Effect Of Anions Research Articles

Degradation mechanisms of antibiotics in UV222/H2O2 and UV222/persulfate systems: Dual roles of inorganic anions

Advanced oxidation processes based on KrCl* excimer lamps (UV222-AOPs) have recently received widespread attention in water treatment due to their high radical yields. In this investigation, the degradation of two typical antibiotics, florfenicol (FLO) and ciprofloxacin (CIP), by UV222 and its combination with hydrogen peroxide (H2O2) or persulfate (PDS) were studied, respectively. The dual effects of inorganic anions on the degradation performance of UV222/UV222-AOPs were determined. It was found that NO3– significantly enhanced the photolysis of CIP, and the degradation rate constants increased from 1.03 × 10-4 mJ−1 cm2 (without NO3–) to 2.56 × 10-4 mJ−1 cm2 (with 1 mM NO3–). However, NO3– markedly inhibited the photolysis of FLO, leading to a decrease in the degradation rate constants from 1.18 × 10-3 mJ−1 cm2 (without NO3–) to 5.27 × 10-4 mJ−1 cm2 (with 1 mM NO3–). HCO3– was found to have a certain promoting effect on the photolysis of FLO and CIP, and SO42- has a negligible effect on the photolysis of both antibiotics. The above three inorganic ions decelerated the degradation of CIP and FLO in UV222-AOP, where NO3– exerted the most inhibition. Through LC-MS analysis and ECOSAR model, the main transformation products were individually determined and evaluated for toxicity. In addition, the performance of UV222-AOPs and UV254-AOPs in reclaimed wastewater (RWW) treatment were compared, and the steady-state concentration of radicals was measured. This study provided novel insight into the application of UV222-AOPs in RWW treatment.

Preparation of imidazole-based polymeric ionic liquid catalysts and their catalysis in the copolymerization with sulfur dioxide

Sulfur dioxide (SO2) is one of the primary air pollutants, and its reaction with epoxides to produce sulfur-containing polymers is an efficient means of resource utilization for SO2, however, catalysts play a crucial role in this reaction. Polymeric ionic liquids (PILs) have become a hot topic in catalysis research due to their dual characteristics of ionic liquids and polymers. Therefore, a series of heterogeneous PILs were prepared, characterized, and employed for the copolymerization of SO2 with epoxides in this study. The impact of different halide anions and hydrogen bond donors on catalytic performance was investigated. Optimal reaction conditions for copolymerization were determined by examining reaction temperature, reaction time, molar ratio of catalyst to epoxide, and other factors. Furthermore, PILs demonstrated recyclability for more than 6 cycles without a significant decrease in catalytic activity, and PILs exhibited broad applicability to various epoxides. Finally, density functional theory (DFT) calculations were employed to further elucidate the activation effect of halide anions and hydrogen bond donors on epoxides to propose a potential mechanism for the copolymerization of SO2 with epoxides catalyzed by PILs.

Efficient Extraction of Wool Keratin Governed by Simultaneous Cation and Anion Effects: From Secondary Structure Studies to High α-Helix Keratin Content

Efficient Extraction of Wool Keratin Governed by Simultaneous Cation and Anion Effects: From Secondary Structure Studies to High α-Helix Keratin Content

Effect of inorganic anions on precipitation of desilication products based on low-temperature Bayer process

The effect of inorganic anion impurities in sodium aluminate solution on the composition, structure and micro-morphology of desilication products (DSPs) based on the low-temperature Bayer process was systematically investigated via XRD, FT-IR, SEM and PSD methods. The sodalites with chloride-type, carbonate-type and nosean-type precipitate in the presence of chloride, sulfate and carbonate in solution, and the aluminate ions in DSPs are partly replaced by the incorporation of anion impurities. The binding capability of sulfate to the DSPs cage is stronger than aluminate, chloride and carbonate. The particle size, agglomeration degree and thickness of the circular lamellar structure of DSPs are increased by rising the concentration of anion impurities. The anions enhance the dissolution of the zeolite framework and the formation of tetradentate rings in sodalite, which promotes the transformation of zeolite to sodalite.

