https://cyberleninka.org/article/n/309915.pdf

A critical review on solvent extraction of rare earths from aqueous solutions

https://apam.columbia.edu/files/seasdepts/applied-physics-and-applied-math/pdf-files/06-salk-chan.pdf

Cerium and yttrium oxide nanoparticles are neuroprotective.

In this review, we have examined the different models for polymer-electrolyte fuel cells operating with hydrogen. The major focus has been on transport of the various species within the fuel cell. The different regions of the fuel cell were examined, and their modeling methodologies and equations were elucidated. In particular, the 1-D fuel-cell sandwich was discussed thoroughly because it is the most important part of the fuel-cell assembly. Models that included other effects such as temperature gradients and transport in other directions besides through the fuel-cell sandwich were also discussed. Models were not directly compared to each other; instead they were broken down into their constitutive parts. The reason for this is that validation of the models is usually accomplished by comparison of simulation to experimental polarization data (e.g., Figure 3). However, other data can also be used such as the net flux of water through the membrane. In fitting these data, the models vary not only in their complexity and treatments but also in their number and kind of fitting parameters. This is one reason it is hard to justify one approach over another by just looking at the modeling results. In general, it seems reasonable that the more complex models, which are based on physical arguments and do not contain many fitting parameters, are perhaps closest to reality. Of course, this assumes that they fit the experimental data and observations. This last point has been overlooked in the validation of many models. For example, a model may fit the data very well for certain operating conditions, but if it does not at least predict the correct trend when one of those conditions is changed, then the model is shown to be valid only within a certain operating range. This review has highlighted the important effects that should be modeled. These include two-phase flow of liquid water and gas in the fuel-cell sandwich, a robust membrane model that accounts for the different membrane transport modes, nonisothermal effects, especially in the directions perpendicular to the sandwich, and multidimensional effects such as changing gas composition along the channel, among others. For any model, a balance must be struck between the complexity required to describe the physical reality and the additional costs of such complexity. In other words, while more complex models more accurately describe the physics of the transport processes, they are more computationally costly and may have so many unknown parameters that their results are not as meaningful. Hopefully, this review has shown and broken down for the reader the vast complexities of transport within polymer-electrolyte fuel cells and the various ways they have been and can be modeled.

Modeling transport in polymer-electrolyte fuel cells.

Membrane contactors represent an emerging technology in which the membrane is used as a tool for inter phase mass transfer operations: the membrane does not act as a selective barrier, but the separation is based on the phase equilibrium. In principle, all traditional stripping, scrubbing, absorption, evaporation, distillation, crystallization, emulsification, liquid‐liquid extraction, and mass transfer catalysis processes can be carried out according to this configuration. This review, specifically addressed to membrane distillation (MD), osmotic distillation (OD), and membrane crystallization (MCr), illustrates the fundamental concepts related to heat and mass transport phenomena through microporous membranes, appropriate membrane properties, and module design criteria. The most significant applications of these novel membrane operations, concerning pure/fresh water production, wastewater treatment, concentration of agro food solutions, and concentration/crystallization of organic and biologica...

Membrane Distillation and Related Operations—A Review

This report presents the findings from a study of the life cycle inventories (LCIs) for petroleum diesel and biodiesel. An LCI is a comprehensive quantification of all the energy and environmental flows associated with a product from “cradle to grave.” It provides information on raw materials extracted from the environment; energy resources consumed; air, water, and solid waste emissions generated.

/pdf/life-cycle-inventory-of-biodiesel-and-petroleum-diesel-for-16rzoo114v.pdf

Life Cycle Inventory of Biodiesel and Petroleum Diesel for Use in an Urban Bus

Part 1 Introduction: definitions and principles. Part 2 Fluid mechanics: fluid statics and its applications fluid flow phenomena basic equations of fluid flow flow of incompressible fluids in conduits and thin layers flow of compressible fluids flow past immersed bodies transportation and metering of fluids agitation and mixing of liquids. Part 3 Heat transfer and its applications: heat transfer by conduction principles of heat flow in fluids heat transfer to fluids without phase change heat transfer to fluids with heat change radiation heat transfer heat-exchange equipment evaporation. Part 4 Mass transfer and its applications: equilibrium stage operations distillation introduction to multicomponent distillation leaching and extraction principles of diffusion and mass transfer between phases gas absorption humidification operations drying of solids adsorption membrane separation processes crystallization. Part 5 Operations involving particulate solids properties, handling and mixing of particulate solids size reduction mechanical separations.

Julian C. Smith

Papers

Unit Operations of Chemical Engineering

Operaciones básicas de Ingeniería Química

Operasi Teknik Kimia

School of chemical engineering faculty of engineering and technology

Unit Opearations of Chemical Engineering