Presence Of Chloride Research Articles

Design and comparative characterization of RecA variants

RecA plays a central role in DNA repair and is a main actor involved in recombination and activation of the SOS response. It is also used in the context of biotechnological applications in recombinase polymerase isothermal amplification (RPA). In this work, we studied the biological properties of seven RecA variants, in particular their recombinogenic activity and their ability to induce the SOS response, to better understand the structure–function relationship of RecA and the effect of combined mutations. We also investigated the biochemical properties of RecA variants that may be useful for the development of biotechnological applications. We showed that Dickeya dadantii RecA (DdRecA) had an optimum strand exchange activity at 30 °C and in the presence of a dNTP mixture that inhibited Escherichia coli RecA (EcRecA). The differences between the CTD and C-tail of the EcRecA and DdRecA domains could explain the altered behaviour of DdRecA. D. radiodurans RecA (DrRecA) was unable to perform recombination and activation of the SOS response in an E. coli context, probably due to its inability to interact with E. coli recombination accessory proteins and SOS LexA repressor. DrRecA strand exchange activity was totally inhibited in the presence of chloride ions but worked well in acetate buffer. The overproduction of Pseudomonas aeruginosa RecA (PaRecA) in an E. coli context was responsible for a higher SOS response and defects in cellular growth. PaRecA was less inhibited by the dNTP mixture than EcRecA. Finally, the study of three variants, namely, EcPa, EcRecAV1 and EcRecAV2, that contained a combination of mutations that, taken independently, are described as improving recombination, led us to raise new hypotheses on the structure–function relationship and on the monomer–monomer interactions that perturb the activity of the protein as a whole.

In situ acetonitrile/water mixed solvents: An ecofriendly synthesis and structure Explanations of Cu(II), Co(II), and Ni(II) complexes of thioxoimidazolidine

ABSTRACT. The bidentate oxoacetate derivative of 4-oxo-2-thiazolidine 4ligand (L1) synthesized by the reaction of 1-(1-(Pyridin-3-yl)ethylideneamino)-2-thioxoimidazolidin-4-one 3 with diethyl oxalate with both traditional and microwave irradiation methods. The metal ion complexes of mixed ligands L1 and L2 (acetonitrile) were prepared by condensation a solution mixture of Co(II) Ni(II), and Cu(ІІ) metal chloride salts with the ligands (L1 and L2) in distilled water with stirring. The complexes were characterized by the micro analysis (C, H, N), chloride content, FT-IR, UV-Vis spectra, thermal gravimetric analysis (TGA), molar conductivity as well as magnetic susceptibility measurement. According to the obtained data the suggested coordination geometries of these complexes were suggested as octahedral structure. All the synthesized complexes were found to be electrolyte due to the presence of chloride ions outside the coordination sphere. The antibacterial activity of the L1 ligand and their metal ion complexes have been studied by screening against various microorganisms, G+ bacteria (Bacillus subtillis, Streptococcus pneumonia, and Staphyloccoccus aurease), G-bacteria (E. coli, and Pesudomonas Sp.) and fungi (Aspergillus nigaer, and Penicillium Sp.). The metal ion complexes gave the formulae: [M(L1)(L2)2(H2O)2]Cl2where M = Co(II) Ni(II), and Cu(ІІ).
 
 KEY WORDS: Imidazolidine, Microwave irradiation, Transition metals complexes, Biological activity
 
 Bull. Chem. Soc. Ethiop. 2021, 35(2), 351-364.
 DOI: https://dx.doi.org/10.4314/bcse.v35i2.10