Adjustable anion and cation vacancies CoSe catalysts on improving activity in photoelectrochemistry and electrocatalysis

Vacancies have a significant impact on catalysts as crystal structure, band structure and surface active sites. The effect of anion and cation vacancies on the catalytic performance of CoSe was studied. Catalysts with cation Co vacancies, anion Se vacancies and anion cation double vacancies were obtained. The results show that the single Co vacancy CovSe will form many pores as the active sites in the lattice and the position of the conduction band greatly moves from 0.55 eV of CoSe to −0.46 eV. This significantly improves the electrocatalytic hydrogen evolution performance, with overpotential of 161 mV and Tafel slope of 58 mV/dec. As a comparison, the overpotential of CoSe is 401 mV (Tafel slope of 171 mV/dec). In addition, Co vacancies can also improve carrier mobility and separation efficiency, demonstrating excellent photocurrent of 11.82 mA/cm2 at 1.23 eV (RHE), with 5.91 % conversion efficiency. The overall performance of CoSev with individual Se anion vacancies is not as good as CovSe. This indicates that cationic vacancies have a greater impact on the catalyst. There was no significant improvement in the performance of the sample with double vacancies of anions and cations, indicating that the two vacancies may have offset each other.

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.

Degradation of Orange G Using PMS Triggered by NH2-MIL-101(Fe): An Amino-Functionalized Metal-Organic Framework.

As an azo dye, OG has toxic and harmful effects on ecosystems. Therefore, there is an urgent need to develop a green, environmentally friendly, and efficient catalyst to activate peroxymonosulfate (PMS) for the degradation of OG. In this study, the catalysts MIL-101(Fe) and NH2-MIL-101(Fe) were prepared using a solvothermal method to carry out degradation experiments. They were characterized by means of XRD, SEM, XPS, and FT-IR, and the results showed that the catalysts were successfully prepared. Then, a catalyst/PMS system was constructed, and the effects of different reaction systems, initial pH, temperature, catalyst dosing, PMS concentration, and the anion effect on the degradation of OG were investigated. Under specific conditions (100 mL OG solution with a concentration of 50 mg/L, pH = 7.3, temperature = 25 °C, 1 mL PMS solution with a concentration of 100 mmol/L, and a catalyst dosage of 0.02 g), the degradation of OG with MIL-101(Fe) was only 36.6% within 60 min; as a comparison, NH2-MIL-101(Fe) could reach up to 97.9%, with a reaction constant k value of 0.07245 min-1. The NH2-MIL-101 (Fe)/PMS reaction system was able to achieve efficient degradation of OG at different pH values (pH = 3~9). The degradation mechanism was analyzed using free-radical quenching tests. The free-radical quenching tests showed that SO4•-, •OH, and 1O2 were the main active species during the degradation of OG.

Anion–Induced Amyloid Fibrillation of Human Insulin In vitro

AbstractIn the present study, we have focused on the effect of three biologically important salt anions on insulin aggregation. The result of the present study reveals that salts differing in their anions (NaI, NaOAc, and NaNO3) induce the self–assembly formation of insulin even at low physiological (in the micromolar range) salt concentration with efficacy that follows the order I−>CH3COO−>NO3−. Here, the anion–driven aggregation of insulin does not follow either the Hofmeister series or electroselectivity series at very low salt concentrations; instead, the binding of anions at low pH to the positively charged residues of insulin is determined by a mechanism where the salt anions promote the fibrillation of insulin and modify the morphology of the monomeric precursor molecule. Both the nucleation and fibril elongation are controlled by the electrostatic forces and hydrophobic interactions. Aggregation mechanism and aggregate morphology were investigated employing a combination of Thioflavin T (ThT) and ANS fluorescence, circular dichroism (CD), dynamic light scattering (DLS), and transmission electron microscopy (TEM). Overall, the present data will enhance the idea to rationalize the anion effects on the aggregation of amyloid‐prone protein and to understand the influence of charged biomolecules in cellular compartments.

