This study level process design represents an economically viable method for extracting thorium dioxide and other rare earth elements from monazite ore. This paper incorporates results from the 2019 capstone project from the honors Design Internship in Green Engineering in Chemical and Biomolecular Engineering. In this activity, senior students in Chemical Engineering at the University of Tennessee (UT) focused on the development and study of a process for the recovery of thorium dioxide and P2O5 from monazite. While not mandated, the process offers rare earth oxides as attractive byproducts. The project focused on recovery of byproducts rather than the creation or addition to waste streams. Additionally, (1) the process economics relied heavily on recovery of rare earth byproducts, (2) thorium handling portions of the process could be effectively segregated from rare earth and phosphate handling portions of the process, and (3) thorium and uranium content of waste streams should be carefully managed and eliminated where possible.

The loading ratio of a solvent extraction process is the ratio of moles of metal extracted to moles of extractant fed. Since the efficiency has several limitations, it is recommended to quantify a metal-extraction system in terms of its loading ratio in addition to its efficiency or extraction rate coefficient. In this study, the loading ratio was compared to the efficiency and equations relating the two metrics were derived. It was shown that due to competing effects of the extractant concentration on the loading ratio, an optimum extractant concentration exists for nearly all metal-extraction systems. This optimum is dependent solely on the equilibrium data and the phase ratio. A method to predict the optimum extractant concentration and the loading ratio at any extractant concentration was presented. The method was validated by comparing the predicted loading ratios to the observed loading ratios for previous metal-extraction studies. The advantages of quantifying a process by its loading ratio and targeting the optimum extractant concentration to maximize the loading ratio were discussed. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

A comparison of the ion exchange properties of the inorganic resin Isolute SCX-2 with alkali metal cations, including francium, to the organic Dowex 50X8 resin is presented. The purpose of this study was to investigate the ion exchange properties of the alkali metal cations with a resin containing a less hydrophobic backbone structure. It was found that the less hydrophobic Isolute SCX-2 resin had a smaller range of values for the distribution coefficients when exchanged with the alkali metals than Dowex 50X8.

Extraction of yttrium (Y) from sulfuric acid was studied using di(2-ethylhexyl) phosphate (DEHPA). A portion of the organic phase was recycled back into the mixer after extraction for the mixer to operate at a moderate organic-to-aqueous volumetric phase ratio while processing at a low organic-to-aqueous flow rate ratio. The effective performance of the mixer was evaluated when operating at different organic-phase flow fractions. To model the extraction rate coefficient, a 2-factor designed experiment was performed by conducting both equilibrium and mixer-settler tests. The organic-phase flow fraction was varied over four discrete levels while the extractant concentration was varied over three discrete levels. Increasing the organic-phase flow fraction yielded a continual increase in the extraction rate coefficient. In contrast, increasing the extractant concentration yielded an initial increase followed by a subsequent decrease in the extraction rate coefficient. The decline in the extraction rate coefficient was attributed to a decrease in the yttrium-extractant complex's diffusion coefficient. High metal loading caused an elevated organic-phase viscosity and thus the low diffusion coefficient. An extraction rate coefficient model is proposed to describe the effects of extractant concentration, viscosity and organic-phase flow fraction. Mass transfer resistance was largely in the organic phase.

Frequently optimizations of chemical processes are presented in terms of the maximization of fractional conversion, but the primary concern when implementing a process is much more likely to be the economic viability. These are distinct optima that tend to occur at very different points. It was the purpose of this paper to integrate leaching experimental data with cost analysis to arrive upon economically optimized leaching conditions for the recovery of rare earth elements from phosphogypsum, a water phosphate byproduct. The variables under consideration were the number of leaching reactors and the residence time of each reactor. The modeling results indicated that the optimum residence time was 270 minutes and that the optimum number of stages was one.

