptide by Ion Mobility Mass Spectrometry.

The study of metal ion's role in the biological processes of Alzheimer's disease has spurred investigations into the coordination chemistry of amyloid beta peptide and its fragments. Nano-electrospray ionization mass spectrometry (nESI-MS) has been utilized to examine the stabilization of bound anions on multiprotein complexes without bulk solvent. However, the effects of anions on metal ion binding interactions with amyloid beta peptide have not been explored. This study directly examined metal-peptide complexes using nESI-MS and investigated the effects of various anions on the binding ratio and stability of these complexes from ammonium salt solutions. The results indicate that different anions have distinct effects on the binding ratio and stability of various metal-peptide complexes. Of these, the bicarbonate ion exhibits the highest binding ratios for metal-peptide complexes, while binding ratios for these complexes in phosphate are comparatively low. Our results suggest that acetate, formate, bicarbonate, and phosphate have weak affinities and act as weak stabilizers of the metal-peptide complex structure in the gas phase. Intriguingly, chloride and sulfate act as stabilizers of the metal-peptide complex in the gas phase. The rank order determined from these data is substantially different from the Hofmeister salt series in solution. Although this outcome was anticipated due to the reduced influence of anions and water solvation, our findings correlate well with expected anion binding in solution and emphasize the importance of both hydration layer and anion-metal-peptide binding effects for Hofmeister-type stabilization in solution. This approach proved useful in examining the interactions between metal ions and amyloid beta peptide, which are relevant to Alzheimer's disease, using direct ESI-MS.

UV light and [formula omitted] catalysed COD removal of AO 8 using NaOCl as oxidant

The present study aims to establish NaOCl as a potential oxidant in the COD removal of Acid Orange 8 using UVC light (λ = 254 nm) and Fe2+ as catalysts. The different systems used in this study are NaOCl, Fe2+/NaOCl, UV/NaOCl, and Fe2+/NaOCl/UV. All these process were found to be operative in acidic, neutral and basic medium. The initial decolorisation and COD removal efficiency (CODeff) for different systems follow the order: Fe2+/NaOCl/UV > UV/NaOCl >Fe2+/NaOCl > NaOCl. Nevertheless, NaOCl can alone be used in the treatment process considering its CODeff to the extent of 95% in 90 min. The change in pH of the solutions after treatment is an important observation – for non-UV systems it remained around 11.0 and 7.0 in other systems. Thus, UV systems are environmental benign. The effect of various anions on CODeff was tested in Fe2+ systems. Presence of F− ions were found to accelerate CODeff in both the systems. However, the effect is more pronounced in Fe2+/ NaOCl/UV, where complete CODeff was observed in the presence of 9.0 gl−1 of F−. The COD removal kinetics for all systems was studied using zero–order, first–order, second–order, and BMG kinetic models. BMG model was found to be more suitable among all and is in good agreement with CODeff of all systems. It is, therefore, established that NaOCl can serve as a powerful oxidant in the advanced oxidation process.

Corrosion and Protection of Synthetic Intermetallic Compounds and Bulk Aluminum Alloy Under Simulated Atmospheric Conditions

