Sulfate Conversion Rate Research Articles

Recovery of LiNi0.5Mn0.3Co0.2O2 cathode material from spent lithium-ion batteries with oxygen evolution reduction in ammonium sulfate low-temperature molten salt

The advancement and extensive application of lithium-ion batteries (LIBs) as an energy storage device has led to an increase in the number of spent LIBs, and recycling spent LIBs is an urgent need to address their resource and environmental sustainability issues. Herein, an efficient and comprehensive recycling method for spent LiNi0.5Mn0.3Co0.2O2 cathode material (NMC 532), one of the most important materials for electric vehicles and grid storage applications, is developed based on ammonium sulfate low-temperature molten salt (LTMS) reduction with oxygen evolution, and the feasibility of the strategy is systematically investigated. The results demonstrate that (NH4)2SO4 LTMS can effectively realize the sulfate conversion of spent NMC 532, in which the sulfate conversion rates of Li, Ni, Mn, and Co all reach more than 90%. Through mechanism analysis, it is found that the induced superoxide ion (O2·-) and H+ are the keys to the reduction of transition metal oxides in LTMS. Meanwhile, O2·-, as a single electron reducing agent in the intermediate state, can be used to explain the reduction behavior of transition metal oxides in other ammonium salts, mineral acids, and H-containing salts in molten. Based on (NH4)2SO4 LTMS reduction, water leaching, thermodynamic analysis of coprecipitation, and a series of precipitation and separation experiments, this study provides an effective strategy for recycling spent cathode materials, which can realize the combination of spent material recycling and electrode material regeneration.

Developing a Safety Management Method for Endosulfan Using Biochar in Ginseng Fields

Endosulfan is an endocrine disruptor that negatively affects the human central nervous system. Although perennial root vegetable crops have high risks of endosulfan absorption and transfer in soil, safety management studies addressing this problem are lacking. We evaluated endosulfan absorption and transition, as well as plant growth in ginseng cultivation soil, and developed a safety management method for field application. Total endosulfan residual concentrations in the soil and biochar 0.1–1.0% treatment groups were 52–73% after 532 d of spraying, and there was no reduction effect owing to biochar treatment. However, the endosulfan sulfate conversion rate decreased by 21.6–47.1% as the biochar amount increased. Further, there was a 47–95% reduction in the absorption and migration of endosulfan into ginseng in the biochar treatment compared to the control, demonstrating a reduction effect (p < 0.05). Ginseng grown in soil treated with 0.1% biochar showed no growth parameter differences compared to the control (p > 0.05); however, germination rates decreased to <59% when the soil was treated with ≥0.3% biochar. Soil treatment with 0.1% biochar can reduce endosulfan absorption and migration without adversely affecting crop growth. This treatment can be used at the cultivation site, depending on soil conditions.

Enriching distinctive microbial communities from marine sediments via an electrochemical-sulfide-oxidizing process on carbon electrodes.

Sulfide is a common product of marine anaerobic respiration, and a potent reactant biologically and geochemically. Here we demonstrate the impact on microbial communities with the removal of sulfide via electrochemical methods. The use of differential pulse voltammetry revealed that the oxidation of soluble sulfide was seen at +30 mV (vs. SHE) at all pH ranges tested (from pH = 4 to 8), while non-ionized sulfide, which dominated at pH = 4 was poorly oxidized via this process. Two mixed cultures (CAT and LA) were enriched from two different marine sediments (from Catalina Island, CAT; from the Port of Los Angeles, LA) in serum bottles using a seawater medium supplemented with lactate, sulfate, and yeast extract, to obtain abundant biomass. Both CAT and LA cultures were inoculated in electrochemical cells (using yeast-extract-free seawater medium as an electrolyte) equipped with carbon-felt electrodes. In both cases, when potentials of +630 or +130 mV (vs. SHE) were applied, currents were consistently higher at +630 then at +130 mV, indicating more sulfide being oxidized at the higher potential. In addition, higher organic-acid and sulfate conversion rates were found at +630 mV with CAT, while no significant differences were found with LA at different potentials. The results of microbial-community analyses revealed a decrease in diversity for both CAT and LA after electrochemical incubation. In addition, some bacteria (e.g., Clostridium and Arcobacter) not well-known to be capable of extracellular electron transfer, were found to be dominant in the electrochemical cells. Thus, even though the different mixed cultures have different tolerances for sulfide, electrochemical-sulfide removal can lead to major population changes.

