Excess Sulfuric Acid Research Articles

A simple and cost-efficient route to prepare sulfonated dihalo-monomers for synthesizing sulfonated aromatic PEMs.

We present a simple and cost-efficient route for the preparation of sulfonated dihalo-monomers for the synthesis of hydrocarbon ionomers. After conventional monomer sulfonation, excess sulfuric acid is quantitatively removed by neutralization with BaCO3. This leads to the precipitation of excess H2SO4 as insoluble BaSO4, which is easily separated from the sulfonated monomers in their soluble Ba-forms by filtration. Compared to conventional methods, the proposed approach leads to higher yields, drastically reduces the number of purification steps, and can easily be expanded to the preparation of other sulfonated monomers. The specific monomers presented here are suitable for the preparation of sulfonated polyarylenes and sulfonated polyphenylenes.

Recovery of excess sulfuric acid in the lithium-ion batteries recycling process

Excess sulfuric acid which is needed for the leaching process of spent lithium-ion batteries is commonly neutralized generating significant waste streams. This research aims to extract and recover sulfuric acid using tri-n-octylamine as an extraction agent. 1-octanol, 2-ethylhexanol, and tributyl phosphate are investigated as synergetic extractants and phase modifiers. An equilibrium study is carried out on both, sulfuric acid and leachate. The equilibrium constant and the stoichiometric coefficient for the overall equilibrium reaction are determined by slope analysis. The enthalpy and Gibb’s enthalpy are studied by investigation of the effect of temperature. Regarding the experiments using leachate, the co-extraction of aluminum, cobalt, copper, iron, lithium, manganese, and nickel is studied, too. Moreover, the co-extraction of water is investigated as a significant increase in metal concentration in the raffinate is observed.

Effect of sulfuric residual acid on the physicochemical properties, thermal behavior, and decomposition kinetics of nitrocellulose

The acid remaining in the nitrocellulose (NC) during the production process have some influence on its structure and stability. Herein, physicochemical properties, thermal behavior, and decomposition kinetics of NC before and after sulfuric acid treatment were thoroughly investigated using a series of analytical instruments in this paper. It is found that the nitrogen content and relative molecular weight of NC-0.968% that undergoing impregnation with sulfuric acid and drying is decreased by 0.58% and 16% (decreasing rate), respectively, suggesting that the presence of excess sulfuric acid leads to denitrification of NC at room temperature as well as breakage of the glucoside bond, with a greater effect on the latter. Moreover, the results of X-ray diffraction (XRD), scanning electron microscopy (SEM), and dynamic vapor sorption (DVS) indicate that the presence of sulfuric acid did not cause significant changes in the crystalline structure of NC, but severely damage the microscopic morphology, resulting in a large number of micropores appearing on its fiber surface, which enhances the hygroscopicity of NC. In addition, the combined Model-based kinetic results indicate that the decomposition reaction process of NC- 0.968% has a step one more than that of pure NC, which is attributed to the acid-catalyzed denitrification of NC and the breaking of glucoside bonds. Combined with the experimental results of TG-DSC-FITR, it shows that the presence of acid mainly affects the initial decomposition process of NC, while the fracture of the glucose ring frame and oxygen bridge in the NC molecular structure is more dependent on the action of NO2 and the decomposition temperature.

The structure of protic ionic liquids based on sulfuric acid, doped with excess of sulfuric acid or with water.

