Chemical Oxidation Process Research Articles

Review of chemical looping process for carbonaceous feedstock Conversion: Rational design of oxygen carriers

• Metal oxides as oxygen carriers and corresponding performances in the chemical looping partial oxidation process for hydrogen/syngas production are summarized. • The regulation strategies for further improving reactivity and cycling stability are discussed. • The ion diffusion and surface reactions are anatomized via theory calculations and characterizations. The chemical looping partial oxidation (CLPO) process as a technology of chemical looping process (CLP) is recognized as a potential strategy for the efficient and clean conversion of fuels into syngas/H 2 . Herein, in view of the importance of low-cost high-performance metal oxides as oxygen carriers (OCs) for this conversion, we systematically review the classification and CLPO applications of such OCs and discuss the improvement of OC reactivity and stability via the creation of metal–metal or metal–support synergism, the generation of oxygen vacancies, and the enhancement of deactivation resistance. Further, we present the results of theoretical and experimental characterizations probing ion diffusion and surface reactions to provide insights into the related reaction mechanisms and touch on the challenges and opportunities of developing metal oxides with excellent reactivity and long-term cycling stability in CLP. Thus, this review facilitates the design and performance regulation of OCs for future energy conversion systems.

In situ/operando structural tracking of Ni-Fe LDH

Deciphering <i>in situ</i> structure of layer double hydroxides (LDHs) and their corresponding mechanism of oxygen evolution reaction (OER) is essential to further development of LDH-based OER catalysts. In this issue of <i>Chem Catalysis</i>, Ko et al. demonstrated a scalable synthesis of ultrathin Ni-Fe LDH nanostructure, its chemical oxidation process, and its catalytic mechanism by <i>in situ/operando</i> spectroscopies, paving a solid pathway to potential practical application of LDH-based catalysts.

Measurement and Interpretation of the Effect of Electrical Sliding Speed on Contact Characteristics of On-Load Tap Changers

This paper analyzes the effect of sliding speed on the electrical conductivity and friction properties of the contact pair of an on-load tap changer (OLTC). Reciprocating current-carrying tribological tests were carried out on a rod–plate–copper–tin–copper contact galvanic couple at different sliding speeds in air and insulating oil media. The results show that as the sliding speed increases from 24 mm/s to 119 mm/s, the average contact resistance in air increases from 0.2 Ω to 0.276 Ω, and the average contact resistance in insulating oil also increases from 0.2 Ω to 0.267 Ω. At 119 mm/s, the maximum contact resistance in insulating oil reaches 0.3 Ω. The micro-topography images obtained by scanning electron microscopy show that with the increase in sliding speed, the wear mechanisms in the air are mainly abrasive wear and adhesive wear, and the wear mechanisms in oil are mainly layered wear and erosion craters; high sliding speed and arcing promote contact surface fatigue and crack generation. X-ray photoelectron spectroscopy was used to analyze the surface. The copper oxide in the air and the cuprous sulfide in the insulating oil cause the surface film resistance, and the total contact resistance increases accordingly. In addition, the test shows that 119 mm/s in air and 95 mm/s in insulating oil are the speed thresholds. Below these speed thresholds, the increase in contact resistance is mainly caused by mechanical wear. Above these thresholds, the increase in contact resistance is mainly caused by arc erosion and chemical oxidation processes. Non-mechanical factors exacerbate the deterioration of the contact surface and become the main factor for the increase in contact resistance.

Фотокаталитическая очистка воды от фенола и формальдегида

Industrial development leads to an increasing number of persistent and highly toxic organic compounds such as phenol and formaldehyde. Chemical oxidation processes (in particular, photooxidation) are widely used for water treatment and wastewater and groundwater treatment. As part of the work done, an assessment of the possibility of using photocatalysis for post-treatment of wastewater from phenol, formaldehyde, and their mixtures has been carried out. The processes of photooxidation of formaldehyde, phenol and their mixtures in an aqueous medium under the individual and combined effects of ultraviolet radiation and titanyl sulfate have been studied. The high efficiency (up to 90%) of photocatalytic post-treatment of wastewater containing phenol and formaldehyde has been determined. It has been established that ultraviolet water treatment under static conditions can significantly reduce the concentrations of phenol and formaldehyde to the values of the discharge standard into the city water canal. It has been proven that the introduction of titanyl sulfate microadditives (homogeneous photocatalytic process) makes it possible to intensify the oxidation process, while the addition of titanium(IV) compounds, due to its chemical inertness, will not have a toxic effect on the activated sludge biocenosis. Possible intermediate products of photooxidative degradation of phenol and formaldehyde are qualitatively determined. The kinetic dependences of the oxidation of phenol, formaldehyde and their mixtures are obtained, which allow further scaling up the process of photodegradation with the introduction of homogeneous catalysts for industrial facilities into the system. The proposed post-treatment method is included in the Best Available Techniques directory and will improve environmental and industrial safety.

