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<p> This thesis demonstrates two concepts, one a viable fabrication process for an FeCr alloy supported solid oxide fuel cell (SOFC), and second, the use of CozMn04 (spinel)as the cathode material. Ni/YSZ and YSZ layers were used as anode and electrolyte respectively. The fabrication process consisted of tape casting of iron and chromium oxide powders for the support, dip coating of NiO-YSZ-Fe30 4-Crz03-C and YSZ as anode and electrolyte respectively, synthesis of CozMn04 from Co304 and MnOz as the , cathode material and finally screen printing of the CozMn04 cathode. The support, the anode, and the electrolyte were co-fired at 1350°C in air for 10 hours, then CozMn04 was screen printed and the cell was again fired at 1250°C for 4 hours in air. The complete cell was reduced in pure Hz at 950°C for 10 hours to convert the major part of support into Fe-Cr alloy, leaving approximately 20% unreduced FeCrz04. </p> <p> The fully fabricated cell was tested at 820°C using 7% Hz, 93% Nz as the fuel and air as the oxidant. The Co2MnO4 cathode which reduced to MnO + Co during the final processing stage was recovered in-situ at the start of the test. Pt mesh was used for current collection. The power density was in the range of 80-120 mW/cm2. </p> / Thesis / Master of Applied Science (MASc)

<p> Electrochemical supercapacitors (ES) are urgently needed as components in many advanced power systems. The development of advanced ES is expected to enable radical innovation in the area of hybrid vehicles and electronic devices. Nanostructured manganese oxides in amorphous or various crystalline forms have been found to be promising electrode materials for ES. The use of composite electrodes of manganese oxide with carbon nanotubes is being proposed to improve the overall electrochemical performance of the ES.</p> <p> Electrodeposition methods have been developed for the fabrication of manganese oxide films with/without carbon nanotubes for applications in ES. Electrolytic deposition of manganese oxides was found to be possible using Mn2+ and Mn7+ species, co-deposition of multi wall carbon nanotubes (MWNT) and manganese oxide using cathodic electrosynthesis was successfully achieved.</p> <p> Novel chemical process has been developed for the synthesis of nano-size manganese oxide particles. Electrophoretic deposition of the nano-size manganese oxide particles was able to be performed in both aqueous and non-aqueous solutions. Electrophoretic co-deposition of the nano-size manganese oxide particles with carbon nanotubes was successfully achieved.</p> <p> The mechanisms and kinetics of all the deposition methods are discussed. Charge storage properties of the films prepared by different deposition methods are investigated and compared.</p> / Thesis / Master of Applied Science (MASc)

The automotive industry, has been innovating in the field of materials development in order to meet the demand for lower emissions, improved passenger safety and performance. Despite various attempts of introducing other lightweight materials (Al, Mg or polymers) in car manufacturing, steel has remained as the material of choice till date due to its excellent adaptability to systematic upgradation and optimization in its design and processing. One of the outcomes is the development of second generation high Mn TWin Induced Plasticity (TWIP) steels with excellent strength-ductility balance suitable for automotive applications. Cost effective high performance TWIP steel design is mostly based on its alloy design and advanced up and down stream processing methods (thermomechanical controlled processing (TMCP)) which can help achieve suitable microstructure to meet the property requirements. It has been observed that grain boundary migration (GBM) in austenite during high temperature TMCP stage dictates grain growth to control the final microstructure. This research work initially investigates the grain growth in Fe-30%Mn steel within a temperature regime of 1000-1200°C. Compared to conventional low Mn steel, austenite boundary mobility in Fe-30%Mn was found to be 1-2 orders of magnitude smaller. Atom probe tomography results showed no Mn segregation at austenite high angle grain boundaries (γ-HAGB) which rules out the effect of Mn solute drag on growth kinetics in Fe-30%Mn steels. Grain boundary character distribution (GBCD) study showed that the sample consists of two different population of grain boundaries. 