Neutron scattering with isotopic substitution was used to study the structure of concentrated sulfuric acid, and two protic ionic liquids (PILs): a Brønsted-acidic PIL, synthesised using pyridine and excess of sulfuric acid, [Hpy][HSO4]·H2SO4, and a hydrated PIL, in which an equimolar mixture of sulfuric acid and pyridine has been doped with water, [Hpy][HSO4]·2H2O. Brønsted acidic PILs are excellent solvents/catalysts for esterifications, driving reaction to completion by phase-separating water and ester products. Water-doped PILs are efficient solvents/antisolvents in biomass fractionation. This study was carried out to provide an insight into the relationship between the performance of PILs in the two respective processes and their liquid structure. It was found that a persistent sulfate/sulfuric acid/water network structure was retained through the transition from sulfuric acid to PILs, even in the presence of 2 moles (∼17 wt%) of water. Hydrogen sulfate PILs have the propensity to incorporate water into hydrogen-bonded anionic chains, with strong and directional hydrogen bonds, which essentially form a new water-in-salt solvent system, with its own distinct structure and physico-chemical properties. It is the properties of this hydrated PIL that can be credited both for the good performance in esterification and beneficial solvent/antisolvent behaviour in biomass fractionation.

Beckmann Rearrangement with Improved Atom Economy, Catalyzed by Inexpensive, Reusable, Bro̷nsted Acidic Ionic Liquid

Inexpensive protic ionic liquids, synthesized from di- or triamines and excess sulfuric acid, were used as solvents and catalysts for the Beckmann rearrangement. The use of ionic liquids in place of oleum or sulfuric acid allowed the base neutralization step, which is required in the conventional Beckmann rearrangement, to be entirely avoided, thereby dramatically improving the atom economy. Using a biphasic water/organic solvent extraction system, it was possible to recover and reuse the ionic liquid. The proposed method was found applicable for the synthesis of a range of primary and secondary amides.

Preparation and Crystal Structure of a New Uranyl Sulfate Templated by a Bis‐isothiouronium Cation

Crystals of a new uranyl sulfate (C2N4H8S2)[UO2(SO4)2]·0.3H2O (1) templated by a relatively rare bis‐isothiouronium cation, were formed upon evaporation of aqueous solutions containing uranyl acetate, thiourea, and excess sulfuric acid. The new compound is orthorhombic, P212121, a = 6.928(2) Å, b = 13.398(3) Å, c = 15.225(3) Å, Z = 2. Its crystal structure is comprised of [UO2(SO4)2] moieties linked by hydrogen bonds formed between the template cations and terminal oxygen atoms of the sulfate tetrahedra. The C2N4H8S22+ template is most likely formed in situ during a redox reaction between uranyl cation and thiourea in a strongly acidic medium, with UO22+ partially reduced to U4+.

α-Nickel sulfate hexahydrate crystals: relationship of growth conditions, crystal structure and properties

Studies on α-nickel sulfate hexahydrate (NSH) crystals grown under different conditions are undertaken to investigate how changes in growth conditions affect crystal properties and whether or not there is any modification of the average crystal structure due to changes in crystallization conditions. Thermogravimetric and microhardness studies were carried out on the crystals grown from two different aqueous solutions, one of them containing an excess of sulfuric acid. Raman spectra were recorded and a single-crystal neutron diffraction investigation was conducted on both crystals. A detailed comparison between the two crystal structures and their Raman spectra showed that, although the two crystal structures are very similar, there are slight differences, such as the change in unit-cell volume, differences in the ionic structure, particularly of the sulfate ions, and changes in the hydrogen-bonding network. During solution crystal growth of a salt like NSH, varying the ionic environment around the solute ions influences the interionic interactions between them. Hence it is suggested that the above-mentioned structural differences result from a fine-tuning of the interionic interaction between the cations and anions of NSH in the solution phase. This difference is finally carried over to the crystalline phase. The resulting small crystal structure differences are enough to produce measurable changes in the thermal stability and fragility of the crystals. These differences in crystal properties can be explained on the basis of the observed structural differences between the two crystals grown under different conditions.