The Study on the Inhibiting Effect of Denitrifying Bacteria on Sulfate-Reducing Process

The average concentration of H2S in Changqing oil Field is higher than 100mg/m3,which is much higher than the demand of “Operational Site Harm Factor Occupation Contact Limiting Value” (GBZ2-2002). Taking this factor into consideration, the experiment aimed at reducing H2S concentration in crude oil gatering and transferring systems by using the denitrifying bacteria. The experiment has two parts: First sulphat reduction process and then denitrification inhibit process. Therefore, two UASB reactors are used in a series to achieve these two processes. The first UASB reactor are mainly used to create SRB bacteria and H2S gas .After the first UASB reactor successfully starting, sodium nitrite are added in the second UASB to achieve denitrification inhibit process. The experiment showed that after the first UASB reactor start, the S2- can achieve 120mg/L and SO42- concentration is about 200 mg/L. So the Sulfate conversion rate can achieve 75%. Then, when the second UASB reactor started successfully, the S2- concentration sharply droped into 20 mg/L and SO42- concentration increased to 400mg/L, the sulphat reduction can achieve 83%. Also, advanced research showed that both SO42-concentration ratio and ORP value can contribute to restraining the SRB bacteria.Finally，through DGGE technology,many kinds of bacteria take into this process, for example pseudomonas aeruginosa. The results of this experiment has a great value to refrain the concentration of H2S in oil fields.

Impact of fair-weather cumulus clouds and the Chesapeake Bay breeze on pollutant transport and transformation

Two fine-scale meteorological processes, fair-weather cumulus cloud development and a bay breeze, are examined along with their impacts on air chemistry. The impact of model resolution on fair-weather cumulus cloud development, transport of pollutants through clouds, sulfur dioxide to sulfate conversion in clouds, and the development of the Chesapeake Bay breeze are examined via 13.5, 4.5, 1.5, and 0.5 km resolution simulations covering the Washington – Baltimore area. Results show that as the resolution increases, more pollutants are transported aloft through fair-weather cumulus clouds causing an increase in the rate of oxidation of sulfur dioxide to sulfate aerosols. The high resolution model runs more nearly match observations of a local pollutant maximum near the top of the boundary layer and produce an increase in boundary layer venting with subsequent pollutant export. The sensitivity of sulfur dioxide to sulfate conversion rates to cloud processing is examined by comparing sulfur dioxide and sulfate concentrations from simulations that use two different methods to diagnose clouds. For this particular event, a diagnostic method produces the most clouds and the most realistic cloud cover, has the highest oxidation rates, and generates sulfur dioxide and sulfate concentrations that agree best with observations. The differences between the simulations show the importance of accurately simulating clouds in sulfate simulations. The fidelity of the model’s representation of the bay breeze is examined as a function of resolution. As the model resolution increases, a larger temperature gradient develops along the shoreline of the Chesapeake Bay causing the bay breeze to form sooner, push farther inland, and loft more pollutants upward. This stronger bay breeze results in low-level convergence, a buildup of near surface ozone over land and a decrease in the land-to-sea flux of ozone and ozone precursors as seen in measurements. The resulting 8 h maximum ozone concentration over the Bay is 10 ppbv lower in the 0.5 km simulation than in the 13.5 km simulation.

In situ measurements of tropospheric volcanic plumes in Ecuador and Colombia during TC4

A NASA DC-8 research aircraft penetrated tropospheric gas and aerosol plumes sourced from active volcanoes in Ecuador and Colombia during the Tropical Composition, Cloud and Climate Coupling (TC^4) mission in July–August 2007. The likely source volcanoes were Tungurahua (Ecuador) and Nevado del Huila (Colombia). The TC^4 data provide rare insight into the chemistry of volcanic plumes in the tropical troposphere and permit a comparison of SO_2 column amounts measured by the Ozone Monitoring Instrument (OMI) on the Aura satellite with in situ SO_2 measurements. Elevated concentrations of SO_2, sulfate aerosol, and particles were measured by DC-8 instrumentation in volcanic outflow at altitudes of 3–6 km. Estimated plume ages range from ~2 h at Huila to ~22–48 h downwind of Ecuador. The plumes contained sulfate-rich accumulation mode particles that were variably neutralized and often highly acidic. A significant fraction of supermicron volcanic ash was evident in one plume. In-plume O_3 concentrations were ~70%–80% of ambient levels downwind of Ecuador, but data are insufficient to ascribe this to O_3 depletion via reactive halogen chemistry. The TC^4 data record rapid cloud processing of the Huila volcanic plume involving aqueous-phase oxidation of SO_2 by H_2O_2, but overall the data suggest average in-plume SO_2 to sulfate conversion rates of ~1%–2% h^(−1). SO_2 column amounts measured in the Tungurahua plume (~0.1–0.2 Dobson units) are commensurate with average SO_2 columns retrieved from OMI measurements in the volcanic outflow region in July 2007. The TC^4 data set provides further evidence of the impact of volcanic emissions on tropospheric acidity and oxidizing capacity.