50% of the grain boundaries are random HAGBs with high mobility. Remaining 50% are special in nature which introduce low mobility boundary/boundary segments in the global boundary network. The special boundaries are mostly in the form of Σ3 CSL boundaries or its variants like Σ9, Σ 27. These boundary/ boundary segments were introduced by the formation of annealing twins and their interactions with the random HAGBs. An attempt to investigate the effect of Mn on growth kinetics at 1200°C showed that Mn slows down growth kinetics up to 15 wt% predominantly by the formation of annealing twins. A qualitative study of the microstructures showed that as Mn concentration is increased from 1% to 15%, the annealing twin density increases resulting in Σ3 frequency to be 30%. The increased twinning frequency is attributed to the effect of Mn on lowering the stacking fault energy (SFE). Annealing twins, belonging to Σ3 CSL family, intersect the HAGBs resulting into twin induced boundary segments which possess very low mobility. In the light of this idea, slow grain growth in high Mn steel was attributed to the population of low mobility boundaries. The proposed ‘twin inhibited grain growth’ model clearly points to the low mobility boundary/boundary segments to be the rate controlling factor during grain growth in high Mn steels. The effect of carbon on grain growth in Fe-30%Mn steel showed that the presence of carbon makes the growth kinetics faster by a factor of 4 and 6 at 1200°C and 1100°C respectively. Although, atom probe tomography results indicated that in presence of carbon, Mn segregation takes place at γ-HAGBs in Fe-30%Mn steel, solute drag does not appear to play a role as it was seen that with increase in Mn content beyond 1%, the solute effect of Mn in slowing down HAGB migration becomes weak. Also, abovementioned higher mobility values are obtained from the growth kinetics of Fe-30Mn-0.5C. This once again highlights the fact that effect of Mn in slowing down grain growth is due to the low mobility of twin/twin related boundaries or boundary segments. Controlling grain growth has been commonly proposed to be accomplished through small addition (<0.1%) of microalloying elements (Nb, V and Ti) which can slow down GBM at high temperature by solute drag and at low temperature by precipitate pinning (Zener drag). This research work has also experimentally quantified the solute drag of Nb in a series of Fe- 30%Mn steels. Grain boundary mobility was estimated for various temperatures and niobium contents. An attempt was made to calculate the grain boundary mobility in presence of niobium using Cahn’s solute drag model. This calculated mobility, when used in the proposed ‘twin inhibited grain growth’ model, the predicted growth kinetics which showed very good fit with the experimentally obtained growth kinetics in case of Fe-30Mn-0.03Nb and Fe-30Mn-0.05Nb steels at 1100°C. The effect of Nb solute drag, thus captured using Cahn’s model, was shown to be slowing down only the HAGB migration in the microstructure, whilst the special boundary mobility was not affected by solute Nb. Another attempt was made through grain boundary engineering (GBE) to control grain growth in Fe-30Mn-0.5C steel. Using different TMCP schemes, GBCD was modified to produce maximum frequency of special boundary. Preliminary studies on grain growth of single step-grain boundary engineered samples did show a significant lowering of grain size compared to a no-GBE sample after grain growth. However, the effect of iterative GBE didn’t show any significant effect in controlling grain growth in spite of the fact that it increased Σ3 frequency to 64%. This probably indicates that the effect of GBE on grain growth by the formation of annealing twins/special low mobility boundaries is a complicated process which might involve twin/special boundary morphology, annihilation kinetics and formation of grain clusters in the microstructure other than the formation of immobile special triple junctions through the intersection of twins/special boundaries with the random HAGBs. / Thesis / Doctor of Philosophy (PhD)

