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To evaluate the potential of compost based on municipal solid waste (MSW) and 20% legume pruning under a pyrolysis process, generated products, including solids (biochar), liquids (bio-oil), and gases (non-condensable gases), through experimentation in a pilot plant with a fluidized bed reactor at 450°C and gas chromatography/mass spectrometry have been analysed. In addition, the compost kinetic behaviour by thermogravimetric analysis (TGA), using the Flynn–Wall–Ozawa (FWO) method, has been investigated. Four different reaction zones, associated with lignocellulosic materials (hemicellulose, cellulose, and lignin) with a first step for water evaporation, in TGA curve have been observed. A biochar with low stability and aromaticity, considering high and low O/C and H/C ratios, respectively, has been obtained. The obtained pyrolytic liquids contain a high concentration of phenolic compounds because of a significant presence of lignins and other high molecular weight compounds in the original material. Moreover, the generated non-condensable gases consist mainly of short-chain compounds, such as alcohols, aldehydes, and alkenes produced from hemicellulose, cellulose, and proteins. [ABSTRACT FROM AUTHOR]

The electrochemical behavior of gentisaldehyde (2,5-dihydroxibenzaldehyde) on a glassy carbon electrode is studied by linear-sweep cyclic voltammetry finding one to three oxidation peaks, depending on both the number of cycles recorded and the pH, and one reduction peak. The oxidation product was the formyl-p-benzoquinone, generated by the oxidation of the biphenolic ring, and not the 2,5-dihydroxybenzoic acid (gentisic acid) that could be formed by oxidation of the aldehyde group. The mechanism proposed at pH < pK1 (8.42) from the analysis of cyclic and convoluted voltammograms involves the loss of an H+ ion from one hydroxyl group, a first quasi-reversible electron transfer to give a radical, and the release of a proton in a third step (the r.d.s.) followed by the second electron transfer to give the product. At pK1 < pH < pK2, the electroactive species is the anion that losses an ion H+ to give the dianion, the process being of the CEE type (chemical-electrochemical-electrochemical steps). At pH > pK2 (10.93) the process becomes of the EE type (electrochemical-electrochemical steps), no H+ ions being involved. Radicals species found justify the antioxidant capacity of gentisaldehyde. [ABSTRACT FROM AUTHOR]

The oxidation process occurring on mercury electrodes in the presence of hydrogen peroxide has been analized in basic solutions by polarography and voltammetry in their linear scan and differential pulse modes. The process involves Hg(I) ion - in addition to Hg(II) ion - and hydroperoxide radicals, these last formed at trace levels. To demonstrate this radical generation radical scavengers (antioxidants), characterized with the DPPH* radical scavenging assay, were employed. The interaction of the radicals with the antioxidant originate the decrease in signal, but the antioxidant itself does not react with the hydrogen peroxide in the absence of Hg. In the absence of antioxidant, the process is two-electron, being the rate-determining step the second electron transfer; at high concentrations of antioxidant, the oxidation corresponds to a reversible one-electron transfer followed by a chemical reaction between the hydroperoxide radicals and the antioxidant. A reaction scheme is proposed for intermediate antioxidant concentrations. [ABSTRACT FROM AUTHOR]

The dissociation constant of Sesamol (5-hydroxy-1,3-benzodioxol) was determined from the dependence of the UV-visible spectra with the medium acidity. A pK value of 10.1 ± 0.1, corresponding to the hydroxyl group, was obtained. The oxidation of sesamol was investigated on carbon electrodes using controlled-potential electrolysis, linear-sweep cyclic voltammetry and measurements at the foot of the first oxidation peak. Up to three oxidation peaks and one reduction peak were found. The dioxol ring of the dissociated sesamol undergoes a cleavage to give 3-substituted 1,4-benzoquinone, being the rate-determining step the second electron transfer. The formation of radicals in the ring cleavage explains in part the ability of sesamol to interact with reactive oxygen species (ROS). [ABSTRACT FROM AUTHOR]

Antioxidant products present a very high added value and are demanded in the market. The optimization of their extraction is a high-stakes matter for both economic and environmental points of view. Ultrasound extraction has been considered one of the most promising methods, so the relative importance of key parameters may have decisive economic significance. For this reason, different parameters that have influence on the extraction capacity such as ultrasound power, time, temperature, pH and % ethanol in water have been studied to know the relationships between the independent parameters and their influence on the extraction from Eucalyptus globulus leaves. An experimental Box-Behnken factorial design and subsequent analysis by neural networks have been used. The relative influence of each parameter varies according to the nature of the extracted compound. In this regard, the higher capacity of extraction of the selected antioxidant compounds by means of the variation of the operation conditions can be facilitated. For all the studied compounds, temperature has been the most important parameter for their extraction. The relative content (%) of bioactive compounds (terpenes) in the optimized Eucalyptus globulus extract has been performed by GC-MS analysis., (Copyright © 2021 The Author(s). Published by Elsevier B.V. All rights reserved.)

