AbstractsBiology & Animal Science


by Tedros Mesfin Berhane

Institution: Miami University
Department: Geology
Degree: PhD
Year: 2015
Keywords: 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
Record ID: 2059045
Full text PDF: http://rave.ohiolink.edu/etdc/view?acc_num=miami1429882830


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…