Low Concentration Of Sulfuric Acid Research Articles

The Effect of Acid Hydrolysis on the Pickering Emulsifying Capacity of Tartary Buckwheat Flour.

The effect of sulfuric acid hydrolysis on the Pickering emulsifying capacity of Tartary buckwheat flour (TBF) rich in starch was evaluated for the first time. The results indicate that the sulfuric acid concentration and hydrolysis time had a significant impact on the Pickering emulsifying capacity of acid-hydrolyzed Tartary buckwheat flour (HTBF). A low sulfuric acid concentration (1-2 mol/L) could reduce the particle size of HTBF, but it also decreased the Pickering emulsifying ability. At a sulfuric acid concentration of 3 mol/L, appropriate treatment time (2 and 3 days) led to particle aggregation but significantly improved wettability, thereby resulting in a rapid enhancement in emulsifying capacity. Under these conditions, the obtained HTBF (HTBF-D2-C3 and HTBF-D3-C3) could stabilize medium-chain triglyceride (MCT)-based Pickering high-internal-phase emulsions (HIPEs) with an oil-phase volume fraction of 80% at the addition amounts (c) of ≥1.0% and ≥1.5%, respectively. Its performance was significantly superior to that of TBF (c ≥ 2.0%). Furthermore, at the same addition amount, the droplet size of HIPEs constructed by HTBF-D3-C3 was smaller than that of HTBF-D2-C3, and its gel strength and microrheological performance were also superior to those of HTBF-D2-C3, which was attributed to the higher wettability of HTBF-D3-C3. The findings of this study can facilitate the in-depth application of Tartary buckwheat and provide references for the development of novel Pickering emulsifiers.

Valorization of Chlorella Microalgae Residual Biomass via Catalytic Acid Hydrolysis/Dehydration and Hydrogenolysis/Hydrogenation

Microalgal biomass can be utilized for the production of value-added chemicals and fuels. Within this research, Chlorella vulgaris biomass left behind after the extraction of lipids and proteins was converted to valuable sugars, organic acids and furanic compounds via hydrolysis/dehydration using dilute aqueous sulfuric acid as a homogeneous catalyst. Under mild conditions, i.e., low temperature and low sulfuric acid concentration, the main products of hydrolysis/dehydration were monomeric sugars (glucose and xylose) and furanic compounds (HMF, furfural) while under more intense conditions (i.e., higher temperature and higher acid concentration), organic acids (propionic, formic, acetic, succinic, lactic, levulinic) were also produced either directly from sugar conversion or via intermediate furans. As a second valorization approach, the residual microalgal biomass was converted to value-added sugar alcohols (sorbitol, glycerol) via hydrogenation/hydrogenolysis reactions over metallic ruthenium catalysts supported on activated carbons (5%Ru/C). It was also shown that a low concentration of sulfuric acid facilitated the conversion of biomass to sugar alcohols by initiating the hydrolysis of carbohydrates to monomeric sugars. Overall, this work aims to propose valorization pathways for a rarely utilized residual biomass towards useful compounds utilized as platform chemicals and precursors for the production of a wide variety of solvents, polymers, fuels, food ingredients, pharmaceuticals and others.

Comparative Study on the Corrosion Behavior of Materials in Heat Recovery Steam Generators for Combined Cycle Power Plant, Based on Sulfuric Acid Concentrations: Carbon Steels vs. Duplex Stainless Steel (UNS S32205)

This study examined the effects of sulfuric acid concentrations on the corrosion behaviors of three types of commercial steels, conventional carbon steel (SA192), sulfuric acid dew resistant steel (S-TEN), and duplex stainless steel (S32205), considered to be potential materials for the heat recovery steam generator (HRSG) in combined cycle power plants. Based on the results of electrochemical polarization, immersion and wet-dry cycle tests, when exposed to a high sulfuric acid concentration (50%), SA192 and S-TEN exhibited higher corrosion resistance than S32205, which was due to the formation of a stable FeSO4 scale on the carbon steel materials. With prolonged exposure, S-TEN with slightly higher concentrations of Cu and Sb showed lower weight loss than SA192. Conversely, when subjected to low sulfuric acid concentrations (5 and 10%), S32205 exhibited passivation behavior, and showed significantly superior corrosion resistance (i.e., much smaller weight loss) than the other two steel samples. The examination of localized corrosion damages through cross-section observation using a scanning electron microscope revealed also that S32205 suffered less damages from the wet-dry cycling. The long-term superior corrosion resistance of duplex stainless steel in low sulfuric acid concentrations, compared to carbon steel and sulfuric acid due resistant steel, make it a promising candidate material for the HRSG in combined cycle power plants.

