Fenton chemistry encompasses reactions of hydrogen peroxide in the presence of iron to generate highly reactive species such as the hydroxyl radical and possibly others. In this review, the complex mechanisms of Fenton and Fenton-like reactions and the important factors influencing these reactions, from both a fundamental and practical perspective, in applications to water and soil treatment, are discussed. The review covers modified versions including the photoassisted Fenton reaction, use of chelated iron, electro-Fenton reactions, and Fenton reactions using heterogeneous catalysts. Sections are devoted to nonclassical pathways, by-products, kinetics and process modeling, experimental design methodology, soil and aquifer treatment, use of Fenton in combination with other advanced oxidation processes or biodegradation, economic comparison with other advanced oxidation processes, and case studies.

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Advanced Oxidation Processes for Organic Contaminant Destruction Based on the Fenton Reaction and Related Chemistry

This paper reviews recent progress made in identifying electrocatalysts for carbon dioxide (CO2) reduction to produce low-carbon fuels, including CO, HCOOH/HCOO−, CH2O, CH4, H2C2O4/HC2O4−, C2H4, CH3OH, CH3CH2OH and others. The electrocatalysts are classified into several categories, including metals, metal alloys, metal oxides, metal complexes, polymers/clusters, enzymes and organic molecules. The catalyts' activity, product selectivity, Faradaic efficiency, catalytic stability and reduction mechanisms during CO2 electroreduction have received detailed treatment. In particular, we review the effects of electrode potential, solution–electrolyte type and composition, temperature, pressure, and other conditions on these catalyst properties. The challenges in achieving highly active and stable CO2 reduction electrocatalysts are analyzed, and several research directions for practical applications are proposed, with the aim of mitigating performance degradation, overcoming additional challenges, and facilitating research and development in this area.

A review of catalysts for the electroreduction of carbon dioxide to produce low-carbon fuels

A major portion of the toxicity of hydrogen peroxide in Escherichia coli is attributed to DNA damage mediated by a Fenton reaction that generates active forms of hydroxyl radicals from hydrogen peroxide, DNA-bound iron, and a constant source of reducing equivalents. Kinetic peculiarities of DNA damage production by hydrogen peroxide in vivo can be reproduced by including DNA in an in vitro Fenton reaction system in which iron catalyzes the univalent reduction of hydrogen peroxide by the reduced form of nicotinamide adenine dinucleotide (NADH). To minimize the toxicity of oxygen radicals, the cell utilizes scavengers of these radicals and DNA repair enzymes. On the basis of observations with the model system, it is proposed that the cell may also decrease such toxicity by diminishing available NAD(P)H and by utilizing oxygen itself to scavenge active free radicals into superoxide, which is then destroyed by superoxide dismutase.

https://science.sciencemag.org/content/sci/240/4857/1302.full.pdf

DNA damage and oxygen radical toxicity

The increase in atmospheric carbon dioxide is linked to climate changes; hence there is an urgent need to reduce the accumulation of CO2 in the atmosphere. The utilization of CO2 as a raw material in the synthesis of chemicals and liquid energy carriers offers a way to mitigate the increasing CO2 buildup. This review covers six important CO2 transformations namely: chemical transformations, photochemical reductions, chemical and electrochemical reductions, biological conversions, reforming and inorganic transformations. Furthermore, the vast research area of carbon capture and storage is reviewed briefly. This review is intended as an introduction to CO2, its synthetic reactions and their possible role in future CO2 mitigation schemes that has to match the scale of man-made CO2 in the atmosphere, which rapidly approaches 1 teraton.

The teraton challenge. A review of fixation and transformation of carbon dioxide

Because sunlight is diffuse and intermittent, substantial use of solar energy to meet humanity’s needs will probably require energy storage in dense, transportable media via chemical bonds. Practical, cost effective technologies for conversion of sunlight directly into useful fuels do not currently exist, and will require new basic science. Photosynthesis provides a blueprint for solar energy storage in fuels. Indeed, all of the fossil-fuel-based energy consumed today derives from sunlight harvested by photosynthetic organisms. Artificial photosynthesis research applies the fundamental scientific principles of the natural process to the design of solar energy conversion systems. These constructs use different materials, and researchers tune them to produce energy efficiently and in forms useful to humans. Fuel production via natural or artificial photosynthesis requires three main components. First, antenna/reaction center complexes absorb sunlight and convert the excitation energy to electrochemical ener...

