Cs137 is generated from fission nuclear reactor operations. It has a half-life time of 30 years, and it is considered to be an excellent source of gamma radiation. Cs137 needs to be separated from nuclear waste before its disposal. Electrically switched ion exchange (ESIX) is one method which can be used for its separation from nuclear waste. ESIX consists of an ion exchange film that is deposited onto a conductive electrode surface. Typically, for Cs+ removal, this film is composed of nickel hexacyanoferrate, which is known for its selectivity for that ion. The ESIX method involves the sequential application of reduction and oxidation potentials to an ion exchange film to induce the respective loading and unloading of Cs+. ESIX can be used to separate Cs137 from nuclear radioactive waste as well as Cs+ from industrial wastewater. The goal of this research was to enhance the capacity of the nickel hexacyanoferrate ion exchange film deposited on nickel electrodes by modulating the applied potential for the ESIX film preparation. This goal was achieved by preparing an ESIX film on a nickel substrate using a two-step process in which voltage is applied to a nickel electrode surface prepared prior to the film deposition using diamond sand paper 2500 grit. The results show the preparation of a film with capacity 63 times higher than that which is previously reported in the literature. Another four ESIX films composed of nickel hexacyanoferrate were deposited on nickel substrates with varying potentials, again in a two-step process and with surface treatment using 800 grit diamond sand paper prior to the film deposition. The surface morphology of the films was studied using scanning electronic microscope (SEM) to note any differences which could have occurred from the changes in deposition procedures. Electrospray ionization-mass spectroscopy was used to quantify the Cs+ loaded and unloaded onto the film. The results show that all of the four prepared ESIX film have a high capacity compared to those reported in the literature and that their performance regarding Cs+ loading was affected by the applied potential used for the ESIX film preparation. Another goal of this research was to enhance the capacity of the nickel hexacyanoferrate ESIX film by changing the substrate from nickel to graphite. This goal was achieved by adsorbing the film into the pores of graphite electrodes. X-ray tomography was used to visualize the nickel hexacyanoferrate film inside the graphite electrodes. Cyclic voltammetry was conducted to detect the response of the prepared film with Cs+. Electrospray ionization-mass spectroscopy was used to quantify the amount of Cs+ adsorbed and desorbed by the electrode. The x-ray tomography results show that the graphite electrode adsorbed nickel hexacyanoferrate material. The cyclic voltammetry figures confirm that the response of each electrode prepared with Cs+ was related to the concentration of nickel hexacyanoferrate in the graphite electrode. Finally, the results obtained from electrospray ionization-mass spectroscopy about how much Cs+ was adsorbed and desorbed confirms that the two prepared electrodes have a higher capacity for Cs+ adsorption based on their interaction with a prepared Cs+ solution as a test solution. Another goal was to observe the performance of a new ESIX film material, namely nickel hexacyanocobaltate. This film was also adsorbed by graphite electrodes. Cyclic voltammetry was conducted to measure the performance of the hexacyanocobaltate film with regard to Cs+, and the results show a significant increase in the nickel hexacyanocobaltate material inside the graphite electrode and Cs+ in the test solution. Electrospray ionization-mass spectroscopy was used to quantify the Cs+ adsorbed and desorbed by the electrode. The Results show that nickel hexacyanocobaltate as an ESIX have high capacity for Cs+ adsorption from test solution. / Thesis / Doctor of Philosophy (PhD)

Indiana University-Purdue University Indianapolis (IUPUI) / Ion Mobility Spectrometry (IMS) is an analytical technique for separation of charged particles in the gas phase. The history of IMS is not very old, and in this century, the IMS technique has grown rapidly in the advent of modern instruments. Among currently available ion mobility spectrometers, the DTIMS, FAIMS, TWIMS, DMA are notable. Though all the IMS systems have some uniqueness in case of particle separation and detection, however, all instruments have common shortcomings. They lack in resolution, which is independent of mobility of different charged particles and they are not able to separate bigger particles (20 120 nm) with good accuracy. The work presented here demonstrates a new concept of IMS technique at atmospheric pressure which has a resolution much higher than that of the currently available DTIMS (Drift Tube Ion Mobility Spectrometry) instruments. The unique feature of this instrument is the diffusion auto-correction. Being tunable, It can separate the wide range of particles of different diameters. The working principle of this new IMS technique is different from the typical DTIMS and to simply put, it can be considered as an inversion of commonly used technique, so termed as Inverted Drift Tube (IDT).The whole work performed here can be divided into three major phases. In the first phase, the analytical solution was derived for two new separation techniques: IPF (Intermittent push flow) and NSP (Nearly stopping potential) separations. In the next phase, simulations were done to show the accuracy of the analytical solution. An ion optics simulator software called SIMION 8.1 was used for conducting the simulation works. These simulations adopted the statistical diffusion (SDS) collision algorithm to emulate the real scenario in gas phase more precisely. In the last phase, a prototype of experimental setup was built. The experimental results were then validated by simulated results.

No description available.

Environmental separation processes such as removal of heavy metals from aqueous solutions, electrosorption in groundwater remediation, and capacitive desalination, as well as energy storage in supercapacitors, are based on the electrical double layer (EDL) formation within nanoporous carbon materials. This research is focused on the nano-scale phenomena of EDL formation inside the confined space of nanopores. The electrosorption behavior of nanoporous carbon materials was characterized by measuring the double-layer capacitance using cyclic voltammetry. The presence of micropores results in the occurrence of EDL overlapping, corresponding to a considerable loss of the double-layer capacitance. Hence, pore size distribution plays an important role in determining the double-layer capacitance. EDL formation has significant influence on ion transport and sorption inside nanopores. The data obtained by simple diffusion and electrochemically-aided diffusion experiments demonstrated the size-exclusion effects on pore accessibility by ions. A larger ion-exclusion volume prevents larger ions from penetrating inside the pores. Batch equilibrium electrosorption experiments using nanoporous carbon materials showed that selective electrosorption, imposed by the difference in the size of hydrated ions, occurs in a competitive environment. Molecular modeling based on Monte Carlo methods was developed to simulate the EDL formation in a slit-type nanopore. Simulation results indicated that the competition in asymmetries of ion charge and size not only determines the screening of surface charge but also affects the electrolyte distribution within charged pores. In a mixture of electrolytes, the charge/size competitive effects can dominate pore accessibility. Multivalent counterions with large size have the energetic advantage of screening surface charge. On the other hand, small monovalent counterions present a ¡§size affinity¡¨ to access the pores. Therefore, electrosorption selectivity of counterions with different properties is a result of a counterbalance between minimization of potential energy and size-exclusion effects. Manipulation of electrosorption selectivity to separate ions could in principle be achieved via tuning the EDL formation inside the pores. The findings of the thesis have several significant implications for the development of advanced techniques for selective separation of ions in environmental systems and energy storage.

HPLC has been used and can quickly determine several ions simultaneously. The method of determination described for transition metals [Cr(III), Fe(III), Ni(II), Co(II), Cu(II), Zn(II), Cd(II), Mn(II)] and [Ca(II), Pb(II)] using HPLC with UV-VIS detection is better than the PAR complexation method commonly used. The effects of both eluent pH and detector wavelength were investigated. Results from using different pHs and wavelengths, optional analytical conditions for the separation of [Ni(II), Co(II), Cu(II)], [Cr(III), Fe(III), Ca(II), Ni(II), Cu(II)], and [Ca(II), Zn(II), Pb(II)] in one injection, respectively, are described. The influence of adding different concentrations of Na_2EDTA solvent to the sample is shown. Detection limits, linear range, and the comparisons between this study and a post-column PAR method are given.