Effect of the Application of a Green Preservative Strategy on Minced Meat Products: Antimicrobial Efficacy of Olive Mill Wastewater Polyphenolic Extract in Improving Beef Burger Shelf-Life.

The mincing process of raw meat favors microbial spoilage as well as chemical and enzymatic oxidation processes. In order to limit this degradative process, preservatives are routinely added to minced meat products. The role of olive mill wastewater polyphenolic extract as a replacement for synthetic preservatives in beef burger was assessed. The antioxidant capacity of the extract experimentally added to beef burger was evaluated using the oxygen radical absorbance capacity method (ORACFL) to assess the shelf-life, while the lipid oxidation was measured by thiobarbituric reactive substance (TBAR) determination. The antimicrobial activity was assayed by means of classical methods and predictive microbiology. The experimental addition of polyphenolic extract led to 62% lower lipid oxidation and 58% higher antioxidant capacity; it also successfully modulated spoilage microbial populations with an average growth reduction of 15% on day 7. Results indicate that olive mill wastewater polyphenolic extracts could be added to raw ground beef meat to act as natural antioxidants and to modulate microbial growth.

Highly response and humidity-resistant gas sensor based on polyaniline-functionalized Bi2MoO6 with UV activation

The bismuth molybdate (Bi2MoO6) has shown great application potential in the field of gas sensing owing to its abundant Lewis acid sites, suitable energy band and unique layered structure. In this work, a room temperature, highly response, selectivity and humidity-resistant NH3 gas sensor based on the Bi2MoO6/Polyaniline (BMO/PANI) nanocomposite was successfully developed by an in-situ chemical oxidative polymerization process. The obtained samples were characterized by X-ray diffractometer, UV–vis diffuse reflectance spectra, Transmission electron microscopy, X-ray photoelectron spectroscopy, etc. A series of gas-sensing properties studies were conducted with the assistance of UV light, which indicate that UV light illumination could significantly enhance the response of the prepared BMO/PANI sensor and short recovery time (71s). Additionally, the sensor also demonstrated excellent selectivity, repeatability, long-term stability, and moisture resistance. These outstanding characteristics of the sensor are attributed to the dramatic increase of surface state density upon activation by the UV light and the distinctive heterogeneous interface strengthens the interfacial charge transfer.

Understanding the nonradical activation of peroxymonosulfate by different crystallographic MnO2: The pivotal role of MnIII content on the surface

Manganese oxide-activated persulfate plays a critical role in water purification and in situ chemical oxidation processes, but the underlying mechanism needs to be further revealed. Herein, the detailed mechanism of MnO2 with various crystallographic structures (α-, β-, γ-, and δ-MnO2) towards peroxymonosulfate (PMS) activation was investigated. PMS activated by tunnel structured α-, β-, and γ-MnO2 showed higher acetaminophen (ACE) removal than layer structured δ-MnO2 with the removal efficiency following an order of α-MnO2 (85%) ≈ γ-MnO2 (84%) > β-MnO2 (65%) > δ-MnO2 (31%). Integrated with chemical quenching experiments, electron paramagnetic resonance, Raman spectra, X-ray photoelectron spectroscopy, and Langmuir-Hinshelwood model on kinetic data, both surface-bound PMS complexes and direct oxidation by surface manganese species (Mn(Ⅳ, Ⅲ)(s)) were disclosed as the dominant oxidation mechanism for ACE degradation in α-, β-, and γ-MnO2/PMS, which were rarely observed in previous reports. Moreover, the catalytic activity of α-, β-, and γ-MnO2 was positively correlated to the MnIII(s) content on the catalyst surface. Higher content of MnIII(s) would stimulate the generation of more oxygen vacancies, which was conducive to the adsorption of PMS and the formation of reactive complexes. Overall, this study might provide deeper insight into the nonradical activation mechanism of PMS over different crystallographic MnO2.

