Research Initiation: Micromixing Effects in Fast Aluminum Neutralization-Precipitation

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The objective of this project is to determine whether combining mathematical models of flow and small scale mixing with kinetic models for the neutralization-precipitation of aluminum in water treatment processes could predict the nature of the speciation of aluminum that occurs during fast-base neutralization in small, batch turbine reactors. While equilibrium chemical models have advanced the understanding of the chemistry of the aluminum system and its efficacy as a chemical coagulant for the treatment of potable waters, current approaches are unable to provide a prediction of the commonly observed effects of variable mixing and reactant injection techniques on final aluminum product distribution during treatment of drinking waters with aluminum coagulants. This project involves a study of the kinetics of aluminum product transformation in near-homogeneous base neutralization experiments (stopped-flow technique). Membrane filtration techniques and photon correlation spectroscopy will be used to monitor the formation of aluminum polymers and precipitate particles. The kinetic data will be incorporated in trial kinetic expressions and combined with specification for large and small scale mixing ("micromixing") of aluminum and base in turbulent reactors. The predictions of this mathematical model will be compared with experimental results for aluminum product speciation in larger scale aluminum neutralization studies with variable mixing and reactant injection techniques. Results of this work are likely to be applied toward improving the engineering design of water and wastewater treatment processes and systems.