Tag: Spring 2010

Electrolytic Copper Refining: Pre-Passivation Behavior of Copper Anodes

Friday March 19
Chem. Sci. & Engineering Room 101
10:00 a.m.

Presenter: Dr. J. Brent Hiskey, University of Arizona, College of Engineering

Abstract: Commercial copper electrorefining accounts for the majority of refined copper produced worldwide.  Anode passivation is often encountered in these facilities with dire effects on operational efficiency and cathode quality.  Passivation results in an immediate increase in power consumption and possibility of floating slimes that can adversely affect the cathode quality.  This presentation discusses the period just prior to passivation onset.  Fast scan chronopotentiometry (FSCP) was used to obtain detailed information regarding potential oscillations in the prepassivation region.  The periodic oscillations indicate that the surface is fluctuating between unsynchronized and synchronized dissolution and formation of a sulfate salt-film.  These results yield valuable information regarding the passivation mechanism involving  commercial copper anodes.

Application of Common Analytical Methods to Complex Transport Phenomena Problems

Friday February 26
Chem. Sci. & Engineering Room 101
10:00 a.m.

Presenter: Dr. Norman W. Loney, New Jersey Science & Technology University, Otto H. York Department of Chemical, Biological and Pharmaceutical Engineering

Abstract: “For more than a decade, researchers and educators in engineering and science have agreed that computational and simulation engineering sciences are fundamental to the security and welfare of the United States” -National Science Foundation report (February 2006) on Simulation-Based Engineering Science (SBES).  The already diverse field of Chemical Engineering is expanding to include nano-materials, biological sciences with Pharmaceutical and Medical applications. The common language between all the different subjects is mathematics.    Traditionally, industrial type problems or applied research problems of a mathematical nature are solved using numerical analysis approaches.  However, a number of industrially relevant problems can be simplified enough to allow the application of appropriate analytical methods.  Extraction of particular information from such results will aid in further improving a process or at least help to focus on the important variables for further experimentation.     In this presentation we will review briefly some of the properties that facilitate application of analytical methods and discuss three contemporary examples. Each example provides relevant results that have been benchmarked with available independently published experimental data.

When metabolism goes awry! The case of maple syrup urine disease

Wednesday February 12
Chem. Sci. & Engineering Room 101
10:00 a.m.

Presenter: Dr. K. Michael Gibson, Michigan Technological University, Department of Biological Sciences

Abstract: Maple syrup urine disease (MSUD; branched chain keto acid dehydrogenase (BCKDH) deficiency) is a rare, inherited disorder affecting the breakdown of branched chain amino acids (BCAA; L-isoleucine, L-valine, L-leucine).  Incidence is about 1:200,000 live-births, but much higher in selected populations (Amish, Mennonites, etc).  State screening in newborn bloodspots for leucine levels has been mandated for many years.  Treatment consists of dietary protein restriction, a liquid formulation low in branched chain amino acids, or orthotopic liver transplantation (OLT) in some instances.  While effective, these interventions remain problematic, since they are either unpalatable, treatment is lifelong, compliance is challenging (especially in adolescents), and immunosuppressive interventions are necessary.  Accordingly, our laboratory seeks alternative approaches for long-term treatment of MSUD.Since OLT is effective, we have sought to treat MSUD mice using hepatocyte transplantation (HTx), using isolated cells with normal BCKDH activity.  To provide an engraftment advantage, HTx has been performed in newborn mice, whose livers are rapidly expanding.  Thus far, preliminary studies have shown ~3% engraftment of exogenous hepatocytes, transient improvement of blood BCAA levels, enhanced expression of BCKDH activity, and improved body weight and lifespan.  Importantly, HTx corrects abnormalities in monoamine (dopamine, serotonin) levels in brain known to be associated with MSUD.

A Review of Gold Metallurgy

Wednesday February 3
Chem. Sci. & Engineering Room 211
8:00 a.m.