This thesis presents a review of the theory of evaporation of pure substances with respect to kinetic and mechanistic models. These concepts are applied to multi-component evaporation and a model for the evaporation of solute atoms from a solvent is postulated. The evaporation experiments were performed on Fe 1% Mn melts at a constant pressure of approximately 10 microns over a temperature range of 1320° to 1810°C. The correlation between the experimental results and the expected theoretical results is discussed thoroughly in terms of surface control and diffusion control. / Thesis / Master of Engineering (ME)

The solid state structures and the physical, solution magnetic, solid state magnetic, and spectroscopic (NMR and UV/Vis) properties of a range of oxygen- and nitrogen-free dialkylmanganese(II) complexes are reported, and the solution reactivity of these complexes towards H2 and ZnEt2 is described. The dialkyl compounds investigated are [{Mn(μ-CH2SiMe3)2}∞] (1), [{Mn(CH2CMe3)(μ-CH2CMe3)2}2{Mn(μ-CH2CMe3)2Mn}] (2), [Mn(CH2SiMe3)2(dmpe)] (3) (dmpe = 1,2-bis(dimethylphosphino)ethane), [{Mn(CH2CMe3)2(μ-dmpe)}2] (4), [{Mn(CH2SiMe3)(μ-CH2SiMe3)}2(μ-dmpe)] (5), [{Mn(CH2CMe3)(μ-CH2CMe3)}2(μ-dmpe)] (6), [{Mn(CH2SiMe3)(μ-CH2SiMe3)}2(μ-dmpm)] (7) (dmpm = bis(dimethylphosphino)methane), and [{Mn(CH2CMe3)(μ-CH2CMe3)}2(μ-dmpm)] (8). Syntheses for 1-4 have previously been published, but the solid state structures and most properties of 2-4 had not been described. Compounds 5 and 6, with a 1:2 dmpe:Mn ratio, were prepared by reaction of 3 and 4 with base-free 1 and 2, respectively. Compounds 7 and 8 were accessed by reaction of 1 and 2 with 0.5 or more equivalents of dmpm per manganese atom. An X-ray structure of 2 revealed a tetrametallic structure with two terminal and six bridging alkyl groups. In the solid state, bis(phosphine)-coordinated 3-8 adopted three distinct structural types: (a) monometallic [LMnR2], (b) dimetallic [R2Mn(μ-L)2MnR2], and (c) dimetallic [{RMn(μ-R)}2(μ-L)] (L = dmpe or dmpm). Compound 3 exhibited particularly desirable properties for an ALD or CVD precursor, melting at 62-63 °C, subliming at 60 °C (5 mTorr), and showing negligible decomposition after 24 h at 120 °C. Comparison of variable temperature solution and solid state magnetic data provided insight into the solution structures of 2-8. Solution reactions of 1-8 with H2 yielded manganese metal, demonstrating the thermodynamic feasibility of the key reaction steps required for manganese(II) dialkyl complexes to serve, in combination with H2, as precursors for metal ALD or pulsed-CVD. By contrast, the solution reactions of 1-8 with ZnEt2 yielded a zinc-manganese alloy with an approximate 1:1 Zn:Mn ratio. Wilkinson’s manganese(I) ethylene hydride complex trans-[(dmpe)2MnH(C2H4)] (10) can react as a source of a low-coordinate manganese(I) ethyl complex. This is illustrated in the reactivity of 10 towards a variety of reagents in this work (vide infra). The proposed low-coordinate intermediate, [(dmpe)2MnEt] (13), was not observed spectroscopically, but could be trapped using isonitrile ligands; reaction of 10 with CNR (R = tBu, o-xylyl) afforded the manganese(I) ethyl complexes [(dmpe)2MnEt(CNR)] (14a: R = tBu, 14b: R = o-xylyl). Ethyl complex 14a did not react further with CNtBu at 80 °C. By contrast, complex 14b reacted with excess o-xylyl isonitrile to form 1,1 insertion products, including the iminoacyl complex [(dmpe)Mn(CNXyl)3{C(=NXyl)CEt(=NXyl)}] (15, Xyl = o-xylyl). Complexes 14a-b and 15, as well as previously reported 10, were crystallographically characterized, and DFT calculations were employed to probe the accessibility of cis ethylene hydride and ethyl isomers of 10. Reaction of the ethylene hydride complex trans-[(dmpe)2MnH(C2H4)] (10) with H2SiEt2 at 20 °C afforded the silylene hydride [(dmpe)2MnH(=SiEt2)] (16Et2) as the trans isomer. By contrast, reaction