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Thesis (Ph. D.)--University of Pennsylvania, 1942. / Reproduced from type-written copy. Bibliography: p. 44.

The rapid development of advanced technologies has led to an increase in demand for critical elements that are essential in the manufacturing of high-tech products. Among these critical elements, manganese (Mn), cobalt (Co), and nickel (Ni) are used in the production of batteries, electronics, and other advanced applications. The demand for these elements has been growing exponentially in recent years, driven by the rise of electric vehicles, renewable energy, and other emerging technologies. However, the United States is heavily dependent on foreign sources of critical minerals and on foreign supply chains, resulting in the potential for strategic vulnerabilities to both economy and military. To address this problem and reduce the Nation's vulnerability to disruptions in the supply of critical minerals, it is important to develop critical minerals recycling technologies. A systematic study was conducted to develop a process for producing high-purity Mn, Co, and Ni products from an acid mine drainage (AMD). As major contaminants, Fe and Al in the solution were sequentially precipitated and eliminated by elevating the pH. After that, a pre-concentrated slurry containing Mn, Co, Ni, and Zn was obtained by collecting the precipitates formed in the pH range of 6.50 to 10.00. The pre-concentrated slurry was redissolved for further purification. Sodium sulfide was added into the redissolved solution to precipitate Co, Ni, and Zn selectively while retaining Mn in the solution. Almost 100% of Co, Ni, and Zn but only around 15% of Mn were precipitated using a sulfur-to-metal molar ratio of 1 at pH 4.00. The sulfide precipitate was calcined and then completely dissolved. The critical elements existing in the dissolved solution were efficiently separated using a two-stage solvent extraction process. Ultimately, Co and Ni products with almost 94% and 100% purity were obtained by sulfide and alkaline precipitation, respectively. AMD also contains rare earth elements (REEs), which can be recovered through selective chemical precipitation. REE removal improved at pH 4.0 after converting ferrous to ferric ions with H2O2. Aluminum species in the solution hindered REE adsorption on ferric precipitates, and ferrous ions reduced REE adsorption on aluminum precipitates at lower pH, but at higher pH, REE removal increased due to ferrous ion precipitation. Various tests and analyses were conducted to understand the partitioning mechanisms of REE during the precipitation process of AMD. Sulfide precipitation is crucial to separate Mn from other elements, but the presence of contaminants like Fe and Al can affect sulfide precipitation efficiency. The effects of Al3+ iii and Fe2+ on the precipitation characteristics of four valuable metals, including Mn2+, Ni2+, Co2+, and Zn2+, were investigated by conducting solution chemistry calculations, sulfide precipitation tests, and mineralogy characterizations. It was found that the ability of the valuable metals to form sulfide precipitates followed an order of Zn2+ > Ni2+ > Co2+ > Mn2+. The sulfide precipitate of Zn2+ was the most stable and did not re-dissolve under the acidic condition (pH 4.00 ± 0.05). In addition, the sulfide precipitation of Zn2+ was barely affected by the contaminant metal ions. However, in the presence of Al3+, the precipitation recoveries of Mn2+, Ni2+, and Co2+ in a solution containing all the valuable metals were noticeably reduced due to simultaneous hydrolysis and competitive adsorption. The precipitation recoveries of Ni2+ and Co2+ in solutions containing individual valuable metals also reduced when Fe2+ was present, primarily due to competitive precipitation. However, the recovery of Mn2+ was enhanced due to the formation of ferrous sulfide precipitate, providing abundant active adsorption sites for Mn species. In the solution containing all the valuable metals, Fe2+ promoted the recoveries of the valuable metals due to the higher concentration of Na2S and the formation of ferrous sulfide precipitate. / Doctor of Philosophy / The rapid development of advanced technologies has increased the demand for critical elements essential in manufacturing high-tech products. In this study, a process was developed for producing high-purity Mn, Co, and Ni products from an acid mine drainage (AMD). A product with around 30 wt.% Mn was produced. Co and Ni products with 94% and 100% purity were also obtained. However, when developing the process, it was found that a portion of the REEs is often lost to the precipitates of the dominant metal contaminant ions (Fe and Al) in the staged precipitation. It was found that the REE removal increase was realized through adsorption onto the surfaces of the ferric precipitates. In sulfide precipitation, the presence of Fe and Al in the solution can significantly influence the separation efficiency of the critical elements. The effect of Al3+ on the sulfide precipitation is due to the simultaneous hydrolysis of aluminum and sulfur ions. The reduction of the recovery of valuable metals caused by the Fe2+ is due to the form of iron sulfides.