Aluminum alloy 7075-D6 is often used for aircraft parts and is thus exposed to atmospheric conditions. AA7075-D6 is susceptible to corrosion due to high Zn, Mg and Cu contents in the form of various intermetallic particles having more or less noble electrochemical potential regarding the matrix (1,2). Usually, corrosion of aluminum alloys is simulated using solutions of various concentrations of chloride ions. However, aircraft are exposed to atmospheric conditions, where Cl- is not the only pollutant. Namely, in industrial and urban areas, major inorganic species such as ammonium (NH4 +), sulfate (SO4 2−) and nitrate (NO3 −) ions are found in the form of NH4NO3 and (NH4)2SO4 (or NH4HSO4). Therefore, these should also be considered because they represent corrosive agents for many aluminum alloys (3). Corrosive conditions may be thus better simulated by the so-called dilute Harrisonʼs solution (DHS) (0.35 wt.% (NH4)2SO4 + 0.05 wt.% NaCl), which in addition to Cl− also contains SO4 2− and nitrate NO3 − reflecting the environmental and atmospheric conditions. The first part of our study was focused on the corrosion of AA7075-T6 in DHS and comparison with NaCl solution. In addition to AA7075-T6, major intermetallic compounds (IMCs) synthesized in bulk form to represent the major intermetallic constituents (Al2Cu, Al2CuMg, Al7Cu2Fe and MgZn2) were also investigated. For IMCs, electrochemical measurements were performed using a microcell, and a standard cell was used to study the bulk alloy.Bulk AA7075-T6 was less susceptible to corrosion in DHS than in chloride solution stemming from the beneficial presence of sulfate ions and lower chloride concentration. The susceptibility of IMCs to corrosion in DHS increased as Al2Cu < Al7Cu2Fe < Al2CuMg < MgZn2 due to the increased dissolution of Mg in the presence of ammonium ions. The relative nobility of IMCs was determined based on the galvanic current density.In the second part of our study, we addressed the role of cerium salts in the corrosion protection of AA7075-T6 in DHS. Cerium salts are non-toxic compounds and demonstrate corrosion inhibition by inhibiting redox reactions by forming a protective cerium-containing precipitated conversion layer (4). Ce salts acted as inhibitors for the alloy during 14-day testing, forming a Ce hydroxide layer. The degree of protection depended on the type of anion, being the highest for Ce acetate. For the IMC, however, inhibition by Ce salts did not occur during short measurements, indicating the importance of galvanic interaction with the alloy matrix in the inhibition, which was confirmed by long-term measurements of the alloy. Micro and macro approaches give essential information on the galvanic relation between the IMPs and Al matrix under different conditions in the presence and absence of different cerium salts or other inhibitions (5). This brought about valuable information concerning corrosion inhibition and synergism with other ions in the corrosion media. Figure. Schematic presentation of (a) effect of various anions (NH4 +, SO4 2 - and Cl-) in dilute Harrison’s solution, and (b) effect of cerium(III) cations and corresponding anions (Cl-, NO3 - and CH3COO-) on the surface of AA7075-T6. Corrosion inhibition due to the deposition of the cerium layer is presented in (c). The precipitation of Ce species proceeds mainly on the cathodic sites and progressively spreads over the alloy surface; meanwhile, the Mg and Al are slowly dissolved from the anodic sites.

Thermally activated persulfate oxidation of Basic Fuchsin dye: Effect of different operating parameters, kinetic, and thermodynamic study

AbstractThe present paper aims to investigate the efficiency of thermal activation persulfate in eliminating the organic dye “Basic Fuchsin” (BF). In addition, the study attempts to elucidate the effect of different operating parameters, such as persulfate dosage (0.44–4.4 mM), the initial solution pH of (3–10), and temperature (25–50°C), on the process. The effects of various anions and water matrices on BF discoloration were investigated. Thus, the findings revealed that 94.15% of BF can be eliminated using persulfate at a concentration of 4.4 mM and a temperature equal to 50°C. It occurs under the following operating conditions: oxidation time of 60 min, initial pH equal to 6, the pollutant concentration of 10 ppm, and stirring speed equal to 300 rpm. Furthermore, the kinetic study indicated that the degradation of the BF dye using PS followed a first‐order pattern with rate constants varying within a range of 15.3 × 10−3–43.2 × 10−3 min−1. Based on the Arrhenius equation, the activation energy of the studied process was determined to be 29 kJ mol−1, suggesting that a moderate activation energy is required for BF discoloration. The results of the thermodynamic study confirm that the oxidation process is non‐spontaneous and endothermic. Coexisting inorganic anions delayed BF discoloration to varying degrees, and the inhibitory action followed the following order: carbonate &gt; chloride &gt; sulfate &gt; nitrate. Organic pollutants oxidation by the thermal activation of the persulfate is a simple and effective method for the depollution of waste textile water.