Role of Retained Austenite in Corrosion Resistance of Si-Mn Steel

Si-Mn steels are used for many industrial applications because of their high strength. One of the most important characteristics of the microstructure of Si-Mn steels is the retained austenite embedded in the matrix of martensite or bainite. The existence of the retained austenite promotes TRIP (Transformation-Induced Plasticity) effect, and therefore, provides Si-Mn steels with their excellent strength. While the retained austenite has the beneficial effect on the mechanical properties, corrosion mechanisms of the steels with the retained austenite have been unclear. In reality, the actual application of high-strength steels almost always involves outdoor corrosion environments which can be characterized as predominantly near-neutral pH environments with chloride ions. Even if the steels are successfully protected from corrosion by coating and/or painting, pitting corrosion readily occurs at the cut edges and in coating defect areas due to the presence of chloride ions. In this research, the objective is to clarify the effect of the retained austenite on the corrosion resistance of the Si-Mn steel in near-neutral pH environments.The specimens were Si-Mn steel (0.39%C, 1.51%S, 2.01%Mn, 0.010%P, 0.002%S, 0.04%Al, 0.004%N). The metallographic inspection was performed to ascertain the characteristics of the microstructure of the specimen by using EPMA (Electron Probe Micro Analyzer). It was confirmed that the microstructure consisted of the retained austenite and the matrix of martensite. To assess the corrosion behavior of the specimen, immersion tests were performed in the boric-borate buffer solutions with NaCl (pH 7.0). It was confirmed that the pits were initiated only in the matrix and not in the retained austenite.To clarify the reason for the high corrosion resistance of retained austenite, the corrosion behavior of two types of specimens were compared: Full martensitic specimen (0.44%C, 0.20%S, 0.85%Mn, 0.008%P, 0.002%S, 0.035%Al, 0.003%N) and full austenitic specimen (0.45%C, 0.32%S, 29.40%Mn, 0.014%P, 0.002%S, 0.025%Al, 0.005%N). In the case of the austenitic specimen, higher amount of Mn was added to form full austenitic structure even at room temperature. The austenitic and martensitic specimens simulated the retained austenite and matrix phases in the Si-Mn steel. The depassivation pH values of the austenitic and martensitic specimens were measured in boric-borate buffer solutions. The pH of the solution was decreased stepwise with 0.35 M H3BO3, and the open circuit potentials were measured. It was confirmed that the depassivation pH of the austenitic specimen was lower than that of the martensitic specimen. In other words, the depassivation occurred more readily on the martensite than the austenite. AES (Auger Electron Spectroscopy) depth analysis was performed to investigate the thickness of the surface oxide films on the austenitic and martensitic specimens. It was clarified that the oxide film on the austenite was about 1 nm thicker than that on the martensite, suggesting that the protective ability of the oxide film formed on the austenite is higher than that on the martensite. According to the above results, the high corrosion resistance of the retained austenite in Si-Mn steels appeared to be related with the nature of the oxide film formed on the austenite.

Degradation of Shotcrete Materials Subjected to Sulfate and Chloride Attack in Varying Exposure Regimes

Durability of in situ shotcrete under external sulfate attack was investigated, taking into consideration the addition of mineral admixtures, along with the presence of chloride ions. Three water-to-binder ratios (w/b), i.e., 0.35, 0.45, and 0.55, and two types of supplementary cementitious materials (SCMs), namely, fly ash (FA) and silica fume (SF), were considered in the current study. Two different laboratorial immersion regimes (continuously full immersion and partial immersion with cycling temperature and relative humidity) were carried out to induce chemical/physical sulfate attack. Results show that loss of strength was the typical feature of chemical sulfate attack on shotcrete, while surface spalling dominated in deterioration caused by physical sulfate attack. The presence of chloride ions can globally mitigate these deteriorations. Meanwhile, the lower w/b ratio proved to be efficient in increasing the resistance to both sulfate attacks. Adding fly ash (FA) in shotcrete mixtures enhanced the long-term performance but invited massive white efflorescence on surface layer under partial-immersion exposure condition. Silica fume (SF) admixture can compensate the undesired reduction of early-age strength caused by FA addition, but make these specimens more susceptible to sulfate attack. Mercury intrusion porosimetry (MIP) analysis, scanning electron microscopy (SEM), and X-ray diffraction (XRD) tests reveal that these consequences were strongly related to the refinement of microstructure resulted from pozzolanic reactions and hydration kinetics.