Quantification and Mechanistic Investigation of the Spontaneous H2O2 Generation at the Interfaces of Salt-Containing Aqueous Droplets.

There is now much evidence that OH radicals and H2O2 are spontaneously generated at the air-water interface of atmospheric aerosols. Here, we investigated the effect of halide anions (Cl-, Br-, I-), which are abundant in marine aerosols, on this H2O2 production. Droplets were generated via nebulization of water solutions containing Na2SO4, NaCl, NaBr, and NaI containing solutions, and H2O2 was monitored as a function of the salt concentration under atmospheric relevant conditions. The interfacial OH radical formation was also investigated by adding terephthalic acid (TA) to our salt solutions, and the product of its reaction with OH, hydroxy terephthalic acid (TAOH), was monitored. Finally, a mechanistic investigation was performed to examine the reactions participating in H2O2 production, and their respective contributions were quantified. Our results showed that only Br- contributes to the interfacial H2O2 formation, promoting the production by acting as an electron donor, while Na2SO4 and NaCl stabilized the droplets by only reducing their evaporation. TAOH was observed in the collected droplets and, for the first time, directly in the particle phase by means of online fluorescence spectroscopy, confirming the interfacial OH production. A mechanistic study suggests that H2O2 is formed by both OH and HO2 self-recombination, as well as HO2 reaction with H atoms. This work is expected to enhance our understanding of interfacial processes and assess their impact on climate, air quality, and health.

Anions mediated electron-rich metalloporphyrin ionic framework as recyclable catalyst for conversion of urea into cyclic carbonates

As CO2 typical derivative, urea has the potential to be uniquely economical and green raw materials in generating cyclic carbonates via alcoholysis. Nonetheless, the existing processes for obtaining cyclic carbonates from urea alcoholysis reaction pose considerable challenges in achieving efficient catalyst recycling. Functional organic heterogeneous compounds are emerging materials for catalysis and enhanced reusability due to their large number of coordination sites, but they still fall short of effectively modulating the charge distribution of metal ions. Herein, drawing inspiration from the capacity of ionic liquids (ILs) to effectively control the distribution and transfer of spatial charges within materials, metalloporphyrin ionic framework catalysts were developed by combining metal ions and ILs for the transformation of urea into cyclic carbonates. This heterogeneous catalyst, featuring an adjustable structure and stable metal coordination sites on its surface, exhibits remarkable stability, resulting in a 2.7-fold reduction in catalyst dosage compared to other reported supported catalysts. Based on detailed experiments and DFT calculations, this tunable performance can be mainly explained by the effect of porphyrin zinc (II) and IL anions via molecular engineering. These atom-economical transformations provide a direct and selective access to valuable compounds from cheap and available urea using an efficient organic heterogeneous catalyst.

A Ferricyanide Anion-Philic Interface Induced by Boron Species within Carbon Framework for Efficient Charge Storage in Supercapacitors.

Carbon materials with hierarchical porous structures hold great potential for redox electrolyte-enhanced supercapacitors. However, restricted by the intrinsic inert and nonpolar characteristics of carbon, the energy barrier of anchoring redox electrolytes on the pore walls is relatively high. As such, the redox process at the interface less occurs, and the rate of mass transfer is impaired, further leading to a poor electrochemical performance. Here, a ferricyanide anion-philic interface made of in situ inserted boron species into carbon rings is constructed for enhanced charge storage in supercapacitors. Profiting from the unique component-driven effects, the polar anchoring sites on the pore wall can be built to grasp the charged redox ferricyanide anion from the bulk electrolyte and promote the redox process; the dynamics process is fastened correspondingly. Especially, the boron atoms in BC2O and BCO2 units with higher positive natural bond orbital values in the carbon skeleton are pinpointed as intrinsic active sites to bind the negatively charged nitrogen atoms in the ferricyanide anion via electrostatic interaction, confirmed by density functional theoretical calculations. This will suppress the shuttle and diffusion effects of the ferricyanide anion from the surface of the electrode to the bulk electrolyte. Finally, the well-designed PC-3 with high content of BC2O and BCO2 units can reach 1099 F g-1 at 2 mV s-1, which is a more than 2-fold increase over boron-free units of carbon (428 F g-1). The work offers a novel version for designing high-performance carbon materials with unique yet reaction species-philic effects.