of 10 with H2SiPh2 at 60 °C afforded [(dmpe)2MnH(=SiPh2)] (16Ph2) as a mixture of the cis (major) and trans (minor) isomers, featuring a Mn–H–Si interaction in the former. The reaction to form 16Ph2 also yielded [(dmpe)2MnH2(SiHPh2)] (18Ph2); [(dmpe)2MnH2(SiHR2)] {R = Et (18Et2) and Ph (18Ph2)} were accessed cleanly by reaction of 16R2 with H2. Both 16Et2 and 16Ph2 engaged in unique reactivity with ethylene, generating the silene hydride complexes cis-[(dmpe)2MnH(R2Si=CHMe)] {R = Et (19Et2) and Ph (19Ph2)}. Compounds trans-16Et2, cis-16Ph2, and 19Ph2 were crystallographically characterized, and bonding in 16Et2 and 19Et2 was probed computationally. trans-[(dmpe)2MnH(C2H4)] (10) reacted with primary hydrosilanes H3SiR (R = Ph, nBu) at 60 °C to afford ethane and the manganese disilyl hydride complexes [(dmpe)2MnH(SiH2R)2] (20Ph: R = Ph, 20Bu: R = nBu). 20R reacted with ethylene to form silene hydride complexes [(dmpe)2MnH(RHSi=CHMe)] (19Ph,H: R = Ph, 19Bu,H: R = nBu). Compounds 19R,H reacted with a second equivalent of ethylene to generate [(dmpe)2MnH(REtSi=CHMe)] (19Ph,Et: R = Ph, 19Bu,Et: R = nBu), resulting from apparent ethylene insertion into the silene Si–H bond. Furthermore, in the absence of ethylene, silene complex 19Bu,H slowly isomerized to the silylene hydride complex [(dmpe)2MnH(=SiEtnBu)] (16Bu,Et). Reactions of 20R with ethylene likely proceed via low-coordinate silyl {[(dmpe)2Mn(SiH2R)] (17Ph: R = Ph, 17Bu: R = nBu)} or silylene-hydride {[(dmpe)2MnH(=SiHR)] (16Ph,H: R = Ph, 16Bu,H: R = nBu)} intermediates accessed from 20R by H3SiR elimination. DFT calculations and high temperature NMR spectra support the accessibility of these intermediates, and reactions of 20R with isonitriles or N-heterocyclic carbenes yielded the silyl isonitrile complexes [(dmpe)2Mn(SiH2R)(CNR')] (21a-d: R = Ph or nBu; R' = o-xylyl or tBu), and NHC-stabilized silylene-hydride complexes [(dmpe)2MnH{=SiHR(NHC)}] (22a-d: R = Ph or nBu; NHC = 1,3-diisopropylimidazolin-2-ylidene or 1,3,4,5-tetramethyl-4-imidazolin-2-ylidene), respectively, all of which were crystallographically characterized. Manganese silyl dihydride complexes [(dmpe)2MnH2(SiHR2)] {R = Ph (18Ph2) or Et (18Et2)} and [(dmpe)2MnH2(SiH2R)] {R = Ph (18Ph) or nBu (18Bu)} were generated by exposure of silylene hydride complexes, [(dmpe)2MnH(=SiR2)] (16R2), and disilyl hydride complexes, [(dmpe)2MnH(SiH2R)2] (20R), respectively, to H2 at room temperature. In solution, 18R and 18R2 exist as an equilibrium mixture of a central isomer with a meridional H–Si–H arrangement of the silyl and hydride ligands {this isomer may be considered to contain an η3-coordinated silicate (H2SiR3–) anion}, and a transHSi isomer with trans-disposed hydride and nonclassical hydrosilane ligands (the latter is the result of significant but incomplete hydrosilane oxidative addition). Additionally, DFT calculations indicate the thermodynamic accessibility of lateralH2 and transH2 isomers with cis- and trans-disposed silyl and dihydrogen ligands, respectively. Compounds 18Ph2 and 18Ph crystallized as the central isomer, whereas 18Bu crystallized as the transHSi isomer. Bonding in the central and transHSi isomers of 18R and 18R2 was further investigated through 29Si_edited 1H–1H COSY solution NMR experiments to determine both the sign and magnitude of J29Si,1H coupling (negative and positive values of J29Si,1H are indicative of dominant 1-bond and 2-bond coupling, respectively). These experiments afforded J29Si,1H coupling constants of –47 Hz for η3-(H2SiR3) in the central isomer of 18Et2 (calcd. –40 to –47 for 18R and 18R2), –38 to –54 Hz for η2-(R3Si–H) in the transHSi isomer of 18R and 18R2 (calcd. –26 to –47 Hz), and 5 to 9 Hz for the terminal manganese hydride ligand in the transHSi isomer of 18Et2, 18Ph, and 18Bu (calcd. 