Synergistic Effect of Silver-Based Ionic Liquid for Ethylene/Ethane Separation

Separation of ethylene (C2H4) and ethane (C2H6) is one of the most significant processes in the petrochemical industry. In terms of industrial application, silver nitrate aqueous solution is the most widely used absorbent, but the activity of Ag+ and the absorption of C2H4 are not optimistic. Thus, it is urgent to explore new technologies for efficient separation of C2H4 and C2H6. In this work, several silver-based ionic liquid (Ag-IL) solutions are prepared with ionic liquids (ILs), silver salts, and ethylene glycol (EG). Pure and mixed gas absorption experiments were conducted to explore the effects of various anions and cations of ILs, the molar ratio of IL to silver salt, the EG proportion on absorption performance, and recycling of absorbents. Due to the synergy between ILs, EG, and Ag+, the absorption of C2H4 in [Emim][BF4]/AgBF4/EG (2:1:0.1) is up to 101.75 mg/g (2.17 mol C2H4/mol Ag+), which is the highest value of IL absorbents reported so far, and the highest selectivity is 37.8. Furthermore, the cyclic stability kept constant after five cycles of absorption–desorption. The interaction mechanism of Ag-ILs was studied by NMR and FTIR spectroscopies. ILs and EG synergistically weaken the electrostatic effect between the anion and cation of AgBF4 and increase the amount of active silver to enhance the absorption of C2H4. These task-specific Ag-ILs are expected to be a new medium with commercial potential for C2H4/C2H6 separation.

Phosphine-based ionic liquids for CO2 chemical fixation: Improving stability and activity by asymmetric flexible steric hindrance

Among various strategies for CO2 chemical fixation, the CO2 cycloaddition with epoxides is one of the most promising and efficient approaches, in which ionic liquid (ILs) is a typical relatively environmentally friendly catalyst and medium. However, ILs decomposition and catalytic stability have not been in-depth investigated, and the structure-activity relationship of cations and anions has remained obscure, which would affect the understanding of catalytic behavior and catalyst loss, and limit the theoretical research and industrial application in CO2 utilization. Therefore, based on a variety of phosphonium ILs we have designed and synthesized for CO2 cycloaddition, the structure-activity relationship, steric hindrance and electronic effect of various anions and cations have been systematically studied in main and side reactions. Especially, a regulation strategy of cationic flexible steric hindrance and anionic electron effect have been developed to improve both ILs’ activity and stability. Remarkably, the synergistic action of electron-donating effect, hydrogen bond and decreased acidity from flexible steric alkyl groups result in the spatial shielding of cation center and enhancement of the Br's leaving. Consequently, the quaternary phosphonium ILs with asymmetric flexible steric hindrance exhibit the optimal performance, showing propylene oxide (PO) conversion of 99.15% and propylene carbonate (PC) yield of 98.86%, which can efficiently decrease the formation of phosphine oxide, avoiding the decomposition of ILs. This discovery provides a new idea for developing stable and efficient CO2 fixation system in sustainable industry.

Regenerative macroporous polyzwitterionic gels for brackish/sea water desalination

Ensuring the availability of clean water is one of the most critical sustainable development goals. To contribute to this objective, we report on a novel approach for desalination of brackish/sea water using regenerative, highly porous, thermally stable polyzwitterionic gels (labeled PZG-1, PZG-2, PZG-3, and PZG-4). The synthesized PZGs were used for the removal of commonly found salts from water by electrostatic interaction. The effect of various anions and cations, crosslink density in PZGs, and competitive absorption were systematically investigated. The maximum absorption capacity observed was ~97% and ~89% for I− anion and K+ cation, respectively. Regeneration studies demonstrated that the gels could be reused for more than 5 cycles with ~93% retention of absorption capacity. Our approach, when extended to sea and tap water samples, showed ~87% and 89% reduction in conductivity. Utilizing PZGs is a promising alternative to traditional processes for the desalination of water, as the results from this study show their high efficiency for the removal of salts from wastewater even at very low concentration. Moreover, their efficient and ease of synthesis from relatively inexpensive raw materials, reusability, and the desalination process being more energy efficient in comparison with conventional techniques make this approach unique and highly desirable.

