Showing papers in "International Journal of Chemical Engineering in 2011"

A Review on Heavy Metals (As, Pb, and Hg) Uptake by Plants through Phytoremediation

Abstract: Heavy metals are among the most important sorts of contaminant in the environment. Several methods already used to clean up the environment from these kinds of contaminants, but most of them are costly and difficult to get optimum results. Currently, phytoremediation is an effective and affordable technological solution used to extract or remove inactive metals and metal pollutants from contaminated soil and water. This technology is environmental friendly and potentially cost effective. This paper aims to compile some information about heavy metals of arsenic, lead, and mercury (As, Pb, and Hg) sources, effects and their treatment. It also reviews deeply about phytoremediation technology, including the heavy metal uptake mechanisms and several research studies associated about the topics. Additionally, it describes several sources and the effects of As, Pb, and Hg on the environment, the advantages of this kind of technology for reducing them, and also heavy metal uptake mechanisms in phytoremediation technology as well as the factors affecting the uptake mechanisms. Some recommended plants which are commonly used in phytoremediation and their capability to reduce the contaminant are also reported.

Enhancement of Heat Transfer by Ultrasound: Review and Recent Advances

Abstract: This paper summarizes some applications of ultrasonic vibrations regarding heat transfer enhancement techniques. Research literature is reviewed, with special attention to examples for which ultrasonic technology was used alongside a conventional heat transfer process in order to enhance it. In several industrial applications, the use of ultrasound is often a way to increase productivity in the process itself, but also to take advantage of various subsequent phenomena. The relevant example brought forward here concerns heat exchangers, where it was found that ultrasound not only increases heat transfer rates, but might also be a solution to fouling reduction.

Tuning Genetic Algorithm Parameters to Improve Convergence Time

Abstract: Fermentation processes by nature are complex, time-varying, and highly nonlinear. As dynamic systems their modeling and further high-quality control are a serious challenge. The conventional optimization methods cannot overcome the fermentation processes peculiarities and do not lead to a satisfying solution. As an alternative, genetic algorithms as a stochastic global optimization method can be applied. For the purpose of parameter identification of a fed-batch cultivation of S. cerevisiae altogether four kinds of simple and four kinds of multipopulation genetic algorithms have been considered. Each of them is characterized with a different sequence of implementation of main genetic operators, namely, selection, crossover, and mutation. The influence of the most important genetic algorithm parameters—generation gap, crossover, and mutation rates has—been investigated too. Among the considered genetic algorithm parameters, generation gap influences most significantly the algorithm convergence time, saving up to 40% of time without affecting the model accuracy.

Peptide-Loaded Solid Lipid Nanoparticles Prepared through Coacervation Technique

Abstract: Stearic acid solid lipid nanoparticles were prepared according to a new technique, called coacervation. The main goal of this experimental work was the entrapment of peptide drugs into SLN, which is a difficult task, since their chemical characteristics (molecular weight, hydrophilicity, and stability) hamper peptide-containing formulations. Insulin and leuprolide, chosen as model peptide drugs, were encapsulated within nanoparticles after hydrophobic ion pairing with anionic surfactants. Peptide integrity was maintained after encapsulation, and nanoparticles can act in vitro as a sustained release system for peptide.

Uniform Chitosan Microparticles Prepared by a Novel Spray-Drying Technique

Abstract: Particle size and morphology are important properties of pharmaceutical particles. Preparation of microparticles with uniform particle size and morphology is necessary in order to systematically relate these properties to the release behavior and other functionalities such as drug encapsulation and dissolution. In this study, we successfully prepared monodisperse, nonagglomerated chitosan microparticles in a single step by a novel spray-drying technique. The control of particle size and morphology of spray-dried microparticles was investigated experimentally. Microparticles with larger particle size can be produced when chitosan precursor of higher concentration was used. Storage time of chitosan precursor, drying temperature, and addition of lactose were shown to be crucial parameters that affect the particle morphology. Appropriate choice of the drying temperature and precursor storage time permitted control of the particle morphology, ranging from nearly spherical to cap-shaped. Surface characteristics of the particles can be finely tuned by the amount of lactose added into the chitosan precursor.

