The Role of Sulphate and Phosphate Ions in the Recovery of Benzoic Acid Self-Enhanced Ozonation in Water Containing Bromides

The ozonation of aromatic compounds in low-pH water is ineffective. In an acidic environment, the decomposition of ozone into hydroxyl radicals is limited and insufficient for the degradation of organic pollutants. Radical processes are also strongly inhibited by halogen ions present in the reaction medium, especially at low pH. It was shown that even under such unfavorable conditions, some compounds can initiate radical chain reactions leading to the formation of hydroxyl radicals, thus accelerating the ozonation process, which is referred to as so-called “self-enhanced ozonation”. This paper presents the effect of bromides on “self-enhanced ozonation” of benzoic acid (BA) at pH 2.5. It is the first report to fully and quantitatively describe this process. The presence of only 15 µM bromides in water inhibits ozone decomposition and completely blocks BA degradation. However, the effectiveness of this process can be regained by ozonation in the presence of phosphates or sulphate. The addition of these inorganic salts to the bromide-containing solution helps to recover ozone decomposition and BA degradation efficiency. As part of this research, the fractions of hydroxyl, sulphate and phosphate radicals reacting with benzoic acid and bromides were calculated.     

Layered Oxide Cathodes Promoted by Crystal Regulation Strategies for Potassium-Ion Batteries

Layered oxide cathodes have demonstrated great potential for potassium-ion batteries (PIBs) on account of high reversible capacity, appropriate diffusion paths, and low cost. However, their electrochemical performance in PIBs is generally worse than that in lithium-ion batteries due to large structural changes and deformations during charging and discharging. To improve their potassium storage performance, a series of strategies have been developed in recent studies. In this review, we summarize the latest advancements in layered oxide cathodes for PIBs through different crystal regulation strategies, including transition metal layer doping, potassium content optimization, oxygen partial substitution, functional morphology construction and air stability improvement. Meanwhile, the relationship between the electrochemical properties and structural evolution of these modified cathodes is also investigated. In addition, the challenges and prospects of these layered oxide cathodes in PIBs are analyzed in detail, providing constructive insights for future applications of PIBs.     

Upgrading and expanding the electro-Fenton and related processes

The Fenton-based electrochemical advanced oxidation processes are currently recognized as the most effective technologies to achieve fast and complete degradation of target organic contaminants in water. Electro-Fenton was the pioneering process, but a larger mineralization is attained via UV and solar photoelectro-Fenton processes due to the occurrence of key photoreduction reactions. In practice, the decontamination effectiveness turns out to be limited as solution pH increases and the two-electron oxygen reduction reaction occurring at the cathode becomes inefficient or insufficient. Here, we focus on the current opinion in two crucial features of the reviewed processes: (i) trends in cathodic H₂O₂ electrogeneration, showing the oxygen reduction reaction upgrading upon use of new and/or more sustainable electrocatalysts, cathode configurations and reactor designs; and (ii) advances in iron-based catalysts, with the main purpose of expanding the application to a much wider pH range, eventually surpassing the classical acidic limitation associated to conventional Fenton's reaction.     

Enhanced degradation of 2,4-dinitrotoluene by ozonation in the presence of manganese(II) and oxalic acid

Manganese catalytic ozonation of 2,4-dinitrotoluene (DNT) in the presence of oxalic acid was studied. The addition of manganese ion (Mn²⁺) or oxalic acid alone in ozonation process did not enhance DNT degradation, but the addition of Mn²⁺ coupled with oxalic acid accelerated degradation of DNT. The DNT degradation efficiency was influenced by carbonate in the catalytic ozonation process. Kinetics study showed that Mn²⁺ catalytic ozonation significantly promoted the decomposition of ozone. Experimental results of electron spin resonance (ESR) demonstrated that addition of Mn²⁺ and oxalic acid produced much hydroxyl radicals in catalytic ozonation system than that in single ozonation system. These results suggested that catalytic ozonation followed hydroxyl radical-type mechanism. Mn²⁺ promoted decomposition of ozone to produce hydroxyl radical and it was oxidized into manganese oxide. Manganese oxide was reduced into Mn²⁺ by oxalic acid, which is the key step of catalytic process. Based on above results, a cycle catalytic mechanism of Mn²⁺ was proposed. Intermediates were determined by HPLC and GC–MS, and they mainly included aromatic organics and aliphatic carboxylic acids.     