Treating Industrial Discharges by Thermophilic Sulfate Reduction Process with Molasses as Electron Donor

Thermophilic sulfate reduction process with molasses as an electron donor was investigated for the removal of zinc from rayon industry wastewater. Sulfide rich effluent from the process was used to remove zinc as zinc sulfide precipitate. The investigations with sulfate reduction process were conducted with synthetic (Stage I) as well as real wastewater from Rayon industry (Stage II) as feed. The effect of feed COD: sulfate ratio, which is the key factor for operating the sulfate reduction process, was focused on in this study. The experimental results showed that the process could achieve a high sulfate conversion rate of about 7.22 ± 1.91 g SO4 l−1.d−1 at COD: sulfate ratio of 1.5:1 and 7.20 ± 2.27 g SO4 l−1.d−1 at COD: sulfate ratio of 3:1 during stage I and stage II, respectively. At the end of the operation of stage II, a maximum sulfide production of 496.2 mg S l−1 was achieved at COD: sulfate ratio of 3:1. Furthermore, sulfide rich effluent from sulfate reduction process was used for zinc sulfide precipitation. The results showed that more than 95% of zinc was removed from a high sulfate-containing wastewater.

High rate biological treatment of sulfate-rich wastewater in an acetate-fed EGSB reactor

An expanded granular sludge bed reactor, inoculated with acclimated sulfidogenic granular sludge, was operated at 33 °C and fed with acetic acid as COD source and sulfate as electron acceptor. The bioreactor had a sulfate conversion efficiency of 80–90% at a high sulfate loading rate of 10.4 g SO4 2--S/l.d after only 60 days of start-up. This was achieved by implementing a dual operational strategy. Firstly acetic acid was dosed near stoichiometry (COD over sulfur ratio = 2.0 to 2.2) which allowed almost complete sulfate removal. Secondly the pH in the bioreactor was kept slightly alkaline (7.9 ± 0.1) which limited the concentration of the inhibitory undissociated hydrogen sulfide H2S (pKa = 7). This allowed the acetotrophic sulfate reducing bacteria to predominate throughout the long term experiment. The limitations of the EGSB technology with respect to the sulfate conversion rate appeared to be related to the biomass wash-out and granule deterioration occurring at superficial upflow velocities above 10 m/h. Increasing the recirculation flow caused a drop in the sulfate reduction rate and efficiency, an increase of the suspended sludge fraction and a considerable loss of biomass into the effluent, yielding bare mainly inorganic granules. Elemental analysis revealed that a considerable amount of the granular sludge dry matter at the end of the experiment, at an upflow velocity of 20 m/h, consisted of calcium (32%), mainly in the form of carbonate deposits, while organic matter only represented 7%.

Biological sulfate reduction using synthesis gas as energy and carbon source

Biological sulfate reduction was studied in laboratory-scale gas-lift reactors. Synthesis gas (gas mixtures of H(2)/CO/CO(2)) was used as energy and carbon source. The required biomass retention was obtained by aggregation and immobilization on pumice particles. Special attention was paid to the effect of CO addition on the sulfate conversion rate, aggregation, and aggregate composition.Addition of 5% CO negatively affected the overall sulfate conversion rate; i.e., it dropped from 12-14 to 6-8 g SO(2-) (4)/L day. However, a further increase of CO to 10 and 20% did not further deteriorate the process. With external biomass recycling the sulfate conversion rate could be improved to 10 g SO(2-) (4)/L day. Therefore biomass retention clearly could be regarded as the rate-limiting step. Furthermore, CO affected the aggregate shape and diameter. Scanning electron microscopy (SEM) photographs showed that rough aggregates pregrown on H(2)/CO(2) changed into smooth aggregates upon addition of CO. Addition of CO also changed the aggregate Sauter mean diameter (d(32)) from 1.7 mm at 5% CO to 2.1 mm at 20% CO. After addition of CO, a layered biomass structure developed. Acetobacterium sp. were mainly located at the outside of the aggregates, whereas Desulfovibrio sp. were located inside the aggregates.