Strategies towards a green solvent biorefinery: Efficient delignification of lignocellulosic biomass residues by gamma-valerolactone/water catalyzed system

Biorefineries promote the integral use of lignocellulosic biomass by separating lignin, cellulose, and hemicelluloses, so environmentally friendly solvents with good efficiency in lignin removal at mild conditions (low temperatures and pressures) are under thorough research. This study evaluates the optimization of γ-Valerolactone (GVL) systems using a solvent complying with the principles of green chemistry as an efficient delignification strategy for lignocellulosic biomass residues such as sugarcane bagasse and pine sawdust. First, depithed sugarcane bagasse was delignified by a solvent system composed of GVL/water and a low concentration of sulfuric acid (SA), considering temperature, reaction time, GVL, and SA concentration in the liquor as variables, organized following a 4-factor Draper-Lin Central Composite Design (CCD). Milder treatments compared with literature were applied, with extreme points at 130–180 °C, 40–140 min, 43–77 wt% GVL, and 0–0.01 M SA, respectively. The experimental conditions involving pine sawdust were assessed at the highest delignification point of sugarcane bagasse. Delignification from 75% to 96% was obtained for sugarcane bagasse. In the same conditions, pine sawdust delignification was slightly lower. The solid fraction characterization involved yield, ISO brightness, crystallinity index, intrinsic viscosity in cupriethylenediamine, structural carbohydrates, and lignin content, whereas sugars, byproducts, and degradation products were analyzed in the liquid fraction. The study compares different properties combined into one single combined severity factor. The evaluation also involved optical properties relevant to some uses, such as dissolving pulps or nanocellulose.

Theoretical Study of the Gas-Phase Hydrolysis of Formaldehyde to Produce Methanediol and Its Implication to New Particle Formation.

Aldehydes were speculated to be important precursor species in new particle formation (NPF). The direct involvement of formaldehyde (CH2O) in sulfuric acid and water nucleation is negligible; however, whether its atmospheric hydrolysate, methanediol (CH2(OH)2), which contains two hydroxyl groups, participates in NPF is not known. This work investigates both CH2O hydrolysis and NPF from sulfuric acid and CH2(OH)2 with quantum chemistry calculations and atmospheric cluster dynamics modeling. Kinetic calculation shows that reaction rates of the gas-phase hydrolysis of CH2O catalyzed by sulfuric acid are 11-15 orders of magnitude faster than those of the naked path at 253-298 K. Based on structures and the calculated formation Gibbs free energies, the interaction between sulfuric acid/its dimer/its trimer and CH2(OH)2 is thermodynamically favorable, and CH2(OH)2 forms hydrogen bonds with sulfuric acid/its dimer/its trimer via two hydroxyl groups to stabilize clusters. Our further cluster kinetic calculations suggested that the particle formation rates of the system are higher than those of the binary system of sulfuric acid and water at ambient low sulfuric acid concentrations and low relative humidity. In addition, the formation rate is found to present a negative temperature dependence because evaporation rate constants contribute significantly to it. However, cluster growth is essentially limited by the weak formation of the largest clusters, which implies that other stabilizing vapors are required for stable cluster formation and growth.

Regenerative Strategy of Gold Electrodes for Long-Term Reuse of Electrochemical Biosensors.