Anode with the Active Layer for Electrosynthesizing Ozone in a System with Solid Polymer Electrolyte

The synthesis of catalytic coatings on porous titanium electrodes by the method of magnetron sputtering is considered. The content of dopant ions Fe³⁺ and F^– is optimized as regards the activity and stability of the PbO₂ catalyst in the reaction of ozone electrogeneration as well as the current efficiency with respect to ozone. It is shown that the best characteristics of the electrochemical ozone generator are observed on the PbO₂ catalyst doped with Fe³⁺ and F^– ions in the amount of 3–4 and 1–2 at %, respectively.     

锂硫电池硫正极催化转换反应的研究进展

单质硫作为电池的正极材料,其电化学过程历经多个步骤,完全放电生成最终产物是一个2电子反应. 低阶多硫化锂的生成需克服一定的能垒,且由Li₂S₂得到一个电子还原生成Li₂S的反应是速控步骤. 硫正极的反应动力学是决定锂硫电池电化学性能,如比能量、比功率、低温性能等的关键因素. 提高速控步骤的反应动力学还能加速可溶性多硫化锂Li₂S₄向不溶性Li₂S₂和Li₂S的转化,有利于减缓或消除多硫化锂的“穿梭效应”. 近年,已有大量的过渡金属氧化物、硫化物、碳化物、氮化物、磷化物,单原子催化剂和氧化还原电子中继体等被应用于催化硫正极反应,提高了电极的电化学性能和循环稳定性. 但是,目前详细的催化反应机制尚不完全清晰. 本文重点综述了这些化合物在硫正极反应中的作用机制,总结了近年来的研究进展,并对硫正极催化转换反应的研究和发展进行了展望.     

Cement-containing catalysts of ozone decomposition based on iron oxides

Cement-containing catalysts of ozone decomposition were synthesized on the basis of iron oxides obtained by ozonation of iron-containing aqueous solutions. X-ray diffraction analysis and Mössbauer spectroscopy showed that α-Fe₂O₃ occurs in the catalyst as highly dispersed nanoparticles. The catalysts obtained are efficient in the reaction of ozone decomposition and are as active as the best representatives of cement-containing catalysts of the GTT type.     

Developments in electrode materials for wastewater treatment

This review provides a current opinion about the most recent advances in the development of novel materials (i.e., anodes and cathodes), as well as new synthesis methodologies, which have been used in water and wastewater treatment by electrochemically driven oxidation technologies. The first section focuses on the advances to produce novel anodic materials comprising the active anodes — which play a key role in direct and indirect oxidation and the nonactive materials — which attract attention due to their high capacity to generate hydroxyl radicals. The second section describes recent progress on the novel emerging cathodic materials that are directly related to in situ electrogeneration of oxidants and are commonly applied in the electro-Fenton technology. Finally, the perspectives and prospects of these novel electrode materials for environmental applications are given.     

