Topic
Oxalic acid
About: Oxalic acid is a research topic. Over the lifetime, 11584 publications have been published within this topic receiving 173263 citations. The topic is also known as: ethanedioic acid & H2ox.
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TL;DR: Au-chitosan nanocomposites are successfully proposed as sensitive and selective electrochemical sensors for the determination of caffeic acid, an antioxidant that has recently attracted much attention because of its benefits to human health.
Abstract: In this work, colloidal gold nanoparticles (AuNPs) stabilized into a chitosan matrix were prepared using a green route. The synthesis was carried out by reducing AuIII to Au0 in an aqueous solution of chitosan and different organic acids (i.e., acetic, malonic, or oxalic acid). We have demonstrated that by varying the nature of the acid it is possible to tune the reduction rate of the gold precursor (HAuCl4) and to modify the morphology of the resulting metal nanoparticles. The use of chitosan, a biocompatible and biodegradable polymer with a large number of amino and hydroxyl functional groups, enables the simultaneous synthesis and surface modification of AuNPs in one pot. Because of the excellent film-forming capability of this polymer, AuNPs–chitosan solutions were used to obtain hybrid nanocomposite films that combine highly conductive AuNPs with a large number of organic functional groups. Herein, Au–chitosan nanocomposites are successfully proposed as sensitive and selective electrochemical sensors...
106 citations
TL;DR: The use of FTIR to probe the adsorption of oxalic and salicylic acids, and of mixtures of both, onto TiO 2 (Degussa P-25) demonstrates the potential of the technique to characterise the evolution of the catalyst with time, including surface poisoning.
106 citations
TL;DR: In this paper, the ozone-hydrogen peroxide (O3/H2O2) system was applied in a closed reactor with oxalic acid and 1,1,2 trichloroethane.
106 citations
TL;DR: In this paper, the authors evaluate the production of ethanol by Scheffersomyces (Pichia ) stipitis CBS6054, a native xylose fermenting yeast, from sugars contained in the giant reed ( Arundo donax L.) hemicellulosic hydrolysate.
Abstract: The objective of this study was to evaluate the production of ethanol by Scheffersomyces ( Pichia ) stipitis CBS6054, a native xylose fermenting yeast, from sugars contained in the giant reed ( Arundo donax L.) hemicellulosic hydrolysate. A response surface methodology with two input parameters, severity factor and oxalic acid concentration ranging from 2.87 to 4.05 and from 2 to 8 (% w oxalic acid/w solid dry matter), respectively, was employed to minimize degradation products and maximize sugar release. However, at the optimum condition for sugar release (43.8 g l −1 ), levels of toxic degradation products (acetic acid, furfural, HMF and phenolic compounds) were considered too high for yeast fermentation. The condition to minimize degradation products and maximize sugar yields was judged to be 2.87 severity factor and 5.0% oxalic acid concentration. At this condition 26.0 g l −1 xylose, 5.0 g l −1 glucose and 2.4 g l −1 arabinose were recovered in giant reed hydrolysate fraction. Adjustment of pH to 5.0 with Ca(OH) 2 decreased xylose, glucose and acetic acid, 22%, 8% and 27% respectively. Increasing the initial pH from 5.0 to 5.5, 6.0 and 6.5, respectively, significantly improved the fermentability of the giant reed hemicelluloses hydrolysate; no fermentation was observed at pH 5.0 after 96 h, while 8.20 g l −1 of ethanol was obtained at pH 6.0 after 48 h, with an ethanol yield of 0.33 ( g e / g s ) and a productivity of 0.17 g l −1 h −1 . The optimum pH of acid hydrolysate fermentation for ethanol production was 6.0–6.5.
106 citations
TL;DR: The properties of copper-based pillared clays (Cu-PILC) have been studied and compared with those of the analogous iron-based clays in the wet hydrogen peroxide catalytic oxidation (WHPCO) of model phenolic compounds (p-coumaric and p-hydroxybenzoic acids) and real olive oil milling wastewater (OMW) as discussed by the authors.
Abstract: The properties of copper-based pillared clays (Cu-PILC) have been studied and compared with those of the analogous iron-based clays (Fe-PILC) in the wet hydrogen peroxide catalytic oxidation (WHPCO) of model phenolic compounds (p-coumaric and p-hydroxybenzoic acids) and real olive oil milling wastewater (OMW). These two catalysts show comparable performances in all these reactions, although they show some differences in the rates of the various steps of reaction. In particular, Cu-PILC shows a lower formation of oxalic acid (main reaction intermediate) with respect to Fe-PILC. Both catalysts show no leaching of the transition metal differently from other copper-based catalysts prepared by wetness impregnation on oxides (alumina, zirconia) or ion-exchange of clays (bentonite) or zeolite ZSM-5. No relationship was observed between copper reducibility in the catalyst and the performance in WHPCO, as well as between the rate of copper leaching and catalytic behavior. Cu-PILC shows a comparable activity to dissolved Cu2+ ions, although the turnover number is lower assuming that all copper ions in Cu-PILC are active. Cu-PILC shows a high resistance to leaching and a good catalytic performance, which was attributed to the presence of copper essentially in the pillars of the clay. A high efficiency in H2O2 use in the first hour of reaction with the participation of dissolved O2 in solution was also shown. For longer reaction times, however, the efficiency of H2O2 use considerably decreases.
105 citations