Reduction in sulfur deposition from power plant emissions has resulted in lower amounts of soil sulfur and, perhaps, in inadequate sulfur availability for corn. The objective of this study was to determine if corn (<i>Zea mays</i> L.) grain yield was responsive to S fertilization in Indiana and what soil and cropping system factors contributed to the likelihood of a response. Field scale experiments were conducted at 28 sites from 2017 to 2020, the majority in corn-soybean (<i>Glycine max</i> (L.) Merr) rotation. In-season measurements included soil sulfate-S concentration and soil texture from 0 to 60 cm in 20 cm increments, plant nutrient concentration in the whole plant at V3-V7, in the earleaf, and in the grain. Additional measurements were 1,000 kernel dry weight, total kernel rows per ear, and kernels per row. Sulfur treatment rates ranged from 0 to 34 kg S ha^‑1 as ammonium thiosulfate, and were applied as starter, sidedress, and both combined. Fertilizer S increased grain yield by 0.2 to 3.0 Mg ha^-1 at 10 of 28 Indiana site-years, approximately a 36% frequency of response. When a response to S fertilizer occurred, the lowest sidedress rate examined in that site-year, which ranged from 8 to 17 kg S ha^-1,was enough to maximize grain yield. On soils with 26 to 31 g kg^-1 OM, S fertilization increased yield 0.2 to 0.3 Mg ha^-1 at 2 of 10 site-years. Response to S fertilization at 8 of 10 site-years with soils with lower OM, 10 to 25 g kg^-1, had higher yield increases ranging from 0.7 to 3.0 Mg ha^-1. Grain yield responses occurred in both coarse- and fine-textured soils and were consistent and large at 2 sites. Sulfate-S concentration in the soil and S concentration in the whole plant (V4-V7) were not good indicators of response to S fertilization. For the majority of the site-years where grain yield increased with S fertilization, the grain S concentration, earleaf S concentration, and earleaf N:S were respectively <0.9 g kg^-1, <1.8 g kg^-1, and >15:1 without S treatment. These parameters improved with the addition of S but some site-years with these values did not have a yield response. These earleaf S and N:S ‘critical values’ may serve as reference for potentially S responsive sites, but more observations are necessary to validate these critical levels. Sites with higher basal values (without fertilizer treatment) for earleaf and grain S concentration and lower earleaf N:S still showed increased tissue S concentration upon S fertilizer application, albeit with no increase in grain yield. We encourage farmers to consider S fertilization at rates ranging from 8 to 17 kg S ha^-1 applied at sidedress. this recommendation for fields showing S deficiency symptoms or where R1 earleaf S concentration and N:S are below 1.8 g kg^-1 and above 15:1, respectively.

Thermochemical water splitting cycles have been conceptualized and researched for over half a century, yet to this day none are commercially viable. The heavily studied Sulfur-Iodine cycle has been stalled in the early development stage due to a difficult HI-H₂O separation step and material compatibility issues. In an effort to avoid the azeotropic HI-H₂O mixture, an imidazolium-based ionic liquid was used as a reaction medium instead of water. Ionic liquids were selected based on their high solubility for SO₂, I₂, and tunable miscibility with water. The initial low temperature step of the Sulfur-Iodine cycle was successfully carried out in ionic liquid reaction medium. Kinetics of the reaction were investigated by I₂ colorimetry. The reaction also evolved H₂S gas, which led to the conceptual idea of a new Sulfur-Sulfur thermochemical cycle, shown below: / 4I₂(l)+4SO₂(l)+8H₂O(l)↔4H₂SO₄(l)+ 8HI(l) / 8HI(l)+H₂SO₄(l)↔ H₂S(g)+4H₂O(l)+4I₂(l) / 3H₂SO₄(g)↔ 3H₂O(g)+3SO₂(g)+1½O₂(g) / H₂S(g)+2H₂O(g)↔ SO₂(g)+3H₂(g) / The critical step in the Sulfur-Sulfur cycle is the steam reformation of H₂S. This highly endothermic step is shown to successfully occur at temperatures in excess of 800˚C in the presence of a molybdenum catalyst. A parametric study varying the H₂O:H₂S ratio, temperature, and residence time in a simple tubular quartz reactor was carried out and Arrhenius parameters were estimated. All reactive steps of the Sulfur-Sulfur cycle have been either demonstrated previously or demonstrated in this work. A theoretical heat-to-hydrogen thermal efficiency is estimated to be 55% at a hot temperature of 1100 K and 59% at 2000 K. As a highly efficient, all-fluid based thermochemical cycle, the Sulfur-Sulfur cycle has great potential for feasible process implementation for the transformation of high quality heat to chemical energy. / Graduation date: 2012

