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Fernandez-Garcia M.P.,University of Porto | Teixeira J.M.,University of Oviedo | Machado P.,University of Porto | Enis Leblebici M.,Process Engineering for Sustainable Systems ProcESS | And 3 more authors.
Chemical Engineering Science | Year: 2015

We herein demonstrate an in-situ device and a real time method to observe the vital stages of Fe-oxide nanoparticles' (NPs) preparation by coprecipitation reaction. The reaction volume is monitored by a home-made AC susceptometer to analyze the magnetic response of the growing NPs. Three different regions (nucleation, growth and diffusion) could be identified in the recorded in-phase and out-of phase curves. The morphological and magnetic characterization of the obtained Fe-oxide NPs reveal minute particle dimensions (<3. nm), narrow polidispersity (1-7. nm), superparamagnetic behavior (null coercivity) and narrow distribution of blocking temperatures (<. TB>~67. K). We show that the device and technique enable real time assessment of the mixing speed which has paramount impact on the physical and chemical properties of the final product. © 2015 Elsevier Ltd. Source


Gebrekidan A.,Mekelle University | Weldegebriel Y.,Ezana Analytical Laboratory in Ezana Mining Development PLC | Hadera A.,Mekelle University | Van der Bruggen B.,Process Engineering for Sustainable Systems ProcESS
Ecotoxicology and Environmental Safety | Year: 2013

The accumulation of heavy metals in vegetables resulting from irrigation with contaminated water obtained from industrial effluents may create a potential public health risk. We quantified the concentration of heavy metals (Cu, Zn, Fe, Mn, Cr, Cd, Ni, Co and Pb) in soil, vegetables and the water used for irrigation at two sites (Laelay Wukro and Tahtay Wukro) around Wukro Town, Tigray, Northern Ethiopia. The concentrations of heavy metals in irrigation water measured during this study were lower than permissible limits of heavy metals allowed for irrigation water. The mean concentrations of heavy metals in irrigated soil samples obtained from Tahtay Wukro were higher for Mn, Zn, Cr, and Cu. The overall results of soil samples ranged 2.62-827, 1.4-51.6, 25.5-33.6, 23.5-28.2, 2.52-25.1, 15-17.8, 3-4, 2.5-40.49 and 0.7-0.8. mg/kg for Mn, Zn, Cr, Ni, Cu, Co, Pb, Fe and Cd, respectively. Higher concentrations of heavy metals were also observed in vegetable samples from Tahtay Wukro. Pb was found to accumulate the most in all vegetable samples. It was observed that green pepper and lettuce accumulate high amounts of Cu and Zn; Swiss chard accumulates excessive amounts of Fe, Mn, Cr, Cd, Ni and Co; lettuce and tomato higher amounts of Cd; and green pepper, tomato and onion a higher concentration of Pb. Significant differences in the elemental concentrations between the vegetables analyzed from Laelay and Tahtay Wukro were observed. This was attributed in part to the geological nature of the study area and the discharges from the town and from a tannery. The results also indicate that Fe, Pb and Cd have high transfer factor values (mean values: 42.89, 0.84 and 0.37, respectively). The transfer pattern for heavy metals in different vegetables showed a trend in the order: Fe>Pb>Cd>Mn>Cu>Zn>Ni>Zn>Cr=Co. The heavy metal contamination of vegetables grown in Tahtay Wukro, located downstream of the tannery, may pose increased health risks in the future to the local population through consumption of vegetables. © 2013 Elsevier Inc. Source


Jamali A.,Process Engineering for Sustainable Systems ProcESS | Vanraes R.,Light and Lighting Laboratory | Hanselaer P.,Light and Lighting Laboratory | Van Gerven T.,Process Engineering for Sustainable Systems ProcESS
Chemical Engineering and Processing: Process Intensification | Year: 2013