Wastewater treatment plants act as essential sources of microplastic formation in aquatic environments: A critical review

According to extensive in situ investigations, the microplastics (MPs) determined in current wastewater treatment plants (WWTPs) are mostly aged, with roughened surfaces and varied types of oxygen-containing functional groups (i.e., carbonyl and hydroxyl). However, the formation mechanism of aged MPs in WWTPs is still unclear. This paper systematically reviewed MP fragmentation and generation mechanisms in WWTPs at different treatment stages. The results highlight that MPs are prone to undergo physical abrasion, biofouling, and chemical oxidation-associated weathering in WWTPs at different treatment stages and can be further decomposed into smaller secondary MPs, including in nanoplastics (less than 1000 nm or 100 nm in size), suggesting that WWTPs can act as a formation source for MPs in aquatic environments. Sand associated mechanical crashes in the primary stage, microbes in active sewage sludge-related biodegradation in the secondary stage, and oxidant-relevant chemical oxidation processes (light photons, Cl2, and O3) in the tertiary stage are the dominant causes of MP formation in WWTPs. For MP formation mechanisms in WWTPs, external environmental forces (shear and stress forces, UV radiation, and biodegradation) can first induce plastic chain scission, destroy the plastic molecular arrangement, and create abundant pores and cracks on the MP surface. Then, the physicochemical properties (modulus of elasticity, tensile strength and elongation at break) of MPs shift consequently and finally breakdown into smaller secondary MPs or nanoscale plastics. Overall, this review provides new insights to better understand the formation mechanism, occurrence, fate, and adverse effects of aged microplastics/nanoplastics in current WWTPs.

Microstructural effect of various polyaniline-carbon nanotube core-shell nanocomposites on electrochemical supercapacitor electrode performance

Various carbon nanotubes-polyaniline (CNT-PANI) core-shell nanocomposites such as multiwalled carbon nanotube-PANI (PAM), carboxylic acid functionalized MWCNT (cMWCNT)-PANI (PACM) and amine-functionalized MWCNT (nMWCNT)-PANI (PANM) core-shell composites are successfully prepared by in-situ chemical oxidation process using ammonium persulphate (APS). Fourier transform infrared spectrum (FTIR) analysis proves the bonding nature between CNT core and PANI shell in nanocomposites. High-resolution transmission electron microscopy (HRTEM) and Field emission scanning electron microscopy (FESEM) images confirm the nanometer-sized PANI layer over CNT or core-shell structure of CNT-PANI nanocomposites. Further, the specific capacitance of the PAM electrode is 647 Fg−1 at scan rate 1 mV s−1 and 491 Fg−1 at current density 1 Ag−1 through cyclic voltammetry (CV) and galvanostatic charge-discharge respectively (GCD) in H2SO4 (1 M) medium under an applied potential between −0.2 to +0.8 V. Among the other CNT-PANI core-sell electrodes, the PAM electrode exhibits the highest retention of specific capacitance of 98 % and maximum Coulombic efficiency of 100 % after 5000th cycles of galvanostatic charge-discharge in the same applied potential. Due to its high specific capacitance and exceptional capacitance retention, PAM composite was fabricated as symmetric supercapacitors. The highest specific capacitance of 483 Fg−1 at a scan rate of 1 mV s−1 and 268 Fg−1 at a current density of 1 Ag−1 in 6 M H2SO4 is found for PAM composite. The symmetric device delivered the maximum energy density of 37 Wh kg−1 at a power density of 166 W kg−1.