Characterization of atenolol transformation products in ozonation by using rapid resolution high-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry

This experiment investigated the transformation pathway of atenolol, a widely used β-blocker, in the ozonation process through the identification of generated intermediate compounds. In order to characterize the contribution of ozone and hydroxyl radical (•OH) in the transformation of atenolol, ozonation were performed at pH 2, 7 and 9. 15 major transformation products have been identified based on the chromatographic behavior of these compounds and the information obtained from accurate mass MS and MS/MS spectra. By comparing to the elution pattern of the identified transformation products and its fragmentation pattern in the MS/MS spectrum, a variety of isomers of the transformation products were characterized.Identified transformation products of atenolol are including its mono-, di and tri-hydroxylated derivatives as well as the aliphatic and aromatic ring breakdown products. Transformation of atenolol in the ozonation involved hydroxylation reaction, aromatic ring opening reaction, oxidation and cleavage of 2-hydroxy-3-(isopropylamino)propoxy group of atenolol. In ozonation, aromatic ring of atenolol was transformed through the reaction with both ozone and •OH whereas the aliphatic chain of atenolol was degraded mainly through the reaction with •OH. The results also indicated that both •OH and ozone involved in the aromatic ring opening reaction.     

Behavior of two different constituents of natural organic matter in the removal of sodium dodecylbenzenesulfonate by O3 and O3-based advanced oxidation processes

The objective of this study was to analyze the role played by two components of natural organic matter (NOM), gallic acid (GAL) and humic acid (HUM), in the removal of the surfactant sodium dodecylbenzenesulfonate (SDBS) from waters by O(3)-based oxidation processes, i.e., O(3)/H(2)O(2), O(3)/granular activated carbon (GAC), and O(3)/powdered activated carbon (PAC). It was found that the presence of low concentrations of these compounds (1 mg/L) during SDBS ozonation increases both the ozone decomposition rate and the rate of SDBS removal from the medium. Because of the low reactivity of SDBS with ozone, these effects are mainly due to an increase in the transformation rate of ozone into HO(*) radicals. Results obtained demonstrate that the presence of GAL and HUM during SDBS ozonation increases the concentration of O(2)(-*) radicals in the medium, confirming that GAL and HUM act as initiating agents of ozone transformation into HO(*). It was also found that this effect was smaller with a larger molecular size of the acid. Presence of GAL and HUM during SDBS removal by O(3)/H(2)O(2), O(3)/GAC, and O(3)/PAC systems also increases the SDBS degradation rate, confirming the role of these compounds as initiators of ozone transformation into HO(*) radicals.     

Ozone pretreatment and fermentative hydrolysis of wheat straw

Principles of the ozone pretreatment of wheat straw for subsequent fermentation into sugars are investigated. The optimum moisture contents of straw in the ozonation process are obtained from data on the kinetics of ozone absorbed by samples with different contents of water. The dependence of the yield of reducing sugars in the fermentative reaction on the quantity of absorbed ozone is established. The maximum conversion of polysaccharides is obtained at ozone doses of around 3 mmol/g of biomass, and it exceeds the value for nonozonated samples by an order of magnitude. The yield of sugar falls upon increasing the dose of ozone. The process of removing lignin from the cell walls of straw during ozonation is visualized by means of scanning electron microscopy.     

铜和铝离子/UV催化臭氧降解偶氮二异丁腈废水研究

利用多相催化臭氧(O3)工艺处理偶氮二异丁腈(AIBN)废水,探讨不同催化O3体系(Cu2+、Al3+、Cu2++Al3+/UV催化O3)对AIBN废水中氰类污染物的降解特性,并对不同催化O3体系的动力学特性进行研究。结果表明,金属离子对催化O3工艺的处理效率具有明显影响,不同催化O3工艺对CN-去除作用都呈现起始去除速率较高而后减弱的特点,其中Cu2+和Al3+共同催化O3工艺的整体去除率较高,优于单独Cu2+和Al3+的催化性能。这可能是由于p H变化、金属离子与CN-配合作用、金属离子和O3作用的综合影响结果。动力学研究结果表明,不同催化O3体系降解AIBN废水中的CN-污染物的氧化反应符合准一级动力学反应,表观反应速率常数k在0.0245~0.00301 min-1之间。     

Chlorherstellung mit Sauerstoffverzehrkathoden. Energieeinsparung bei der Elektrolyse