Photocatalytic degradation of phenol by titanium dioxide illuminated by one light emitting diode (LED) in a batch photocatalytic reactor is reported in this paper. The effect of catalyst loading, catalyst type, phenol-hydrogen peroxide ratio, pH, initial phenol concentration and irradiance by applying pulse width modulation (PWM) was studied. The effect of the beam width on photocatalytic degradation of phenol is also included in this paper as is the use of different type of reflectors outside the reactor. With both an LED beam width of 120° and optimal chemical conditions of 10. ppm phenol concentration with a hydrogen peroxide-phenol molar ratio of 100 and pH of 4.8, a degradation rate of 42% was achieved after 4. h. Decreasing the beam width to 40° raised degradation to 87%.In order to study the irradiance distribution and its effect on the reactor performance, experiments were conducted incorporating various catalysts loading, reactor heights and beam widths. The irradiance was measured for different amount of catalyst loading ranging from 0.17 to 1.8gL-1at different reactor heights. The results are compared with optimal catalyst loading measurement to assess the correlation between phenol degradation and irradiance distribution. The UV LED in combination with titanium dioxide is appropriate for water treatment to degrade organic pollutants at low concentration. © 2013 Elsevier B.V. Source


John J.J.,Process Engineering for Sustainable Systems ProcESS | Kuhn S.,Process Engineering for Sustainable Systems ProcESS | Braeken L.,Catholic University of Leuven | Van Gerven T.,Process Engineering for Sustainable Systems ProcESS
Chemical Engineering and Processing: Process Intensification | Year: 2016

A new method to apply ultrasound to a microchannel for liquid-liquid extraction was explored. The microchannel tubes are subjected to the ultrasound by direct contact with the transducer without the presence of a liquid medium. The design was constructed with the objectives of reproducibility, proper control of the ultrasound parameters and visibility of the behaviour of the two phase flow under the influence of ultrasound throughout the length of the channel. Two mechanisms of emulsion formation were observed. The effectiveness of the system under the influence of various operating and design parameters was quantified by calculating the yields of the two phase hydrolysis reaction of p-nitrophenyl acetate. The behaviour under various frequencies and amplitude was explored. At a frequency of 20.3. kHz, amplitude of 840. mV and flow rate of 0.1. ml/min the highest increase in yield was observed, which was almost 2.5 times that of the silent condition. A comparison was also made against silent batch and flow conditions to determine the actual effectiveness of the system. To obtain an identical yield of 75% the required residence time could be reduced by a factor of 20 in the sonicated flow condition compared to the silent batch condition. © 2016 Elsevier B.V. Source


Leblebici M.E.,Process Engineering for Sustainable Systems ProcESS | Ronge J.,Center for Surface Chemistry and Catalysis | Martens J.A.,Center for Surface Chemistry and Catalysis | Stefanidis G.D.,Process Engineering for Sustainable Systems ProcESS | Van Gerven T.,Process Engineering for Sustainable Systems ProcESS
Chemical Engineering Journal | Year: 2015

Photocatalytic breakdown of organic pollutants was modelled and experimentally validated using phenol as probe molecule and UV-LEDs as the radiation source. A nanocrystalline TiO2 film was immobilized in a quartz continuous parallel plate reactor and illuminated by an array of 88 LEDs, each emitting 375nm radiation. The degradation of phenol in steady state conditions was recorded for different irradiances and a pseudo first order reaction rate constant was obtained for this process. The rate constant was found to be of the order of 10-4s-1. A computational fluid dynamics (CFD) coupled with reaction model for the studied reactor was developed. The model considers the catalyst coating as a porous medium instead of a surface. It accounts for the mass transfer and light penetration within the immobilized catalyst. The model has one degree of freedom which was validated for different light intensities and flow rates. The degree of freedom in the model can be defined as "rate of free radical generation" and the unit is molL-1s-1. This variable was experimentally coupled by a linear relation to the irradiance on the catalyst coating. Photonic efficiency of the system was also investigated. A photonic efficiency range of 0.44-1.4% was obtained at light intensities of 2000 and 200μWcm-2, respectively. The model and the data obtained are scalable and applicable to different reactors. Comparison of photonic efficiencies obtained, show that the immobilized TiO2 reactor has similar efficiency to referred works which considered slurry reactors. © 2014 Elsevier B.V. Source

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