Department of Environmental Science,

Policy and Management

Environmental Geochemistry @Cal

Projects

 

 Phosphates - the building blocks of vertebrate skeletal materials - have the fascinating ability to accommodate a vast range of elements in their crystalline lattice. We are investigating the nucleation and growth kinetics and mechanisms of these phases to improve technologies for nutrient recovery from municipal and distributed wastewater streams and for heavy metal remediation in contaminated soils and sediments.

Phosphate growth for contaminant remediation and nutrient recovery and reuse

(left) SEM image of synthetic hydroxyapatite crystals.

(right) AFM image of uranium phosphate nanocrystals decorating the surface of a Caulobacter crescentus bacterium.

 

 

 

 

Clay minerals are essential components of soil due to their nanoparticulate nature, their very high surface area, and in some cases their structural charge. These properties enable clay to immobilize or adsorb nutrients and contaminants from the aqueous phase and can provide a useful catalytic substrate.

 

We are using classical molecular dynamics simulations (MD) to investigate the adsorption of the Cs-137 radionuclide to surface and interlayer sites of the clay mineral illite. These simulations could provide information on the mechanisms by which illite strongly retains Cs deep within the clay interlayer structure, giving us insights into the transport of Cs in contaminated soil.

 

 

 

 

Clay minerals are essential components of soils and geologic reservoir rocks due to their impact on bulk mechanical properties and permeability as well as their incredible capacity to adsorb ions and organic species. We are using a variety of molecular simulation techniques to investigate the kinetics and thermodynamics of ion exchange and swelling. These findings improve our understanding of contaminant radiocesium transport and helps refine models of Engineered Barrier Systems for nuclear waste storage.

Four layer nanoparticle of K-illite in aqueous solution (water molecules not shown).

Clay interface and interlayer reactivity for radionuclide management

 

Carbonate minerals are crucial phases for the permanent sequestration of carbon dioxide. Moreover, the isotopic and trace element compositions of these phases are widely used to reconstruct the paleo-environment.

 

We investigate the interfacial processes governing carbonate mineral growth and recrystallization in soils and marine carbonate sediments, emphasizing the interplay between impurity uptake, thermodynamic stability and growth kinetics, with the goal of controlling carbonate mineralization for negative emissions technologies (NETs) and for contaminant remediation.

Carbonate mineralization for negative emissions technologies

(left) Schematic of the custom double-titration chemostat apparatus used to perform crystal growth experiments under fixed chemical conditions, including solution saturation state, pH, and temperature.

(right) Electron probe image of magnesian calcite overgrowth material precipitated over pure calcite seed crystals to investigate Mg partitioning and its influence on the stable isotope composition of calcite.