Chlorine is one of the most important base chemicals and is required for the manufacture of about two‐thirds of all chemical products such as polymers, crop protection and pharmaceutical products, products for drinking water purification, and ultrapure silicon for photovoltaics and electronics applications. The industrial chlorine production through the chlor‐alkali electrolysis has since 1975 mainly been based on the advanced membrane process. Chlorine recycling by manufacturing processes based on hydrogen chloride has also become increasingly important. The still very high energy demand for the electrochemical chlorine synthesis can be significantly reduced by up to 30 % if the hydrogen evolving cathodes in the classical processes are replaced by oxygen depolarized cathodes (ODC) which are well known from fuel cells. Hydrogen chloride electrolysis with ODCs is already carried out in world‐scale plants. The more important chlor‐alkali process with ODCs will be realized for the first time in 2011 in a demonstration unit with a chlorine capacity of 20000 tons per year in Uerdingen, Germany.     

Primary stage of the reaction between ozone and chloride ions in aqueous solution: Can chloride ion oxidation by ozone proceed via electron transfer mechanism?

It is found that chloride-ion oxidation by ozone via electron transfer mechanism does not occur due to its extremely high endoergicity and negligibly low rate. It is concluded that all processes supposedly associated with this reaction, particularly ozone decomposition in sodium chloride solution initiated by Cl^· atoms, do not take place either. It is shown that experimental data on the products and kinetic regularities of the interaction of O₃ with Cl⁻ contradict the assumption that the electron transfer reaction is its primary stage. In fact, chloride-ion oxidation by ozone proceeds via the mechanism of oxygen atom transfer. It is noted that in order to estimate the possibility of using an ozonated physiological saline in medicine, the formation of chloride-ion oxidation products and ozonation byproducts must be taken into account.     

Degradation Mechanism of Cationic Red X-GRL by Ozonation

The degradation mechanism of Cationic Red X-GRL was investigated when the intermediates, the nitrate ion and the pH were analyzed in the ozonation. The degradation of the Cationic Red X-GRL includes the de-auxochrome stage, the decolour stage, and the decomposition of fragment stage. During the degradation process, among the six nitrogen atoms of Cationic Red X-GRL, one is transferred into a nitrate ion, one becomes the form of an amine compound, and the rest four are transformed into two molecules of nitrogen. In the course of the ozonation of Cationic Red X-GRL, the direct attack of ozone is the main decolour effect.     

Porous Carbon Hosts for Lithium–Sulfur Batteries

Lithium–sulfur batteries (LSBs) are considered to be one of the most promising alternatives to the current lithium-ion batteries (LIBs) to meet the increasing demand for energy storage owing to their high energy density, natural abundance, low cost, and environmental friendliness. Despite great success, LSBs still suffer from several problems, including undermined capacity arising from low utilization of sulfur, unsatisfactory rate performance and poor cycling life owing to the shuttle effect of polysulfides, and poor electrical conductivity of sulfur. Under such circumstances, the design/fabrication of porous carbon–sulfur composite cathodes is regarded as an effective solution to overcome the above problems. In this review, different synthetic methods of porous carbon hosts and their corresponding integration into carbon–sulfur cathodes are summarized. The pore formation mechanism of porous carbon hosts is also addressed. The pore size effect on electrochemical performance is highlighted and compared. The enhanced mechanism of the porous carbon host on the sulfur cathode is systematically reviewed and revealed. Finally, the combination of porous carbon hosts and high-profile solid-state electrolytes is demonstrated, and the challenges to realize large-scale commercial application of porous carbon–sulfur cathodes is discussed and future trends are proposed.     

