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KINETIC AND EQUILIBRIUM SORPTION EXPERIMENTS INVESTIGATING PALYGORSKITE-MONTMORILLONITE AS A POTENTIAL FILTER MEDIUM FOR REMOVAL OF PHARMACEUTICALS AND ENDOCRINE-DISRUPTING COMPOUNDS

Berhane, Tedros Mesfin
http://orcid.org/0000-0003-0671-9131
http://rave.ohiolink.edu/etdc/view?acc_num=miami1429882830

Abstract Details

2015, Doctor of Philosophy, Miami University, Geology and Environmental Earth Science.
Water resources contamination by pharmaceutically-active and endocrine-disrupting compounds (EDCs) is widespread. Sewage treatment plants (STPs) are the main gateway of these compounds to the natural environment, posing acute and chronic health risks to aquatic organisms once discharged to rivers and streams as well as a potential human health concern through induced infiltration to municipal groundwater supplies. Concentrations of many of these compounds in the environment tend to be very low; however, the ecosystem and human health effects associated with chronic exposure to low-level concentrations are unknown. Also unknown are the effects when a synergic mix of these compounds and other chemicals that are consumed over a long period of time. There is therefore a need to research cost-effective, innovative alternative treatment technologies to remove pharmaceuticals and EDCs from STP effluent. Sorption is one of the main treatment mechanisms that is employed in sewage- and drinking-water treatment plants due to its low cost, simplicity and effectiveness. This dissertation used batch kinetic and batch equilibrium sorption-desorption experimental approaches to explore the use of the palygorskite-montmorillonite (PM) mix of clay minerals as a function of granule size for removing a selected group of pharmaceuticals and EDCs. This optimization based on granule size is mainly to maximizing both water-flow through the medium while still achieving significant retention of the compounds under common sewage effluent and environmental conditions (pH, ionic strength and temperature). This project also focused on improving the sorptive removal capacity of PM through surfactant-intercalation of PM for a selected group of pharmaceuticals and EDCs. Results from the batch experiments were fit to appropriate kinetic and equilibrium sorption models. For those compounds that followed a Langmuir equilibrium isotherm, a best fit-kinetic model was related to the Langmuir kinetics. This generated a true kinetic, predictive model that was independent of initial experimental conditions and that could be used to evaluate the transport and fate of the compounds through the filter media. The PM had a mix of fibrous and plate-like morphologies. Equilibrium sorption/ desorption data were best fit to the Freundlich isotherm for carbamazepine (with the Freundlich exponent >1) and to the Langmuir isotherm for bisphenol A and ciprofloxacin. As expected, sorption was inversely dependent on granule size. For carbamazepine, given the small differences in sorption between the smallest and medium granules sizes, the medium granule sizes would be appropriate for optimizing both flow and sorption. For ciprofloxacin, and bisphenol A, the smaller granule size would be the most appropriate. Carbamazepine had a higher relative sorption at elevated concentrations (Freundlich exponent greater than one) indicating cooperative sorption. For ciprofloxacin, and bisphenol A, the fit of the Langmuir isotherm implied that there were a limited number of sorption sites. When the batch equilibrium experiments were conducted with incremental dilutions (i.e., net desorption) the degree of sorption was always greater than during the experiments with net sorption. This net sorption-desorption hysteresis (isotherm non-singularity) was observed for all of the compounds, possibly indicating some degree of irreversible sorption. Carbamazepine sorption increased with ionic strength and decreased with temperature. Bisphenol A sorption decreased with increasing temperature while ciprofloxacin sorption increased with temperature. Thermodynamics parameters indicated carbamazepine and bisphenol A sorption were exothermic while ciprofloxacin sorption was endothermic. For all of the compounds, the best fit of the kinetic sorption experimental data was with the pseudo-second-order kinetic model. The dependency of the kinetic sorption rate constant on PM granule size indicated that chemisorption and possibly some intraparticle-diffusion were the main sorption rate controlling factors. Overall, PM is a promising filter material for the amine compounds considered and surfactant-intercalated PMs have shown promising potential for filtering nonionic and anionic organic contaminants.
Jonathan Levy, PhD (Advisor)
Mark Krekeler, PhD (Committee Co-Chair)
Neil Danielson, PhD (Committee Member)
Hailiang Dong, PhD (Committee Member)
Samuel Mutiti, PhD (Committee Member)
136 p.
Environmental Geology; Environmental Studies; Geology; Hydrologic Sciences; Hydrology; Water Resource Management
Palygorskite, montmorillonite, pharmaceuticals, EDCs; surfactant, sorption, desorption, hysteresis, Freundlich, Langmuir, kinetic-sorption, pseudo-second-order, Elovich, intraparticle diffusion

Recommended Citations

Citations

  • Berhane, T. M. (2015). KINETIC AND EQUILIBRIUM SORPTION EXPERIMENTS INVESTIGATING PALYGORSKITE-MONTMORILLONITE AS A POTENTIAL FILTER MEDIUM FOR REMOVAL OF PHARMACEUTICALS AND ENDOCRINE-DISRUPTING COMPOUNDS [Doctoral dissertation, Miami University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=miami1429882830

    APA Style (7th edition)

  • Berhane, Tedros. KINETIC AND EQUILIBRIUM SORPTION EXPERIMENTS INVESTIGATING PALYGORSKITE-MONTMORILLONITE AS A POTENTIAL FILTER MEDIUM FOR REMOVAL OF PHARMACEUTICALS AND ENDOCRINE-DISRUPTING COMPOUNDS. 2015. Miami University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=miami1429882830.

    MLA Style (8th edition)

  • Berhane, Tedros. "KINETIC AND EQUILIBRIUM SORPTION EXPERIMENTS INVESTIGATING PALYGORSKITE-MONTMORILLONITE AS A POTENTIAL FILTER MEDIUM FOR REMOVAL OF PHARMACEUTICALS AND ENDOCRINE-DISRUPTING COMPOUNDS." Doctoral dissertation, Miami University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=miami1429882830

    Chicago Manual of Style (17th edition)

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This open access ETD is published by Miami University and OhioLINK.