Phase Behaviour of 1-Ethyl-3-methylimidazolium Thiocyanate Ionic Liquid with Catalytic Deactivated Compounds and Water at Several Temperatures: Experiments and Theoretical Predictions

Abstract: Density, surface tension and refractive index were determined for the binary mixture of catalytic deactivated compounds with 1-ethyl-3-methylimidazolium thiocyanate {[EMIM][SCN]} at temperature of (298.15 to 323.15) K. For all the compounds with ILs, the densities varied linearly in the entire mole fraction with increasing temperature. From the obtained data, the excess molar volume and deviation of surface tension and refractive index have been calculated. A strong interaction was found between similar (cation-thiophene or cation-pyrrole) compounds. The interaction of IL with dissimilar compounds such as indoline and quinoline and other multiple ring compounds was found to strongly depend on the composition of IL at any temperatures. For the mixtures, the surface tension decreases in the order of: thiophene g quinoline g pyridine g indoline g pyrrole g water. In general from the excess volume studies, the IL-sulphur/nitrogen mixture has stronger interaction as compared to IL-IL, thiophene-thiophene or pyrrole-pyrrole interaction. The deviation of surface tension was found to be inversely proportional to deviation of refractive index. The quantum chemical based COSMO-RS was used to predict the non-ideal liquid phase activity coefficient for all mixtures. It indicated an inverse relation between activity coefficient and excess molar volumes.

Separation Strategies for Processing of Dilute Liquid Streams

Abstract: Processing of dilute liquid streams in the industries like food, agro-, biotechnology, pharmaceuticals, environment, and so forth needs special strategy for the separation and purification of the desired product and for environment friendly disposal of the waste stream. The separation strategy adopted to achieve the goal is extremely important from economic as well as from environmental point of view. In the present paper we have reviewed the various aspects of some selected universal separation strategies such as adsorption, membrane separation, electrophoresis, chromatographic separation, and electroosmosis that are exercised for processing of dilute liquid streams.

Study of the Pressure Drop and Flow Field in Standard Gas Cyclone Models Using the Granular Model

Abstract: A particle-laden flow inside solid gas cyclones has been studied using computational fluid dynamics (CFD). The effects of high temperatures and different particle loadings have been investigated. The Reynolds stress (RSM) model-predicted results, in the case of pure gas, are within engineering accuracy even at high temperatures. Using the granular mixture model for the cases of particle-laden flow, discrepancies occurred at relatively high loadings (up to 0.5 kg/m3). Since the pressure drop is strongly related to the friction inside the cyclone body, the concept of entropy generation has been employed to detect regions of high frictional effects. Friction has been observed to be important at the vortex finder wall, the bottom of the conical-part wall, and the interface separating the outer and the core streams. The discrepancies between the present numerical simulation and the experimental results taken from the existing literature, which are caused by the mixture and turbulence models simplifying assumptions, are discussed in this paper.

Catalyst Initiation in the Oscillatory Carbonylation Reaction

Abstract: Palladium(II) iodide is used as a catalyst in the phenylacetylene oxidative carbonylation reaction that has demonstrated oscillatory behaviour in both pH and heat of reaction. In an attempt to extract the reaction network responsible for the oscillatory nature of this reaction, the system was divided into smaller parts and they were studied. This paper focuses on understanding the reaction network responsible for the initial reactions of palladium(II) iodide within this oscillatory reaction. The species researched include methanol, palladium(II) iodide, potassium iodide, and carbon monoxide. Several chemical reactions were considered and applied in a modelling study. The study revealed the significant role played by traces of water contained in the standard HPLC grade methanol used.

Reduced Chemical Kinetic Model for Titan Entries

Abstract: A reduced chemical kinetic model for Titan's atmosphere has been developed. This new model with 18 species and 28 reactions includes the mainfeatures of a more complete scheme, respecting the radiative fluxes. It has been verified against three key elements: a sensitivity analysis, the equilibrium chemical composition using shock tube simulations in CHEMKIN, and the results of computational fluid dynamics (CFDs) simulations.