Effects of chloride ion in sea sand on properties of fresh and hardened concrete incorporating supplementary cementitious materials

This study aims to explore the applicability of non-desalted sea sand (NSS) for concrete production by investigating the effects of chloride ion on properties of fresh and hardened concrete incorporating fly ash (FA) and ground granulated blast furnace slag (BFS). All mixtures were prepared with a constant water-to-cementitious materials ratio of 0.50. The results showed that chloride ion in NSS had no effect on the slump loss and air content reduction of fresh concrete for 60 min after mixing. Thermal analysis and pore structure results clarified that chloride ion accelerated the pozzolanic reactivity of FA and hydraulicity of BFS at early ages. The presence of chloride ion also contributed to the increase in the mechanical properties and durability (permeability and sorptivity) of concrete at later ages. The outcomes of this study could validate the potential application of NSS for concrete incorporating supplementary cementitious materials as the alternative fine aggregate at coastal areas.

Electrochemical oxidation of chloramphenicol with lead dioxide-surfactant composites.

The PbO2 -2 wt.% sodium dodecyl sulfate composite formed from methanesulfonate electrolyte consists of 93.1% of α-phase PbO2 in contrast to the similar one synthesized from nitrate electrolyte, which contains 73.3% of β phase. The electrocatalytic activity of the obtained composites in the oxygen evolution reaction and oxidation of chloramphenicol was investigated. It was found that the Tafel slope significantly exceeds the theoretical value, which indicates a decrease in the degree of filling of the electrode surface with oxygen-containing particles. In the presence of organic compound and chloride ions in the solution, irreversible adsorption of the intermediate is observed, which leads to additional blocking of active centers on the oxide surface, which are involved in the oxidation of organic substance. It was established that the maximum rate of chloramphenicol conversion is 83.5% and 85% at 50 and 80 mA cm-2 , respectively, under kinetic control. The heterogeneous oxidation rate constant of chloramphenicol is 0.0035 min-1 . Oxidation of chloramphenicol occurs through the formation of 4-(-2-amino-1,3-dihydroxy-propanyl)-nitrobenzene with cleavage of dichloroacetic acid. Next, the amino group is oxidized to the nitro group to form 4-(2-nitro-1,3-dihydroxy-propanyl)-nitrobenzene. Subsequent electrolysis produces nitrobenzoic acid, which is oxidized to benzoic acid, later hydroquinone, then benzoquinone and a set of aliphatic compounds. PRACTITIONER POINTS: The PbO2 -2 wt.% SDS composite consists of 93.1% of α phase of PbO2 in contrast to those synthesized from nitrate electrolyte. The Tafel slope indicates a decrease of surface filling with oxygen-containing particles. Irreversible adsorption of the intermediate is observed in the presence of chloride ions.

Biochar/iron oxide composite as an efficient peroxymonosulfate catalyst for the degradation of model naphthenic acids compounds

Naphthenic acids (NAs) are a mixture of aliphatic and alicyclic carboxylic acids which are persistent in the environment. In this study, a sludge-based biochar/iron oxide (B-FeOx) catalyst with 3D flower-like shaped structure was prepared through a facile hydrothermal method. For the first time, the B-FeOx catalyst was employed to activate peroxymonosulfate (PMS) for the removal of two model NA compounds (1-adamantanecarboxylic acid (ACA) and 4-methylheptanoic acid) at pH 8.50. Compared to biochar or FeOx alone, a higher degradation efficiency (96.1%) and faster degradation rate (k = 0.100 min−1) of ACA were obtained by the B-FeOx composite at a catalyst dose of 2.0 g/L and PMS dose of 2.5 mM. The higher degradation efficiency of B-FeOx was attributed to the improved surface area and pore volume as well as the abundant reactive sites induced by the flower-like structure. Furthermore, the hydroxyl radical (•OH) generated in the B-FeOx/PMS system was the dominant radical for both ACA and 4-methylheptanoic acid degradation as demonstrated through radical quenching experiments. The presence of chloride ions in the B-FeOx/PMS system showed a suppression effect on the degradation of ACA and 4-methylheptanoic acid at Cl− concentrations between 5 and 20 mM. No significant difference in the degradation rates of ACA and 4-methylheptanoic acid was observed at different Cl− concentrations. Overall, the results of this study showed that the sludge (waste material)-based B-FeOx composite may have the potential to be utilized as PMS catalyst for the removal of NAs that are especially abundant in oil sands process water.