Gold is of considerable interest for electrochemical active surfaces because thiol-modified chemicals and biomolecules can be easily immobilized with a simple procedure. However, most gold surfaces are damaged with repetitive measurements, so they are difficult to reuse. Here we demonstrate a novel electrochemical cleaning method of gold surfaces to reuse electrodes with a simple protocol that is easy and nontoxic. This electrochemical cleaning consists of two steps by using different solutions. The 1st step is a cyclic voltammetry sweep using a very low concentration of sulfuric acid, and the 2nd step is a cyclic voltammetry sweep using potassium ferricyanide. Different cleaning methods were also considered for comparison. Consequently, after assembling and desorption of the cell and antigen, the changes in gold electrode performance, as immunosensor and cytosensor, were investigated by electrochemical impedance and cyclic voltammetry. It was found that repetitive measurement is possible until five times while maintaining the reproducibility. It is believed that this method is capable of enabling reuse of gold electrodes and can be used for long-term and accurate monitoring of biological effects, especially at a low cost.

An environmental and highly active Ce/Fe-Zr-SO42- catalyst for selective catalytic reduction of NO with NH3: The improving effects of CeO2 and SO42-

A series of Ce/Fe-Zr-SO42- catalysts have been prepared and developed for selective catalytic reduction of NO with ammonia (NH3-SCR). The catalysts were characterized by XRD, H2-TPR, N2 adsorption-desorption, NH3-TPD and DRIFTS. The characterization results demonstrated that the coexistence of cerium and sulfuric acid on Fe-Zr catalyst could contribute to excellent SCR performance. Among all samples, Ce/Fe-Zr-0.3 S catalyst showed the optimal NOX conversion, reaching more than 80% at 250 °C at a GHSV of 60,000 h−1. Moreover, the optimum concentration of SO42- to modify Ce/Fe-Zr catalyst was 0.3 mol/L. The low sulfuric acid concentration contributed to improving low-temperature activity, while high concentration leaded to outstanding high-temperature activity. According to H2-TPR and NH3-TPD, the presence of SO42- increased the total amount of acid sites and more stable sulfate species were formed with higher concentration of sulfuric acid. In situ DRIFTS revealed the NH3 molecule was mainly activated at the Lewis acid site and reacted with the adsorbed NOX species (such as bidentate nitrates) to produce N2 and H2O, which conformed to the L-H reaction mechanism.

The nucleation mechanism of succinic acid involved sulfuric acid - Dimethylamine in new particle formation

Succinic acid (SUA) is a common dicarboxylic acid frequently observed in aerosols. Understanding the role of succinic acid in atmospheric new particle formation is essential to study the complicated nucleation mechanism. In this study, high-precision quantum chemical calculations and atmospheric clusters dynamic code (ACDC) simulations are used to investigate the nucleation mechanism of the (SA)x(SUA)y(DMA)z (0 = x, y, z ≤ 3) multicomponent system. The most stable molecular structures show that SUA can form relatively stable clusters with the SA-DMA system by hydrogen bond and proton-transfer interactions. Similar to SA molecules, SUA can provide protons to DMA when excess DMA molecules are available. ACDC simulations indicate that SUA can contribute to the cluster formation, especially at low sulfuric acid concentration and high succinic acid concentration. Moreover, the main cluster flux out of the SUA-containing system is along the non-diagonal (the number of acid molecules is greater than that of base molecules), which is different from the pure SA-DMA system. These clusters are stable enough to be present at a fairly high concentration, and could be a platform for growth into the larger sizes. This organic acid involved cluster formation may explain high nucleation rate at low sulfuric acid concentration and high organic acid concentration.

Influence of atmospheric conditions on the role of trifluoroacetic acid in atmospheric sulfuric acid–dimethylamine nucleation

Abstract. Ambient measurements combined with theoretical simulations have shown evidence that the tropospheric degradation end-products of Freon alternatives, trifluoroacetic acid (TFA), one of the most important and abundant atmospheric organic substances, can enhance the nucleation process based on sulfuric acid (SA) and dimethylamine (DMA) in urban environments. However, TFA is widespread all over the world under different atmospheric conditions, such as temperature and nucleation precursor concentration, which are the most important factors potentially influencing the atmospheric nucleation process and thus inducing different nucleation mechanisms. Herein, using the density functional theory combined with the Atmospheric Cluster Dynamics Code, the influence of temperature and nucleation precursor concentrations on the role of TFA in the SA–DMA nucleation has been investigated. The results indicate that the growth trends of clusters involving TFA can increase with the decrease in temperature. The enhancement on particle formation rate by TFA and the contributions of the SA–DMA–TFA cluster to the cluster formation pathways can be up to 227-fold and 95 %, respectively, at relatively low temperature, low SA concentration, high TFA concentration, and high DMA concentration, such as in winter, at the relatively high atmospheric boundary layer, or in megacities far away from industrial sources of sulfur-containing pollutants. These results provide the perspective of the realistic role of TFA in different atmospheric environments, revealing the potential influence of the tropospheric degradation of Freon alternatives under a wide range of atmospheric conditions.

