Experimental Investigation and CFD Simulation of Top Spray Fluidized Bed Coating System

Experimentally investigated in this work is the hydrodynamics of particulates motion in a cylindrical fluidized bed equipped with a pneumatic nozzle jet flow. Subsequently, the computational fluid dynamics (CFD) is combined with the Eulerian formulation of multiphase flow to describe the hydrodynamics of particulates motion. Similar to free spray jet velocity profile, the velocity profile of output gas from nozzle is obtained based on the Schlichting equation. Particle trajectories, time dependent fluidization height, gas and solid particles velocity distributions and the fluidization height distribution of particles in different radial positions within the bed have been also considered in the course of experimental and modeling studies. The comparison between the predicted and experimental height of fluidized bed indicates a good agreement between simulation results and experimental data

Evaluation of almond shells magnetized by iron nano-particles for nitrate removal from Aqueous Solution: study of adsorption isotherm

زمینه: یکی از شایع‌ترین آلاینده‌های محیط زیست که در آب‌های زیرزمینی و سطحی وجود دارد نیترات است. غلظت بالای نیترات در آب آشامیدنی سبب بیماری‌هایی مثل متهموگلوبین در کودکان، سرطان معده و سقط جنین می‌شود. هدف از این مطالعه بررسی ایزوترم جذب کربن پوست بادام فعال شده با نانو ذرات مغناطیسی آهن و بررسی کارایی آن در حذف نیترات از محیط‌های آبی بوده است. روش بررسی: این مطالعه به روش تجربی انجام گرفت. مرفولوژی جاذب سنتز شده با استفاده از روش‌های FESEM و BET مورد آنالیز قرار گرفت. پارامترهای موثر بر فرایند جذب یون نیترات از جمله pH (8-4)، میزان جاذب(1-25/0 گرم در لیتر)، غلظت اولیه یون نیترات(400-25 میلی گرم در لیتر) و زمان تماس(100-20 دقیقه) مورد بررسی قرار گرفت. در این مطالعه از روش تاگوچی جهت تعیین حجم نمونه و آنالیز آماری استفاده شد. یافته: یافته های حاصل از روش‌های FESEM و BET تایید کرد که نانوذرات مغناطیسی آهن در جاذب سنتز شده دارای اندازه متوسطnm 27-23 و سطح ویژه برابر با g/m2 480/105 بوده است. نتایج نشان داد که درpH بهینه برابر با 4 و زمان تعادل 20 دقیقه، کارایی جذب با افزایش مقدار جاذب تا g/l 1و کاهش غلظت اولیه یون نیترات افزایش یافت (6/4 86/85 ). نتایج ایزوترم تعادلی نشان داد که فرآیند جذب نیترات از ایزوترم لانگمیر (924/0=R2) پیروی می‌کند. نتیجه‌گیری: یافته‌ها نشان دادند که پوست بادام فعال شده با نانوذره آهن از توانایی مطلوبی در حذف یون نیترات از محلول های آبی برخوردار است. بنابراین با استفاده از این فناوری نسبتا راحت و ساده، می توان گام موثری را در حذف نیترات آبها برداشت

Determination of kinetic parameters and hydrogen desorption characteristics of MgH2-10 wt% (9Ni-2Mg-Y) nano-composite

Hydrogen desorption kinetic parameters of MgH2 compounds were measured and compared with published gas solid reaction models. The compounds investigated in this study were as-received MgH2, ball milled MgH2, and MgH2 ball milled with 9Ni-2Mg-Y catalyst compound. It was determined that different models were necessary to fit the hydrogen desorption data collected at different temperatures on the same sample, indicating that desorption mechanisms changed with respect to temperature. Addition of (9Ni-2Mg-Y) alloy as a catalyst to MgH2 increased the hydrogen desorption capacity of MgH2 from zero (for as-received MgH2) to about 5 wt% at 350 degrees C within 500 s. The activation energy value was determined as 187 kJ/mol H-2 for the as-received MgH2, 137 kJ/mol H-2 for 20 h ball milled MgH2, and 62 kJ/mol H-2 for 20 h ball milled MgH2-10 wt% (9Ni-2Mg-Y) nano-composite by the Arrhenius and Kissinger methods. Moreover, the integral heat of H-2 desorption for the MgH2-10 wt% (9Ni-2Mg-Y) nano-composite was measured to be about 78 +/- 0.5 kJ/mol H-2 by adsorption micro-calorimetry consistent with the results of the Arrhenius and Kissinger methods. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved

Effect of process control agents on synthesizing nano-structured 2Mg-9Ni-Y catalyst by mechanical milling and its catalytic effect on desorption capacity of MgH2