The hydrogen economy is a possible component of an energy future based on use of alternative and renewable energy sources, deemed desirable from the general consensus of the worldwide community that we do not want to further exacerbate the climate problems that we have introduced over the last two centuries from burning fossil fuels. The burning of fossil fuels emits toxic pollutants into the air, such as sulfur compounds and oxidized forms of nitrogen (NOx) but also emit copious amounts of the inert carbon dioxide. The latter is widely recognized as the major cause of the global warming phenomenon. For a hydrogen economy to develop, efficient means of hydrogen generation are required. Thermochemical cycles were conceived in the 1960s but only one operating pilot plant and no commercial installations based on the processes have been built. In the present work the use of a membrane reactor to enable the newly conceived Sulfur-Sulfur cycle, based on equations 1 - 3 is modeled. / 4H₂O+4SO₂ -> H₂S + 3H₂SO₄ Eq. 1 / H₂SO₄ -> SO₂ + H₂O + 1/2O₂ Eq. 2 / H₂S + 2H₂O -> SO₂ + 3H₂ Eq. 3 / The rationale for the use of a membrane reactor to enable the cycle is based on enhancing extent of reaction beyond its predicted equilibrium point due to the severely unfavorable thermochemical parameters for the steam reforming of hydrogen sulfide reaction (Eq. 3 above) which has a low equilibrium concentration of products. The membrane reactor will employ a molybdenum sulfide catalyst driving the steam reformation of hydrogen sulfide reaction and simultaneous extraction of hydrogen (one of the products) will allowing for the reaction to occur to higher extent. A computational model of a catalytic membrane reactor was constructed using the well-known finite element model package Comsol v4.1 in which a catalytic microchannel reactor separated from a sweep gas by a thin hydrogen permeable membrane is built and parametric sweeps to evaluate the effect of membrane transport parameters, pressure and gas feed velocities are calculated. Though the steam reforming of hydrogen sulfide reaction has a competing thermal cracking reaction, the present work focuses on modeling one reaction only (the steam reformation reaction) for simplicity. Fully dense metallic membranes with chemselective permeability to hydrogen are modeled with transport parameters derived from reported literature values for similar applications. The results show that employing a membrane reactor does significantly affect the completeness of the reaction by product extraction (if you do run the model with membrane transport set to zero, compare the extent at zero with extent at 3.6x10⁻⁶ mol.s⁻¹.m⁻²). The effect of changing sweep gas velocity is contingent on membrane properties, and membranes with small diffusion coefficients severely limit the ability of extraction of hydrogen from the feed. Therefore, it is more important that membranes with very high hydrogen permeability be employed in designing a reactor to implement this process, allowing for effective hydrogen separation and high conversion of the reactants in the process. Reactor pressure has minimal effect on the extent of reaction and therefore reactors designed to implement the process may be designed to operate at close to ambient pressure. / Graduation date: 2012

Sulfur dioxide (SO₂), a well-known pollutant emitted from fossil fuel combustion, has major adverse health and environmental impacts. It is harmful at low concentration with a permissible exposure limit of two ppm for the eight-hour time-weighted average (TWA) value. Fortunately, its atmospheric concentration, like other air pollutants, has gradually reduced in Canada in the past years. However, despite the well-established flue gas desulfurization technologies, they have the disadvantages of being energy-intensive, not very efficient to achieve very low concentrations (at ppm level) and they operate at high temperatures. Moreover, emission standards are becoming more stringent. Novel methods are therefore investigated to capture SO₂, such as adsorption processes using zeolites and metal oxides (e.g., Iron (Fe) and Vanadium (V) based) which tend to sustain wide ranges of temperatures and pressures. Graphene oxide (GO) was also shown to physisorb SO₂ at low temperatures. In this work, we propose to metal functionalize GO as a step forward on the path for efficient SO₂ capture, by promoting the SO₂ oxidation reaction into sulfur trioxide (SO₃) for increased capacity due to a possible higher affinity with the surface. The GO has a high surface area, high porosity, and controllable surface chemistry. The aim is to achieve outlet concentration of SO₂ as low as 1 ppm through combined physisorption and reaction promoted that the presence of GO and metal, at low operating temperature. Iron oxide functionalized GO was synthesized using two different techniques: a polyol process (GO-FeₓOᵧ-P) and using a hydrolysis method (GO-FeₓOᵧ-H). The characterization analysis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM), performed on the materials before and after SO₂ reaction show changes on the surface due to metal adding and to the sulfur capture. The breakthrough curves and the capacity calculations of the performed experiments have shown that with the addition of FeₓOᵧ on the surface of GO, the capturing capacity increases by a factor of three to four, indicating a possible change in the capturing mechanism. The evaluation of the temperature effect (from room temperature to 100℃) showed an increasing trend in the capture capacity for SO₂ with an increase in temperature, for both functionalized and non-functionalized GO, indicating it is not driven only by surface adsorption. The presence of sulfur species captured from the gas stream has been confirmed by energy-dispersive X-ray (EDXS) analysis. The future work would be focused on the investigation of the mechanisms and capturing phenomenon and the regeneration step for the materials in order to further improve the capturing capacity and process applicability.

