Use of magnetic nanoparticles for wastewater treatment
Author(s)Parekh, Asha, 1942-
Massachusetts Institute of Technology. Department of Chemical Engineering.
T. Alan Hatton.
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Contamination of marine sediments and water environments by urban runoffs, industrial and domestic effluents and oil spills is proving to be of critical concern as they affect aquatic organisms and can quickly disperse to large distances as highlighted by the recent Gulf oil spill disaster. Polycyclic aromatic hydrocarbons (PAHs), poly chlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and heavy metals like mercury, lead and manganese are among the ubiquitous trace contaminants of marine and freshwater systems. Presence of these contaminants raise concerns as small quantities of the organic chemicals have been shown to be carcinogenic to mammals and can pose a risk to both human health and the aquatic biota. We have proposed a remediation technique based on a magnetically enhanced separation technology as an alternative to existing methods to separate the target contaminants from a sediment matrix or wastewater stream. This technology uses specifically tailored surface modified magnetic nanoparticles (MNP) that are capable of a high uptake of trace metals. These particles have a magnetic core that facilitates their recovery, a shell that provides stability, protection from oxidation and a surface to which contaminant specific ligands are attached. The advantages of this alternative are that it involves low cost chemicals and magnets, can be implemented in continuous manner and is target specific. To evaluate the feasibility of this project, we have explored thermodynamics of adsorption of contaminants on particles and transport of these particles through their medium of application (water and porous media). This work focuses on treating effluents contaminated with heavy metals, in particular, mercury. For the treatment, dithiocarbamate functionalized magnetic nanoparticles were synthesized and their adsorptive properties for mercury at different pH conditions, ionic strengths and in presence of salinity and competing ions were explored. A competitive adsorption model based on mercury speciation was developed to explain the experimental results. In addition to the adsorption experiments, theoretical models to determine binding constants of the functional group on these particles to the mercury species were evaluated using Gaussian. Transport properties through porous (representing sediment like structures) and nonporous (representing effluents) media were studied using finite element models. The simulations provided a fundamental understanding of how magnetic nanoparticles would behave differently under magnetic field gradients and in porous media. In addition, parametric results of a continuous separation model that quantifies the trend in separation as a function of system parameters were also investigated. Bench scale runs for treating wastewater-containing mercury with these particles were demonstrated. Apart from adsorption, this process uses a well-studied high gradient magnetic separation (HGMS) system to capture the magnetic nanoparticles. Breakthrough analysis of mercury and particles through the entire system, capture on particles by the HGMS system, recovering magnetic nanoparticles by stripping off the contaminant were studied in this work. As part of the PhDCEP Capstone paper, commercialization prospects of this technology have been examined for industrial applications, particularly heavy metal removal. An in-depth market analysis of North America's water and wastewater treatment chemicals market was carried out to determine market attractiveness. This was followed by competitor analysis and evaluation of this technology's value proposition based on economics and technical applicability. A roadmap of strategies that need to be adopted based on key market insights was discussed. This chapter concludes with the verdict on magnetic nanoparticles' potential as a disruptive game changer in industrial wastewater treatment market
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2013.Cataloged from PDF version of thesis.Includes bibliographical references.
DepartmentMassachusetts Institute of Technology. Department of Chemical Engineering.
Massachusetts Institute of Technology