Lithium-ion batteries (LIBs) play a significant role in our highly electrified world and will continue to lead technology innovations. Millions of vehicles are equipped with or directly powered by LIBs, mitigating environmental pollution and reducing energy use. This rapidly increasing use of LIBs in vehicles will introduce a large quantity of spent LIBs within an 8- to10-year span and proper handling of end-of-life (EOL) vehicle LIBs is required. Over the last several years, the Worcester Polytechnic Institute (WPI) team in the Department of Mechanical Engineering has developed a closed-loop lithium ion battery recycling process and it has been demonstrated that the recovered NMC 111 has similar or better electrochemical properties than the commercial control powder with both coin cells and pouch cells, which have been independently tested by A123 Systems and Argonne National Laboratory. In addition, the different chemical compositions of the incoming recycling streams were shown to have little observed effects on the recovered precursor and resultant cathode material. Therefore, the WPI-developed process applies to different spent Li-ion battery waste streams and is, therefore, general. During the last few years, industry has the tendency to employ higher-nickel and lower-cobalt cathode material since it can provide higher capacity and energy density and lower cost. However, higher-nickel cathode material has the intrinsic unstable properties and surface modifications can be applied to slow down its degradation. Here, two facile scalable Al2O3 coating methods (dry coating and wet coating) were applied to recycled NMC 622 and the resultants were systematically studied. The Al-rich layer from the dry coating process imparted improved structural and thermal stability in accelerated cycling performed at 45 °C between 3.0 and 4.3 V, and the capacity retention of pouch cells with dry coated NMC 622 (D-NMC) cathode increased from 83% to 91% compared to Al-free NMC 622 after 300 cycles. However, for wet coated NMC 622 (W-NMC), the increased surface area accompanying by formation of NiO rock-salt like structure could have negative impacts on the cycling performance. There exist three challenges for current LIBs’ recycling research. First of all, most of the research is done in lab-scale and the scale-up ability needs to be proven. The scale-up ability of our recycling process has been verified by our scale-up experiments. The second challenge resides in the flexibility, here once again, with our intentionally designed experiments that having various incoming chemistries, the flexibility is validated. The last challenge is the lack of reliable testing because most of the testing is conducted with coin cells. Coin cells are relatively simple format and lacks persuasion. Here, with various industrial-level cell formats that ranging from coin cell, single layer pouch cell, 1Ah cell and 11Ah cell, a reliable and trustworthy testing is established. With this validation, the hesitation of recruiting recycled materials into industry shouldn’t exist.

A thesis submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering, Johannesburg August 2018 / The flotation process is widely used for upgrading valuable minerals in the field of mining. Many diverse minerals, including most of the world’s base and precious metals are processed by flotation process. Most valuable products produced by flotation pass through the froth phase of the flotation process. The froth phase has attracted more research in recent times because of its significant role in determining the mineral grade and recovery achieved from a flotation operation. The complex processes that occur in the froth phase – detachment, re-attachment, coalescence of bubbles, and competition for attachment sites, mixing and transport all combine to affect the net transfer of mineral particles into the concentrate. Bubbles are formed at different sizes in the pulp phase and coalesce at different rates and as a result the bubble size distribution varies from point to point in the froth phase. Substantial coalescence gives rise to loss of bubble surface area and hence loss of recovery. Competition for attachment sites gives rise to an increase in grade. No method for measuring the variation of froth bubble size distribution (FBSD) was available until Bhondayi and Moys developed one. The method measures the intrabubble impact distance in the froth using a probe dropped at known height through the froth. The average of these intra bubble impacts was considered to be a proxy for froth bubble size distribution; this was calibrated using FBSD. However the measured in the laboratory using photographs taken through the transparent wall of a laboratory cell. A 31 % of error was found and compared to the photographic method, which indicated that the technique over-estimates the actual froth bubble size distributions. This is due to the use of an average IID (proxy) as an estimate of the bubble. In response to the known of actual froth bubble size distribution FBSD in order to quantify the complex processes in the froth phase, an application of a stereological technique/model was developed and tested to obtain estimates of the actual froth bubble size distribution FBSD in lab flotation and Mintek pilot rougher cells as a function of froth height, frother dosage and superficial gas velocity. The model was first validated for a system of flotation with variable froth height in a transparent Wits lab flotation cell. The two-parameter normal distribution model FBSD was considered to fit the model-predicted intrabubble impact distance distribution IIDDs to measured intrabubble impact distance distribution IIDDs. The model was seen to accurately iii predict the FBSD compared to actual FBSD data obtained from above-mentioned conventional photographic method using a calibration scale attached to the transparent flotation cell wall, wherein the experimental IIDDs were accurately fitted by the model-predicted IIDDs. Similar estimation of froth bubble size distribution were also found with the inversion matrix technique. Secondly, the model was then evaluated for flotation condition with variable frother dosage in the Mintek pilot plant rougher cell. The model was seen to estimate the actual FBSD, wherein the IIDDs were precisely predicted compared to experimental IIDDs. Finally, the model validity was then tested for various systems of flotation conditions with variable superficial gas velocity. The model was seen to estimate the actual FBSD for these cases compared to both model-predicted IIDD and experimental IIDDs. The performance of the present model for these systems of flotation was seen to estimate froth bubble size in froth phase from measured IIDD information. Froth bubble size increases with increasing in froth height, and decreases with increasing in frother dosage and superficial gas velocity. Froth height, frother dosage and superficial gas velocity have a strong effect on froth bubble size distribution. / XL2019

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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)

In general, the velocity of inversion of sucrose ie a function of several variables; namely, the temperature, the viscosity, and the concentrations of hydrogen ions, undissociated acid, sucrose, added salts, and non-electrolytes. It can readily be seen, then, that this reaction offers a broad field for research with decidedly varied and diversified lines of attack.

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