Rare earth elements (REEs) are critically important for high-tech, renewable energy and defense industries. However, rare earth minerals (REMs) are stable compounds, requiring aggressive conditions to decompose them for their extraction and use. One exception is the ion-adsorption clays (IACs) that are mined in South China. They were formed in nature via the adsorption of the REE ions on clay minerals; therefore, they can be readily extracted into solution under mild conditions using the ion-exchange leaching process using (NH4)2SO4 as lixiviant. It also happens that IACs are the largest source of the heavy rare earth elements (HREEs) that are critical, especially for the defense industry. At present, more than 80% of the HREEs are produced commercially from the IACs mined in Southeast Asia. The objective of the present research was to study the fundamental mechanisms involved in the formation and processing of IACs using the ion-change leaching process. The first part of the project was the synthesis of IACs by contacting kaolinite samples with known concentrations of rare earth chloride (REECl3) solutions at different pHs and analyzing the synthetic IACs for XPS studies. It was found that the REE adsorption on kaolinite stays constant in acidic pHs. At pH 7 and above, adsorption density increases sharply, possibly due to the formation of REE(OH)3 and/or REE(OOH). The IACs formed under these conditions responded well to the ion-exchange leaching process by reducing the pH to below 7. In the second part of the study, the effect of iron (Fe3+) species co-adsorbing with REEs on the kaolinite surface was studied. Unlike the colloidal phases of IACs formed at pH > 7, the synthetic IACs formed in the presence of iron did not respond to the ion-exchange leaching process using (NH4)2SO4 as lixiviant. This problem has been solved by subjecting the synthetic IACs to a reducing condition to convert the Fe3+ to soluble Fe2+ species at pH < 7. The driving force for the standard exchange leaching process is the large differences between the hydration enthalpies of the Ln3+ ions that are in the range of -3,400 kJ/mole and that of the NH4+ ions (-320 kJ/mole). In the present work, alkylammonium ions (CnH2nNH4+) of varying chain lengths were used as novel lixiviants and obtained excellent results. Since these are surface active species, their concentrations in the vicinity of the clay minerals that are negatively charged would be substantially higher than in the bulk. As a result, it was possible to achieve the same level of leaching efficiencies as obtained using ammonium sulfate at approximately ten times lower reagent dosages. One of the problems associated with extracting REEs from coal-based clays is that the REE concentrations are typically in the range of 300 to 600 ppm, which makes it difficult to extract the critical materials economically using ion-exchange leaching and other processes. As a means to overcome this issue, the REE-bearing particles, including IACs and REMs, were liberated by blunging and subsequently upgraded using the hydrophobic-hydrophilic separation (HHS) process. The results showed that blunging outperformed grinding in liberating the REE-bearing particles from the clayey materials in coal. It was shown that one can improve blunging by increasing the disjoining in the thin liquid films present between clay and other minerals by controlling the double-layer (EDL) forces. These findings should enhance our understanding of the fundamental mechanisms involved in upgrading critical materials and thereby increase the economic viability of REE recovery from coal-based materials. / Doctor of Philosophy / Rare earth elements (REEs) play a vital role in numerous modern industries, advanced technological applications, and defense industries. The United States accounts for about 15 % of the global demand for REEs. However, the country heavily relies on imported Chinese raw materials, creating vulnerability in the U.S. supply chain. REEs are rarely found in concentrations suitable for mining, and in certain cases, extracting and processing conventional REE deposits come with significant environmental hazards. The limited availability of rare earth elements (REEs) raises concerns regarding their production despite their critical role in high-tech industries. Consequently, various federal agencies and private enterprises have recently attempted to identify promising alternative resources due to these complex challenges. REEs have been found in several major coal basins and are evidenced to be associated with coal byproducts such as kaolinite clays–one of the major host materials of IACs. This research investigates the recovery of rare earth elements (REEs) from clayey materials through various processes. Emphasis is placed on the synthesis of ion-adsorption clays from kaolinite, and the factors influencing the ion-exchange leaching process are being studied. Furthermore, the impact of iron co-adsorption on REE binding to kaolinite is being examined, and reductive leaching is being evaluated as a means to overcome the hindrance caused by iron passivating layers. Novel lixiviants are being tested as alternatives to conventional lixiviant ((NH4)2SO4) for REE extraction. The application of hydrophobic-hydrophilic separation techniques for extracting REE-bearing particles from coal clay samples is also being explored, with a comparison made between grinding and blunging processes. Overall, valuable insights into the efficient recovery of REEs from clay minerals are being obtained, contributing to the development of cost-effective and novel approaches for their extraction.