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Hydrogen sulfide is a naturally occurring compound that is very toxic, highly flammable and has a characteristic “rotten egg” smell. It can irritate eyes and airways or even cause death when highly concentrated in air. It can exist both in gaseous and aqueous form where the dissolution of hydrogen sulfide in water is highly affected by pH. There are several industries with hydrogen sulfide related problems, either for safety or economic reasons (e.g., the mining industry, pulp and paper processing, oil and gas refineries, and wastewater treatment plants). The aim was to construct and test a filter of iron oxides to treat water from dissolved hydrogen sulfide. This was done through column experiments where the columns were filled with hematite and slag from the steel industry. Both the hematite and slag columns had sulfide precipitation, evident in the black discoloration, and the sulfide concentrations drastically reduced in the outlet water compared to the inlet water, indicating that the columns worked. However, there were some signs of preferential flow. Calculations indicate that the iron in the columns would be sufficient to precipitate approximately 1138 mg L−1 H2S at a flow rate of 0.2 ml min−1 for roughly 66 days, based on mean values for the three hematite columns. This was only a small-scale column experiment, and if scaled up from 0.2 ml min−1 to 0.5 L s−1 in the field, the amount of hematite used would have to be increased by 150 000 to last the same amount of time. This method would hence be difficult to apply in the field since it would be difficult to change the filter. / Vätesulfid (H2S) är en naturligt förekommande förening som är väldigt giftig, mycket brandfarlig och har en karaktäristisk ”ruttet ägg” lukt. Det kan irritera ögon och luftvägar, samt orsaka dödsfall vid höga koncentrationer. Vätesulfid kan förekomma både som gas och upplöst i vätska, där dess vattenlöslighet påverkas kraftigt av pH. Det finns flera industrier som har problem med vätesulfid i sina verksamheter, ur ett säkerhets- och ekonomiskt perspektiv (t.ex. vattenreningsverk, gruv-, pappers-, och oljeindustrier). Syftet var att konstruera och testa ett filter på järnoxider för att rena vatten från vätesulfid. Filtret fungerar genom att vätesulfid och järnoxider reagerar för att fälla som järnsulfid och elementärt svavel. Undersökningen genomfördes som kolonnförsök där kolonnerna fylldes med hematit eller slagg från stålindustrin. Både hematit och slaggkolonnerna påvisade järnsulfidutfällning, tydliggjort på de svarta missfärgningarna, samt minskningen av sulfidkoncentrationen i utloppsvattnet jämfört med inloppsvattnet. Dessvärre uppstod problem med preferentiellt flöde. Beräkningar visar att järnet i kolonnerna skulle räcka för att fälla ca 1138 mg L−1 H2S vid ett flöde på 0,2 ml min−1 i uppskattningsvis 66 dagar, baserat på medelvärden för de tre hematitkolonnerna. Med tanke på att det här enbart är ett småskaligt experiment skulle en ökning från 0,2 ml min−1 till 0,5 L s−1 i fältskala innebära att mängden hematit skulle behöva ökas med 150 000 för att fungera lika lång tid. Den här metoden är således svår att applicera storskaligt med tanke på att det skulle bli komplicerat att byta filtret. / SULFREM