|
Current Research Strengthening of polymers by electro-osmotically driven, in-situ precipitation of nanoparticles This
project is exploring the ability of electro-osmosis to transport reactive
ions to sites within a polymeric matrix where the ions can precipitate
as nanosized ceramic particles. The objective is to produce nanostructured
composites with exceptionally well-controlled nanostructures, and outstanding
mechanical properties. Granules of polymers, such as polymehtylmethacryslate
(PMMA), are being partially functionalized to introduce anionic functional
groups on the surface, and increase the hydrophilicity of the polymer.
Sequential elecrto-osmosis flow of calcium and phosphate ions will then
be induced, to promote the nucleation and growth of nanosized particles
of hydroxyapatite at the sites of the original functional groups. After
precipitation, the composite material will be stabilized by melting or
dissolution followed by forming, and finally by re-esterifying unreacted
functional gorups to restore the original PMMA structure. Removal of Heavy Metals from Acidic Manganese Chloride Solution
A manganese ore from Azul Mine in Brazil is currently being leached with
HCl, to remove heavy metals selectively, thereby producing battery-grade
MnO2. We have identified a way of selectively separating Cu, Ni, Co, Pb
and Zn from the resulting acidic manganese chloride solution, to detoxify
it and produce marketable chloride solution. Chelating ion exchange resins,
particularly Dow M 4195, have proved more promising for this separation
than solvent extraction with commercially-available reagents. The
effect of pH on the uptake of different metal ions has been studied. Foam separation of metal ions from dilute waste streams A significant
current problem in minerals and materials processing, and in environmental
remediation, is developing economic methods for removing metal ions from
comparatively dilute solutions, either for recovery, or to comply with
waste discharge requirements. Conventional separations techniques are
rarely economic for large volumes of dilute solutions. A relatively new
approach involves complexing the ions with relatively high molecular weight
organic complexing agents, to generate hydrophobic species that can be
removed from the bulk solution by flotation. Work already done has elucidated
the underlying physical chemistry of the process. Current work is examining
the surface chemistry that determines the interaction of ionic contaminants
with different collectors, and redesigning flotation equipment. Future
work will investigate more thoroughly the solution chemistry and adsorption
behavior, and tackle overall flowsheet design. Effect of Salinity on Generation of Acid Rock Drainage Acid rock
drainage (ARD) occurs when the mineral pyrite, FeS2, is exposed
to air and water. Acid is
released, which often leaches other minerals, introducing toxic metals
into the drainage. ARD can
be extremely deleterious to aquatic organisms.
This project is focusing on a site where industrial wastes
containing pyrite are present on the shores of the San Francisco Bay. The wastes are subject to tidal influence, but the effect
of salinity on the rate at which acid is released from pyrite is
unknown. Columns have been
set up to subject cores of the waste to a simulated tidal action, and
measure the rate at which acid is released.
The results will influence the eventual remediation strategy
to be used at the affected site. Attenuation of Heavy Metal Contaminants by Sorption on Organic Constituents of Soil coated
onto inert particles will be equilibrated with solutions containing different
levels of copper, cadmium anThis project seeks to characterize the uptake
of heavy metal contaminants onto the organic constituents of soil, and
their later release, to allow modeling of the attenuation of contaminant
plumes in soils. Well-characterized
organic material d lead, which will serve as model heavy metal contaminants.
Sets of adsorption/desorption isotherms will be generated
for single and mixed metals, at various ionic strengths and pH’s.
Concurrent theoretical analysis of the solution chemistry
and partition behavior will assess the ideality of the adsorption behavior.
The adsorption isotherms are intended for incorporation
into a model for the attenuation of heavy metals in soils, to be developed
as future work. Electrochemistry of Chemical Mechanical Planarization (CMP) Chemical
mechanical planarization is becoming increasingly important in the fabrication
of multilayer semiconductor devices. Ideally, one wants a slurry that
does not etch planar metallization layers, yet does dissolve metallic
fragments abraded from the device surface. This requires the planarization
process to be under kinetic control, and the leaching of fragments to
be under, or closer to, thermodynamic control. As a first step towards
better understanding the underlying surface science, with an eventual
goal of developing better polishing slurries, we are examining the chemical
and electrochemical action of different complexing agents at specific
pH and redox potentials. Our results are evaluated with reference to the
Eh-pH diagram for the system. A different project will examine the
fundamental physicochemical phenomena controlling the behavior of polishing
slurries, with a view to formulating better slurries, reducing the consumption
of slurries, and allowing recycle and detoxification of slurries. Remediation of acid mine drainage Acid mine drainage (AMD) occurs when pyrite, FeS2, is exposed to air and water. Acid is released, which often leaches other minerals, introducing toxic metals into the drainage. AMD can be extremely deleterious to aquatic organisms, and may be produced indefinitely from exposed mine wastes. The oxidation of pyrite to Fe(II) and sulfate occurs by a chemical reaction that is slow at neutral pH, but becomes faster at pH values below 4, due to microbial action. This creates an autocatalytic process. The major goal of the project is to use specific chemical species produced by pyrite oxidation to precipitate insoluble compounds that can coat unreacted pyrite and reduce the permeability of waste-rock, tailings and disturbed ore-bodies, thereby reducing the rate of pyrite oxidation in future. Appropriate treatments are constrained by the need for environmental acceptability.
|