In this work 23Na MAS NMR was validated as a successful quantitative method for studies of exchanging sodium in bentonites useful, in particular, for studies of ion-exchange kinetics. Na-enriched bentonites equilibrated in a re-circulated process water at iron-oxide pelletizing plants may acquire properties of Ca-bentonites after already 20 minutes of the equilibration time, since &gt;50 % of sodium ions will be exchanged by calcium ions during first minutes of bentonite placed in contact with the process water. It was shown that all sodium activated bentonites used in this study exchange &gt;50% of sodium in Na+/Ca2+ and ca 20 % of sodium in binary Na+/Mg2+ systems with the same bentonite/solution ratio and same concentrations of these ions in aqueous solutions as in the process water at a pelletizing plant. In total, approximately 50 % of the exchangeable sodium in original bentonites was exchanged after equilibrating of bentonites in the process water already after 20 minutes. Experimental Na+/Ca2+ exchange curves for ‘model’ Ca2+(aq) solutions and for process water are very similar as Ca2+ is the dominant constituent in the process water. Since bivalent ions (Ca2+ and Mg2+) that present in the process water readily replace Na+ ions, Na-bentonite transforms into Ca- or Mg- bentonite, which have worse rheological, swelling and, therefore, binding properties. This ion-exchange process can influence the binder performance in the pelletizing process. Taking into account that fluorapatite is one of the components present in a blend of minerals processed, possible interactions between orthophosphate (the principal anionic component of apatites) and bentonites in aqueous suspensions are considered. It was found that sorption of orthophosphate on Ca-montmorillonite follows a different pattern from sorption of orthophosphate on aluminum oxides and kaolinite. While there is a small amount of sorption below pH 7, which may involve inner-sphere complexation and precipitation of AlPO4 to Al-OH edge sites on the montmorillonite crystals, most sorption of orthophosphate occurs at higher pH. Both macroscopic sorption measurements and solid-state 31P MAS NMR suggest that above pH 7 there is precipitation of proton depleted calcium phosphate phases. Based on both 31P chemical shifts and 31P chemical shift anisotropies it was concluded that the principal precipitated phased are most likely ‘brushite-like’ phases. Very short spin-lattice T2(31P) relaxation times (≤100 μs) for the orthophosphate/bentonite systems can possibly be explained by the presence of paramagnetic Fe in bentonites. Since there are insufficient concentrations of soluble Fe species in the supernatant solution that may give rise to the observed effects, it is likely that orthophosphate is precipitated as thin layers on the surfaces of montmorillonite crystals, where phosphorus may interact with Fe atoms present in the crystal lattice. PO4-tetrahedra in sorbed species can be also distorted giving rise to a larger 31P CSA than for pure ‘apatite-like phases’. 29Si MAS and 1H-29Si CP/MAS NMR experiments on bentonite samples also performed in this work provide information about impurities of quartz in bentonites, a level of substitution of aluminum by iron atoms in the structure of montmorillonite and about the degree of hydration of montmorillonite. 29Si NMR experiments on bentonite incubated with waterglass in aqueous suspensions at concentrations of sodium silicates as in the process water demonstrated that one can follow the process of polymerization of waterglass in solutions and also detect sodium silicates polymerized on surfaces of bentonites already after 1 hour of incubation. Polymerized waterglass sorbed on bentonite surfaces may also alter rheological, swelling and, therefore, binding properties of sodium-activated bentonites used in pelletization of iron-oxide ores.