The valorization of urban solid waste compost (MSW) in two different composting conditions (different aeration and humidity) has been studied (we work with the hypothesis that the composting process can have a significant influence on a subsequent pyrolysis process). The influence of composting on subsequent pyrolysis of the material was assessed by examining the kinetics of the process, maximizing hydrogen production and minimizing the activation energy. The thermogravimetric analysis carried out on the samples have shown that they have a greater loss of weight of 9-14% at 270-275 °C and 22-27% at 444-446 °C. Using the Kissinger-Akahira-Sunose method, the activation energy values are found to be in the range of 57.78-581.69 kJ mol -1 , and the assumption that pyrolysis of compost could be modeled by a first-order reaction may be a suitable approximation. The analysis of the gases produced from the pyrolysis process revealed that hydrogen increases in concentration as composting time advances until intermediate time. In this form, the composting process could be a suitable previous treatment for improving the pyrolysis process. In fact, decreasing aeration and moisture in the MSW composting process led to the production of an increased amount of hydrogen (8.3%) by pyrolysis of the resulting compost and also to a decreased activation energy (102.8 kJ mol -1 ). These effects were also observed before the end of the composting process in the form of maximum hydrogen production and minimum activation energy after 20 days., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

The anodic oxidation of mercury in the presence of hydrogen peroxide in differential pulse voltammetry (DPV) was used to determine the antioxidant (AO) character of radical scavengers. Hydroperoxide radical is formed at the potentials of the oxidation peak on mercury electrodes, such radical reacting with the antioxidants in different extension. The parameter C10 (antioxidant concentration at which the peak area decreases by 10%) is used to measure the scavenging activity of the individual antioxidants. To establish the scavenging activity of antioxidant mixtures as a whole, the parameter, μ10 as the reverse of V10, V10 being the volume necessary to decrease the peak area in DPV by 10%, was selected. Higher μ10 values correspond to higher scavenging activity. The studies have been extended to aqueous extracts of some species. The results may be useful in explaining the effect of spices in vitro and in vivo studies.

Antioxidant activity of a number of small (low molecular weight) natural compounds found in spices, condiments or drugs (gallic acid, sesamol, eugenol, thymol, carvacrol, vanillin, salicylaldehyde, limonene, geraniol, 4-hexylresorcinol, etc.) has been evaluated using electrochemical and DPPH• radical scavenging measurements. Structural analysis of the tested compound suggest a remarkable activity for phenol derivatives and the importance of the -R groups located on the phenolic ring in the molecule's ability to act as free radical scavenging as well as their influence in the electrochemical behavior. The voltammetric method can be used for the determination of the antioxidant capability in the same manner as the DPPH• radical scavenging because of the correlation found between oxidation potentials and anti-radical power (ARP = 1/EC₅₀). Such electrochemical determination is fast and cheap and allows making measurements under a variety of experimental conditions. The accuracy of the electrochemical measurements is the same for all the compounds, irrespective of their scavenging activity, the opposite of what occurs in the DPPH• test.

The influence of control parameters (aeration, moisture, and C/N ratio) during composting of a municipal solid waste (MSW)-legume-trimming residue (LTR) mixture was studied at a pilot plant scale. Factors measured included the composition of the main volatile organic carbons (VOCs) emitted including limonene, β-pinene, 2-butanone, undecane, phenol, toluene, and dimethyl disulfide. Polynomial models were found to reproduce the experimental results with errors at less than 10%. The relative influence of the independent variables on temperature and selected VOCs followed the order: aeration > moisture > C/N. A high aeration rate results in higher (strong negative effect) values on selected VOCs emissions (41-71% on emitted VOCs variation). Moisture had a positive and negative effect depending on the selected VOCs. A high C/N ratio caused lower production of VOCs except for undecane and 2-butanone. Providing an aerobic environment (0.05 Lair kg(-1) min(-1)), high C/N ratios (>50), and medium moisture (55%) minimize emitted VOCs during MSW composting, ultimately resulting in less odors in the surrounding environment.

The mutagenic activities in the Ames test against S. typhimurium TA100 for a series of alpha-dicarbonyl compounds are examined together with the formation constants of the adducts formed between such compounds and guanine and guanosine. Correlations between the equilibrium constants, the apparent reaction enthalpies, and the mutagenic activity are presented. These correlations imply that the mutagenic activity is related to the chemical reactivity of the dicarbonyl compounds with the puric bases.