Electrochemical activation of peroxymonosulfate (PMS) by carbon cloth anode for sulfamethoxazole degradation

Electrochemical activation of peroxymonosulfate (PMS) at carbon cloth anode (E (Carbon cloth Anode)/PMS system) was investigated for sulfamethoxazole (SMX) degradation. The results indicated that PMS could be activated at carbon cloth anode during electrolysis, resulting in the improvement of SMX degradation. The degradation efficiency of SMX was facilitated with the higher PMS concentration and current density, respectively. The degradation rate constant of SMX increased with the rising pH from 3.6 to 6.0, and reached the highest value at pH 6.0, and then decreased with further increasing pH to 8.0. The presence of chloride ion (Cl−, 5–100 mM) significantly enhanced SMX degradation, while addition of humic acid (HA, 1–5 mgC L−1) inhibited SMX degradation. Addition of carbonate (HCO3−, 5–20 mM) had a negligible impact on SMX degradation. Small amounts of phosphate (PO43−, 0–5 mM) could promote degradation, while a large amount of PO43− (10–20 mM) inhibited the degradation. Moreover, the quenching experiments demonstrated that sulfate radical (SO4·−), hydroxyl radical (·OH) and singlet oxygen (1O2) contributed to SMX degradation in E (Carbon cloth Anode)/PMS system. The degradation intermediates of SMX were identified by LC-MS/MS and the degradation pathways were deduced to be hydroxylation, the cleavage of S–N bond, and oxidation of aniline group. Moreover, the micronucleus test of Vicia faba root tips indicated that the E (Carbon Cloth Anode)/PMS system could reduce the genetic toxicity of SMX contaminated water to some extent.

Oligomeric membranes for simultaneous chemical reaction and separation

Thin films of oligomers were synthesized on PTFE substrates and they were studied for separation of product from liquid chemical reaction mixture. Three different types of membranes were fabricated using a technique called ‘covalent molecular assembly’. Covalent molecular assembly is a synthesis technique in which a substrate is sequentially immersed in chemical solutions to grow molecular moieties with covalent bonding to the underlying layer of molecules on the substrate. The first membrane was oligoimide PMDA-ODA. The second membrane was crosslinked oligoamide TC-TAB. The third membrane was Nickel terminated oligoimide Ni-PMDA-ODA. The first two membranes were studied for Friedel-Crafts’ alkylation reaction between benzene and methyl chloride in presence of ferric chloride catalyst. With 30psia chloromethane pressure, the reaction proceeded to 100% conversion and the first two membranes provided a permeate of 99% pure toluene product. The third membrane was catalytically active to convert p-nitrophenol to p-aminophenol in presence of sodium borohydride in ethanol. The purity of the permeate stream reached 98% in 40 min and was stable for 2 h. Thus, novel membranes were synthesized for enhanced separations.

