Search results for "Chemical engineering"
showing 10 items of 5892 documents
Endocrine disrupter compounds removal in wastewater using microalgae: Degradation kinetics assessment
2018
[EN] This paper describes a study carried out to determine the removal kinetics of four micropollutants (4-tert-octylphenol (OP), technical-nonylphenol (t-NP), 4-nonylphenol (4-NP) and bisphenol-A (BPA)) usually found in wastewater streams. The kinetic experiments were carried out in batch reactors containing the effluent of an Anaerobic Membrane BioReactor (AnMBR) in the presence of light, oxygen and microalgae. As the degradation process of the studied micropollutants obeyed a pseudo-first-order kinetics, the second-order kinetics for each micropollutant was then calculated. The second order rate constants for the hydroxyl radical (k.(OH)) ranged from 7.0.10(+10) to 6.6.10(+12) L.mol(-1).…
Hydrated Layer Formation on Tricalcium and Dicalcium Silicate Surfaces: Experimental Study and Numerical Simulations
2001
In this paper, an original approach is used to study the calcium silicate hydrate (C−S−H) layer formation on the surface of grains of anhydrous silicate during tricalcium and dicalcium silicate hydration from the variation of the rate of hydration with lime concentration. The effects of C−S−H nucleation and growth on the curves for the degree of reaction against time have been separated in both experimental study of the rate of hydration in controlled conditions and numerical simulation of the growth of C−S−H on a surface from a particle aggregation model. The influence of the number of nuclei and of the different growth modes has been quantified.
Biobased Epoxy Resin by Electrochemical Modification of Tall Oil Fatty Acids
2019
A biobased epoxy resin was prepared from tall oil fatty acids (TOFAs), a byproduct of the pulping industry. As free carboxylic acids compromise resin stability, TOFA was subjected to non-Kolbe decarboxylation to give alkenes upon loss of CO2. Thereby, the degree of unsaturation is significantly increased. This electrosynthetic protocol using an undivided cell setup and inexpensive graphite electrodes in a galvanostatic operation mode was scaled to a 1.5 L reactor, making use of electric current as a green and waste-free reagent. Simple, cost-efficient epoxidation using oxone subsequently gives an epoxy resin of low viscosity. Curing with anhydrides yields thermoset materials. Dynamic mechan…
Determination of molecular species of oil triacylglycerols by reversed-phase and chiral-phase high-performance liquid chromatography
1991
A method is described for the determination of molecular species of oil triacylglycerols. The method is based on the analytical separation of the enantiomericsn-1,2-andsn-2,3-diacylglycerols, derived from triacylglycerols, by high-performance liquid-chromatography (HPLC) on a chiral column containing N-(R)-1-(α-naphthyl)ethylaminocarbonyl-(S)-valinecarbonyl-(S)-valine as stationary phase. Model triacyl-glycerol molecules comprising three known fatty acids were isolated from peanut oil and cottonseed oil by a combination of argentation-TLC and reversed-phase HPLC and submitted to partial chemical deacylation. The derivedsn-1,2(2,3)-diacylglycerols were analyzed and fractionated as 3,5-dinitr…
Effects of Demand Side Management on the Operation of an Isolated LV Microgrids
2019
The work presents the results of a study regarding the impact of Demand Side Management actions on flexible loads distributed at the domestic end-users' facilities in an isolated low voltage microgrid. Aim of the research study is to evaluate how the implementation of local control actions on the end-user's side can impact on the operation of the isolated microgrid. The Demand Side Management is applied by each domestic user to optimize the operation of its own resources following well-defined operative steps. The study is carried out implementing a suitable model of the microgrid in Neplan environment, while the daily controlled load profiles of the end-users are evaluated using the Montec…