Theoretical study of the formation and nucleation mechanism of highly oxygenated multi-functional organic compounds produced by α-pinene.

In recent years, highly oxygenated organic molecules (HOMs) derived from photochemical reactions of α-pinene, the most abundant monoterpene, have been considered as important precursors of biogenic particles. However, the specific reactions of HOMs remain largely unknown, especially the corresponding formation and nucleation mechanism in the nanoscale. In this study, we implemented quantum chemical calculations and molecular dynamics (MD) simulations to explore the mechanism of the formation of HOM monomers/dimers by ozonolysis and autoxidation of α-pinene. Furthermore, we investigated the mechanisms of HOMs with different oxygen-to‑carbon (O/C) ratios and functional groups participating in neutral and ion-induced nucleation. The results show that the formation of HOMs is hardly affected by water, sulfuric acid and ions. In the ion-induced nucleation, HOM can dominate the initial nucleation steps; however, in the neutral nucleation, HOMs are more likely to participate in the growth stage. In addition, the nucleation ability of HOM has a bearing on the O/C ratio and the types of the functional groups. The current calculations provide valuable insight into the formation mechanism of the pure organic particles at low sulfuric acid concentrations.

Mechanism for Rapid Conversion of Amines to Ammonium Salts at the Air-Particle Interface.

The effect of sulfuric acid (SA) concentrations on heterogeneous reactions of amines such as methylamine (MA), dimethylamine (DMA), and trimethylamine (TMA) at the air-particle interface is investigated using combined classical molecular dynamics, Born-Oppenheimer molecular dynamics, and quantum chemical calculations. The results show that the mixtures of these amine vapors can accumulate at the air-particle interface and then participate in two types of heterogeneous reactions depending on the SA concentrations in the aqueous particles. At high SA concentrations, amines are neutralized by H3O+ and form ammonium salts within only a few picoseconds. At low SA concentrations, amines mainly proceed by hydrolysis reactions and produce ionic pairs of ammonium and OH-. However, the formed ionic pair is extremely unstable, and the reverse reaction takes place. Considering that the salt conversion time scales of amines at high SA concentrations are 2.5-15 times faster than those at low SA concentration, amine accumulation at high acidity particles is more favored.

Effect of Sulfuric Acid Concentration on the Corrosion Rate of ASTM A213-T12 Steel

Even though carbon steel is susceptible to corrosion degradation, carbon steel is widely used for applications in the industry. Impurities in steel composition are known to affect the mechanical and corrosion properties. There are many studies on the corrosion of steel, but for a specific application, further research still required. The present work is conducted to determine the effect of low concentration of sulfuric acid on the corrosion rate of power plant steel ASTM A213-T12 with a solution concentration from 0.01-0.05 M H2SO4. The corrosion rate was determined by using an immersion test as well as a polarization method using a potentiostat. The result shows that increasing the concentration of sulfuric acid molarity, the corrosion rate tended to increase. Furthermore, the effect of phosphor contents significantly affects the corrosion rate in which steel with high phosphor contents has a high corrosion rate.

A molecular-scale study on the role of methanesulfinic acid in marine new particle formation