Synthesizing 2Mg-9Ni-Y catalyst was investigated by mechanical alloying of Mg, Ni, and Y elemental powder mixture and subsequent heat treatment. Accordingly, effects of milling time, process control agent (PCA) type (stearic acid and toluene), and heat treatment time on the powder microstructure, phase composition, and powder morphology were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and laser particle size analyzer (LPSA). Results showed that particle size of the samples prepared by toluene were smaller than those of the samples prepared by stearic acid. Also, it was found that the ternary Mg2Ni9Y compound was not formed by mechanical milling alone. This intermetallic compound was partially formed after the heat treatment of ball milled powders for 8 h at 800 degrees C. Effect of toluene on powder particle was higher than that of stearic acid. According to XRD patterns, it seems that the amount of formed Mg2Ni9Y in the samples which were ball milled for 15 h using stearic acid and subsequently heat treated at 800 degrees C for 8 h was more than the powders that used toluene in the same conditions. Furthermore, results of hydrogen desorption tests of MgH2 doped with 10 wt% sample prepared by toluene after the desorption time of 2500 s at 300 degrees C showed that it desorbed 1 wt% more hydrogen than MgH2 doped with 10 wt% sample prepared by acid stearic. (C) 2014 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved

Investigating layer-by-layer chitosan-dextran sulfate-coated mesoporous silica as a pH-sensitive drug delivery system

Abstract Mesoporous silica nanoparticles (MSNPs) coated by chitosan (CS) were shown to be a proper candidate as a carrier for drug delivery purposes. However, choosing the suitable drug-containing complexes to be applied on MSNPs-CS is of much greater importance to evaluate the possible candidate for an efficient combination of cell viability, drug release kinetics, and atherosclerosis prevention. In this regard, this study concentrates on the synthesis and assessment of coated MSNPs-CS designed for drug delivery purposes. The MSNPs are coated with polyelectrolyte complexes (PEC) composed of CS and dextran sulfate (MSNPs-CS-DX), serving as a versatile drug carrier with favorable biological characteristics. CS-DX is applied to MSNPs without requiring complex or multi-step synthesis procedures. Rosuvastatin, a cholesterol-lowering medication, is chosen for its therapeutic relevance. Additionally, CS-DX is found to relatively impede the uptake of low-density lipoproteins (LDLs) by macrophages, enhancing their potential therapeutic utility. FTIR pattern, FESEM, and TEM images prove MSNPs-CS-DX formation. DLS measurement demonstrates the average particle size of 110 nm for MSNPs, with the combined thickness of CS and DX layers ranging from 10 to 15 nm. BET test is carried out to evaluate the pore size and porosity of structure, showing outstanding results that cause an entrapment efficiency of 57% for MSNPs-CS-DX. Furthermore, the findings demonstrate the pH sensitivity of MSNPs-CS-DX on drug release kinetics. Notably, the CS-DX layer exhibits a significant enhancement in cell viability of human umbilical vein endothelial cells (HUVEC) by approximately 24% within a 24 h timeframe compared to MSNPs lacking CS-DX. Graphical Abstrac

A comparative study for synthesis methods of nano-structured (9Ni-2Mg-Y) alloy catalysts and effect of the produced alloy on hydrogen desorption properties of MgH2

9Ni-2Mg-Y alloy powders were prepared by arc melting, induction melting, mechanical alloying, solid state reaction and subsequent ball milling processes. The results showed that melting processes are not suitable for preparation of 9Ni-2Mg-Y alloy due to high losses of Mg and Y. Therefore, 9Ni-2Mg-Y alloy powder was prepared by three methods including: 1) mechanical alloying, 2) mechanical alloying + solid state reaction + ball milling, and 3) mixing + solid state reaction + ball milling. The prepared 9Ni-2Mg-Y alloy powders were compared for their catalytic effects on hydrogen desorption of MgH2. It is found that 9Ni -2Mg-Y alloy powder prepared by mechanical alloying + solid state reaction + ball milling method has a smaller particle size (1-5 mu m) and higher surface area (1.7 m(2)g(-1)) than that of other methods. H-2 desorption tests revealed that addition of 9Ni-2Mg-Y alloy prepared by mechanical alloying + solid state reaction + ball milling to MgH2 decreases the hydrogen desorption temperature of MgH2 from 425 to 210 degrees C and improves the hydrogen desorption capacity from 0 to 3.5 wt.% at 350 degrees C during 8 min. Copyright (c) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved

The Influence of La and Ce Addition on Inclusion Modification in Cast Niobium Microalloyed Steels

The main role of Rare Earth (RE) elements in the steelmaking industry is to affect the nature of inclusions (composition, geometry, size and volume fraction), which can potentially lead to the improvement of some mechanical properties such as the toughness in steels. In this study, different amounts of RE were added to a niobium microalloyed steel in as-cast condition to investigate its influence on: (i) type of inclusions and (ii) precipitation of niobium carbides. The characterization of the microstructure by optical, scanning and transmission electron microscopy shows that: (1) the addition of RE elements change the inclusion formation route during solidification; RE > 200 ppm promote formation of complex inclusions with a (La,Ce)(S,O) matrix instead of Al2O3-MnS inclusions; (2) the roundness of inclusions increases with RE, whereas more than 200 ppm addition would increase the area fraction and size of the inclusions; (3) it was found that the presence of MnS in the base and low RE-added steel provide nucleation sites for the precipitation of coarse niobium carbides and/or carbonitrides at the matrix–MnS interface. Thermodynamic calculations show that temperatures of the order of 1200 °C would be necessary to dissolve these coarse Nb-rich carbides so as to reprecipitate them as nanoparticles in the matrix.We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI).The authors from the University of Tehran gratefully acknowledge the financial support provided by the Office of International Affairs and the Office for Research Affairs, College of Engineering, for the project number 8107009.6.34. The authors from Centro Nacional de Investigaciones Metalúrgicas (CENIM) that belong to the Consejo Superior de Investigaciones Científicas (CSIC) would like to acknowledge the financial support from Comunidad de Madrid through the project Diseño Multiescala de Materiales Avanzados (DIMMAT-CM_S2013/MIT-2775). Javier Vivas acknowledges financial support in the form of a FPI (Formación de Personal Investigador) Grant BES-2014-069863. Authors are grateful to the Phase Transformations and Microscopy labs from CENIM-CSIC and to the Centro Nacional de Microscopia Electronica (CNME), located at Complutense Metals 2017, 7, 377 16 of 17 University of Madrid (UCM), for the provision of laboratory facilities. Mr. Javier Vara Miñambres from the Phase Transformations lab (CENIM-CSIC) is gratefully acknowledged for their continuous experimental suppor

Removal of Cadmium and Lead Ions from Aqueous Solution by Nanocrystalline Magnetite Through Mechanochemical Activation

In this study, the removal of cadmium and lead ions from aqueous solution by nanocrystalline magnetite was investigated. The nanocrystalline magnetite was synthesized by mechanochemical activation of hematite in a high energy planetary mill in argon atmosphere for 45 hours. The ability of the synthesized nanocrystalline magnetite for removal of Cd(II) and Pb(II) from aqueous solutions was studied in a batch reactor under different experimental conditions with different pHs, contact times, initial metal ion concentrations and temperatures. The solution’s pH was found to be a key factor in the adsorption of heavy metal ions on Fe3O4. The optimum pH of the solution for adsorption of Cd(II) and Pb(II) from aqueous solutions was found to be 6.5 and 5.5, respectively. The best models to describe the kinetics and isotherms of single adsorption were both the pseudo first and second-order kinetic models and Langmuir models, respectively, indicating the monolayer chemisorption of Cd(II) and Pb(II) on Fe3O4 nanoparticles. Moreover, the thermodynamic parameters (i.e., ∆H°, ∆S°, ∆G°) were evaluated which indicated that the adsorption was spontaneous and exothermic. The results suggested that the synthesized material (magnetite nanocrystalline particles) may be used as effective and economic absorbent for removal of Cd(II) and Pb(II) from aqueous solutions

Properties of activated MgH2 + mischmetal nanostructured composite produced by ball-milling

Abstract MgH2 + mischmetal nanostructured composite was synthesized from MgH2 plus 6 and 10 wt% of mischmetal by ball-milling at various times. XRD studies revealed that cerium hydride was produced during the milling in all samples. Sievert test results indicated that the samples containing 6 wt% of mischmetal showed a higher desorption compared with the ones containing 10 wt% of mischmetal. The high amount of cerium hydride in the samples may be the reason, while hydrogen desorption properties decreased by adding more catalyst. Furthermore, BET results showed that the addition of the catalyst to the samples resulted in agglomerate formation in shorter milling times. The agglomerate formation increased with adding more amounts of mischmetal, thus decreasing the hydrogen desorption properties of the composite. The best results were obtained from the 30 h-milled sample containing 6 wt% of catalyst. The on-set desorption temperature of this sample was 100 °C lower than that of as-received MgH2