Benzofuran-oxadiazole hybrids: Design, Synthesis and antimicrobial activity studies

The six benzofuran-oxadiazole derivatives (4a-d) and (5a-b) have been designed, synthesized, characterized and evaluated for antimicrobial activity. The key synthetic intermediate 5-bromo-N'-hydroxybenzofuran -2-carboxamidine (3) was prepared from 5-bromobenzofuran-2-carboxylic acid (1) in two consecutive steps involving reaction with NaN3, in presence of TEA, Xtalfluor-E, PPh3 in dry DCM at 0oC followed by the treatment of resulting carbonitrile (2) with hydroxylamine hydrochloride in presence of sodium methoxide under reflux in aqueous ethanol. Reaction of carboxamidine (3) with different aryl esters in presence of K2CO3 under reflux conditions in toluene afforded 3-(5-bromobenzofuran-2-yl)-5-substituted phenyl-1,2,4-oxadiazoles (4a-d) while the refluxion of a solution of carboxamidine (3) in dichloromethane with chloro/bromo acetyl chloride in presence of TEA and a catalytic amount of HBTU furnished 3-(5-bromobenzofuran-2-yl)-5-(chloromethyl)-1,2,4-oxadia zole (5a) and 3-(5-bromobenzofuran-2-yl)-5-(bromomethyl)-1,2,4-oxadiazole (5b).

Corrosion behavior of carbon steel in H2S-CO2-H2O-methyldiethanolamine (MDEA) solution under the presence of chloride ions

PurposeThis paper aims to study the effect of chloride ions concentration on the corrosion behavior of carbon steel in methyldiethanolamine (MDEA) aqueous solution in the sight of different process parameters of purification plant.Design/methodology/approachDue to the decrease of filtration efficiency and separation efficiency, the chloride ion in the desulfurization solution is enriched. The corrosion behavior of carbon steel under chloride ion enrichment environment was studied by weight-loss method, electrochemical impedance spectroscopy, cyclic polarization curve, X-ray photoelectron spectroscopy and scanning electron microscopy.FindingsThe results show that temperature and hydrogen sulfide loads are the main factors of corrosion in CO2-MDEA-H2O-H2S environment. The enrichment of chloride ions reduces the corrosion rate at low temperature but promotes the corrosion rate at high temperature. The chloride concentration should be controlled below 3000 mg/L, and no pitting corrosion was found under the experimental conditions.Originality/valueThe effect of chloride ion enrichment on MDEA solution corrosion shows that at low temperature, the increase of chloride ion will reduce the acid gas load and increase the density of corrosion products, so as to reduce the corrosion; on the contrary, at high temperature, the density of corrosion products will decrease and the corrosion will be intensified as well. It is believed that the chloride ion should be controlled below 3000 mg/L according to the results of the tests.

Local structure in lithium chloride solution: a Monte-Carlo simulation study

ABSTRACT Monte-Carlo simulations and the nearest neighbour approach have been employed in the present study to investigate the structural properties of aqueous solutions of LiCl salt at ambient conditions. The calculations are performed at increasing concentration of LiCl starting from c = 0.1 m up to 10 m. The analysis shows that increasing salt concentration results in a reduction of the tetrahedral arrangement of water in favour of a non-tetrahedral arrangement characterised by an O–O–O angle between the reference oxygen and two of its four closest oxygen neighbours at 60°. Moreover, the LiCl concentration has a considerable effect on the hydrogen-bonding structure of water. By correctly choosing the nearest neighbours, it is found that the deviation in water structure is due to the presence of chloride ion, not lithium ion, in the first solvation shell of water. It is also demonstrated that in concentrated LiCl solution Cl− ions can substitute the fourth water neighbour which leads to a tetrahedral network formed by water molecules and Cl− ions around a central water molecule. The analysis of the effect of concentration increase on the arrangement of the four closest water molecules neighbours from a reference lithium cation allows us to elucidate a structural maker role of Lithium ion.