Sulfur species have profound impacts on the formation of secondary organic aerosols in marine regions. As one of the most important organic-sulfur components over the ocean, methanesulfinic acid (MSIA) has received attention. However, its potential role in new particle formation (NPF) is still not fully raveled at the molecular level. Using density functional theory (DFT) combined with the Atmospheric Clusters Dynamic Code (ACDC), the effect of MSIA on the nucleation process of NPF under different atmospheric conditions (varying temperatures and precursor concentrations) has been investigated here. Configuration analysis suggests that MSIA can improve the thermodynamic stability of sulfuric acid (SA) and dimethylamine (DMA)-based clusters via strengthening the proton transfer between SA and DMA. Moreover, the kinetic simulations by ACDC indicate that MSIA can enhance the cluster formation rates of SA-DMA-based clusters, especially at lower temperatures and lower concentrations of SA and DMA. Furthermore, MSIA has been identified to not only promote the growth of small clusters following a catalytic mechanism but also directly participate in the formation of critical clusters according to the traced cluster formation pathways. By analyzing the corresponding branch ratios of growth pathways, the contribution of MSIA to cluster formation increases as the MSIA concentration increases, and decreases with the increasing of DMA concentration. The results indicate that MSIA may be essential to nucleation at regions with insufficient DMA and relatively high concentration of MSIA. This finding may help to reveal some missing sources of marine NPF and to understand the atmospheric organic-sulfur cycle.

In-situ and ex-situ comparison of the electrochemical oxidation of SO2 on carbon supported Pt and Au catalysts

Electrochemical characterizations are performed using thin films and commercial carbon supported platinum and gold catalysts for sulfur dioxide oxidation, the primary electrochemical oxidation reaction in the Hybrid-sulfur (HyS) thermochemical process. Electrochemical evaluation of metal thin films qualitatively confirms the higher activity of Au over Pt, AuPt, Pd, and Ir for the electrochemical oxidation of SO2. Ex-situ testing, using rotating disk electrode (RDE), shows an earlier onset potential for Au/C at low sulfuric acid concentrations (C ≤ 3.5 M) and a higher turnover frequency than Pt/C at sulfuric acid concentrations ranging from 3.5 M to 9 M. In-situ electrolysis experiments using low catalyst loadings (0.1 mgAu cm−2, a factor of ≥5 lower than typical loadings) confirm that Au nanoparticles exhibit higher current densities and greater stability than Pt nanoparticles. This is consistent with the thin film screening studies, which showed higher activity with increasing gold content in AuPt thin films. This work reveals an alternative material to state-of-the-art Pt to lower the energy needs and aid the HyS cycle in reaching the target of $2/kg H2 set forth by the Department of Energy to achieve economic feasibility of large-scale hydrogen generation.

PRODUKSI BUBUK SINBIOTIK DARI HIDROLISATEucheuma cottonii MENGGUNAKANSPRAY DRYING

Eucheuma cottonii is red algae that contain high carbohydrates, especially carrageenan. Carrageenan is a sulfated polygalactan with 15-40% of ester-sulfate content. It is formed by alternate units of D-galactose and 3,6-anhydro-galactose joined by α-1,3 and β-1,4-glycosidic linkage. The galactose polymer therein can be hydrolyzed into Galactooligosaccharide (GOS)type prebiotics. Hydrolysis was done by low concentration of sulfuric acid and crude enzyme from inactivation of Vibrio algynoliticus cell broth. Combination of prebiotic and probiotic provide lactic acid bacteria (BAL) as well as its food sources in the colon. The aim of this research is to know the characteristics of BALgrowth and fermentation in hydrolysateof E. cottonii and to know the best method in producing synbiotic powdersfrom BAL grown in hydrolysate. Analysis conducted include the characteristics of synbiotic powders using two types of BAL, namely Lactobacillus casei and kefir bacteria (Lactobacillus spp.). Characteristics of the two types of BAL produced during fermentation were qualified as probiotics which were amounted to more than 108 cell/mL, pH value 0.2%. The results showed that the number of living bacteria was higherin the method of synbiotic productions after dryingof hydrolysates followed by inoculum addition, than the method of synbiotic productions which inoculum addition was donebefore drying. Keywords:Eucheuma cottonii, Lactobacillus casei,Lactobacillus spp.in kefir

Complex Rare Earth Minerals Sulfate Decomposition Techniques Investigation

This article presents a study of Tomtor rare earth ore decomposition. This material contains a lot of valuable components such as REE and niobium (mas., %: 12,8 ΣREO (rare earth oxides), 0.039 Sc, 18.4 P2O5, 9.9 Fe, 9.0 Al, 0.24 ThO2, 8.2 Nb2O5). The study aims to find efficient ways of processing this deposit. Technologies using the sulfuric acid as the main reagent to leach are described in this article. Investigation has three trends. The first trend is agitation leaching at low sulfuric acid concentrations, temperatures up to 95 °C and atmospheric pressure. The second trend is pressure leaching at low sulfuric acid concentrations, high temperatures (up to 180 °C) and high pressure. The third trend is high temperature sulfatization with concentrated sulfuric acid at elevated temperature (up to 180 °C) and atmospheric pressure followed by aqueous leaching. The dependence of target components (rare earth elements, scandium, phosphorus) and the impurity (iron, aluminum, thorium) extractions into solution from major factors was studied.

