Characterization of the surface interacting ability of carbon black by means of electron paramagnetic resonance analysis of adsorbed Cu2+, supported by surface analysis and atomic absorption

Overcoming Acidic H2O2/Fe(II/III) Redox-Induced Low H2O2 Utilization Efficiency by Carbon Quantum Dots Fenton-like Catalysis

Fenton reaction has important implications in biology- and environment-related remediation. Hydroxyl radicals (^•OH) and hydroxide (OH^-) were formed by a reaction between Fe(II) and hydrogen peroxide (H₂O₂). The acidic H₂O₂/Fe(II/III) redox-induced low H₂O₂ utilization efficiency is the bottleneck of Fenton reaction. Electron paramagnetic resonance, surface-enhanced Raman scattering, and density functional theory calculation indicate that the unpaired electrons in the defects of carbon quantum dots (CQDs) and the carboxylic groups at the edge have a synergistic effect on CQDs Fenton-like catalysis. This leads to a 33-fold higher H₂O₂ utilization efficiency in comparison with Fe(II)/H₂O₂ Fenton reaction, and the pseudo-first-order reaction rate constant (k_obs) increases 38-fold that of Fe(III)/H₂O₂ under equivalent conditions. The replacement of acidic H₂O₂/Fe(II/III) redox with CQD-mediated Fe(II/III) redox improves the sluggish Fe(II) generation. Highly effective production of ^•OH in CQDs-Fe(III)/H₂O₂ dramatically decreases the selectivity of toxic intermediate benzoquinone. The inorganic ions and dissolved organic matter (DOM) in real groundwater show negligible effects on the CQDs Fenton-like catalysis process. This work presents a process with a higher efficiency of utilization of H₂O₂in situ chemical oxidation (ISCO) to remove persistent organic pollutants.

Electron spin resonance. Part two: a diagnostic method in the environmental sciences

A review is presented of some of the ways in which electron spin resonance (ESR) spectroscopy may be useful to investigate systems of relevance to the environmental sciences. Specifically considered are: quantititave ESR, photocatalysis for pollution control; sorption and mobility of molecules in zeolites; free radicals produced by mechanical action and by shock waves from explosives; measurement of peroxyl radicals and nitrate radicals in air; determination of particulate matter polyaromatic hydrocarbons (PAH), soot and black carbon in air; estimation of nitrate and nitrite in vegetables and fruit; lipid-peroxidation by solid particles (silica, asbestos, coal dust); ESR of soils and other biogenic substances: formation of soil organic matter carbon capture and sequestration (CCS) and no-till farming; detection of reactive oxygen species in the photosynthetic apparatus of higher plants under light stress; molecular mobility and intracellular glasses in seeds and pollen; molecular mobility in dry cotton; characterisation of the surface of carbon black used for chromatography; ESR dating for archaeology and determining seawater levels; measurement of the quality of tea-leaves by ESR; green-catalysts and catalytic media; studies of petroleum (crude oil); fuels; methane hydrate; fuel cells; photovoltaics; source rocks; kerogen; carbonaceous chondrites to find an ESR-based marker for extraterrestrial origin; samples from the Moon taken on the Apollo 11 and Apollo 12 missions to understand space-weathering; ESR studies of organic matter in regard to oil and gas formation in the North Sea; solvation by ionic liquids as green solvents, ESR in food and nutraceutical research.

Structural studies of marine exoskeletons: redox mechanisms observed in the Cu-supported CaCO3 surfaces tudied by EPR

Electron Paramagnetic Resonance (EPR), optical and infrared (IR) spectral studies have been performed on the pure and Cu-adsorbed exoskeletons of marine environment. The EPR spectrum of exoskeletons at room temperature exhibits a sharp signal at g approximately 1.9970. The possible redox mechanisms have been noticed on heating these exoskeletons in which the low spin Mn(3+) reduces to Mn(2+). The optical absorption spectra also give the evidence of the presence of Mn(3+) ions. The effects of thermal sintering on the EPR spectra have been studied and discussed in detail. The Cu-adsorbed samples clearly showed the adsorption of the Cu(2+) ions over CaCO(3) and the redox mechanism in these samples have been monitored by EPR.