Waste phosphatic clay presents a difficult disposal problem and a significant loss of P2O5. Recent developments make this study on the use of phosphatic clay as a feed material for H3PO4 production worthwhile. (a) New data from Florida Industrial and Phosphate Research Institute (FIPR) suggest that the “clay” waste can be effectively treated by improved solid separation coupled with flotation to produce feed material for recovering additional phosphate. (b) The use of “OLI Flowsheet” provides capability to predict performance of aqueous-based processes for a range of possible operating conditions. Using the new FIPR data and “OLI Flowsheet” enabled the design of a new process that can potentially extend the usefulness of current P2O5 ore deposits. Predictions using OLI Flowsheet were able to identify process conditions that effectively overcome the difficulty of high Mg content of phosphatic clay. Estimated manufacturing cost in the current study lead to valuation of the P2O5 content of the phosphatic clay recovered/utilized at 60 to 70% of that of the phosphate rock feed material currently used. Phosphatic clay should be considered as a valuable material that is currently given zero value. The new FIPR data and “OLI Flowsheet” enables the design of a new process that can potentially extend the usefulness of current phosphate ore deposits by extending the fraction P2O5 of recovered.

The performance of two inorganic ion exchange resins, Isolute SCX and Isolute SCX-2, were compared to the performance of the organic resin AG-50X8 in the separation of the radionuclide bismuth-213 from its parent solution of actinium-225. The breakthrough of the actinium-225 for all three columns was well below the toxicity level but the Isolute SCX and Isolute SCX-2 produced less of the bismuth-213 available on the column.

The sorption/desorption of gallic acid, a simple phenolic compound, was studied experimentally in a batch system. The motivation for this project was to provide insight into the recovery of phenolic compounds from switchgrass. Recovery of phenolic compounds could enhance the sustainability and economics of biorefining facilities. The sorption/desorption of gallic acid was shown to be qualitatively similar to that of phenolics extracted from switchgrass; so more extensive studies were made using gallic acid as a surrogate for the complex mixtures of phenolic compounds leached from switchgrass. The kinetics indicate that an approximation of equilibrium was reached within 48 h. Activated carbon was demonstrated to sorb gallic acid and phenolics from water and aqueous switchgrass leachate. The loading capacity of activated carbon for the gallic acid water-activated carbon system increased with temperature for 20 to 60 degrees C. Ethanol was shown to be a preferable elution agent for desorbing gallic acid from activated carbon. Experimental observations and data from this study provide suitable design information that can be used for preliminary evaluation of conceptual designs of an activated carbon based packed-bed process for recovery of phenolic compounds from aqueous switchgrass leachate.

The use of haloaluminate room temperature molten salts has potential for interesting battery chemistries. This is particularly true for acidic (excess Lewis acid, e.g. AlCl 3 , over the organic chloride salts) compositions. In that case, Al is readily plated and stripped, as we discussed some time ago. 1 A particularly interesting battery combination arises when the aluminum negative electrode is paired with the evolution of the halogen from the acidic melt. In that case, maximum redox active species concentration is achieved and maximum voltage can be obtained since the entire electrochemical window is utilized. However, several issues with chlorine evolution are known. First, in an acidic melt chlorination of imidazolium cations occurs. This can be partly mitigated by appropriate modification of the cation. A second problem is the somewhat sluggish catalysis of chlorine evolution observed on carbon surfaces. In this work, we report results of efforts to improve on the latter aspect. Specifically, we describe the catalysis of chlorine evolution by catalytically active surfaces. In particular, we show significant enhancements in onset potential for chlorine evolution using supported Ru catalysts. In Figure 1, we compare the chlorine evolution voltammetry in 1.5:1.0 AlCl 3 :EMIC on bare glassy carbon to that observed on the same electrode coated with a sample of 60 wt% Ru on multiwalled nanotubes (prepared in-house). The onset of chlorine evolution occurs on the order of 300 mV less positive with the supported Ru catalysts. We have deposited the Ru on various carbon structures to explore the applicability of this catalyst system for batteries and flow batteries. Studies of the same reaction on Pt electrodes show that the supported Ru nanoparticles have similar activity to that of Pt for this reaction. In addition, similar results were also obtained for bromine evolution. In that case, the lower volatility of the product allowed us to readily observe the bromine oxidation on the reverse scan. This reaction is substantially more reversible on these catalyzed surfaces. Figure 1: Voltammetry of 60%Ru on MWNT on glassy carbon compared to that of the bare glassy carbon electrode. Figure 1

This paper utilizes new data on voltage efficiency for all-vanadium redox flow batteries to show improved system costs for grid-level applications. As more and more renewable power production is added to the grid the need increases for large scale storage alternatives.