Leaching of White Metal in a NaCl-H2SO4 System under Environmental Conditions

The effect of NaCl on the leaching of white metal from a Teniente Converter was investigated in NaCl-H2SO4 media under environmental conditions. The copper dissolution from white metal was studied using ferric ions in the range of 1–10 g/L, NaCl in the range of 30–210 g/L, and sulfuric acid in the range of 10–50 g/L. The test without NaCl produced a dissolution of 55%; through the addition of NaCl, the dissolution increased to nearly 90%. The effect of sulfuric acid on the copper dissolution was not significant in the studied range, as the excess sulfuric acid simply increased the iron precipitation. The positive effect of NaCl seems to be related to the action of chloro-complex oxidizing agents in relation to the Cu+2/Cu+ couple. A simplified two-stage mechanism is proposed for the leaching of white metal. In the first stage, the white metal produces covellite and Cu2+, and in the second stage it produces elemental sulfur and Cu2+. The first stage is very rapidly compared to the second stage.

Stoichiometry of water-soluble ions in PM2.5: Application in source apportionment for a typical industrial city in semi-arid region, Northwest China

Water-soluble ions (WSIs) are major components of PM2.5 and it is valuable for understanding physical and chemical characteristics, sources, behaviors and formation mechanism of WSIs. Baotou is a traditionally industrial city in semi-arid region and frequently subjected to dust storms from March to May. In recent years, air pollution has been listed as one of the most important environmental problems in Baotou. To investigate the seasonal variations and sources of WSIs in PM2.5, the WSIs including SO42−, NO3−, Cl−, F−, NH4+, K+, Na+, Ca2+ and Mg2+ were monitored at six urban sites in Baotou. The results showed that high concentrations of Ca2+ and Na+ were found responding to dust storm events, while high concentrations of SO42−, NO3−, NH4+, K+ and Cl− were observed during haze days. The correlations analysis indicated that excess sulfuric and nitric acid was likely neutralized by carbonate minerals such as calcite, aragonite and dolomite in normal days and cations were fully neutralized during all the sampling periods, while cations were excessive in dust storm days. The concentrations of [NH4+ + SO42− + NO3−], [Na+ + Ca2+ + Mg2+] and [Cl− + K+ + F−] indicated the northwest and southeast region of Baotou presented comparatively high contributions of secondary aerosol and crustal dust, respectively, which were mainly related to the industrial distribution and urbanization process. The cluster analysis, ternary diagram and principal component analysis have a good agreement in source apportionment, where crustal dust sources, secondary aerosol source and the mixture of coal combustion, biomass burning and industrial pollution sources were the main sources of WSIs in PM2.5. The seasonal pattern of sulfur oxidation ratio (SOR) was September > April > November > January, while the nitrogen oxidation ratio (NOR) April > January > November > September in Baotou. This work evaluated the seasonal variation, distribution and source of WSIs on the basis of its stoichiometry in PM2.5, which help to explore the potential sources of these inorganic aerosols and provide scientific suggestion for air quality improvement in Baotou.

Solvated proton as the main reagent and a catalyst in the single-stage aromatic sulfonation and protodesulfonation of sulfonic acids

This review is devoted to the critical analysis of the existing contradictory ideas about kinetic description and the mechanisms of electrophilic aromatic substitution (EAS), ie, reversible arene sulfonation and hydrolysis (protodesulfonation) of arenesulfonic acids. Contemporary scientific and educational literature contains prevailing, widespread points of view on the multistage nature processes of the EAS that proceed via π- and σ-complexes and are accompanied by arenium ion formation. This interpretation does not account for determining influence of the medium, and the process accompanies the loss of aromaticity. The review presents an alternative point of view: These processes proceed via single-stage and the same transition state. To substantiate this position, we reviewed in detail the contemporary ideas on the solvated proton structure, the limits of applicability of acidity function Но and excess acidity Х scales, and the experimental solubility data of arenesulfonic acid hydrates in sulfuric acid. This solubility depends on the medium acidity (ho), which provides the formation of 3 conjugated types of hydrates: anionic (АrSO3−·H2O), hydroxonium-arene sulfonated (АrSO3−·H3O+), and the hydroxonium complex with the H-form of АrSO3Н·H3O+ acid. In sulfuric acid solutions with an excess of water, irreversible hydrolysis proceeds with the participation of ArSO3−·H3O+. However, protodesulfonation becomes reversible and proceeds with the participation of ArSO3Н·H3O+in solutions with an excess of sulfuric acid. A conclusion has been made about determining the role of the hydrated proton environment by means the formation of a cyclic transition state. An alternative 2-stage mechanism of EAS is logically and energetically unsubstantiated and, therefore, should be rejected.