Effect of Potential and Chlorides on Photoelectrochemical Removal of Diethyl Phthalate from Water

Removal of persistent pollutants from water by photoelectrocatalysis has emerged as a promising powerful process. Applied potential plays a key role in the photocatalytic activity of the semi-conductor as well as the possible presence of chloride ions in the solution. This work aims to investigate these effects on the photoelectrocatalytic oxidation of diethyl phthalate (DEP) by using TiO2 nanotubular anodes under solar light irradiation. PEC tests were performed at constant potentials under different concentration of NaCl. The process is able to remove DEP following a pseudo-first order kinetics: values of kapp of 1.25 × 10−3 min−1 and 1.56 × 10−4 min−1 have been obtained at applied potentials of 1.8 and 0.2 V, respectively. Results showed that, depending on the applied potential, the presence of chloride ions in the solution affects the degradation rate resulting in a negative effect: the presence of 500 mM of Cl− reduces the value of kapp by 50 and 80% at 0.2 and 1.8 V respectively.

Freezing-induced activation of the binary chloride-Oxone system to free chlorine and its application in water treatment

Accelerated chemical reactions in frozen solutions can be applied in the degradation of organic pollutants in water. Herein we propose a novel freezing system that enables the degradation of various organic compounds in a frozen solution. Although the degradation of 4-chlorophenol (4-CP) by Oxone as the sole primary oxidant did not take place in aqueous solutions (25 °C) regardless of the presence of chloride ions (Cl−, micromolar levels) and only took place to a minor extent in frozen solutions (−20 °C) in the absence of Cl−, the addition of Cl− (micromolar levels) to the freezing/Oxone system significantly accelerated the degradation of 4-CP. Various analytical characterizations and pH measurements of the frozen solution suggested that the enhanced degradation of 4-CP in the freezing/Oxone/Cl− system could be because Cl−, Oxone, and protons are concentrated in the liquid brine upon freezing. This process subsequently facilitates the formation of hypochlorous acid (HOCl) as a secondary oxidant. The positive effect of Cl− was observed under widely varying conditions (i.e., [Cl−] = 25–1000 μM, pHi = 3–11, and freezing temperature = from −10 to −30 °C), and the freezing/Oxone/Cl− system described herein successfully degraded all 12 tested organic pollutants. In addition, outdoor freezing experiments carried out on winter days confirmed the successful performance of the freezing/Oxone/Cl− system without the requirement for electrical energy.

Electrochemical Degradation of Methylene Blue Using a Ni-Co-Oxide Anode

The potential of using thermally prepared Ni0.6Co0.4-oxide for the electrochemical degradation of organic contaminants was investigated using methylene blue (MB) in an aqueous solution, as a model pollutant. The results of UV spectroscopy obtained during galvanostatic electrolyses at the anode indicated the complete removal of the methylene blue dye. The high removal of chemical oxygen demand (COD) and total organic carbon (TOC) suggested a high level of mineralization of its intermediates. It was found that the electrocatalytic performance of the electrode in the anodic degradation of the organic pollutant was significantly enhanced by the presence of chloride ions in the solution. The improvement in the degradation rate of MB was attributed to the in situ electrogeneration of chlorine active species. The results show that Ni0.6Co0.4-oxide anode can be employed as a stable energy-efficient electrocatalyst in the electrochemical purification of wastewater.

Enhanced sono-assisted adsorptive uptake of malachite green dye onto magnesium ferrite nanoparticles: Kinetic, isotherm and cost analysis

In this study, the performance of magnesium ferrite nanoparticles (MgF-NPs) as adsorbent was assessed for removal of toxic malachite green (MG) dye from aqueous solution under ultrasonic irradiation. The MgF-NPs exhibited specific surface area of 70.266 m2/g and pore volume of 0.311 cc/g with an average pore diameter of 7.354 nm. Optimum solution pH was found to be 8.0 for sono-assisted MG dye adsorption, which is favourable for large scale field application of the proposed method. The adsorption reaction aided by ultrasonication could yield more than 90% MG dye removal within 15 min of reaction due to enhancement of mass transfer. However, instead of ultrasonication when overhead stirring and shaking was used as mixing methods then the MG dye removal efficacy was dropped to 70% and 65%, respectively. The adsorption kinetic strictly followed the pseudo-second-order model and equilibrium isotherm analysis followed the Langmuir isotherm model with maximum monolayer adsorption capacity of 487.60 mg/g. The presence of chloride ion hindered the MG dye removal efficiency from 91% to 67%, whereas the presence of nitrate, sulfate and phosphate ions in the dye solution could not affect the dye removal efficacy significantly. The cost analysis for synthesis of MgF-NPs revealed that the cost involvement of 50.88 USD/Kg of adsorbent which may be considered as economical for large scale industrial application.