12 to 14 Hz for 18R and 18R2), experimentally supporting the nonclassical nature of bonding in the central and transHSi isomers. Exposure of disilyl hydride complexes 20R to diisopropylcarbodiimide {C(NiPr)2} afforded manganese(I) amidinylsilyl complexes [(dmpe)2Mn{κ2-SiHR(NiPrCHNiPr)}] {R = Ph (25Ph,H) or nBu (25Bu,H)}. DFT calculations and analysis of XRD bond metrics suggest that the structure of 25R,H involves a contribution from a resonance structure featuring a neutral base-stabilized silylene and an anionic amido donor on manganese. Reactions of 20R, as well as the silylene hydride complex 16Et2, with CO2 yielded the manganese(I) formate complex trans-[(dmpe)2Mn(CO)(κ1-O2CH)] (26), with a polysiloxane byproduct. Compound 26 was found to undergo reversible CO2 elimination at room temperature, and was only stable under an atmosphere of CO2. Complexes 25R,H and 26 were crystallographically characterized. Silyl, silylene, and silene complexes in this work were accessed via reactions of [(dmpe)2MnH(C2H4)] (10) with hydrosilanes, in some cases followed by ethylene. Therefore, ethylene (C2H4 and C2D4) hydrosilylation was investigated using [(dmpe)2MnH(C2H4)] (10) as a pre-catalyst, resulting in stepwise conversion of primary to secondary to tertiary hydrosilanes. Various catalytically active manganese-containing species were observed during catalysis, including silylene and silene complexes, and a catalytic cycle is proposed. The proposed catalytic cycle is unusual due to the involvement of silylene hydride and silene hydride complexes, potentially as on-cycle species. The reaction of [(dmpe)2MnH(C2H4)] (10) with H2 at 60 °C afforded ethane and the dihydrogen hydride complex [(dmpe)2MnH(H2)] (11), which has previously been prepared by an alternative route. Complex 10 reacted with hydroborane reagents 9-BBN or HBMes2 at 60 °C to afford EtBR2 and Mn(I) borohydride complexes [(dmpe)2Mn(μ-H)2BR2] (29: R2 = C8H14, 30: R = Mes); two intermediates were observed in each of these reactions. Deuterium labelling experiments using the deuterated hydroborane DBMes2 suggest that this reaction proceeds via the 5-coordinate ethyl isomer of 10; [(dmpe)2MnEt] (13). By contrast, exposure of 10 to BH3∙NMe3 required a higher temperature (90 °C) to yield [(dmpe)2Mn(μ-H)2BH2] (28), and ethylene was formed as the reaction byproduct; this reaction presumably proceeded by ethylene substitution. Deuterium incorporation into both the MnH and BH environments of 28 was observed under an atmosphere of D2 at 90 °C. Reactions of 10 with free dmpe yielded ethylene and a mixture of [{(dmpe)2MnH}2(μ-dmpe)] (31) and [(dmpe)2MnH(κ1-dmpe)] (32), which could be isolated by washing/recrystallization or sublimation, respectively. Similar reactivity was observed between 10 and HPPh2, which afforded ethylene and [(dmpe)2MnH(HPPh2)] (33) at 90 °C. Exposure of 10 to HSnPh3 yielded the manganese(II) stannyl hydride complex [(dmpe)2MnH(SnPh3)] (34) along with ethylene and, presumably, additional unidentified products. However, the mechanism for formation of 34 is unclear, it could not be isolated in pure form due to decomposition to form various species including SnPh4, and the mechanism of the decomposition process remains obscure. Previously reported complex 11, along with new complexes 28-31 and 33-34, were crystallographically characterized. This work provides valuable insights to unusual metal–ligand bonding motifs and reactions, and as such contributes to the fundamental understanding of organometallic chemistry. / Dissertation / Doctor of Philosophy (PhD) / The focus of this work is the synthesis and investigation of manganese-containing complexes with Mn–P, Mn–C, Mn–H, and/or Mn–Si linkages. Many of these complexes feature unusual bonding motifs, including the first group 7 complexes bearing an unstabilized silylene (:SiR2) ligand and the first 1st row transition metal complexes bearing an unstabilized silene (R2Si=CR2) ligand. Variable temperature Nuclear Magnetic Resonance (NMR) spectroscopy and X-ray crystallography were employed to investigate the structures of these complexes, while Density Functional Theory (DFT) calculations and trapping experiments were employed to understand the mechanisms for various unusual chemical transformations. Some of the complexes were evaluated for activity towards catalytic hydrosilylation of ethylene. This work provides valuable insights to unusual metal–ligand bonding motifs and reactions, and as such contributes to the fundamental understanding of organometallic chemistry.