Natural Stibnite for Lithium-/Sodium-Ion Batteries: Carbon Dots Evoked High Initial Coulombic Efficiency

HighlightsThe chemical process of local oxidation–partial reduction–deep coupling forstibnite reduction of carbon dots (CDs) is revealed by in-situ high-temperature X-raydiffraction.Sb2S3@xCDs anode delivers high initial coulombic efficiency in lithium ionbatteries (85.2%) and sodium ion batteries (82.9%), respectively.C–S bond influenced by oxygen-rich carbon matrix can restrain the conversion ofsulfur to sulfite, well confirmed by X-ray photoelectron spectroscopycharacterization of solid electrolyte interphase layers helped with densityfunctional theory calculations.CDs-induced Sb–O–C bond is proved to effectively regulate the interfacialelectronic structure.The application of Sb2S3 with marvelous theoretical capacity for alkali metal-ion batteries is seriously limited by its poor electrical conductivity and low initial coulombic efficiency (ICE). In this work, natural stibnite modified by carbon dots (Sb2S3@xCDs) is elaborately designed with high ICE. Greatly, chemical processes of local oxidation–partial reduction–deep coupling for stibnite reduction of CDs are clearly demonstrated, confirmed with in situ high-temperature X-ray diffraction. More impressively, the ICE for lithium-ion batteries (LIBs) is enhanced to 85%, through the effect of oxygen-rich carbon matrix on C–S bonds which inhibit the conversion of sulfur to sulfite, well supported by X-ray photoelectron spectroscopy characterization of solid electrolyte interphase layers helped with density functional theory calculations. Not than less, it is found that Sb–O–C bonds existed in the interface effectively promote the electronic conductivity and expedite ion transmission by reducing the bandgap and restraining the slip of the dislocation. As a result, the optimal sample delivers a tremendous reversible capacity of 660 mAh g−1 in LIBs at a high current rate of 5 A g−1. This work provides a new methodology for enhancing the electrochemical energy storage performance of metal sulfides, especially for improving the ICE.

Guiding questions for catalyst synthesis and use in selective catalytic oxidation reactions

This paper presents a brief history of catalysis, as well as of the processes of selective oxidation of hydrocarbons. On the other hand, the basic concepts involved in heterogeneous catalysis are mentioned, emphasizing the role of catalytic materials in chemical oxidation processes and posing a series of guiding questions to be followed when approaching a process catalyzed by solid materials. In the same way, the methods of synthesis of catalysts called in the literature as sol-gel and impregnation are shown, identifying the influence of each stage of preparation with the physical and chemical properties of the materials. Finally, a case study applied to the selective catalytic oxidation of methane and methanol using iron, molybdenum and vanadium catalytic materials synthesized by the sol-gel method is presented.

One-step solvothermal synthesis of wood flour carbon fiber/BiOBr composites for photocatalytic activation of peroxymonosulfate towards sulfadiazine degradation: Mechanisms comparison between photo, chemical and photo-chemical oxidation processes

Facile preparation of novel catalysts which can effectively activate peroxymonosulfate (PMS) under visible light is of great significance for rapid degradation of refractory organic chemicals in water. Herein, one-step solvothermal process was introduced to prepare carbon nanofiber incorporated bismuth oxybromide (BiOBr/SCF) composites, in which commercial wood flour was in-situ converted to carbon fiber with graphitic structure and incorporated with BiOBr via the process. At the existence of PMS, the prepared composites exhibited prominent visible-light photocatalytic degradation capability towards sulfadiazine (SDZ) with satisfying adaptability and recyclability. Specifically, the apparent pseudo-first order kinetic constant of BiOBr/SCF-180/PMS/visible light system (0.0724 min−1) exceeded those of both BiOBr/SCF-180/PMS (0.0462 min−1) and BiOBr/SCF-180/visible light (0.0111 min−1) systems. An integrated mechanism in the BiOBr/SCF/PMS/visible light system was elucidated through comparing the mechanisms amongst photo-oxidation, chemical oxidation and photo-chemical oxidation systems, in which photo-induced electron and hole, Bi3+/Bi5+ redox couple, graphitic structure and oxygen functional groups in the SCF all participated in the generation and conversion of the active species. The possible SDZ degradation pathway was also proposed. This work demonstrates a novel strategy to prepare high-efficient catalysts in the field of wastewater treatment.