Thesis (MSc. (Horticulture)) -- University of Limpopo, 2019 / After harvesting litchi fruit, the red pericarp colour is rapidly lost resulting in discolouration and browning during storage and marketing. To mitigate this challenge, the South African litchi industry uses sulfur dioxide fumigation to retain litchi fruit red pericarp colour during extended storage and shelf-life. However, there are health concerns regarding the commercially used (SO2) fumigation for litchi pericarp colour retention due to high levels of SO2 residues in fruit aril. Therefore, this study aimed to explore the possibility of Uvasys slow release SO2 sheets to retain ‘Mauritius’ litchi fruit red pericarp colour when packaged in plastic-punnets and bags. Treatment factors were two packaging materials (plastic-punnets and bags), six SO2 treatments (control; SO2 fumigation and four SO2 sheets viz. Uva-Uno-29% Na2S2O5; Dual-Release-Blue35.85% Na2S2O5; Slow-Release-36.5% Na2S2O5 and Dual-Release-Green-37.55% Na2S2O5) and four shelf-life periods (day 0, 1, 3 and 5). ‘Mauritius’ fruit were assessed for pericarp Browning Index (BI), Hue angle (ho), Chroma (C*) and Lightness (L*). In this study, an interactive significant effect (P < 0.05) between packaging type and SO2 treatments was observed on ‘Mauritius’ fruit pericarp L*, C* and ho during shelf-life. Fruit stored in plastic-bags and treated with SO2 fumigation showed higher pericarp C* and L*, while SO2 fumigated fruit in plastic-punnets had higher pericarp ho. Lower pericarp BI was observed in SO2 fumigated fruit stored in plastic-bags, which showed less pericarp browning than fruit in other treatments. In general, commercial SO2 fumigation resulted in lower pericarp BI, and higher pericarp L*, C* and ho throughout the storage and shelf-life. Our correlation analyses results further showed that litchi fruit red pericarp colour was better preserved as SO2 treatment levels increased, especially in plastic-bags. In retaining ‘Mauritius’ litchi fruit red pericarp colour, Uvasys SO2 sheets were not effective when compared with commercial SO2 fumigation. However, commercially SO2 fumigated fruit were bleached throughout the storage and shelf-life. Furthermore, fruit from all treatments were spoiled due to decay and mould growth after day 5 of shelf-life. Inclusion of pathogen protectants is important in future research to demonstrate whether Uvasys SO2 sheet-packaging technology can retain ‘Mauritius’ litchi fruit pericarp colour. / Agricultural Research Council and National Research Foundation (NRF)

Sulfur (S) deficiencies have become an increasing problem in the United States. A field experiment, in a latin square design, was conducted to investigate effects of S fertilization as 0 and 67 kg/ha as a single or split application on corn (Zea mays L.) forage yield and chemical composition. Sulfur fertilization by either method increased yield of whole plant and grain 7% and increased number of plants with two ears. Total S and sulfate-S concentration in whole corn plants, leaf, stem, and grain were increased with S fertilization. Corn forages were ensiled at harddent stage (35% dry matter). Sulfur fertilized corn silages (N/ S=42 and 43) and non-S fertilized silage (N/ S=62) supplemented at two rates with sodium sulfate (N/ S=l2 and 45) were fed to sheep in metabolism and palatability trials. Both experiments were conducted as a randomized block design with six replications per treatment. All silages were supplemented with urea (6.7 g/ d). Digestibility of dry matter and cell wall components and apparent absorption of Sand N were increased with S fertilization and S supplementation. Nitrogen retention was increased 14% by S supplementation (N/S=l2) and 31% by S fertilization. Sheep fed N/ S=12 silage had lower blood hematocrit and hemoglobin levels then those fed S fertilized or N/ S=45 silages. Blood urea-N levels were higher in sheep fed S fertilized silages. Increasing dietary S by fertilization or supplementation had no measurable effect on dry matter intake. / M.S.

Call number: LD2668 .T4 1961 B48

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Mercury and arsenic are widespread contaminants in aqueous environments throughout the world. The elements arise from multiple sources including mercury from coal-fired power plants and wells placed in natural geological deposits of arseniccontaining minerals. Both elements have significant negative health impacts on humans as they are cumulative toxins that bind to the sulfhydryl groups in proteins, disrupting many biological functions. There are currently no effective, economical techniques for removing either mercury or arsenic from aqueous sources. This thesis will demonstrate a superior removal method for both elements by formation of covalent bonds with the sulfur atoms in N,N’-Bis(2-mercaptoethyl)isophthalamide (commonly called “B9”). That B9 can precipitate both elements from water is unusual since aqueous mercury exists primarily as a metal(II) dication while aqueous arsenic exists as As(III) and As(V) oxyanions.