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theses

Heteroaggregation, the process of aggregation between dissimilar particles is becoming increasingly popular due to the versatile applicability of heteroaggregates. The specific requirements of these widespread application areas require customized heteroaggregates with unique set of properties related mainly to the size and composition of these heteroaggregates. This has created an immense need for a developed understanding of the heteroaggregate process. However, research on heteroaggregates have been very limited, even fundamental questions pertinent to the mechanism of heteroaggregation process remain unanswered to date. The goal of this work is to study and understand the heteroaggregation process both at particle scale to answer some of these fundamental queries about heteroaggregate structure and composition and also use that knowledge to advance the development of process scale models of heteroaggregation. The first aim of this study is to develop a population balance model (PBM) for the second stage of the heteroaggregation process or the agglomeration stage to predict final heteroaggregate particle size distribution (PSD). The model is also used to study the effect of different parameters on the important forces in the system such as electrostatic, van der Waals and hydration force to understand factors that lead to a faster agglomeration dynamics. The model is validated by comparing with experimentally measured final heteroaggregate PSD. The second objective of this work is to develop a model for the first stage of the heteroaggregation process or the layering stage where smaller nanoparticles layer on a larger microparticle and affect its properties, thereby making it more susceptible to aggregation with other such particles in the second stage of heteroaggregation. The model results are compared with the experimental study of monoaggregate structure performed by scanning electron microscopic imaging of the same. This is essential for understanding factors that regulate and limit layering, and in turn affect the monoaggregate distribution and consequently heteroaggregate PSD and the presence of different heteroaggregate regimes. Furthermore, these two models are combined to develop an integrated model for both stages of the heteroaggregation process. The progress of the system towards different heteroaggregation regimes have also been simulated and validated experimentally by studying the final heteroaggregate PSD. The third aim of this study is to investigate the adsorption characteristics of the heteroaggregates for the adsorption of oppositely charged heavy metal ions from single ion as well as mixed ion systems which represent real industrial wastewater more accurately than commonly studied single ion systems. The adsorption capacities of the heteroaggregates from three different regimes are also compared with the adsorption characteristics of the individual components of the heteroaggregates to see if the heteroaggregates offer an advantage over the individual adsorbents. The bio-friendly nature, oppositely charged components and an adsorption capacity comparable to that of industrially popular adsorbents make this system a good choice to replace commonly used adsorbents in the future. This study is expected to advance the field of heteroaggregation by answering some of its most fundamental questions and at the same time aid in the utilization of this knowledge to progress towards the production and use of heteroaggregates in real life applications.

ETD_9487

Ph.D.

Includes bibliographical references

by Anik Kumar Chaturbedi

doi:10.7282/t3-w8qe-8850

ETD doctoral

The author owns the copyright to this work.