Hemin-Modified Halloysite Nanotube as Electrocatalyst for the Enhanced Electrochemical Determination of Nitrite

Halloysite is naturally occurring nanotubular clay with a phyllosilicate structure and widely used as solid support to modify various redox mediators. We prepared a hemin modified halloysite (Hemin/HNT) by a simple impregnation method, in which a known amount of halloysite was dispersed in ethanolic solution of 1% hemin and reacted for 12 h. The resulting pure Hemin/HNT was employed as electrocatalyst for the electrochemical oxidation of nitrite by cyclic voltammetry. The coverage of hemin molecule over the nanotubular halloysite was confirmed by TGA, FT-IR, XRD and XPS studies. The electron transfer behavior of Hemin/HNT was studied by CV and EIS. It was noted that hemin/HNT modified GCE showed two-fold enhanced oxidation peak current for nitrite with a peak potential of + 0.8 V vs Ag/AgCl in 0.1 M PBS. For a quantitative electrochemical analysis of nitrite ion at the trace levels the differential pulse voltammetry (DPV) and amperometry methods were used based on hemin/HNT modified GCE. A linear calibration plot was constructed by plotting the peak current against the concentrations of nitrite in the ranges of 0.6 × 10−6 M to 24.6 × 10−5 M, (R2 = 0.9968) and 0.6 × 10−8 to 43.3 × 10−7 M (R2 = 0.9996) and the detection limit was found to be 42 and 43 nM with a sensitivity of 23.55 and 22.96 μA.μM−1.cm−2 by DPV and amperometry, respectively. The repeatability of the proposed sensor evaluated in terms of relative standard deviation of 1.7% for 5 measurements (3.3 × 10−6 M) nitrite. The inference effect of various anions and cations on nitrite oxidation peak current was studied by amperometry method. A stable and reliable current response was obtained for nitrite analysis in water samples.

Carbonization of methylene blue adsorbed on palygorskite for activating peroxydisulfate to degrade bisphenol A: An electron transfer mechanism

As a natural and environmentally friendly adsorbent, palygorskite (Pal) has been approved to be excellent for the adsorption of dyes. However, the spent Pal is difficult to be regenerated through normal desorption methods, and thus, becoming a solid waste. In this study, methylene blue (MB) was adsorbed by Pal, and the MB absorbed on palygorskite (MP) was carbonized at different temperatures. The carbonized MP (CMP) was used for peroxydisulfate (PDS) activation to degrade bisphenol A (BPA). The effects of carbonization temperature, pH values, PDS concentration, and catalysts dosage on BPA degradation were investigated. The results show that the MP carbonized at 800 °C (CMP800) has the best activation performance due to the high degree of carbon defectivity and high specific surface area. The CMP800 can effectively degrade BPA over a wide pH range from 3 to 9 and is extremely resistant to the effects of various anions, such as Cl−, NO3−, HCO3−, and H2PO4−. Based on quenching experiments, electron spin resonance (ESR), and electrochemical analysis results, a non-radical pathway involving electron transfer from BPA to PDS is responsible for the degradation of pollutants. Moreover, the CMP800 has a high total organic carbon (TOC) removal efficiency of 83%, high stability in three cycles, and low PDS consumption. This study demonstrates the feasibility of the treatment and utilization of the waste Pal, which also provides a carbon-based activator for the activation of PDS to degrade organic contaminants.

Fabrication of nitrogen-doped graphene nanosheets anchored with carbon nanotubes for the degradation of tetracycline in saline water

The treatment of wastewater with high salinity is still a challenge because of the quenching effect of various anions on radical processes. The nonradical process may be a more promising pathway. Herein, a 3D structured nitrogen-doped graphene nanosheet anchored with carbon nanotubes (N-GS-CNTs) was prepared by direct pyrolysis of K3Fe(CN)6. The as-prepared catalyst can effectively activate peroxymonosulfate (PMS) for mineralization of tetracycline (TC) over a wide pH range (from 3 to 11) and even in high saline water (500 mM Cl−, HCO3−, etc.). The degradation mechanism was elucidated by both experimental characterizations and DFT calculations. The high catalytic efficiency was attributed to accelerated electron transfer from donor (TC) to acceptor (PMS) in the presence of the catalyst, which acts as electron shuttle mediators to promote a nonradical process. At the same time, the catalyst also enhances the production of singlet oxygen (1O2), hence further increasing the degradation rate. This study not only provides a simple method for synthesizing N-GS-CNT catalysts but also provides new insights into the electron transfer pathway for the removal of organic pollutants under high salinity conditions.

