- Volume:2 Issue: 3, 2017
- تاریخ انتشار: 1396/02/19
- تعداد عناوین: 6
Improvement in photocatalysts and photocatalytic reactors for water and wastewater treatment: A reviewPages 119-140During recent years, many advanced oxidation techniques have been investigated for water and wastewater treatment to overcome the shortage of clean water. This review summarizes the background and principles of photocatalysis applied as an advanced oxidation technology. In particular, this paper focuses on modification of photocatalysts with various dopants as well as the novel photocatalytic reactors to improve the oxidation efficiency of the pollutants in water and wastewater.Keywords: semiconductor, Photocatalyst, photocatalytic reactor, water, wastewater treatment, pollutants
Pages 141-149The main objective of this work was to design a novel device for compaction of metal powders so that the green parts could be ejected with applying a negligible force and without the need for any lubricant in either an admixed form or applied to the die wall. For this purpose a 40 mm diameter one-piece die was envisaged which would elastically contracted 0.076 mm before compaction and after completion of powder compacting operation, it would be allowed to expand, thus releasing the green compact and so it could be ejected with a force near to weight of the compacts. The experiment indicated that this shrinkage value of 0.076 mm was indeed a realistic estimate which provided sufficient shrinkage to cover both:I The "elastic die deformation of 40 mm diameter during compaction" which shows 0.0433mm elastic deformation.
IIThe "elastic spring back of the specimen of 40 mm diameter" which was 0.0227 mm after completion of compaction and releasing the compaction force.
Also provided sufficient clearance of 0.010mm between the compact and the die wall on release of compacting pressure to allow ejection of compact with a force near to weight of compact while no lubricant was used on the die wall nor admixed with powder.Keywords: Powder Compaction_P- M Lubricants_Die Wall Lubrication_Elastic Die Deformation_Elastic Spring Back
Pages 151-161A new analytical study performed to investigate the effect of the temperature difference between gas and particle in propagation of the spherical flames. The combustible system is containing uniformly distributed volatile fuel particles in an oxidizing gas (Air) mixture. The model includes evaporation of volatile matter of dust particles to known gaseous fuel (methane) and the single-stage reaction of gas-phase combustion. The structure of the flame is composed of a preheat zone, reaction zone, and convection zone. The study is within the framework of large activation energy and quasi-steady assumptions. The validity of theoretical prediction is confirmed by data presented in other literature including burning velocity. The obtained results illustrate the effects of the above parameter on the variations of the flame speed, temperature, particle mass fraction, flame temperature, concentration, and burning velocity for gas and particle.Keywords: Combustion, Spherical Flame, Analytical Method, Dusty Flame, Coal Dust
CFD simulations on natural convection heat transfer of alumina-water nanofluid with Brownian motion effect in a 3-D enclosurePages 163-171The CFD simulation has been undertaken concerning natural convection heat transfer of a nanofluid in vertical square enclosure, whose dimension, width height length (mm), is 40 40 90, respectively. The nanofluid used in the present study is -water with various volumetric fractions of the alumina nanoparticles ranging from 0-3%. The Rayleigh number is . Fluent v6.3 is used to simulate nanofluid considering it as a single phase. The effect of Brownian motion on the heat transfer is examined. A comparison between the two studies of with and without the Brownian motion, shows that when the Brownian motion is considered, the solid volume fraction of nanoparticles has dissimilar effects on the heat transfer. The numerical results show a decrease in heat transfer with increase in particle volume fraction considering Brownian motion effects. Moreover, computed result demonstrates an increase of Nusselt number with Rayleigh number as depicted by experimental results.Keywords: CFD simulation, Natural convection, Nanofluid, Brownian motion
Pages 173-182This paper presents the adsorption of crystal violet (CV) from aqueous solution on surfactant-modified dolomite. Liquid phase batch operations were carried out to observe the effect of various experimental parameters such as initial dye concentration, adsorbent dosage, pH and NaCl concentration. The optimum conditions for these parameters were calculated by Taguchi method. Equilibrium isotherm data were analyzed according to Langmuir, Freundlich and Temkin equations. The experimental data fitted well to Freundlich adsorption model. The maximum adsorption capacities by Langmuir analysis were determined to be 49.261mg/g at 22℃ that indicates suitable performance by of this adsorbent. The pPseudo-first-order and, pseudo-second-order kinetics and the intraparticle diffusion models were also evaluated for the adsorption of CV onto surfactant-modified dolomite. The positive value of free energy change confirmed the nature of physisorption of dye onto adsorbent.Keywords: Adsorption, Crystal violet (CV+), Kinetics, Surfactant-modified dolomite, Taguchi method
Morphology and Mechanical Properties Investigation of Binary Polymer Blends Based on PP/SEBS and PP/PCPages 183-191In this study, eight binary blends of polypropylene (PP)/ poly [styrene-b-(ethylene-co butylene)-b-styrene] tri-block copolymer (SEBS) and polypropylene (PP)/ polycarbonate (PC) were produced at different composition through twin screw extruder. The composition of the minor phases was changed to correlate the morphology and mechanical properties of binary blends (PP/PC and PP/SEBS) through thermal properties. To serve this purpose and to study the composition weight, composition weight ratio of SEBS and PC was change from 10% to 30% in PP/PC and PP/SEBS. With increasing SEBS wt%, toughness grows slightly and in 30wt% of SEBS reached to its maximum value, which uniform morphology created by PP/SEBS plays important role in this matter. On the other hand, with increasing PC wt%, tensile properties have upward trend, but size of holes, due to lack of proper adhesion between two polymeric surface, rose. The results of DCS have shown that SEBS cannot act as nucleation agents (heterogeneous nucleation) but the PC particles in this situation can act as nucleation agent in PP crystallinity. Increasing SEBS percentages leads to immobility of PP segments and hamper the crystallinity. PC particles in PP matrix are heterogeneous nucleation agent, which leads to increasing in crystallinity temperature compared to the pure PP.Keywords: morphology, polypropylene, mechanical properties