Eulerian–Lagrangian modeling and computational fluid dynamics simulation of wire mesh demisters in MSF plants
2016
Abstract This study focuses on computational fluid dynamics model (CFD) for simulation of demisters in multistage flash desalination (MSF). The Eulerian–Lagrangian model (steady-state and two-dimensional) was developed to simulate the demister. The model was used to simulate the flow of water vapor and brine droplets in the demister. The computational domain includes the following three zones: the vapor space above the demister, the vapor space below the demister, and the demister. The demister zone was modeled as tube banks. A sensitivity analysis of the model revealed that vapor velocity is the main parameter that affects demister performance. Additionally, the analysis indicated that vap…
An advanced control strategy for biological nutrient removal in continuous systems based on pH and ORP sensors
2012
[EN] A fuzzy logic-based control system that uses low-cost sensors for controlling and optimizing the biological nitrogen removal in continuous systems has been developed. The novelty of this control system is the use of several pH, ORP, and dissolved oxygen (DO) sensors instead of on-line nitrogen sensors/analyzers. The nitrogen control system was developed and implemented in a UCT pilot plant fed with wastewater from a full-scale plant. The developed nitrification controller allows the effluent ammonium concentration to be maintained below the effluent criteria discharge with the minimum energy consumption. The denitrification process controller allows the energy consumption derived from …
Ferromagnetic coupling through the oxalate bridge in heterobimetallic Cr(III)–M(II) (M = Mn and Co) assemblies
2019
Abstract Two novel compounds, {[Cr(pyim)(ox)2]2Mn}n·2nCH3OH (1) and {[Cr(pyim)(ox)2]2Co(H2O)2}·7.5H2O (2) [pyim = 2-(2′-pyridyl)imidazole and H2ox = oxalic acid], were synthesized by using the mononuclear chromium(III) complex PPh4[Cr(pyim)(ox)2]·H2O (PPh4+ = tetraphenylphosphonium) as metalloligand towards the fully solvated manganese(II) (1) and cobalt(II) (2) ions as perchlorate salts. The structure of 1 consists of neutral double chains, with diamond-shaped units sharing the manganese(II) ions with the two other corners being occupied by the chromium(III) ions. The two metal centres in 1 are connected by bis-bidentate oxalate groups, each [CrIII(pyim)(ox)2]− unit being bound to two mang…
Structural and Luminescent Properties of Homoleptic Silver(I), Gold(I), and Palladium(II) Complexes with nNHC-tzNHC Heteroditopic Carbene Ligands
2019
Novel silver(I), gold(I), and palladium(II) complexes were synthesized with bidentate heteroditopic carbene ligands that combine an imidazol-2-ylidene (nNHC) with a 1,2,3-triazol-5-ylidene (tzNHC) connected by a propylene bridge. The silver(I) and gold(I) complexes were dinuclear species, [M-2(nNHC-tzNHC)(2)](PF6)(2) (M = Ag or Au), with the two bidentate ligands bridging the metal centers, whereas in the palladium(II) complex [Pd(nNHC-tzNHC)(2)]-(PF6)(2), the two ligands were chelated on the same metal center. Because of the presence of two different carbene units, isomers were observed for the gold(I) and palladium(II) complexes. The molecular structures of the head-to-tail isomer for gol…
Effects of electron donating/withdrawing groups in the 5-substituted-2-hydroxybenzaldehyde on the synthesis of neutral cubanes with a NiII4O4core: sy…
2016
Two tetranuclear cubane-like nickel(II) complexes of formula [Ni4(CH3O)4(L1)4(CH3OH)4] (1) and [Ni4(CH3O)4(L2)4(CH3OH)4] (2) (HL1 = 2-hydroxybenzaldehyde and HL2 = 2-hydroxy-5-methylbenzaldehyde) have been prepared by the reaction of NiCl2·6H2O with methanolic solutions of HL1 and HL2 in the presence of triethylamine at room temperature. Complexes 1 and 2 have been characterized by elemental analyses, IR spectra and single-crystal X-ray diffraction. The X-ray crystal structure analysis revealed that 1 and 2 have a cubane-type structural topology with four Ni(II) ions and four methoxo-oxygen atoms regularly alternating at the corners. Each metal ion in 1 and 2 is six-coordinate in a distorte…