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.

Catalytic ozonation of organic pollutants in the presence of cerium oxide–carbon composites

Abstract: Cerium oxide–carbon composites were prepared and tested as ozonation catalysts for the removal of two selected carboxylic acids, oxalic and oxamic, and one textile dye (C.I. Reactive Blue 5). The results were compared with those obtained in non-catalytic ozonation and ozonation catalysed by cerium oxide and carbon materials (activated carbon, carbon xerogel). With the exception of cerium oxide, a total degradation of oxalic acid was obtained in approximately 90 min for all prepared catalysts and the catalytic activity increases with the amount of carbon present in the composites. Despite of oxamic acid be more refractory to ozonation than oxalic acid, 75% of oxamic acid removal was achieved after 10 h of reaction in the presence of the ceria-activated carbon composite with 90% of carbon material. In the mineralization of the textile dye, the catalytic activity of the composites increases with the amount of activated carbon introduced.

Screening, Manufacturing, Photoluminescence, and Molecular Recognition of Co-Crystals: Cytosine with Dicarboxylic Acids

Abstract: A workflow for screening and manufacturing co-crystals was used to produce 4:1 co-crystal of cytosine−oxalic acid dihydrate, 2:1 co-crystal of cytosine−malonic acid, and 2:1 co-crystal of cytosine−succinic acid with melting points of 270.2, 219.2, and 249.5 °C, and Ksp values of 8.21 × 10−12 m5, 4.90 × 10−5 m3, and 3.11 × 10−6 m3 in water at 25 °C, respectively. 4:1 co-crystal of cytosine−oxalic acid dihydrate crystallized in the P21/c space group. Both 2:1 co-crystal of cytosine−malonic acid and 2:1 co-crystal of cytosine−succinic acid crystallized in the P1 space group. Co-crystals of cytosine with dicarboxylic acids all possessed a self-assembled cyclic pattern of R22(12) forming by a pair of N−H···O hydrogen bonds within a dimeric motif of cytosine. The self-recognition pairing of cytosine here resembled the standard hydrogen bonding pattern in the Watson−Crick complementary base pairing of guanine and cytosine but without the middle N−H···N interaction. Both photoluminescence (PL) emission intensity...

Kinetics of Mo, Ni, V and Al leaching from a spent hydrodesulphurization catalyst in a solution containing oxalic acid and hydrogen peroxide

Abstract: The kinetics of molybdenum, nickel, vanadium and aluminium leaching from a spent hydrodesulphur-ization catalyst in a solution containing oxalic acid and hydrogen peroxide was investigated. The effectsof temperature and particle size were examined. In addition, the reaction mechanism for the dissolutionof the spent catalyst was discussed. The results of the kinetic analysis for various experimental condi-tions indicated that the reaction rate of leaching process is controlled by chemical reaction at the particlesurface. The values of the activation energies of 31±2, 36±4, 30±4 and 57±3kJmol −1 for Mo, Ni, V andAl, respectively, are characteristic for mechanism controlled by chemical reaction.© 2010 Elsevier B.V. All rights reserved. 1. IntroductionCatalysts containing nickel, cobalt and molybdenum on the -aluminasupportarecommonlyusedforthehydrodesulphurizationof petroleum fractions. In every catalytic operation, the activity ofthe catalyst gradually decreases. At a certain point the catalystsbecome inactive due to the accumulation of metals like Mo, V, Ni,Co, Fe, Ti, Sn, and As on their surface [1]. As a result, spent catalystsare classified as hazardous materials. However, such waste mate-rials containing high metal concentrations may be considered as“artificial ores”, since they can serve as the secondary raw materi-alswithaconsequentreductioninthedemandforprimarymineralresources. Recycling of spent catalysts has become an unavoidabletask not only to lower their costs but also to reduce the catalystwaste in order to prevent the environmental pollution. A varietyof processing approaches for recovering metal from the spent cat-alysts have been proposed and most of the literature in this field ispatented [2,3]. The spent catalysts are subjected to hydrometallur-gical or hydropyrometallurgical treatment for the metal recovery.In both cases the metals are recovered as mixed solutions, andthen separated by conventional separation techniques (solventextraction, selective precipitation, and ion-exchange). Hydromet-allurgical processing methods are environmental friendly due to