Detta arbete har genomförts i samarbete med Hitachi Sweden AB, beläget iLandskrona. Hitachi använder sig av fyra olika storlekar av tuber, som fyllsmed jonbytarmassa för att kunna användas i ett kylsystem. Det nuvarande fyllningssystemet kräver mycket arbetskraft av operatörerna och det tarlång tid att genomföra hela fyllningsprocessen. Därför önskar Hitachi att fåen lösning som effektiviserar och minskar tiden för operatören att fylla påvarje tub. Konceptframtagning utfördes först för att undersöka och definieraproduktens funktioner, utformning, egenskaper och andra viktiga faktorerför att skapa en vision för slutprodukten. Genom utvecklingsprocessen avhela fyllningssystemet för jonbytarmassan, användes CAD för konstruktion, finita elementmetoden samt ritningar för alla delar. Beräkningar användsför att validera systemet och visa om det uppfyller de specifika kraven ochmaterialvalen. Syftet med arbetet är att minska både arbetet för operatörerna och tiden som krävs för att påfylla, med fokus på att monteringenoch fyllningen ska vara enkel att utföra. Den slutliga konstruktionen bestårav en vibrationsmotor som ska tillföra vibration till en del av konstruktionen för att få massan och flöda genom, där stativet är gjord av låglegeratstål och ett kon av rostfritt stål där massan hälls ned och ett munstycke iABS-plast som kan bytas ut beroende på tubstorlek. Vibratorfjädrar sättspå konstruktionen för att eliminera vibration från hela konstruktionen ochendast ha det på konen och bottenplattan. / This work has been carried out in collaboration with Hitachi Sweden AB,located in Landskrona. Hitachi uses four different sizes of tubes, whichare filled with ion exchange resin to be used in a cooling system. Thecurrent filling system requires a lot of manual labor from the operators andtakes a long time to complete the entire filling process. Therefore, Hitachiwishes to have a solution that streamlines and reduces the time for theoperator to fill each tube. Concept development was first carried out toinvestigate and define the product’s functions, design, features, and otherimportant factors to create a vision for the final product. Throughout thedevelopment process of the entire ion exchange resin filling system, CADwas used for design, finite element method, and drawings for all parts.Calculations were used to validate the system and show whether it meetsthe specific requirements and material choices. The purpose of the workis to reduce both the workload for the operators and the time requiredfor filling, with a focus on making the assembly and filling process easyto perform. The final construction consists of a vibration motor that willprovide vibration to a part of the structure to facilitate the flow of themass. The stand is made of low-alloy steel, and a cone made of stainlesssteel is used for pouring the mass. The nozzle, made of ABS plastic, canbe replaced depending on the tube size. Vibrator springs are placed on thestructure to eliminate vibration from the entire construction and only haveit on the cone and base plate.

