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Title:Characterization of manganese oxide coated porous carbon aerogel to isolate the effects of electro-less deposition time, li+ -ion exchange, and heat treatment on ion selectivity and specific capacitance
Author(s):Kheperu, Mekhakhem S.
Advisor(s):Cusick, Roland D.
Department / Program:Civil & Environmental Eng
Discipline:Environ Engr in Civil Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:M.S.
Genre:Thesis
Subject(s):capacitive deionization, desalination,
Abstract:Motivated by the growing crisis of global water scarcity, this study focuses on an up and coming desalination technique. Capacitive deionization (CDI) is a novel method based on the general concept of ion electro-sorption, with two electrodes acting as capacitors [1]. When polarized in charge/discharge cycles, these cells will remove foreign ions out of brackish water and subsequently expel them into a waste stream. Recently, it has been discovered that when redox-active materials are employed, charge transfer reactions will increase the cell’s ion storage capacity in proportion with mass normalized energy storage [2]. In this study, the performance of porous carbon aerogel electrodes, in terms of energy storage capacity and ion selectivity, is evaluated by varying fabrication techniques - altering electro-less deposition time of amorphous MnO_2, heat treatment for the purposes of phase transition, and Li^+- ion exchange. Additionally, we vary the electrolytic solution (NaCl,KCl,CaCl_2,LiCl) in order to study the cathode's faradaic ion-uptake mechanism and the factors influencing it. Resulting nitrogen adsorption tests on the 15-minute electro-less deposition timed MnO_2- coated aerogel electrodes show low surface area per mass (170 m2 g-1), but high MnO_2 content (14.64% as compared to literature values for the same duration) implying an increased deposition rate [3]. When the pretreated carbon aerogel electrodes of varying electro-less deposition times are characterized using a three-electrode set up, resulting cyclic voltammograms in the voltage window -0.2 to 0.8 V show no relationship between electrode pretreatment and neither capacitance nor ion-uptake. Because specific capacitances are approximately the same at low and high electro-less deposition times, the optimized duration should last for 15 minutes instead of 240 minutes. Future work involves the optimization of operation parameters such as flow rate and current density once the optimized aerogel electrodes can be incorporated into a desalination cell. Additional work was done as educational outreach, for the purpose of investigating the most efficient methods to communicate scientific concepts to middle school students. In light of recent water contamination scandals, the students were taught methods used by engineers and average citizens to clean water containing common contaminants. Two separate student groups were chosen, one in Chicago, Illinois and one in Urbana, Illinois. These groups varied mainly in educational background and neighborhood environment. Either group was presented with a task of using two different types of filters (a granular filter and sand filter) to ‘clean’ contaminated water. This involved a presentation on the overview of water filtration and the engineered water cycle. Subsequently, both groups performed a hands-on activity that involved the assembly and testing of water filtration devices. Observations from presentation to the first group of students helped to better plan the second group's demo session - changes in the lesson plan included making the presentation shorter, more closely walking the students through the assembly and testing procedures, and reduction in the amount of written quizzes taken. Pre and post quizzes show the increase in knowledge of engineering, policies in the field, the engineered water cycle, and confidence in personal ability in the field of science.
Issue Date:2019-07-18
Type:Text
URI:http://hdl.handle.net/2142/105707
Rights Information:Copyright 2019 Mekhakhem Kheperu
Date Available in IDEALS:2019-11-26
Date Deposited:2019-08


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