Research Projects

2021 - 2024

A surface chemistry approach to inhibition of particle-induced hydroxyl radicals generation

Sponsor: National Institute for Occupational Safety and Health | Principal Investigator: Dr. Barbara J. Arnold

The Toxicity of the dust is basically linked to the bioactivity of ultrafine particles, e.g., coal, crystalline silica, pyrite, aluminosilicates, and, in some cases, diesel particulate matter (DPM). Formation of the reactive oxygen species, such as hydroxyl radicals on the surface of these particles, brings about such bioactivity. Inhalation and the subsequent interaction of these particles with human lung tissues entail serious health issues, such as lung cancer. Deterring or reducing the formation of the reactive radicals on the surface of dust particles would, therefore, result in the elimination or reduction of the toxicity. To date, various mechanisms have been offered for the detoxification of dust particles, including the metal-micelle coating, blockage of surface active sites, chelation of the surface metal ions, surface silanization, masking of surface active sites with rare earth elements, and change in surface functional groups via polymer-coating. This clearly speaks to the fact that there is no single universal detoxification mechanism for the dust owing to the complexity in surface chemistry of the various minerals and coal. One feasible promising remedy that may employ one or more of the proposed detoxification mechanisms is the use of chemical additives. Such a practice would require a thorough understanding of the origin/ mechanism of toxicity on the surface of dust minerals and the surface properties of these particles at an atomistic level. While there has been much work in this regard, there are questions yet to be thoroughly explored in the context of surface chemistry. Further, many factors such as water quality, coal rank, synergistic or antagonistic effects of the composing phases, particle size and aging, and potential hazards and cost of target chemical agents should also be considered. Further investigation using Simulated Lung Fluid (SLF) to determine whether the toxicity is enhanced in that medium would also be insightful.

How the free radicals damage our body cells?

Free radicals, Explained!

Water molecule interaction with Quartz-crystalline silica (001) hydroxylated surface

(Electron Depletion [Cyan color] and Electron Accumulation [Yellow color])

Interactions of water and oxygen molecules with Pyrite (100) surface

2019 - 2021

Recovery of phosphorus and rare earth elements from Florida phosphatic waste clay

Supporter: Florida Industrial & Phosphate Research Institute | Principal Investigator: Dr. QingQing Huang

• Over two billion tons of waste clay has been accumulated in Florida to date

• This reserve contains about 600 million tons of P and 600 thousand tons of REEs

• This reserve can satisfy a great portion of U.S. domestic demand for REEs and P

• Waste clay poses severe environmental problems along with economic loss

• Waste clay has been considered as an ultimate processing challenge in the industry

The daily growing demand for critical materials has further highlighted the importance of secondary sources such as industrial waste streams. Waste clay, a phosphate ore process tailing, contains a remarkable amount of critical materials such as P and REEs so that comparing to different phosphate ore process streams, waste clay presents the highest concentration of REEs after phosphate rock. Due to the enormous volume of this waste accumulated in Florida to date, this reserve can satisfy a great portion of U.S. domestic demand for REEs, as an example. However, due to its troublesome nature, this reserve poses severe environmental problems along with economic loss. Two required attempts are the removal of extremely fine-sized clays, followed by the recovery of phosphate content, which can pave the path for the recovery of REE-bearing phases. Different possible remedies or combinations of them have been considered by various research/ industrial trials, including froth flotation, selective-flocculation, floc-flotation, cycloning, gravity separation, magnetic separation, leaching, etc., most of which have shown no promising solution because of failing to address economic and of course environmental concerns. Moving from mostly chemical separation processes to the primarily physical/ physicochemical processes with low operational costs and environmental impacts could be a general solution. This requires detailed mineralogical and elemental characterization, physicochemical, rheological, electrochemistry, surface chemistry, crystal chemistry, solution chemistry, and quantum chemistry investigations on each single and then mixed-phase systems composing waste clay. Such insights can help develop the fundamental knowledge, upon which more versatile and efficient solutions can be established.

2019 - 2023

Flotation of Apatite from phosphatic waste clay – A multiscale investigation

Collaborators: Penn State University, University of Lorraine, West Virginia University | Principal Investigator: Amir Eskanlou

The effect of dissolved multivalent metal ions/ species on the flotation of valuable minerals has been a long-standing mystery. The difficulties in the flotation separation of apatite, a semi-soluble salt-type P-rich mineral from carbonates, silicates, and clays as its major associated gangues, are generally attributed to the similarities in the surface properties, slime-coating and changes in the pulp rheological characteristics, and the effect of dissolved lattice metal ions. Unlike the two former factors, the latter has not been extensively and fundamentally studied so that its various aspects, as well as mechanisms of influence, remain to be addressed. In this study, we aim to explore the effect of Al3+ and Mg2+ metal ions on the flotation performance of apatite using fatty- and hydroxamic acid collectors. As such, ab initio molecular dynamics (AIMD) simulations, zeta potential and XPS studies, UV-Vis adsorption tests, and micro-flotation experiments were conducted to investigate the different aspects of the matter.

Effect of Al3+ and Mg2+  ions on the flotation of Apatite using fatty acid collector

Charge transfer during adsorption of NaOl on Apatite