Melting/freezing points of AlCl3 in saturated chloroaluminate ionic liquids [molar ratio 2:1 AlCl3:1-ethyl-3-methyl imidazolium chloride (EMIC)] are measured by differential scanning calorimetry (DSC). A critical range of temperature data (50–130 °C) for AlCl3 dissolution and precipitation from saturated chloroaluminate ionic liquids is obtained. This range of temperature data is of significance to control phase transition of AlCl3 in saturated chloroaluminate ionic liquids. By applying the chloroaluminate ionic liquids to electrolytes for energy storage usage, solid AlCl3 can be partially dissolved and precipitated out during the charging/discharging cycle of energy storage equipment. Therefore, the energy density of the electrolytes is expected to be greatly improved.

This concept was demonstrated with a regenerative hydrogenvanadium battery (RHVB) by Yfit et al. [1].A RHVB has the potential for lower capital costs by eliminating the need for half of the vanadium

Aluminum electrodeposition and electrodissolution in mixtures of AlCl3 and 1-ethyl-3-methylimidazolium chloride on carbon paper electrodes consisting of graphitized fibers were investigated. Porous electrodes, such as carbon paper electrodes, often offer possible advantages such as higher nominal current densities and less dendrite formation, over solid planar electrodes. Cyclic voltammetry, chronoamperometry and pulse current deposition were used to investigate Al plating and stripping on this porous structure. The Al morphology on the carbon paper was probed using SEM. Composition and temperature affect the Al electrode performance through their influence on the diffusivity of ions. Therefore, control of the diffusion process during Al plating/stripping is essential. (C) 2014 The Electrochemical Society. All rights reserved.

This study investigates the equilibrium absorption of water in various solvents and solvent-mixtures being considered for the counter-current solvent extraction of acetic acid from improved Uranium Extraction (UREX+) process solutions. It then seeks to determine if there is any correlation between the equilibrium water content of these solvents and their equilibrium extraction of 0.25M nitric and 0.025M acetic acid. The UREX+ process is a proliferation resistant version of the Plutonium Uranium Extraction (PUREX) process. The solvents studied were n-Dodecane (nDD), 1,2 Dichloroethane (DCE), and Phenyltrifluoromethyl Sulfone (FS-13), and mixtures of these solvents with Tributyl Phosphate (TBP). After studying both pure water and acidified aqueous systems, it seems the water absorption mechanism is independent of the diluent used and remains constant with the addition of the 0.25M nitric and 0.025M acetic acid.

The purpose of this work is to develop an evolutionary procedure to be used by Chemical Engineering students for the base-case design of a Vanadium Redox-Flow Battery. The design methodology is based on the work of Douglas (1985) and provides a profitability analysis at each decision level so that more profitable alternatives and directions can be indentified before additional time and effort is expended on an impractical design. Ultimately, a base case flow sheet and capital cost estimate are generated; this type of design activity as the work presented here is referred to as creation and analysis of a study level design.

This study investigates the use of annular centrifugal contactors for the liquid-liquid extraction of acetic acid from an acidic aqueous phase into an organic phase consisting of 1.5M Tributyl Phosphate in n-Dodecane. Initial break time tests were performed in order to investigate the mixing/separation viability of the organic/aqueous system, and after determining that centrifugal contactors could be used to perform the liquid-liquid extraction, hydraulic tests established the combination of rotation rate and throughput which should be used to ensure proper separation of the two outlet phases. Finally, extraction efficiency data was collected to examine the system conditions that provided the most efficient removal of acetic acid.

Interest in the development of redox-flow batteries (RFBs) for large-scale grid storage is growing, and considerable investments have been made into the research and development of RFBs over the past few decades. Unfortunately, practical implementation has been hampered by various cost and performance issues typical of an immature state of development. One critical factor for the competitiveness of this technology is the installed cost. In this work, we incorporate recent developments in all-vanadium RFBs research and present an analysis of the associated cost factors. The major components of a RFB that affect installed cost are identified and used as variables to create a capital cost function. The function is then used to calculate the rate of change of the capital costs with respect to the major components. The capital costs are also calculated for a range of component values and plotted. Key findings include a high sensitivity of system capital cost to purity of vanadium and substantial fractions of the cost associated with perflurorosulfonic acid membranes currently used for proton transport.