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Advanced Oxidation Processes for Wastewater Treatment
Published in Sreedevi Upadhyayula, Amita Chaudhary, Advanced Materials and Technologies for Wastewater Treatment, 2021
Gunjan Deshmukh, Haresh Manyar
Ozone is a highly reactive molecule that breaks down to dioxygen and oxygen radicals. It is a powerful oxidizing agent with E0 = +2.07 eV. Ozone readily reacts with a double bond capable of degrading several organic molecules containing double bonds. Ozone may react with water to produce a hydroxyl radical as a source of reactive oxygen molecule. The decomposition of ozone leads to the formation of H2O2, as elaborated in Scheme 8.3. The literature reports different mechanisms based on the catalyst system used. The efficiency of ozonolysis is pH-, temperature-, and pressure-dependent. The activity of ozone is controlled at low pH to prevent discriminative reaction of ozone with organic and inorganic constituents of the mixture. Further, the process demands optimum pressure and temperature to keep a check on the dissolution of ozone in the water. This directly affects the rate of the desired reaction.
Introduction
Published in Robert Bakhtchadjian, Bimodal Oxidation: Coupling of Heterogeneous and Homogeneous Reactions, 2019
Presently, the investigation of the oxidation phenomena of organic and inorganic matter with dioxygen is one of the largest domains of modern science. Despite the existence of the enormous scientific publications in this domain, presently, many aspects of the oxidation processes related to the bimodal reaction sequences do not have necessary interpretation in the literature. In my knowledge, at least, in the recent decades, there is not any comprehensive work on bimodal reaction sequences that is addressed to a wide audience. The existing articles or reviews, mainly, are either very specialized covering narrow areas or were written from the point of view of the subdisciplines of physics, chemistry, biology, or applied sciences. Obviously, this causes certain problems also in the immediate accessibility of the scientific information for readers who are not specialized in these relatively narrow areas. Unfortunately, often, the authors of scientific publications are not too concerned about the accessibility of the works for a wide range of readers2,3 One of the aims of this work is to acquaint the reader with the achievements in this area in an accessible form, however, resting in the frames of the scientific accuracy and terminology, as much as possible.
Basic Water Chemistry
Published in Frank R. Spellman, Handbook of Water and Wastewater Treatment Plant Operations, 2020
Typically we do not find most of the elements as single atoms. They are more often found in combinations of atoms called molecules. Basically, a molecule is the least common denominator of making a substance what it is. A system of formulae has been devised to show how atoms are combined into molecules. When a chemist writes the symbol for an element, it stands for one atom of the element. A subscript following the symbol indicates the number of atoms in the molecule. O2 is the chemical formula for an oxygen molecule. It shows that oxygen occurs in molecules consisting of two oxygen atoms. As you know, a molecule of water contains two hydrogen atoms and one oxygen atom, so the formula is H2O.
Current status of soil and groundwater remediation technologies in Taiwan
Published in International Journal of Phytoremediation, 2021
The Fenton’s reagent uses hydrogen peroxide (H2O2) and iron salts as a catalyst to react with one another. The reaction yields hydroxyl radicals (·OH), which are highly reactive and oxidize contaminants of soil or groundwater, such as chlorinated solvents. Due to the precipitating properties of iron the pH-level of the medium usually has to be decreased, which may have an adverse impact on the ecology. Ozone is a gaseous fluid that only leaves dioxygen (O2) behind after treatment. Unfortunately, this oxidant also reacts easily with other chemicals that are not considered as contaminants. The compounds permanganate (KMnO4) and sodium permanganate (NaMnO4) have a lower reaction time, contributing in penetration of more volume of the medium and further spread. Sodium persulfate Na2S2O8 has high solubility and leaves only a small amount of residual compounds. When applying to soil or groundwater, sodium persulfate is activated to derive the cation sulfate radical SO4¯, which reacts with many contaminants. Persulfate is persistent in soil and less harmful to microorganisms present at the site.
Synthesis, structure and catalytic promiscuity of a napthyl-pyrazole Mn(II) complex and structure–activity relationships
Published in Journal of Coordination Chemistry, 2019
Abhimanyu Jana, Paula Brandão, Harekrishna Jana, Atish Dipankar Jana, Gopinath Mondal, Pradip Bera, Ananyakumari Santra, Ajit Kumar Mahapatra, Pulakesh Bera
Complexes 3 and 4 show higher catecholase activity than recently reported compounds bearing similar scaffolds [24, 25]. A tentative catalytic cycle can be proposed based on the kinetics. The OAPH forms an adduct with the metal complex in the first step. The adduct yields aminophenol radical in the reaction with dioxygen, which is rate-determining step for the process. The OAP radical generates ortho-benzoquinone monoamine [48–51]. Representative CO activities of 3 and 4 are also performed using substrate 3,5-ditert-butyl catechol (3,5-DTBC). 3,5-DTBC has two bulky methyl groups in the ring with low reduction value for quinone-catechol transformation. Upon treatment of methanolic solution of 3 and 4 into 100 equivalents of 3,5-DTBC in aerobic condition, repetitive spectra were recorded (Figure 5). The colorless 3,5-DTBC solution turns into deep brown, indicating the conversion of 3,5-DTBC to corresponding quinone.
Application of RF discharge in oxygen to create highly oxidized metal layers
Published in Surface Engineering, 2018
A. I. Stadnichenko, L. S. Kibis, D. A. Svintsitskiy, S. V. Koshcheev, A. I. Boronin
Oxide films have numerous applications, such as solar cells, flat panel displays, sensors, optoelectronics, etc. [1–3] One of them is the preparation of model catalyst systems for the investigation of catalytic properties of oxidised metal species. This information is very important for understanding the nature of active centres of the catalysts and for establishing the mechanisms of catalytic reaction. Noble metals, such as Pt, Pd, Ag, Au, etc., are widely applied in catalytic processes [4–6], and therefore, analysis of their oxidised surface layers is of high importance. There are a lot of techniques to produce oxidised surfaces. One of the easiest methods is heating of samples in an atmosphere of molecular oxygen. However, this oxidation technique can be successfully applied only to a limited number of metals. Materials such as precious metals are inert towards dioxygen treatment [7]; moreover, a sample heating can lead to the decomposition of weekly bound oxygen species. The oxidised films can also be formed by irradiation of physisorbed O2 layers with low energy electrons or ultraviolet photons [8] or by exposure of atomic oxygen [9–11] or O3 [12,13]. However, these techniques only result in very thin oxidised films.