Chemiluminescence in the ozonation of C60 aqueous dispersions

Two types of chemiluminescence (CL) arising upon ozonation of crystalline, amorphous, and molecular aqueous dispersions of C₆₀ prepared in different ways were discovered and studied. The weak long-wavelength CL-1 (λ_max > 650 nm) is due to thermocatalytic decomposition of ozone on the surface of fullerene micro- and nanoparticles. The bright short-wavelength CL-2 (λ_max = 570 nm) is caused by generation of electronically excited states of the products of C₆₀ oxidation with ozone. CL-1 appears upon ozonation of aqueous dispersions of C₆₀ consisting of surface-hydrated crystalline micro- and nanoparticles by low concentrations of ozone. CL-2 is exhibited upon ozonation of nano-sized C₆₀ aqueous dispersions and colloid solutions, which contain C₆₀ molecules surrounded by a strong aqueous shell and their associates, by higher concentrations of ozone. Owing to shielding by the hydration shell, C₆₀ fullerene in aqueous dispersions is much less reactive towards ozone and forms oxidation products of different composition as compared with C₆₀ in organic solvents.     

Deciphering an Abnormal Layered‐Tunnel Heterostructure Induced by Chemical Substitution for the Sodium Oxide Cathode

Demands for large‐scale energy storage systems have driven the development of layered transition‐metal oxide cathodes for room‐temperature rechargeable sodium ion batteries (SIBs). Now, an abnormal layered‐tunnel heterostructure Na_0.44Co_0.1Mn_0.9O₂ cathode material induced by chemical element substitution is reported. By virtue of beneficial synergistic effects, this layered‐tunnel electrode shows outstanding electrochemical performance in sodium half‐cell system and excellent compatibility with hard carbon anode in sodium full‐cell system. The underlying formation process, charge compensation mechanism, phase transition, and sodium‐ion storage electrochemistry are clearly articulated and confirmed through combined analyses of in situ high‐energy X‐ray diffraction and ex situ X‐ray absorption spectroscopy as well as operando X‐ray diffraction. This crystal structure engineering regulation strategy offers a future outlook into advanced cathode materials for SIBs.     

Decomposition processes of an organic monolayer formed on Si(111) via a silicon-carbon bond induced by exposure to UV irradiation or ozone

The decomposition processes of an organic monolayer, which was formed on Si(111) via a Si-C covalent bond, induced by exposure to UV light irradiation or ozone, were investigated using attenuated total reflectance Fourier transform infrared spectroscopy. Exposure to both ozone and UV light resulted in a reduction of the intensities of the IR peaks corresponding to CH stretching vibration and bending scissors and the appearance of peaks corresponding to CO stretching and COH in-plane bending. The latter peaks initially increased, reached a maximum, and then decreased, indicating that the monolayer was decomposed through the formation of intermediates such as aldehyde and carboxylic acid. The monolayer was also decomposed by exposure only to UV light or ozone but more slowly as the time dependencies of the CH peaks showed. While the peaks corresponding to the CO stretching and the COH in-plane bending behaved similarly under the condition of exposure to ozone, they were not observed during decomposition induced by UV irradiation. These results show that, while the monolayer was decomposed through the formation of oxidized intermediates such as aldehyde and carboxylic acid under the condition of exposure to ozone, the decomposition of the monolayer under the condition of UV irradiation proceeded via cleavage of Si-C bonds by photogenerated electrons or holes without such oxidized intermediates. An increase of gauche defects as the decomposition proceeded was demonstrated by sum frequency generation spectroscopy.     

Intense Electrochemical Oxidation on Graphitized Carbon Electrodes in the Presence of Ozone

A new intense oxidation process for water treatment in which oxidation with ozone is coupled to electrochemical processes is described, and the results from its application to water purification are presented along with the discussion of its practical implementation. The use of graphitized carbon materials for this process is explained and tested experimentally. The use of glassy carbon for the anode enables us to achieve very high (up to 25 vol %) concentrations of ozone in the generated ozone?oxygen mixture. The material used for the cathode—graphitized carbon cloth (GCC) reinforced with Ni allows different electrocatalytic processes to proceed on its developed surface, and combines the high sorption capacity of this cathode and potentialcontrolled selectivity of cathodic electrochemical processes.