Carbon monoxide gas sensing using zinc oxide film deposited by spray pyrolysis

This study was aimed to determine the carbon monoxide (CO) gas sensing ability of zinc oxide (ZnO) film fabricated by spray pyrolysis on glass substrate heated at 3000C using 0.2 M zinc acetate precursor solution. The temperature of the precursor solution was maintained at room temperature. Carbon monoxide gas was synthesized by mixing the required amount of formic acid and excess sulfuric acid in the ratio of 1:6 to produce CO gas concentrations of 100, 200, 300, 400, and 500 parts per million (ppm) v/v. There were five trials for each concentration. The films produced exhibited good sensor characteristics such as high linearity in current voltage relationship and voltage response versus concentration. Electrical characterization using the four-point probe showed a linear relationship between current and voltage with resistivity of 0.49 ohm-cm and R2 value of 0.994 The zinc oxide film exhibited a sensitivity of 0.19 Volt per 100 ppm of CO gas and linearity R2 value of 0.993.

Carbon monoxide gas sensing using zinc oxide deposited by successive ionic layer adhesion and reaction

This study was aimed to determine the carbon monoxide (CO) gas sensing capability of zinc oxide (ZnO) film fabricated by successive ionic layer adsorption and reaction (SILAR) on glass substrate. Films consisting of a mixture of flower-like clusters of ZnO nanorods and nanowires were observed using scanning electron microscopy (SEM). Current-voltage characterization of the samples showed an average resistivity of 13.0 Ω-m. Carbon monoxide gas was synthesized by mixing the required amount of formic acid and excess sulfuric acid to produce CO gas concentrations of 100, 200, 300, 400, and 500 parts per million (ppm) v/v with five trials for each concentration. Two sets of data were obtained. One set consisted of the voltage response of the single film sensor while the other set were obtained from the double film sensor. The voltage response for the single film sensor and the double film sensor showed an average sensitivity of 0.0038 volts per ppm and 0.0024 volts per ppm, respectively. The concentration the single film can detect with a 2V output is 526 ppm while the double film sensor can detect up to 833 ppm with a 2V output. This shows that using the double film sensor is advantageous compared to single film sensor, because of its higher concentration range due to the larger surface area for the gas to interact. Moreover, the measured average resistance for the single film sensor was 10 MΩ while for the double film sensor the average resistance was 5 MΩ.

Reactivity-Controlled Preparation of Ultralarge Graphene Oxide by Chemical Expansion of Graphite

The production of ultralarge graphene oxide (ULGO) is hindered by sluggish diffusion process of the oxidizing agents into graphite layers, as well as sheet fracture resulting from inhomogeneous oxidation. Previous methods rely on an excess amount of oxidants or multiple oxidation to overcome large diffusion resistance, but at the cost of ULGO yield and environmental risk. Here, we discover the chemical expansion of graphite (CEG) with high solvent-accessible surface areas can effectively boost mass diffusion and facilitate exhaustive oxidation at low oxidant dosage (2 wt equiv). The oxidizing reaction is therefore controlled by the chemical reactivity of graphite with oxidant rather than the diffusion of oxidant, which results in a ∼100% yield of ULGO nanosheets with an area-average size of 128 μm. The worm-like structure of CEG and its oxide provides a chance to recover excess sulfuric acid using a 100-mesh filter, where subsequent exfoliation to ULGO nanosheets is achieved by mild agitation or shaking i...