Effects of various anions and cations in ionic liquids on CO2 capture

Blends of ionic liquids (ILs) with monoethanolamine (MEA) in 1-hexanol were employed to enhance CO2 removal in comparison with that of pure MEA. A series of hydrophobic and hydrophilic 1-alkyl-3-methylimidazolium-based ionic liquids ([Cn-mim][Ac], [Cn-mim][Cl], and [Cn-mim][Tf2N] with n = 2 or 4) were studied to investigate the absorption/desorption performance, which is known to be affected by changes in the type of anion used and the alkyl chain length in the cation. Three different weight percentages of ILs were added to 20 wt% MEA, and the maximum amine concentration in the liquid was obtained as 30 wt/wt%. The absorption capacity (or equilibrium solubility) was noted to be highly dependent on the selection of the anion, whereas the choice of cation had a minor effect. The results revealed that the addition of IL significantly improved the CO2 capture performance, and indicated a favorable loading ratio. The [bmim][Ac] IL was found to result in the highest CO2 equilibrium loading (0.89 mol CO2/(mol [bmim][Ac])) compared to that in other blends. Moreover, the interactions between CO2 and the blend systems were characterized using Fourier transform infrared spectrometry (FTIR) to analyze the reusability and potential performance losses of the solvent systems.

Anions effect on ion transport properties of polyelectrolyte modified single conical nanopores

Here we present screening effect of various anions on nanopore fixed surface charges. The anions could not induce significant change in ion transport through negatively charged nanopore. For positively charged nanopore, the order of monovalent anions effect is: H2PO4− > HCO3– > NO3– > BrO3− ~ Cl−. The divalent HPO42− exhibits significant changes in the rectified ion flux, while SO42− could not induce any noticeable change even at higher concentrations. Our experimental results demonstrated the ability of various anions to interact with fixed surface charges and their effect on nanopore transport characteristics.

Functions of MnOx in NaCl Aqueous Solution for Artificial Photosynthesis.

SummaryPhotoelectrochemical water splitting has been intensively investigated as artificial photosynthesis technology to convert solar energy into chemical energy. The use of seawater and salted water has advantages for minimum environmental burden; however, the oxidation of Cl− ion to hypochlorous acid (HClO), which has toxicity and heavy corrosiveness, should occur at the anode, along with the oxygen evolution. Here, O2 and HClO production in aqueous solution containing Cl− on photoanodes modified with various metal oxides was investigated. The modification of MnOx resulted in the promotion of the O2 evolution reaction (OER) specifically without HClO production over a wide range of conditions. The results will contribute not only to the practical application of artificial photosynthesis using salted water but also to the elucidation of substantial function of manganese as the element for OER center in natural photosynthesis.

Degradation of ciprofloxacin by photocatalytic ozonation process under irradiation with UVA: Comparative study, performance and mechanism

The photocatalytic ozonation process (O3/UVA/TiO2) was applied for the removal of ciprofloxacin antibiotic (CIP) from aqueous solutions. The influence of various operational factors such as solution pH, initial pollutant concentration, catalyst content, ozone dose and scavengers was studied on the process. The mineralization, biodegradability, kinetic models, catalyst recyclability, electrical energy consumption and cost estimation of the process were also performed. Various techniques of FE-SEM, EDS, FTIR, XRD and UV–vis were applied to characterize the catalyst. The highest CIP removal (98.5 %) was obtained in ozone and catalyst doses of 0.34 g/h and 1.0 g/L, respectively during 15 min reaction time at pH 9.0. The scavenging experiments approved the contribution of hydroxyl radicals (OH) and superoxide (O2−) as the main active radical species in the process. The competition effect of various anions on the process efficiency was in the order of chloride > carbonate > bicarbonate > sulfate. The process kinetics followed the pseudo-first-order model. The catalyst efficiency was about 95 % of the original one after 6 recycling steps. It can be concluded that the photocatalytic ozonation process (O3/UVA/TiO2), due to the low reaction time and high removal efficiency, can be considered as a suitable and practical technique for the removal of antibiotics from aqueous solutions.