Biological sulfate reduction using synthesis gas as energy and carbon source

Biological sulfate reduction was studied in laboratory-scale gas-lift reactors. Synthesis gas (gas mixtures of H2/CO/CO2) was used as energy and carbon source. The required biomass retention was obtained by aggregation and immobilization on pumice particles. Special attention was paid to the effect of CO addition on the sulfate conversion rate, aggregation, and aggregate composition. Addition of 5% CO negatively affected the overall sulfate conversion rate; i.e., it dropped from 12–14 to 6–8 g SO/L day. However, a further increase of CO to 10 and 20% did not further deteriorate the process. With external biomass recycling the sulfate conversion rate could be improved to 10 g SO/L day. Therefore biomass retention clearly could be regarded as the rate-limiting step. Furthermore, CO affected the aggregate shape and diameter. Scanning electron microscopy (SEM) photographs showed that rough aggregates pregrown on H2/CO2 changed into smooth aggregates upon addition of CO. Addition of CO also changed the aggregate Sauter mean diameter (d32) from 1.7 mm at 5% CO to 2.1 mm at 20% CO. After addition of CO, a layered biomass structure developed. Acetobacterium sp. were mainly located at the outside of the aggregates, whereas Desulfovibrio sp. were located inside the aggregates. © 1996 John Wiley & Sons, Inc.

Development and Active Demonstration of Acid Digestion of Plutonium-Bearing Waste

At the Eurochemic site, 800 kg of combustible alpha waste containing ∼7 kg of plutonium were treated from March 1983 to July 1985 with the aim of concentrating the plutonium by oxidating the waste and converting it into a soluble form so that the established purification processes could be applied.In a batch process, shredded waste is oxidized with nitric acid in sulfuric acid. The digester content is then kept for several hours at digestion temperature to complete the dissolution of plutonium dioxide. The cold digester content is then filtered and the plutonium-containing filter cake is sent to the plutonium purification system. The off-gases generated are freed from the acids by scrubbing.The process is demonstrated in a plant with a daily throughput of 10 kg of waste. For the oxidation of waste and the dissolution of plutonium dioxide, a ring-type digester made of technical glass is used. The following principal results have been obtained: 1. Complete oxidation of the waste material is achieved within 15 min at a digester acid temperature of 250°C under oxidizing conditions provided by nitric acid. 2. At 250°C and with constant stirring of the digester content, a plutonium oxide to plutonium sulfate conversion rate of up to 99% is obtained within 8 h. 3. The average waste throughput achieved has been 4.1 kg per run (maximum of 10.4 kg). The plutonium decontamination factors were 1010 for the cleaned off-gas and 106 for the liquid secondary waste.

Lagrangian measurements of sulfur dioxide to sulfate conversion rates

On the basis of Project MISTT data and proposed homogeneous gas phase oxidation mechanisms for sulfur dioxide, it has been suggested that the degree of mixing with background air, the chemical composition of the background air, and the intensity of the sunlight available are key factors determining the rate of sulfur dioxide to sulfate conversion. These hypotheses are examined in light of Lagrangian measurements of conversion rates in power plant plumes made during the Tennessee Plume Study and Project Da Vinci. It is found that the Lagrangian conversion rate measurements are consistent with these hypotheses. It has also been suggested that the concentration of ozone may serve as a workable surrogate for the concentrations of the free radicals involved in the homogeneous gas phase mechanism. The night-time Lagrangian data remind one that the gross difference in mean lifetime of ozone and free radicals can lead to situations in which the ozone concentration is not a good surrogate for the free radical concentrations.

Measurements of gas-to-particle conversion in the plumes from five coal-fired electric power plants

Airborne measurements of particles and trace gases have been obtained in the plumes from five coal-fired electric power plants situated in the West and Midwest of the United States. From these data, gas-to-particle (g-to-p) conversion rates are estimated from changes in total particle volume, changes in the ratio of the mass of particulate sulfur to the total mass of sulfur (particulate sulfur measured by two techniques), and from particle nucleation ∗ ∗ By nucleation we mean the formation of a particle of detectable size. Thus, our nucleation rate may or may not be the same as the rate of formation of molecular clusters from the gas phase. rates. The g-to-p conversion rates ranged from 0 to 5.7% ± 2.0% of SO 2 h −1 for travel times of 10–162 min. The data suggest differences between plants in the partitioning of g-to-p conversion products between condensation onto existing particles and the nucleation of new particles. The relationship between panicle surface area and the formation rate of particle volume at large reaction times in the plumes was similar to that found in smog chamber studies. Finally, the SO 2-to-particulate sulfate conversion rate was found to correlate well (correlation coefficient — 0.9) with a parameter indicative of the reaction of SO2 in the plumes with ambient OH radicals.

Hydroxyl and peroxy radicals in polluted tropospheric air

Model calculations show that hydroxyl is a rather conservative specie with respect to abundance and diurnal variation. Calculated maximum concentrations range from about 6×10−5 to 4×10−4 ppb for winter and summer, clear and clouded sky, temperatures ranging from 0 to 25°C and pollutant emissions ranging from average values for Western industrialized countries to urban areas. Peroxy radicals show a much stronger variability in concentration partly due to their strong dependence on NO. Gas phase sulfate conversion rates up to 3% hr−1 are calculated. Sulfate and ozone are efficiently generated in moderately polluted air.