A Large-Scale Synthesis and Characterization of Quaternary CuIn x Ga 1−x S 2 Chalcopyrite Nanoparticles via Microwave Batch Reactions

Abstract: Various quaternary CuInxGa1−xS2 (0≤x≤1) chalcopyrite nanoparticles have been prepared from molecular single-source precursors via microwave decomposition. We were able to control the nanoparticle size, phase, stoichiometry, and solubility. Depending on the choice of surface modifiers used, we were able to tune the solubility of the resulting nanoparticles. This method has been used to generate up to 5 g of nanoparticles and up to 150 g from multiple batch reactions with excellent reproducibility. Data from UV-Vis, photoluminescence, X-ray diffraction, TEM, DSC/TGA-MS, and ICP-OES analyses have shown high reproducibility in nanoparticle size, composition, and bandgap.

Synthesis and Structural Investigations of Ag-Added BaTiO-CuO Mixed Oxide for CO Gas Sensing

Abstract: Compositions having the general formula BaTiO 3- C u O + 𝑥 wt% Ag, where 𝑥 = 0 , 1 , 1 . 5 , and 2 have been prepared by solid state ceramic processing and sintered at 500 and 7 0 0 ∘ C for 5 h. Thermogravimetric analysis (TGA), X-ray powder diffraction (XRD), infrared absorption spectra (IR), and scanning electron microscopy (SEM) were used to characterize the obtained sensor pellets. It was found that no solid state reaction took place between BaTiO 3 and CuO during sintering process. The sensitivity of the prepared sensors to CO 2 gas increases with increasing sintering temperature and Ag content. The correlation between Ag content at different sintering temperature and structure characterization is discussed.

Advanced Control of a Continuous Solution Copolymerization Process

Abstract: A model-based predictive control system is designed for a copolymerization reactor. These processes typically have such a high nonlinear dynamic behavior to make practically ineffective the conventional control techniques, still so widespread in process and polymer industries. A predictive controller is adopted in this work, given the success this family of controllers is having in many chemical processes and oil refineries, especially due to their possibility of including bounds on both manipulated and controlled variables. The solution copolymerization of methyl methacrylate with vinyl acetate in a continuous stirred tank reactor is considered as an industrial case study for the analysis of the predictive control robustness in the field of petrochemical and polymer production. Both regulatory and servo problems scenarios are considered to check tangible benefits deriving from model-based predictive controller implementation.

Feasibility of Batch Reactive Distillation with Equilibrium-Limited Consecutive Reactions in Rectifier, Stripper, or Middle-Vessel Column

Abstract: A general overall feasibility methodology of batch reactive distillation of multireaction systems is developed to study all the possible configurations of batch reactive distillation. The general model equations are derived for multireaction system with any number of chemical equilibrium-limited reactions and for any number of components. The present methodology is demonstrated with the detailed study of the transesterification of dimethyl carbonate in two reversible cascade reactions in batch reactive distillation process. Pure methanol is produced as distillate, and pure diethyl carbonate is produced at the bottom simultaneously in middle-vessel column; in each section, continuous feeding of ethanol is necessary. The results of feasibility study are successfully validated by rigorous simulations.

Competition Kinetics of the Nonbranched-Chain Addition of Free Radicals to Olefins, Formaldehyde, and Oxygen

Abstract: Five reaction schemes are suggested for the initiated nonbranched-chain addition of free radicals to the multiple bonds of alkenes, formaldehyde, and oxygen. The schemes include reactions competing with chain propagation through a reactive free radical. The chain evolution stage in these schemes involves three or four types of free radicals. One of them— C H 2 = C ( C H 3 ) • C H 2 , C H 2 = C H • C H O H , H • C = O , 𝑜 − C H 3 C 6 H 4 C H 2 O • 4 , or H O • 4 —is relatively low-reactive and inhibits the chain process by shortening of the kinetic chain length. Based on the suggested schemes, nine rate equations containing one to three parameters to be determined directly are set up using quasi-steady-state treatment. These equations provide good fits for the nonmonotonic (peaking) dependences of the formation rates of the molecular addition products (1 : 1 adducts) on the concentration of the unsaturated component in liquid homogeneous binary systems consisting of a saturated component (hydrocarbon, alcohol, etc.) and an unsaturated component (olefin, formaldehyde, or dioxygen). The unsaturated compound in these systems is both a reactant and an autoinhibitor generating low-reactive free radicals. A similar kinetic description is applicable to nonbranched-chain free-radical hydrogen oxidation. The energetics of the key radical-molecule reactions is considered.