Performance Evaluation of Fe-Al Bimetallic Particles for the Removal of Potentially Toxic Elements from Combined Acid Mine Drainage-Effluents from Refractory Gold Ore Processing

Acid mine drainage (AMD) is a serious environmental issue associated with mining due to its acidic pH and potentially toxic elements (PTE) content. This study investigated the performance of the Fe-Al bimetallic particles for the treatment of combined AMD-gold processing effluents. Batch experiments were conducted in order to eliminate potentially toxic elements (including Hg, As, Cu, Pb, Ni, Zn, and Mn) from a simulated waste solution at various bimetal dosages (5, 10, and 20 g/L) and time intervals (0 to 90 min). The findings show that metal ions with greater electrode potentials than Fe and Al have higher affinities for electrons released from the bimetal. Therefore, a high removal (>95%) was obtained for Hg, As, Cu, and Pb using 20 g/L bimetal in 90 min. Higher uptakes of Hg, As, Cu, and Pb than Ni, Zn, and Mn also suggest that electrochemical reduction and adsorption by Fe-Al (oxy) hydroxides as the primary and secondary removal mechanisms, respectively. The total Al3+ dissolution in the experiments with a higher bimetal content (10 and 20 g/L) were insignificant, while a high release of Fe ions was recorded for various bimetal dosages. Although the secondary Fe pollution can be considered as a drawback of using the Fe-Al bimetal, this issue can be tackled by a simple neutralization and Fe precipitation process. A rapid increase in the solution pH (initial pH 2 to >5 in 90 min) was also observed, which means that bimetallic particles can act as a neutralizing agent in AMD treatment system and promote the precipitation of the dissolved metals. The presence of chloride ions in the system may cause akaganeite formation, which has shown a high removal capacity for PTE. Moreover, nitrate ions may affect the process by competing for the released electrons from the bimetal owing to their higher electrode potential than the metals. Finally, the Fe-Al bimetallic material showed promising results for AMD remediation by electrochemical reduction of PTE content, as well as acid-neutralization/metal precipitation.

Reactive species driven oxidative modifications of peptides—Tracing physical plasma liquid chemistry

The effluence of physical plasma consists of a significant share of reactive species, which may interact with biomolecules and yield chemical modifications comparable to those of physiological processes, e.g., post-translational protein modifications (oxPTMs). Consequentially, the aim of this work is to understand the role of physical plasma-derived reactive species in the introduction of oxPTM-like modifications in proteins. An artificial peptide library consisting of ten peptides was screened against the impact of two plasma sources, the argon-driven MHz-jet kINPen and the helium-driven RF-jet COST-Jet. Changes in the peptide molecular structure were analyzed by liquid chromatography–mass spectrometry. The amino acids cysteine, methionine, tyrosine, and tryptophan were identified as major targets. The introduction of one, two, or three oxygen atoms was the most common modification observed. Distinct modification patterns were observed for nitration (+N + 2O–H), which occurred in kINPen only (peroxynitrite), and chlorination (+Cl–H) that was exclusive for the COST-Jet in the presence of chloride ions (atomic oxygen/hypochlorite). Predominantly for the kINPen, singlet oxygen-related modifications, e.g., cleavage of tryptophan, were observed. Oxidation, carbonylation, and double oxidations were attributed to the impact of hydroxyl radicals and atomic oxygen. Leading to a significant change in the peptide side chain, most of these oxPTM-like modifications affect the secondary structure of amino acid chains, and amino acid polarity/functionality, ultimately modifying the performance and stability of cellular proteins.