The effect of salt anion in ether‐based electrolyte for electrochemical performance of sodium‐ion batteries: A case study of hard carbon

AbstractCompared with the extensively used ester‐based electrolyte, the hard carbon (HC) electrode is more compatible with the ether‐based counterpart in sodium‐ion batteries, which can lead to improved cycling stability and robust rate capability. However, the impact of salt anion on the electrochemical performance of HC electrodes has yet to be fully understood. In this study, the anionic chemistry in regulating the stability of electrolytes and the performance of sodium‐ion batteries have been systematically investigated. This work shows discrepancies in the reductive stability of the anionic group, redox kinetics, and component/structure of solid electrolyte interface (SEI) with different salts (NaBF4, NaPF6, and NaSO3CF3) in the typical ether solvent (diglyme). Particularly, the density functional theory calculation manifests the preferred decomposition of PF6− due to the reduced reductive stability of anions in the solvation structure, thus leading to the formation of NaF‐rich SEI. Further investigation on redox kinetics reveals that the NaPF6/diglyme can induce the fast ionic diffusion dynamic and low charge transfer barrier for HC electrode, thus resulting in superior sodium storage performance in terms of rate capability and cycling life, which outperforms those of NaBF4/diglyme and NaSO3CF3/diglyme. Importantly, this work offers valuable insights for optimizing the electrochemical behaviors of electrode materials by regulating the anionic group in the electrolyte.

Construction of a photo-assisted peroxymonosulfate activation system comprised of iron phthalocyanine/O-doped carbon nitride for efficient tetracycline removal

The integration of peroxymonosulfate (PMS) activation and photocatalysis is an effective advanced oxidation technology for the degradation of water pollutants. In this study, iron phthalocyanine (FePc) is successfully loaded onto O-doped porous carbon nitride (OCN) forming a catalyst working in photo-assisted PMS activation. OCN is a metal-free light absorber with strong visible light absorption, while FePc could serve as a photosensitizer and PMS activator. At the same time, the construction of FePc/OCN heterojunction can form the strong internal electric field for charge migration between FePc and OCN. As a result, complete tetracycline (TC) removal within 30 min can be achieved over optimal FePc/OCN catalyst in the presence of light and PMS. Systematic controlled experiments were also carried out to reveal the effect of pH, anion, and aqueous matrix. Cyclic stability test and Fe leaching experiments indicate that the synthesized FePc/OCN is relatively stable and shows the potential in practical application. Furthermore, a comprehensive investigation was conducted on the reactive species generated during the reaction process as well as the degradation pathways of the target pollutants. This work aims to provide new insights into the design of efficient catalysts for photo-assisted PMS activation.

Sulfidation of nano-Fe/Pd bimetal for highly efficient remediation of Cr (VI) from water: Enhanced reactivity and applicability