The Canadian mining industry is one of Canada’s largest industrial sectors, creating jobs and a significant contributor to the economy. However, the mining activities can be detrimental to the environment due to the release of pollutants. Mining extensively uses nitrogen-based explosives, creating explosive impacted mining wastewaters (EIMWW) that contains substantial quantities of ammonia which is toxic to fish and thus, it has serious environmental repercussions. Ion-exchange (IE) with zeolite is an effective method for ammonia removal as it is easily automated, has a rapid start-up, is not significantly impacted by cold temperature or toxicity effects. Thus, it is particularly suited for Canadian mines. However, the traditional IE regeneration approach of using high concentration NaCl solutions creates a secondary polluting stream. Chlorine regeneration of ammonia-loaded zeolite appears to be a promising option to avoid such a secondary source of contamination. An evaluation of this option and other alternative regeneration are the main focus of this thesis. This thesis includes two initiatives. The first is a set of multi-cycle column loading and regeneration tests to investigate the feasibility of a zeolite (SIR-600) column for ammonia removal from a synthetic EIMWW, containing K and Ca as competing ions, coupled with regeneration using different concentration of chlorine solutions and combined salt+chlorine regeneration solutions. NaOCl regeneration was quite effective, but it was slower than salt regeneration. During the NaOCl regeneration, the main mechanism appears to be the oxidation of ammonia to nitrogen gas and hydrogen ions, however the Na in the NaOCl solution also seems to have a role in the regeneration. This results in pH levels around 3 for approximately half the regeneration cycles. In the combined salt+chlorine regeneration, the incorporation of the salt leads to more rapid elusion of the three ions presumbaly because of the higher sodium concentration (205 meq/L Na versus 14 meq/L Na). The long-term total ammonia nitrogen (TAN) uptake of SIR-600 regenerated with a NaOCl and NaOCl-NaCl were fairly similar, they varied within a relatively small range (0.185meq/g - 0.202meq/g). Thus, the various regeneration schemes did not impact the TAN uptake. The only apparent limitation of NaOCl regeneration is that it required a longer duration. However, the NaOCl is very promising because it resulted in very similar TAN uptakes, the SIR-600 showed a higher preference for TAN over K and avoided creating an additional process waste stream. The second initiative addressed concerns regarding the long-term integrity of SIR-600 arising from its exposure to low pH solutions during the regeneration. Long-term batch tests were performed to expose SIR-600 to low pH conditions (pH=2, pH=3, pH=4) and the characteristics of this IE material were evaluated. The 3-month low batch exposure experiment showed that pH below 4 decreased the TAN uptake capacity by up to 58%. There was no considerable impact on the surface gravimetric analysis (TGA) and Powder x-ray diffraction (PXRD). The exposure to pH=2 and pH=3 led to breakdown of the outer surface of SIR-600 and the creation of fine particles. It also led to decreases in the BET surface area and a decrease in the TAN uptake proportional to the decrease in the BET surface area. Thus, the exposure to pHs below 4 impacts the durability of SIR-600, so SIR-600 may have to be replaced more frequently. However, regeneration with NaOCl solutions still seems very promising as it avoids the creation of a secondary waste stream.

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The emerging contaminants (ECs) such as estrogen hormones, perfluorinated compounds (PFCs), bisphenol A (BPA) and 1, 4-dioxane have been detected in natural water bodies at a noticeable level worldwide. The presence of ECs in the aquatic environment can pose potential threats to aquatic organisms as well as human world. Ion-exchange is a highly efficient technology for the removal of heavy metal ions and natural organic materials (NOMs) due to the nature of exchanging similar charged ions. However, this technology has not been explored for removing ECs. In this study, four categories of ECs: estrogen hormones (12), perfluorinated compounds (10), bisphenol A and 1, 4-dioxane were used as model contaminants. The adsorption of each category of ECs onto various types of polymeric resins (MN100, MN200, A530E, A532E and C115) was investigated. The removal of ECs was tested under batch and column mode. The effects of pH, resin dosage, and contact time on the removal of ECs were studied in batch mode; isotherm and kinetics models were applied to fit the experimental data. Column experiments were conducted to verify the practicability of the polymeric resins. Adsorption results have shown that both MN100 and MN200 resins could efficiently remove estrogen hormones mixture (more than 95%), and bisphenol A (more than 