Bacteria-assisted preparation of nano α-Fe2O3 red pigment powders from waste ferrous sulfate

Massive ferrous sulfate with excess sulfuric acid is produced in titanium dioxide industry each year, ending up stockpiled or in landfills as solid waste, which is hazardous to environment and in urgent demand to be recycled. In this study, waste ferrous sulfate was used as a second raw material to synthesize nano α-Fe2O3 red pigment powders with a bacteria-assisted oxidation process by Acidithiobacillus ferrooxidans. The synthesis route, mainly consisting of bio-oxidation, precipitation and calcination, was investigated by means of titration, thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray fluorescence (XRF) to obtain optimum conditions. Under the optimum conditions, nano α-Fe2O3 red pigment powders contained 98.24wt.% of Fe2O3 were successfully prepared, with a morphology of spheroidal and particle size ranged from 22nm to 86nm and averaged at 45nm. Moreover, the resulting product fulfilled ISO 1248-2006, the standards of iron oxide pigments.

Experimental modeling of hydrogen producing steps in a novel sulfur–sulfur thermochemical water splitting cycle

One of the more well-known examples of thermochemical water splitting cycles is the sulfur–iodine cycle, which utilizes iodine and sulfur dioxide to transform water into hydrogen and oxygen. A novel sulfur–sulfur cycle has been developed based on the original sulfur–iodine cycle, seeking an overall more favorable chemical process. The initial stages of the original and novel cycles are the same, in using sulfur dioxide and iodine with an excess of water to form two strong acids, hydrogen iodide and sulfuric acid. The secondary reactions differ greatly and are based on a previously unwanted side reaction where the two strong acids regenerate iodine and water along with hydrogen sulfide, as shown in the equations below. The hydrogen sulfide can then be steam reformed to hydrogen and sulfur dioxide, completing the cycle. Excess sulfuric acid can also be treated to regenerate water and sulfur dioxide.I2(l)+SO2(g)+2H2O(l)→2HI(l)+H2SO4(l)8HI(l)+H2SO4(l)→4I2(l)+4H2O(l)+H2S(g)This study seeks to explore the reaction kinetics of this two-step reaction by altering the various reaction temperatures and the initial concentration of water and to develop a robust and simple predictive model based on the resulting experimental data. The results suggest that an increase in the initial concentration of water will increase the rate of both reactions substantially and that it is beneficial to carry them out in the same vessel. A predictive model was successfully developed that allows for monitoring the progression of iodine through the reaction system in a batch setting. The results of the experimental and modeling work warrants further development of this novel sulfur–sulfur thermochemical water splitting cycle.

Efficient production of sophorolipids by Starmerella bombicola using a corncob hydrolysate medium

Sophorolipids (SLs) are amphiphilic compounds produced from a variety of saccharides and vegetable oils by the yeast Starmerella bombicola and related strains, and they have commercial uses as detergents. In the present study, SL production was investigated using a corncob hydrolysate (CCH) medium derived from lignocellulosic feedstocks as a source of hydrophilic carbon substrates. Excess sulfuric acid concentrations during pretreatment of the corncobs increased the furfural concentrations and turned the CCH dark brown. The optimal sulfuric acid concentration was 1% (w/v), and the treated CCH, containing 45 g/l glucose, allowed the production of 33.7 g/l of SLs following 4 days of cultivation. Additional autoclaving (121°C, 20 min) inhibited SL production and cell growth by 36% and 40%, respectively. Ammonium nitrate (0.1 g-N/l) restored SL production to the autoclaved CCH. Finally, a cost-effective SL production of 49.2 g/l, with a volumetric productivity of 12.3 g/l/day, was achieved using CCH medium during batch cultivation in a jar fermentor.