Sulfidation of zero-valent iron nanoparticles (S-nZVI) has been considered as a common means to improve its reactivity. In this paper, Pd and Na2S were chosen as the catalyst and sulfidation regent via a modified post sulfidation approach to fabricate a kind of sulfidated bimetallic Fe/Pd nanoparticles (S-nZVIPd). The structure and composition have been clearly confirmed by a combination of various techniques. Morphology analysis showed that S-nZVIPd had a core–shell framework and hierarchical structure. The reactivity performance of S-nZVIPd, nZVIPd and S-nZVI toward Cr (VI) remediation from aqueous solution was compared, and the underlying mechanisms for the improvement effect of Cr (VI) removal were also investigated. S-nZVIPd exhibited a superior remediation reaction to remove Cr (VI) with higher removal capacity of 234.9 mg/g, with the comparison of nZVIPd (192.3 mg/g) and S-nZVI (137.5 mg/g). Additionally, the effects of common anions and cations, pH, and temperature on Cr (VI) removal were also investigated in batch experiments. Also, kinetic fitting of results revealed that remediation obeyed a pseudo-second-order model, where the apparent activation energy was 37.7 KJ/mol, illustrating that the removal of Cr (VI) was mainly dominated by chemical reduction. The enhanced removal rate of Cr (VI) by S-nZVIPd suggested that Pd and FeSx played a dual role in accelerating the corrosion of nZVI, and were facilitated to electron transfer between nZVI and Cr (VI). The results indicated that the research of the novel S-nZVIPd composite delivered new ideas theoretically for specific inquiries in the future.

Molecular mechanism for the interaction of natural products with ionic liquids: Insights from MD and DFT study

Ionic liquids (ILs) as a class of green sustainable solvents, have been widely studied and used for the extraction, separation, recovery, and catalytic conversion of natural products (NPs). It is well known that elucidating the dynamic interaction behavior and mechanism of NPs in ILs can help rationally design efficient IL solvent systems at the molecular level. However, the interaction mechanism of rutin molecules and ILs is still unclear. In this contribution, an exhaustive theoretical study of dynamic interaction behavior and mechanism of rutin in six imidazolium-based IL systems is presented for the first time by combining molecular dynamics (MD) simulations with density functional theory (DFT) calculations. Meanwhile, the synergistic effect of cation and anion on rutin-IL complexes stability is deeply investigated by the frontier molecular orbital (FMO), electrostatic potential (ESP), radial distribution functions (RDF), averaged non-covalent interaction (aNCI) and non-covalent interaction (NCI). The final result provides a comprehensive molecular mechanism of interaction between rutin and ILs. The combination of various nonbonded forces (such as H-bond, van der Waals, repulsion and cation-π stacking) between molecules determines the stability of rutin-IL complexes. In addition, the structure, size and functional groups of ILs play a decisive role in promoting the formation of nonbonded forces. Our work shows that avoiding substituents with steric hindrance and electron-withdrawing effect in anions, considering the symmetry of the alkyl chain of imidazolium cations, and enhancing the cooperation between anions and cations is a promising pathway to develop a new and efficient ILs solvent systems for the NPs extraction, recovery, separation, detection, and catalytic conversion.

Optimized Lithium Ion Coordination via Chlorine Substitution to Enhance Ionic Conductivity of Garnet-Based Solid Electrolytes.

Garnet-type solid-state electrolytes attract abundant attentions due to the broad electrochemical window and remarkable thermal stability while their poor ionic conductivity obstructs their widespread application in all-solid-state batteries. Herein, the enhanced ionic conductivity of garnet-type solid electrolytes is achieved by partially substituting O2- sites with Cl- anions, which effectively reduce Li+ migration barriers while preserving the highly conductive cubic phase of garnet-type solid-state electrolytes. This substitution not only weakens the anchoring effect of anions on Li+ to widen the size of Li+ diffusion channel but also optimizes the occupancy of Li+ at different sites, resulting in a substantial reduction of the Li+ migration barrier and a notable improvement in ionic conductivity. Leveraging these advantageous properties, the developed Li6.35La3Zr1.4Ta0.6O11.85-Cl0.15 (LLZTO-0.15Cl) electrolyte demonstrates high Li+ conductivity of 4.21×10-6Scm-1. When integrated with LiFePO4 (LFP) cathode and metallic lithium anode, the LLZTO-0.15Cl electrolyte enables the solid-state battery to operate for more than 100 cycles with a high capacity retention of 76.61% and superior Coulombic efficiency of 99.48%. This work shows a new strategy for modulating anionic framework to enhance the conductivity of garnet-type solid-state electrolytes.

Nanostructured ZnO with Tunable Morphology from Double-Salt Ionic Liquids as Soft Template.