Ultrasonic degradation of nitrosodipropylamine (NDPA) and nitrosodibutylamine (NDBA) in water.

Nitrosodipropylamine (NDPA) and nitrosodibutylamine (NDBA), two highly toxics and carcinogenic disinfection by-products, cannot be efficiently removed by conventional water treatment processes, while the ultrasound treatment was developed as a promising alternative. In this work, nitrosodipropylamine (NDPA) and nitrosodibutylamine (NDBA) are degraded by ultrasound treatment. Greater than 99% of NDPA and NDBA mixing solution could be decomposed within 60min at neutral pH under optimal ultrasound power and frequency settings of 100W and 600kHz, respectively. Free radical reactions (OH•) played a significant role and the reaction sites were predominately at the bubble interface. The degradation of both NDPA and NDBA exhibited pseudo-first-order degradation kinetics, and the rate constant kapp was influenced by a number of factors including ultrasonic frequency, power, initial concentration, initial pH, various anions and cations frequently present in drinking water, hydroxyl radical scavengers, and water matrices, especially the promoting effect of various anions and cations and water matrices. The results of this study suggest the potential for ultrasound treatment as a method for removing NAms from water.

Enhanced kinetic performance of peroxymonosulfate/ZVI system with the addition of copper ions: Reactivity, mechanism, and degradation pathways

Advanced oxidation processes (AOPs) based on the bimetallic system has been demonstrated as a promising way to enhance the degradation of pollutants in the water. In this study, the degradation of Rhodamine B (RhB) in a zero-valent iron (ZVI)/ peroxymonosulfate system with Cu2+ was thoroughly investigated. RhB could be efficiently removed (99.3 %) in the optimal ZVI/PMS/Cu2+ system, while only 58.2 % of RhB could be degraded in the ZVI/PMS system. The influence of reaction parameters on the degradation of RhB was further investigated. Quenching experiments and electron paramagnetic resonance (EPR) tests revealed that various reactive oxygen species could be generated in the ternary system, of which, 1O2 and O2− were identified for the first time. The effect of various anions, NOM and different water matrix were also considered at different concentrations. A variety of byproducts and degradation pathways were identified using HPLC/MS/MS. Finally, the Quantitative Structure Activity Relationship (QSAR) method of Toxicity Estimation Software Tool (TEST) was applied to estimate the toxicity of the byproducts and the results indicated that the overall toxicity of the target was relatively reduced. This study demonstrated the potential for the removal of environmental reluctant pollutants in water via the combined radical and non-radical pathways.

Effect of Different Anions Upon the WO₃ Morphology and Structure.

In this study the effects of various anions (SO2-₄, ClO-₄ and PO3-₄) were investigated on the hydrothermal treatment of WO₃ from Na₂WO₄ and HCl at 180 and 200 °C. The products were analyzed by XRD and SEM. With the usage of SO2-₄ the obtained product was hexagonal (h-) WO₃ in the form of nanorods at both temperatures. Applying ClO-₄ resulted in a mixture of WO₃·0.33H₂O and small amount of m-WO₃ at 180 °C and pure WO₃·0.33H₂O at 200 °C. The morphology was consisted of cuboid shapes arranged into spherical structures at 180 °C and longitudinal ones at 200 °C. By the application of PO3-₄ no product formed at either temperature. Using the combination of SO2-₄, and ClO-₄ the product was h-WO₃ at both 180 and 200 °C with rod-like crystals; thus, the effect of ClO-₄ was overdominated by the SO2-₄ions. Utilization of PO3-₄ together with SO2-₄, and/or ClO-₄ resulted again in no product, meaning that adding PO3-₄ to the reaction mixture completely blocks the hydrothermal formation of solid products by forming water soluble phosphotungstic acids.