Elucidation of molybdosilicate complexes in the molybdate yellow method by ESI-MS

The formation of molybdosilicate in the molybdate yellow method is elucidated by ESI-MS. Polymeric silicic acids were hydrolyzed to monomers, and molybdosilicates with a Keggin structure were formed. Each step of the formation reaction of molybdosilicate from molybdic and silicic acids between pH 1 and 2 was clarified by ESI-MS at the molecular level. In a solution below pH 0.5, the polymers of the molybdic acids were decomposed because of the high concentration of sulfuric acid. Excess sulfuric acid prevented the formation of molybdosilicate. Thus, none of the silicic acids reacted to form molybdosilicate at this pH, despite the presence of silicic acid and sulfate ions in the solution. Above pH 2, the condensation of molybdic acids occurred to form α-molybdosilicate. ESI-MS provides information on the formation of molybdosilicate and the individual reaction species present in the reaction mixture.

Reaction of enargite (Cu3AsS4) in hot concentrated sulfuric acid under an inert atmosphere. Part III: reaction stoichiometry and kinetics

Based on the extensive insights gained from the acid bake–leach reaction from our previous experiments, a rigorous experimental plan was designed to investigate the effects of time, temperature, particle size, nitrogen flow rate, sulfuric acid concentration and dosage, and reaction surface area on the extraction of Cu and As from a high-quality enargite sample through sulfuric acid baking and leaching. The baking experiments in the temperature range of 170–200°C over 1–4h revealed almost complete Cu and As extraction after 4h baking at 200°C, a sulfuric acid to enargite weight ratio (S/E) of 4, nitrogen flow rate ~100mL/min, and particle size P100=−45μm, and no arsenic was lost to the gas phase. The following reaction is suggested for the sulfuric acid baking of enargite:4Cu3AsS4+28H2SO4=3CuO•CuSO4+6CuSO4+2As2O3+28H2O+19.5SO2g+15.5SLack of a systematic dependence of reaction rate on particle size and the significant dependence of the rate on sulfuric acid concentration suggest that the rate of the baking reaction is controlled by the internal surface area of cracks at which surface the baking reaction occurs. It is expected that these cracks are formed as a result of a major volume increase during the baking reaction. High nitrogen flow rates encouraged arsenic loss to the gas phase. Decreasing the S/E ratio from 4 to 2 resulted in a decrease in the rate of reaction, while increasing sulfuric acid concentration enhanced the rate. Excess sulfuric acid was found to be necessary for both acceptable reaction rates and also for maximum As retention in the condensed phase. Doubling the reaction surface area did not affect the extraction of Cu and As.

Acid-catalyzed hot-water extraction of lipids from Chlorella vulgaris

Acid-catalyzed hot-water treatment for efficient extraction of lipids from a wet microalga, Chlorella vulgaris, was investigated. For an initial fatty acids content of 381.6mg/g cell, the extracted-lipid yield with no heating and no catalyst was 83.2mg/g cell. Under a 1% H2SO4 concentration heated at 120°C for 60min, however, the lipid-extraction yield was 337.4mg/g cell. The fatty acids content, meanwhile, was 935mg fatty acid/g lipid. According to the severity index formula, 337.5mg/g cell of yield under the 1% H2SO4 concentration heated at 150°C for 8min, and 334.2mg/g cell of yield under the 0.5% H2SO4 concentration heated at 150°C for 16min, were obtained. The lipids extracted by acid-catalyzed hot-water treatment were converted to biodiesel. The biodiesel's fatty acid methyl ester (FAME) content after esterification of the microalgal lipids was increased to 79.2% by the addition of excess methanol and sulfuric acid.

Proton conduction properties of nano-titania modified by sulfuric acid impregnation

The proton conduction properties of sulfuric acid-modified nano-titania prepared by impregnation method were investigated. The proton conductivity of sulfuric acid-modified nano-titania was almost the same as that of hydrous sulfated nano-titania investigated in our previous work when the amount of adsorbed sulfate groups was almost the same. The highest conductivity was obtained at an adsorbed sulfate group amount of 0.42 mmol/g, not 0.97 mmol/g. This result indicates that the enhancement of conductivity with increasing amount of adsorbed sulfate groups is limited. This might be attributable to insufficient water molecule adsorption on the Ti4+ site coordinated with a bidentate sulfate group due to the prevention by excess sulfuric acid.