Presenter: Dr. Sevket Acar, Director, R&D, Newmont Metallurgical Services

Abstract: The occurrence of gold defines how it is going to be processed.  Free native gold particles may be concentrated via gravity and/or flotation methods and sold.  Some concentrates may require to be further treated by smelting or leaching to recover gold.  Gold may be associated with oxide ores which may require dump (or heap) leaching or milling.  On the other hand, refractory gold ores may require pretreatment, to render gold leachable, followed by leaching with cyanide.  Pretreatment options may include roasting, pressure oxidation and bio oxidation.  Once the leaching with cyanide is completed then the gold needs to be recovered from pregnant solution via Merrill Crowe or activated carbon.  In this presentation, importance of gold occurrence, mineralogy, oxide and refractory gold ore treatment technologies and recovery of gold from solution will be reviewed

Porous Silicon: Electrochemistry Enabling Microsystem Integration

Friday January 29
Chem. Sci. & Engineering Room 101
10:00 a.m.

Presenter: Dr. Paul L. Bergstrom, Michigan Technological University, Department of Electrical and Computer Engineering

Abstract: This presentation will explore how porous materials, and porous silicon in particular, may be utilized in many microsystem applications that benefit society. An exploration of the processes and fabrication technologies required to utilize porous silicon in applications will be presented through an overview of the porous silicon research underway at Michigan Technological University in Dr. Bergstrom’s research group. The seminar will present the formation of porous silicon by electrochemical anodization and process control parameters impacting the morphology of the resulting material. Nanoporous, mesoporous, and macro porous silicon in various orientations will be presented.  Applications under current investigation will be considered, including submicron particulate filtration, reference evaporation and adsorption preconcentration sources developed for the Environmental Monitoring Testbed under the NSF Engineering Research Center for Wireless Integrated Microsystems, microfluidic devices, chemicaland biological sensing, and other micro electro mechanical system (MEMS) devices based on a variety of porous silicon morphologies.

Mapping Charge-Mosaic Surfaces in Electrolyte Solutions Using Atomic Force Microscopy: New Chapter in Colloid Science

Friday January 22
Chem. Sci. & Engineering Room 101
10:00 a.m.

Presenter: Dr. Jaroslaw Drelich, Michigan Technological University, Department of Materials Science and Engineering

Abstract: Colloidal forces dominate stability of particles in aqueous environment and often dictate strategies in wet processing of minerals and other materials.  The most successful approach to the problem of net interactions between two interfaces in these systems was proposed by Derjaguin, Landau, Verway and Overbeek and is known as the DLVO theory.  This Theory treats the total interaction force between two surfaces in a liquid medium as an arithmetic sum of two components:  van der Waals and electrostatic (electrical double layer) forces.  The DLVO theory has been used as a meanfield approach, where only one surface potential and one Hamaker constant are used to describe the colloidal forces.  On a contrary, a vast majority of surfaces of particles and materials in technological systems are of a heterogeneous (mosaic) nature composed of microscopic and submicroscopic domains of different surface characteristics.  In these systems, the interactions can be dominated by heterogeneities rather than average surface character.  Attractions can be stronger, by orders of magnitude, than would be expected from the classical mean-field model when areaaveraged surface charge or potential is employed.  To detect heterogeneities in surface charge, analytical tools which provide accurate and spatially resolved information about material surface potential—particularly at microscopic and sub-microscopic resolutions—are needed. A novel AFM-based technique for mapping surface charge domains on heterogeneous surfaces was recently introduced by our research team.  It relies on recording colloidal force curves over multiple locations on the substrate surface using small probes.  The experiments are conducted in electrolyte solutions with different ionic strengths and pH values.  The force-distance curve measurements are carried out stepwise across phases of different surface characteristic.  Surface charge densities and surface potentials are then calculated by fitting the experimental data with a DLVO theoretical model.  The surface charge characteristics of the heterogeneous substrate are determined from the recorded colloidal force curves, allowing for the surface charge variation to be mapped.  In this presentation, the AFM technique will be briefly introduced and its use in determination of local surface charges for a multi-phase rock and bitumen will be reviewed.