Aromatic free Fenton process for rapid removal of phenol from refinery wastewater in an oscillatory baffled reactor

The need for clean, safe, and unpolluted water has recently become an important issue. Industrial processes such as petrochemical, pharmaceutical, pulp, and paper industries emit organic products in water, such as phenols, which are extremely toxic to aquatic life. The severe operating conditions, such as high pressure and temperature, of the conventional chemical oxidation processes of phenols cost a lot and limited the extensive application of the process. The present work depicts the development of a highly efficient and rapid oxidation process in an oscillating baffled reactor (OBR) to allow continuous and safe phenol removal under moderate operating conditions. Phenol conversion was studied as a function of initial concentration (300–500 ppm), pH (3–5), residence time (1–5 min), at constant amplitude (A = 4 mm), and frequency (f = 4 Hz) of oscillation and room temperature to achieve up to 94.6%. At 70 °C, 300 ppm starting concentration, pH = 3, 4 Hz frequency, and 4 mm amplitude, an exceptional removal of 99.858% phenol was achieved without additional extraction in just 3 min by optimizing the working parameters. This is a significant improvement over comparable processes at this temperature, and it was done in a reactor that scales up reliably, so this performance can likely be replicated on a large scale. Also, the present process was safe as it produced a nil concentration of the hazardous Fenton intermediate compounds.

Surface Modification of Decellularized Natural Cellulose Scaffolds with Organosilanes for Bone Tissue Regeneration.

The utility of plant tissues as scaffolding materials has been gaining significant interest in recent years owing to their unique material characteristics that are ideal for tissue regeneration. In this study, the degradation and biocompatibility of natural cellulosic scaffolds derived from Borassus flabellifer (Linn.) (BF) immature endosperm was improved by chemical oxidation and surface functionalization processes. Briefly, thus obtained cellulosic scaffolds were sequentially processed via a detergent exchange decellularization process followed by sodium periodate mediated oxidation and organosilane-based surface modification using amino (NH2)-terminated 3-aminopropyltriethoxysilane (APTES) and methyl (CH3)-terminated octadecyltrichlorosilane (OTS). Post oxidation and surface functionalization, the scaffolds showed improved physiochemical, morphological, and mechanical properties. Especially, the swelling capacity, total porosity, surface area, degradation kinetics, and mechanical behavior of scaffold were significantly higher in modified scaffold groups. The biocompatibility analysis demonstrated excellent cellular adhesion, proliferation and differentiation of osteoblasts with an evident upregulation of mineralization. Subcutaneous implantation of these scaffolds in a rat model demonstrated active angiogenesis, enhanced degradation, and excellent biocompatibility with concomitant deposition of a collagen matrix. Taken together, the native cellulosic scaffolds post chemical oxidation and surface functionalization can exclusively integrate the potential properties of native soft tissue with ameliorated in vitro and in vivo support in bone tissue engineering for nonloading bearing applications.

Guiding questions for the synthesis of catalyst and its application in selective catalytic oxidation reactions

This paper presents a brief history of catalysis, as well as the processes of selective oxidation of hydrocarbons. On the other hand, the basic concepts involved in heterogeneous catalysis are mentioned, emphasizing the role of catalytic materials in chemical oxidation processes and posing a series of guiding questions to be followed when approaching a process catalyzed by solid materials. In the same way, the methods of synthesis of catalysts known in the literature as sol-gel and impregnation are shown, identifying the influence of each stage of preparation with the physical and chemical properties of the materials. Finally, a case study applied to the selective catalytic oxidation of methane and methanol using iron, molybdenum, and vanadium catalytic materials synthesized by the sol-gel method is presented.

SEPARATION AND PURIFICATION OF PHARMACEUTICAL INDUSTRIAL WASTE WATER FOR REUSE BY TECHNIQUES OF ELECTRO-COAGULATION AND MICROBIAL ELECTROCHEMICAL CELL LYSIS PROCESS

The Advancement of human living standards within the twenty-first century, the issues of worldwide global climate change, rapid population increase, and environmental pollution have grown increasingly critical. Human activities have put plenty of strain on the ecosystem. Water contamination is one amongst several environmental issues that has to be addressed immediately. The rise in water-related disorders provides a sensible estimate of the extent of environmental degradation. Humans can utilize it day by day. Water will be employed in a pharmaceutical laboratory or industry for the formulation, chemical synthesis, and cleaning, among other things. The ultimate wastewater in numerous pharmaceutical laboratories and industries is treated in a very sort of ways to get rid of effluent and pollutants. That water, on the opposite hand, are often used for gardening and planting. Compared to other traditional procedures like biological, physical, chemical, adsorption, and advanced oxidation processes, the mixture technique of Electro coagulation and Microbial Electro Cell lysis has high de-colorization efficiency, is economically attractive, and produces little sludge. Color, COD, BOD, turbidity, and metal ions are among the pollutants that will be far away from wastewater using the electro coagulation procedure. We are researching the processes of electro coagulation and microbial electro cell lysis in order to make a wastewater treatment system that is reusable and produces better outcomes. It is incredibly inexpensive and easy, with only some substances being utilized within the treatment and administration. We are considering the longer term when creating such a design. KEYWORDS: Laboratory waste water, Electro-coagulation, Microbial electro cell lysis, Electrodes.