/pdf/solar-fuels-via-artificial-photosynthesis-24g8xk966y.pdf

Solar Fuels via Artificial Photosynthesis

Absolute rate constants for reactions of aliphatic carbon‐centered radicals in aqueous solutions have been compiled and evaluated from the literature. Rate constants are included for reactions of radicals with inorganic and organic compounds and for decay by radical–radical reactions. The radicals were generated by radiolysis, photolysis, or other techniques, and their rate constants were determined generally by kinetic spectrophotometry. The tables include data for over 2,500 reactions of 373 radicals from 740 literature references.

Rate Constants for Reactions of Aliphatic Carbon‐Centered Radicals in Aqueous Solution

The role of cobalt and iron corroles in catalytic CO2 reduction has been studied. Chemical, electrochemical, and photochemical reductions of the stable metal corroles Ph3PCoIII(tpfc) (tpfc = 5,10,15-tris(pentafluorophenyl)corrole), ClFeIV(tpfc), and ClFeIV(tdcc) (tdcc = 5,10,15-tris(2,6-dichlorophenyl)corrole) have been carried out in acetonitrile solutions. Stepwise reduction to the [MII(tpfc)]- and [MI(tpfc)]2- states was observed in all cases. Gradual reduction with sodium amalgam permitted recording of the optical absorption spectra of the various oxidation states and showed that the MI state reacts with CO2. Cyclic voltammetry in Ar-saturated acetonitrile solutions permitted determination of the following half-wave potentials:  for Ph3PCoIII(tpfc), 1.11 V, 0.72 V, −0.42 V (Epc), −1.44 V, −2.3 V (Epc); for ClFeIV(tpfc), 0.44 V, −1.01 V (Epc), −1.60 V, −2.2 V (Epc); for ClFeIV(tdcc), 0.24 V, −1.18 V (Epc), −1.78 V vs SCE with a scan rate of 0.1 V s-1. Cyclic voltammetry in CO2-saturated solutions indic...

Reduction of cobalt and iron corroles and catalyzed reduction of CO2

Cinetique et mecanisme de l'oxydation de NADH par l'ion ferroceniumyle et quelques derives substitues de cet ion dans le propanol-1 aqueux

Oxidation of NADH involving rate-limiting one-electron transfer

Iron and cobalt porphyrins (FeP and CoP) are utilized as electron-transfer mediators to effect photochemical reduction of CO2 in homogeneous solutions. The species that activate and reduce CO2 are the Fe0P and Co0P formed by reduction of the starting materials. Reduction of the metalloporphyrins (MP) is achieved by photolysis in dimethylformamide or acetonitrile solutions containing triethylamine (TEA) as a reductive quencher. The photoreduction is efficient for the MIIIP → MIIP stage and probably occurs by an intramolecular electron transfer from an axially bound TEA. However, TEA does not bind to the reduced metal complexes, and the quantum efficiency is much lower for the subsequent reduction steps. Considerably higher quantum yields are obtained by adding p-terphenyl (TP) as a sensitizer. TP is very effectively photoreduced by TEA to form the radical anion, TP•-, which has a sufficiently negative reduction potential to reduce CoIP and FeIP rapidly to their M0P state. The rate constants for these react...

P-terphenyl-sensitized photoreduction of co2 with cobalt and iron porphyrins. interaction between co and reduced metalloporphyrins

Several iron porphyrins have been reduced by photochemical and radiation chemical methods, in organic solvents and in aqueous solutions, from FeIIIP to FeIIP to FeIP and beyond. In aqueous solutions, the FeIP state is relatively stable for the tetrakis(N-methyl-2-pyridyl)porphyrin at high pH but is shorter lived in neutral and acidic solutions. The FeIP state of tetrakis(N-methyl-3-pyridyl)porphyrin and tetrakis(N-methyl-4-pyridyl)porphyrin are short-lived at any pH. Decay of FeIP is accelerated by H+ and by CO2, probably via reaction with the Fe0P state formed upon disproportionation of FeIP. These reactions may lead to formation of H2 and CO, respectively, and to formation of the chlorin, FeIIPH2, as a side product. The FeIP state is also observed as a stable product in several organic solvents. This is observed by photolysis of iron tetraphenylporphyrin and several of its derivatives (e.g., trimethyl-, dichloro- and pentafluorophenyl), mainly in dimethylformamide and acetonitrile solutions, using triet...

J Grodkowski

Papers

Rate Constants for Reactions of Aliphatic Carbon‐Centered Radicals in Aqueous Solution

Reduction of cobalt and iron corroles and catalyzed reduction of CO2

Oxidation of NADH involving rate-limiting one-electron transfer

P-terphenyl-sensitized photoreduction of co2 with cobalt and iron porphyrins. interaction between co and reduced metalloporphyrins

Iron Porphyrin-Catalyzed Reduction of CO2 - Photochemical and Radiation-Chemical Studies