Functionalization of biosourced silica and surface reactions with mercury in aqueous solutions

This study presents the production of pure silica from rice husk and its stepwise functionalization with triethoxysilane (TES) and silver nanoparticles. The derived TES-SiO2 (0.97 mmol TES per g of SiO2) and Ag0@SiO2 (3.70–21.60 mg Ag per g of SiO2) materials were used for the removal of Hg2+ from aqueous solutions in the presence of chloride ions. The removal of Hg2+ was rapid and the equilibrium solid phase loading was between 21 and 101 mg/g. TES-SiO2 was more effective than Ag0@SiO2 in removing mercury due to the highly reactive hydride groups. In the case of Ag0@SiO2 samples the removal of Hg2+ is proportional to the amount of Ag0. The materials were characterized before and after the removal of Hg2+ to allow insights into the interaction mechanism. The reaction products for TES-SiO2 sample were calomel (Hg2Cl2) and AgCl. On the surface of Ag0@SiO2 samples besides these products the silver amalgams Ag1.1Hg0.9 and possibly Ag2Hg3 were identified. These results show that redox reactions between silicon-hydride group, Ag0 and Hg2+ take place on the surface of the materials. The coexistence of calomel and silver amalgams on amorphous silica is observed for the first time while the calomel formation in heterogeneous Hg2+ redox systems is a rare observation. Also, the samples showed extraordinary efficiency in terms of Hg:Ag molar ratio (2.28–3.02), considerably higher than those reported before. Besides the beneficial effect of the Cl- presence on the removal of Hg2+ from the solution there is evidence of a hyperstoichiometric interaction between Ag0 and Hg2+ at the nanoscale.

Electrooxidation of simulated wastewater containing pharmaceutical amoxicillin on thermally prepared IrO2/Ti

<p>The electrooxidation of amoxicillin (AMX) on the iridium oxide electrode thermally prepared (400°C) has been investigated by cyclic voltammetry and preparative electrolysis. Physical characterization by Scanning Electron Microscopy (SEM) showed that the IrO<sub>2</sub> electrode has a rough surface with pores' presence. In cyclic voltammetry, the oxidation of AMX occurs directly at the anode's surface or via the higher degree oxide of iridium oxide (IrO<sub>3</sub>). It is noted that the oxidation process of AMX can be controlled by diffusion combined with the phenomenon of adsorption. In preparative electrolysis, the effect of several parameters has been investigated. These are the current density, the support medium, the initial pH. The findings obtained show a weak degradation of amoxicillin. The Chemical Oxygen Demand (COD) reduction rate is less than 11% under our experimental conditions, indicating that the IrO2 electrode leads to the parent compound's conversion. Also, the degradation of the organic compound is favored in a very acidic medium.<strong></strong></p><p>Furthermore, the effect of inorganic ions such as SO<sub>4</sub><sup>2-</sup>, PO<sub>4</sub><sup>3-</sup>, NO<sub>3</sub><sup>-</sup>, Cl<sup>-</sup> was evaluated. Investigations show that these ions' effects are diverse, with COD reduction rates ranging from 2.47%; 2.68%; 7.7%; 16.41%, and 71.65%, respectively, in the absence and the presence of SO<sub>4</sub><sup>2-</sup>, PO<sub>4</sub><sup>3-</sup>, NO<sub>3</sub><sup>-</sup>, Cl<sup>- </sup>ions. SO<sub>4</sub><sup>2-</sup> have virtually no effect on enhancing the degradation of amoxicillin. PO<sub>4</sub><sup>3-</sup> ions provide a slight improvement in amoxicillin degradation. As for nitrate ions, their influence is 2.31 times that of phosphate ions. Chloride ions improve the performance of the electrooxidation of amoxicillin on IrO2 very significantly. The presence of chloride ions makes it possible to go from 2928.35 (absence of inorganic ions) to 33.19 kWh per Kg of COD. This represents an energy gain of over 98%.</p>