A high-throughput and cost-effective microplate reader method for measuring persulfates (peroxydisulfate and peroxymonosulfate).

Frequent use of persulfates as oxidants, for in situ chemical oxidation and advanced oxidation processes, warrants the need for developing a fast and efficient method for measuring persulfate concentrations in aqueous samples in the lab and on site. Here, we propose a modified method, based on Liang et al.'s (2008) spectrophotometric method, for measuring both peroxydisulfate (PDS) and peroxymonosulfate (PMS) in the aqueous samples. Our method involves a deep 96-well plate, multi-channel pipettes, a small orbital shaker, and a microplate reader; allowing the preparation and analysis of up to 96 samples in one run. Our proposed method shortens the time by 10 folds, consumes only ∼2% of the original reagents, and generates only ∼2% of the liquid waste compared to the Liang et al.'s method, thus, making our method high-throughput, time-efficient, and cost-effective with reduced environmental impact. The presented microplate reader method is validated in terms of linearity, LOD, LOQ, accuracy, precision, robustness, and selectivity. All the parameters satisfied the acceptance criteria, according to ICH guidelines. The linearity of calibration curves was evaluated by performing the F-test. In general, our method has linear ranges from 20 to 42,000 and 5 to 40,960μM for PDS and PMS, respectively. Accuracy (% recovery) results suggested that the LOD and LOQ based on the standard deviation of y-intercepts of the regression lines were the most reliable. The LOD/LOQ values for PDS and PMS were 14.7/44.1 and 4.6/14.4μM, respectively. The proposed method was also modified to work with a standard cuvette spectrophotometer and was validated. A comparison with the UHPLC analysis of PDS showed that our microplate reader method performed equivalently or even outperformed the UHPLC method, in the presence of common groundwater constituents and organic contaminants.

Biogas purification by a chemical absorption and biological oxidation process

Biogas purification by a chemical absorption and biological oxidation process

Facile growth of hierarchical SnO2@PPy composites on carbon cloth as all-solid-state flexible supercapacitors

A novel nanostructure of SnO2 @polypyrrole (PPy) is grown on carbon cloth (CC) by a facile solvothermal method and subsequent chemical oxidative polymerization process in this work. Benefiting from the combination of SnO2 and PPy, the as-obtained SnO2 @PPy/CC composites show significant improvement of electrochemical performances compared to single components. Specifically, the SnO2 @PPy/CC electrode achieves a high areal capacitance of 493.8 mF cm−2 at 1.0 mA cm−2, and good rate capability. Furthermore, all solid state flexible supercapacitors (FSCs) are constructed using SnO2 @PPy/CC electrodes and polyvinyl alcohol-potassium hydroxide gel electrolyte. Remarkably, the SnO2 @PPy/CC//SnO2 @PPy/CC FSCs show a high energy density of 0.7 mWh cm−3 at a power density of 4.74 mW cm−3, superior stability (90.5% capacitance retention after 10,000 cycles at 1.0 mA cm−2) and good mechanical flexibility. This work is expected to bring up inspirations for the development of high-performance FSCs.

Corrosion behaviour of hard coatings on Mg substrates

Abstract TiN and CrN coatings were deposited with magnetron sputtering on magnesium alloy AZ 31 hp. Magnesium oxide and metallic interlayers were used to improve the corrosion resistance of the compound. The magnesium oxide was produced by plasma chemical oxidation process. Polarization curves were recorded and the free corrosion potential was measured to test the corrosion resistance of all samples. The results were compared with uncoated Mg AZ31 alloy. The investigations showed that the corrosion resistance can be improved by the PVD coatings. Thick CrN coatings with Cr interlayer exhibited the best results. The protection with the magnesium oxide layer was insufficient up to now. Here, the etching before plasma chemical oxidation process should be improved.