80%) with the initial concentration of 100 ìg/L; A532E and A530E could remove perfuorinated compounds mixture (more than 99%) with the initial concentration of 100 ìg/L. As pH increased from 9 to 11, the adsorption capacity onto polymeric resins decreased dramatically for estrogen hormones such as 17á-ethinylestradiol, estriol, 17â-estradiol, 17á-estradiol, estrone, 17á-dihydroequilin and equilin as well as bisphenol A. The adsorption of estrogen hormones and bisphenol A onto MN100 and MN200 resins reached the equilibrium within 24 hours, whereas the adsorption of perfluorinated compounds onto A532E and A530E reached the equilibrium within 8 hours. It was also observed that the adsorption of PFCs largely depends on the C-C chain length. PFCs with longer chain yielded lower adsorption efficiency onto the ion-exchange resins A532E and A530E. Adding salinity decreased the first-order rate constants for the adsorption of bisphenol A onto MN100 and MN200 resins. Fixed-bed column experiment results with estrogen hormones mixtures confirmed that the polymeric resins were good candidates in the removal of estrogen hormones. Trimegestone was the first compound detected in the effluent in the column test while 17â-estradiol, 17á-estradiol were the last. 80% of the exhausted resins (MN100 and MN200) by bisphenol A were regenerated by using pure methanol as regeneration solution. Polymeric resins were not effectively removing 1, 4-dioxane from the aqueous solution. / Civil Engineering

A cation exchange method (Chelex 100) that distinguishes weakly bound and strongly bound copper was investigated for its ability to measure bioavailable copper in estuarine waters. Copper bound to the Chelex 100 resin was operationally defined as bioavailable copper. Varying initial copper concentration from 195 to 495 ug/L at a constant 12.5 mg/L natural organic matter (NOM) did not affect percent bioavailability. There were also no noticeable effects when varying total Cu concentration in the presence of 0, 12, and 24 mg/L NOM. An increase in pH from 4 to 8.5 and NOM from 0 mg/L to 12.5 mg/L reduced percent bioavailability. Using the Chelex 100 resin to measure bioavailable copper, about 20 to 40% of the total copper was bioavailable in the absence of NOM, while about 15 to 20% was bioavailable when either 12 or 24 mg/L NOM was present. Acute toxicity bioassays were performed with mysid shrimp (Americamysis bahia) to evaluate the toxic effects of copper in the presence of Suwannee River Fulvic Acid, which served as a source of NOM. Static or static renewal tests, based on EPA method OPPTS 850.1035 with a minimum of 10 mysid shrimp per test condition, were used to determine the LC50 and EC50 of copper and the effects of NOM. Test solutions consisted of artificial synthetic seawater at 20 parts per thousand containing concentrations of 0, 100, 200, 400, 800 ug/L copper with either 0, 12, 24 mg/L NOM. Forty-eight hour acute toxicity tests were performed on larval (2 to 3 day) mysid shrimp that were fed Artemia (brine shrimp); mortality and immobilization were the endpoints. The 48 hour LC50 was 200 ug/L dissolved Cu and 94 ug/L bioavailable Cu without NOM, 340 ug/L dissolved Cu and 98 ug/L bioavailable Cu when 12 mg/L NOM was present, and 495 ug/L dissolved Cu and 105 ug/L bioavailable Cu at 24 mg/L NOM. The consistency of the LC50 measurement using bioavailable Cu suggest that the Chelex 100 resin is a useful technique for toxicity analysis in saline water. / Master of Science

X-ray photoelectron spectroscopy (XPS) has been used to study the bonding of adsorbed metal cations to clay minerals. Binding energy differences of the adsorbed metal cations can be related to changes in the electron density or charge on the atom of interest. Adsorption experiments were carried out in aqueous solution at controlled pH's of 2, 4, 6, 8, and 10 for Ba²⁺, Co²⁺, Cr³⁺, adsroption on the clays kaolinite and ripidolite. Solution processes were monitored by measuring the solution concentrations of dissolved silica and the metal ions Fe³⁺, Mg²⁺, K⁺, Al³⁺, Cr³⁺, and Co²⁺ at the beginning and the end of the experiment. Atomic absorption spectroscopy was used to determine the metal ion concentrations and dissolved silica was determined spectrophotometrically as a molybdate complex. Examination of the adsorbed cation species on the clay surface by XPS indicated that the clays behaved as nucleation centers at or near the pH of precipitation of the cations. Further it was found that high spin Co²⁺ in solution became low spin Co²⁺ or formed a highly covalent bond when adsorbed on kaolinite at pH's 4, 6, and 7 and on ripidolite at pH 2 and 4. Finally, if the clay has a negatively charged surface which donates some of its charge to the positive cation, then the barium XPS data indicated that ripidolite has a greater negative surface charge than kaolinite. This idea was supported by calculations of the surface charge density from CEC and surface area data. / Master of Science