Study of the ZnIIComplexes of 1,1′‐Binaphthyl‐Based Schiff Bases: Fluorescent Detection of Thiocyanate

Two diastereomeric Schiff bases (Sa,R)‐2and (Sa,S)‐2are prepared from the condensation of (S)‐3,3′‐diformyl‐1,1′‐bi‐2‐naphthol withd‐ andl‐2‐phenylglycinol. Upon coordination with Zn2+, (Sa,R)‐2shows much greater fluorescence than (Sa,S)‐2does. The effect of various anions on the fluorescence of these Zn2+complexes is studied. It is found that (Sa,S)‐2exhibits large fluorescence enhancement in the presence of thiocyanate but not with other anions. This compound can be used as a sensitive as well as selective fluorescent probe for thiocyanate that is of significant environment and health importance. Spectroscopic studies have revealed interesting dimeric [2+3] structures of these complexes.

Trace determination of Ag(I) after reduction to Ag nanoparticles and sol–gel entrapment by alginic acid hydrogel

The main goal of this work is development of an effective analytical method for trace determination of Ag(I). The novelty of the Ag(I) preconcentration–determination method is mainly referred to the material and the enrichment–detection process (alginic acid gel phase was employed in a pH-switched sol–gel entrapment/Ag fluorescence detection). Ag(I) was reduced to Ag nanoparticles (AgNPs) and then was enriched by the alginic acid hydrogel phase. Then, the formed gel phase (containing AgNPs) was dissolved in alkali solution prior to Ag detection. The enrichment method was highly compatible with spectrofluorimetry, electrothermal atomic absorption spectrometry (ETAAS) and spectrophotometry. Optimization of the reduction-enrichment procedure was performed employing spectrofluorimetry. The linear working range (LWR) and limit of detection (LOD) for Ag(I) determination were found as 0.1–25 and 0.017 µmol L− 1, respectively. The effects of various anions, cations and organic chemicals on Ag(I) determination were spectrofluorimetrically studied. The applied enrichment-ETAAS Ag(I) determination method showed the LWR and LOD as 0.2–6.9 and 0.05 nmol L− 1, respectively. Also, an enrichment factor equal to 30.3 was obtained for the preconcentration method. The method was successfully applied to determine Ag in different water samples, jewels, antimicrobial suspensions and waste X-ray films. X-ray diffraction, transmission electron microscopy, field emission-scanning electron microscopy and EDX-mapping were also employed to characterize the entrapped AgNPs in the alginic acid gel phase. The complimentary experiments showed the alginic acid gel was also applicable for quantitative recovery of silver from the waste radiographic films.

Alkaline Plating and Striping of Metal-Amine Complexes for Amine Regeneration in Gas Scrubbing Processes

Traditional thermal amine gas scrubbing technology can be energy and capital intensive owing to the enthalpy of formation of amine-CO2 complexes and the complexity in the process integration of a stripper column. An electrochemically mediated amine regeneration cycle in traditional gas scrubbing process has been proposed for post combustion CO2 capture.1 2 We take the advantage of competitive binding of amine with electroactive species, e.g. copper, to facilitate the desorption of CO2 and regeneration of amine in a modular electrochemical reactor.3 We investigated the energy efficiency of this electrochemical process via bulk electrolysis of the electrolyte. The charges applied in electrochemical metal dissolution are compared quantitatively to gas desorption in the electrolyte. Our controlled volume analysis validates the efficacy of the proposed cycle. We benchmarked the polarization of metal electrodes with different metal-amine complexes using a rotating disk electrode. The Tafel expression of the kinetic data assists in gauging the rate of metal dissolution/plating and provides insight into effects of various anions. We examined the quality of metal deposits at different operating conditions using XPS. The surface composition of the electrodes account for long-term stability of the electrodes. These thermo and kinetic data afford qualitative comparison of cell-level performance in the amine regeneration cycle.