Sulfuric acid leaching of high iron-bearing zinc calcine

Sulfuric acid leaching of high iron-bearing zinc calcine was investigated to assess the effects of sulfuric acid concentration, liquid- to-solid ratio, leaching time, leaching temperature, and the stirring speed on the leaching rates of zinc and iron. The results showed that the sulfuric acid concentration, liquid-to-solid ratio, leaching time, and leaching temperature strongly influenced the leaching of zinc and iron, whereas stirring speed had little influence. Zinc was mainly leached and the leaching rate of iron was low when the sulfuric acid concentration was less than 100 g/L. At sulfuric acid concentrations higher than 100 g/L, the leaching rate of iron increased quickly with increasing sulfuric acid concentration. This behavior is attributed to iron-bearing minerals such as zinc ferrite in zinc calcine dissolving at high temperatures and high sulfuric acid concentrations but not at low temperatures and low sulfuric acid concentrations.

The Synthesis Method of Tin Dioxide Nanoparticles by Plasma-Assisted Electrolysis Process and Gas Sensing Property

Tin dioxide nanoparticles are prepared using a newly developed synthesis method of plasma-assisted electrolysis. A high voltage is applied to the tin metal plate to apply a high pressure and temperature to the synthesized oxide layer on the metal surface, producing nanoparticles in a low concentration of sulfuric acid. The particle size, morphology, and size distribution is controlled by the concentration of electrolytes and frequency of the power supply. The as-prepared powder of tin dioxide nanoparticles is used to fabricate a gas sensor to investigate the potential application. The particle-based gas sensor exhibits a short response and recovery time. There is sensitivity to the reduction gas for the gas flowing at rates of 50, 250, and 500 ppm of H2S gas.

Lyotropic Liquid Crystalline Mesophase of Sulfuric Acid-Nonionic Surfactant Stabilizes Lead(II) Oxide in Sulfuric Acid Concentrations Relevant to Lead Acid Batteries.

Concentrated sulfuric acid (SA) and nonionic surfactant (C12H25(OCH2CH2)10OH, C12E10) form lyotropic liquid crystalline (LLC) mesophases in a broad range of SA concentrations; the SA/C12E10 mole ratio may vary from 2 to 11 in the LLC mesophases in the presence of a small amount of water. The mesophase is hexagonal at low SA concentration and cubic at higher concentrations. Three different compositions were prepared (one hexagonal and two cubic) with the SA/C12E10 mole ratio of 2.5, 6, and 9, denoted as 2.5LC, 6LC, and 9LC, respectively. They all display electrochemical SA activity in Pt and Pb systems. Most interestingly, they show the electrochemical formation of stable PbO species in a deeply acidic medium as evidenced by the X-ray diffraction, cyclic voltammetry, and linear sweep voltammetry experiments. The preferable properties of PbO over PbSO4 for lead acid batteries (LABs) make it uniquely positioned as a superior gel electrolyte for the LABs that would mitigate sulfation.

Reducing hydrogen permeation in 304 stainless steel by compound layers of Al, Zr and Ti oxides films

A single and double layer formed by thin films coatings of aluminium oxide, zirconium oxide and titanium oxide were deposited over 304 stainless steel surface by ultrasonic spray pyrolysis technique. The steel samples were conformed for tensile tests. The purpose of these layers is to reduce hydrogen embrittlement effect in steel. An electrochemical cell was used in hydrogen charged, where a low concentration of sulfuric acid is utilized like electrolytic solution. Tension trials show the change the fracture type in samples with or without coating after hydrogen charged. The embrittlement percent factor and SEM micrographs indicate a reduction of hydrogen permeation for coated samples with double layer.