ZnO nanostructures with tunable morphology were synthesized by the hydrothermal method from two ionic liquids (ILs), 1-ethyl-3-methylimidazolium acetate [C2mim]CH3CO2 and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C2mim](CF3SO2)2N and their corresponding double-salt ILs (DSILs). ILs served as soft templates. DSILs were noted for the production of smaller particle size along with uniformity compared to their pure IL counterparts. A changeover of the shape of ZnO from nano-prism to a hexagonal disk-like structure was observed with the addition of [C2mim]CH3CO2 in the medium during synthesis while nano-dice- and rod-shaped particles were obtained from [C2mim](CF3SO2)2N. The effect of concentration of both ILs was explored for the variations of size and shape, and at high concentrations, the morphology was distinct and sharp with uniform size in each case. The synthesized products exhibited excellent phase (wurtzite) purity and polycrystalline nature. The smallest crystallite size was acquired from DSILs, indicating the advantageous effect of the dual anions. The selective adsorption effect of [C2mim]CH3CO2 on certain facets promoted the growth of ZnO clusters along the [1010] direction, while [C2mim](CF3SO2)2N favored the growth along the [0001] direction. Consequently, DSILs rendered interpenetrating hexagonal disks due to the combined action of the anions for controlling the shape. The band gap energies of the nanoparticles (NPs) were consistent with the distribution of size. Extremely strong red emission and negligible UV emission for the synthesized ZnO NPs demonstrate their potential in the advancement of optoelectronic devices.

Physicochemical properties and biological activities of new berberine-based salts with syringic acid as well as 3,5-dimethoxybenzoic acid as anions: Effect of temperature, concentration and anion

Two novel berberine-based salts (berberine syringate ([BBR][SA]) and berberine 3,5-dimethoxybenzote ([BBR][DA])) were prepared and characterized. Their thermal stability, solubility and octanol–water partition coefficient in aqueous solution and simulated physiological fluids (simulated gastric, simulated body, simulated intestinal fluids) were determined. Self-aggregation and association behaviors of two salts in aqueous solution have been investigated by conductimetric method at different temperatures and limiting molar conductivity, critical aggregation concentration, etc for [BBR][SA] and [BBR][DA] were calculated. The minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values of two salts were assessed to evaluate their antibacterial effects on four strains (Staphylococcus aureus, Bacillus subtilis, Candida albicans, and Streptococcus mutans). The effect of two synthetic salts on the esterase-like activity of BSA and their cytotoxicity evaluation against B16-F10 cancer cell line were also carried out. The obtained results were evaluated with regard to the influence of such parameters as temperature, concentration and the nature of the anion.

Novel 3D MIL-53(Fe)/graphene aerogel composites for boosted photocatalytic ibuprofen degradation under visible light: Process and mechanism

A highly efficiency process is urgently needed to remove the active pharmaceuticals contamination of water pollution. Herein, 3D MIL-53(Fe)/graphene aerogel (GMA) composites were designed to photodegrade ibuprofen (IBP) in the presence of persulfate (PS). The GMA composites exhibited high-speed electron-hole pairs transfer efficiency, higher specific surface area, excellent IBP degradation ability and easily recycling. The optimizing GMA-1 composite displayed a significant enhanced IBP photodegradation efficiency, in which the IBP degradation efficiency over GMA-1 reached closed to 100% within 60 min under visible light irradiation in the presence of PS. The effect of some vital anions were investigated. Furthermore, SO4·−, ·OH and ·O2− were identified as the main reactive species during the degradation of IBP. The photolytic degradation pathways of IBP and ecotoxicities of the intermediate products were also analyzed. This study may provide an alternative way for effectively removing IBP by 3D metal organic frameworks/graphene aerogel materials.

Structural effects of the carboxylate anion on Ru-catalyzed C—H arylation of (hetero)aromatic substrates containing N-donor directing group

Structural effects of the carboxylate anion on Ru-catalyzed C—H arylation of (hetero)aromatic substrates containing N-donor directing group