This dissertation describes the current and common problem of removing low concentrations of pollutants known as volatile organic compounds (VOCs) from large volume gas emissions. Silica-supported manganese oxide catalysts with loadings of 3, 10, 15, and 20 wt. % (as MnO2) were characterized using x-ray absorption spectroscopy and x-ray diffraction (XRD). The edge positions in the x-ray absorption spectra indicated that the oxidation state for the manganese decreased with increasing metal oxide loading from a value close to that of Mn2O3 (+3) to a value approximating that of Mn3O4 (+2&#8532;). The XRD was consistent with these results as the diffractograms for the supported catalysts of higher manganese oxide loading matched those of a Mn3O4 reference. The reactivity of the silica-supported manganese oxide catalysts in acetone oxidation using ozone as an oxidant was studied over the temperature range of 300 to 600 K. Both oxygen and ozone produced mainly CO₂ as the product of oxidation, but in the case of ozone the reaction temperature and activation energy were significantly reduced. The effect of metal oxide loading was investigated, and the activity for acetone oxidation was greater for a 10 wt. % MnOx/SiO2 catalyst sample compared to a 3 wt. % MnOx/SiO2 sample. A detailed mechanistic study of acetone oxidation using ozone was performed on a 10 wt. % silica-supported manganese oxide catalyst utilizing Raman spectroscopy, temperature programmed desorption (TPD), and kinetic measurements. In situ Raman spectroscopy at reaction conditions identified a band at 2930 cm-1 due to an adsorbed acetone species on the silica support and a band at 890 cm-1 due to an adsorbed peroxide species on the manganese oxide. A steady-state kinetic analysis, which varied acetone partial pressure (101 – 405 Pa), ozone partial pressure (101 – 1013 Pa), and temperature (318, 333, 343, and 373 K), was used to determine reaction rate expressions, while a transient kinetic study (318 K) was used to determine the role of the adsorbed species in the reaction mechanism. It was found that the rates of the acetone and ozone reactions were equally well described by both a power rate law and a Langmuir-Hinshelwood expression. The transient experiments showed that the rates of formation and reaction of the observed peroxide surface species did not correspond to the overall reaction rate, and it was concluded that it was not directly involved in the rate determining step of the reaction. A mechanism is proposed involving the reaction of an adsorbed acetone intermediate with an atomically adsorbed oxygen species via a dual site surface reaction to form complete oxidation products. / Ph. D.

This work represents an interdisciplinary effort to investigate microbiological and chemical manganese (Mn) cycling in drinking water systems using concepts and tools from civil and environmental engineering, microbiology, chemistry, surface science, geology, and applied physics. Microorganisms were isolated from four geographically diverse drinking water systems using selective Mn-oxidizing and -reducing culture media. 16S rRNA gene sequencing revealed that most are bacteria of the Bacillus spp. (i.e., Bacillus pumilus and Bacillus cereus). These bacteria are capable of performing Mn-oxidation and -reduction under controlled laboratory conditions. Pseudo-first order rate constants obtained for microbiological Mn-oxidation and -reduction (aerobic and anaerobic) of these isolates ranged from 0.02 - 0.66 days⁻¹. It is likely that spores formed by Bacillus spp. protect them from chlorine and other disinfectants applied in drinking water systems, explaining their ubiquitous presence. A new method was developed using X-ray photoelectron spectroscopy (XPS) to identify Mn(II), Mn(III), and Mn(IV) on the surfaces of pure oxide standards and filtration media samples from drinking water treatment plants. A necessary step for the comprehensive analysis of Mn-cycling in drinking water systems is to characterize the chemical properties of filtration media surfaces. Analyses of filtration media samples show that, while Mn(IV) was predominant in most samples, a mixture of Mn(III) and Mn(IV) was also identified in some of the filtration media samples studied. The use of both the XPS Mn 3s multiplet splitting and the position and shape of the Mn 3p photo-line provide added confidence for the determination of the oxidation state of Mn in complex heterogeneous environmental samples. XPS was applied to investigate Mn(II) removal by MnOx(s)-coated media under experimental conditions that closely resemble situations encountered in drinking water treatment plants in the absence and presence of chlorine. Macroscopic and spectroscopic results suggest that Mn(II) removal in the absence of chlorine was mainly due to adsorption, while in the presence of chlorine was due to oxidation. Mn(IV) was predominant in all the XPS analyses while Mn(II) was detected only in samples operated without chlorine. Future research should apply XPS under different experimental conditions to understand the specific mechanisms affecting Mn(II) removal by MnOx(s)-coated media. / Ph. D.