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Urea

About: Urea is a research topic. Over the lifetime, 21394 publications have been published within this topic receiving 382444 citations. The topic is also known as: carbamide & carbonic acid diamide.


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Journal ArticleDOI
TL;DR: A reaction mechanism involving chloramines and chloramides as reaction intermediates, where the initial chlorination is the rate-determining step in the overall sequence of reactions is proposed.
Abstract: This study investigated the transformation of urea by electrochemically generated reactive chlorine species (RCS) Solutions of urea with chloride ions were electrolyzed using a bismuth doped TiO2 (BiOx/TiO2) anode coupled with a stainless steel cathode at applied anodic potentials (Ea) of either +22 V or +30 V versus the normal hydrogen electrode In NaCl solution, the current efficiency of RCS generation was near 30% at both potentials In divided cell experiments, the pseudo-first-order rate of total nitrogen decay was an order of magnitude higher at Ea of +30 V than at +22 V, presumably because dichlorine radical (Cl2(-)·) ions facilitate the urea transformation primary driven by free chlorine Quadrupole mass spectrometer analysis of the reactor headspace revealed that N2 and CO2 are the primary gaseous products of the oxidation of urea, whose urea-N was completely transformed into N2 (91%) and NO3(-) (9%) The higher reaction selectivity with respect to N2 production can be ascribed to a low operational ratio of free available chlorine to N The mass-balance analysis recovered urea-C as CO2 at 77%, while CO generation most likely accounts for the residual carbon In light of these results, we propose a reaction mechanism involving chloramines and chloramides as reaction intermediates, where the initial chlorination is the rate-determining step in the overall sequence of reactions

107 citations

Journal ArticleDOI
01 Apr 1996-Polymer
TL;DR: In this article, the formation of urethane, soluble urea, soluble d-urea, hydrogen-bonded urea and associated d -urea species were monitored during their fast bulk copolymerization with a diisocyanate.

107 citations

Journal ArticleDOI
Fen Guo1, Kui Cheng1, Ke Ye1, Guiling Wang1, Dianxue Cao1 
TL;DR: In this paper, the Ni-cobalt nanowire arrays (Ni-Co NWAs) electrode is prepared by one-step galvanostatic electrodeposition with a polycarbonate membrane as the template.

107 citations

Book ChapterDOI
01 Jan 1980
TL;DR: The chapter describes the biosynthesis of arginine and proline, where glutamic acid contributes the nitrogen atom and most of the carbon atoms and the source of carbon atoms for two in plants.
Abstract: Publisher Summary This chapter discusses arginine synthesis, proline synthesis, and related processes. Glutamic acid is a key compound in nitrogen metabolism in plants. Plants obtain most of their nitrogen as nitrate and reduce it to ammonium. Glutamic acid is central to ammonium metabolism because of the following reasons: (1) it is the product of ammonium assimilation by glutamic dehydrogenase, (2) it is the acceptor of ammonium in glutamine synthesis, and (3) it is the product of glutamate synthetase. Glutamic acid is the immediate precursor of the amino group of most protein amino acids and the source of carbon atoms for two. The chapter describes the biosynthesis of arginine and proline, where glutamic acid contributes the nitrogen atom and most of the carbon atoms. In higher plants, the conversion of ornithine to arginine is necessary for arginine formation. Arginine residues form a significant store of nitrogen in seeds because each arginine molecule has four nitrogen atoms and the release of this nitrogen is important during germination. Nitrogen release from arginine during senescence of plant tissue is also necessary. Plants cannot utilize urea in toto but can readily metabolize the ammonium and carbon dioxide formed by hydrolysis of urea by urease.

107 citations

Journal ArticleDOI
01 May 1998-Fuel
TL;DR: In this paper, activated carbons were prepared by carbonization and steam activation of nitrogen-enriched low-rank coals by reaction of ammonia or its derivatives with the carboxyl groups either naturally occurring in coal or artificially introduced by performic oxidation.

107 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,000
20221,982
2021433
2020502
2019589
2018557