Pure Sulphuric Acid Research Articles

HCF4−n(SO3)n (n=1–4): Designing new series of organic superacids

Superacids are systems that exhibit higher acidity compared to extremely strong mineral acid, i.e. 100% pure sulphuric acid (H2SO4). They can be designed by the protonation of appropriate superhalogen anions. Superhalogens possess higher electron affinity (EA) than halogens. Most recent examples include CF[Formula: see text], which behave as superhalogens for [Formula: see text]. In this work, we studied the protonation of CF[Formula: see text] using density functional theory calculations at the B3LYP/6-311[Formula: see text] level. The Gibbs’ free energies of deprotonation ([Formula: see text]) values of the resulting protonated complexes, HCF[Formula: see text] for [Formula: see text]–4; are either lower or nearly equivalent to that of H2SO4 ([Formula: see text][Formula: see text]kcal/mol). This suggests that all these protonated complexes exhibit superacidic behavior. Notably, the HC[Formula: see text] compound undergoes significant structural relaxation, leading to a remarkably less [Formula: see text] value. Our findings should enrich the literature with a new series of superacids and motivate further studies to explore novel organic superacids.

WITHDRAWN: Phenyl-napthyl substituted pyrazole derivatives for synthesis, characterization and their antibacterial applications

The condensation of either acetophenone or substituted acetophenone with 1-naphthaldehyde in simple basic solutions such as NaOH, a significant number of phenyl and napthyl substituted chalcones have been synthesized. These substituted chalcones were reacted with hydrazine hydrate in the presence of pure sulphuric acid in obtaining linked to substituted pyrazoline derivatives. Compounds synthesized are distinguished by their chemical and spectroscopic properties. Synthesized compounds have been investigated against various bacterial species, such as Escherichia coli, Staphylococcus aureus, Klebsiella pneumonia, and Salmonella typhi, for antibacterial activity. It has been shown that substituted pyrazoline rings make a significant contribution to antibacterial action.

A study of the application of Donnan dialysis to the recycling of lithium ion batteries

A Donnan Dialysis based process utilizing cation exchange membranes to separate and recover lithium, nickel, cobalt, and manganese during hydrometallurgical recycling of lithium ion battery cathodes is proposed. Compared to conventional processes, the process has the potential to achieve higher lithium recoveries and to recycle lixiviant. The present work introduces the process, develops mathematical equations to describe it, presents experimentally found cation mass transfer coefficients through cation exchange membranes, and uses the experimental data and equations to predict theoretical kinetics and recoveries achievable by the process.The simulation predicts that in two days, utilizing 5000dm2 of CMS C-1805 Neosepta monovalent CEM and 2000dm2 of CMX C-1586 Neosepta polyvalent CEM, the proposed process is capable of processing 1000L of leachate containing 285mol of lithium, 95mol each of cobalt, nickel, and manganese. 94.1% of the lithium can be recovered as high purity lithium carbonate and 99.4% of the transition metals as mixed sulphates ready for solvent extraction. At a minimum 422.6mol of pure sulphuric acid and 268mol of potassium bicarbonate are needed.

Approach to graft bioactive polymers on titanium implants by UV irradiations

Event Abstract Back to Event Approach to graft bioactive polymers on titanium implants by UV irradiations Hamza Chouirfa1, Céline Falentin-Daudré1 and Véronique Migonney1 1 LBPS-CSPBAT UMR CNRS 7244, Université Paris 13, France Introduction: Titanium is widely used in orthopedic implants for its excellent resistance to corrosion and its biocompatibility. Nevertheless and despite the prevention rules, 1.5 to 2 % of implanted prostheses are still subject to bacterial infections, threatening their benefit on a long-term basis. That’s the reason why chemical modification of titanium surfaces to confer desirable functional properties is required. In order to prevent bacteria and improve the long-term osteointegration of titanium, bioactive polymers bearing ionic groups (sulfonate) were covalently grafted onto titanium surfaces. Classically, the grafting used the heat to create radicals and lasted more than half day[1]-[6]. We have elaborated a new approach to create radicals (UVs) in only one hour[7]. Methods: Grafting procedure (Figure 1): Titanium surface were cleaned by successive 10 min ultrasound treatments in a bath of distilled water. After drying, samples were oxidized in a solution containing the same volume of pure H2SO4 and H2O2 (30%). After oxidation, samples were rinsed thoroughly in distilled water and then placed directly into a mechanically stirred solution of the monomers. After UV initiation of the radical polymerization, samples were rinsed thoroughly in distilled water and dried. Results and Discussion: Ionic groups (sulfonate) were covalently attached to the titanium surfaces by radical polymerization of sodium styrene sulfonate (NaSS) initiated by radicals issued from titanium peroxide. Immersion of titanium samples in a mixture of pure sulphuric acid and hydrogen peroxide produces on its surface titanium hydroxide and titanium peroxide. The decomposition of titanium peroxide in radicals was been produced by UV irradiations. Amounts of grafted polymers were measured by colorimetric method. Other techniques were used to check the presence of the bioactive polymers at the surface of titanium samples: XPS analysis, IR-ATR, Contact angle analysis. The grafting by UV way showed same results than thermal way, yet the UV way is the fastest (15 times faster). Conclusion: In the last decade, many studies have been devoted to improving the bone cell-implant interaction, with the goal of improving the osseointegration of devices for dental and orthopaedic applications. There are various ways to modify surface implants, and our strategy is to graft polymer model at their surface in using the UVs. The advantage of our method is that the coating is linked by a covalent bond to the titanium substrates. Surface characterization techniques have shown that the UV grafting of bioactive polymers at the surface of titanium reaches 5 µg.cm-2 like by thermal grafting. Our approach is interesting from an industrial point of view because it also needs few time and few quantity of monomers to obtain a high yield of polymer grafting. Excellent biological results were been obtained by thermal grafting and we would like to check biologically the UV grafting. Figure 1: Grafting of bioactive polymers on titanium surfaces.

Hydrogenated superhalogens behave as superacids

Superacids are more acidic than pure sulphuric acid whose acidity is closely associated with the electronic stability of their conjugate-base anions. We have noticed that these anions possess extremely large vertical detachment energies, exceeding to the electron affinity of Cl, and therefore, they belong to a special class namely, superhalogen. Consequently, the superacids can be thought of as hydrogenated superhalogens. To demonstrate this idea, we have studied the hydrogen complexes of typical superhalogens LiF2, LiCl2, BeF3, BeCl3, BF4 and PF6. The order of their gas phase acidities, HBeCl3>HPF6>HLiCl2>HBeF3>HBF4>H2SO4>HLiF2>HCl clearly suggest superhalogens as building blocks of superacids. Various other parameters of hydrogenated superhalogens are also described which are closely associated with their chemical reactivity. This work should provide a suitable path to design new superacids which might be more acidic than HSbF6, the strongest known superacid till date.

Observations of the chemical composition of stratospheric aerosol particles

AbstractRecent instrumentation can distinguish various types of aerosol particles in the stratosphere and determine their relative abundance. In the background lower stratosphere between major volcanic eruptions, most particles are either relatively pure sulphuric acid, sulphuric acid with material from ablated meteoroids or mixed organic‐sulphate particles that originated in the troposphere. The meteoritic iron and magnesium appear to be dissolved whereas the aluminum and silicon appear to be inclusions. Most stratospheric aerosol mass is liquid sulphuric acid and associated water, but a large fraction of particles contain either inclusions of meteoritic elements such as silicon or organic material that is probably effloresced or glassy. These solid phases could have large but unknown implications for the ability of particles to act as freezing nuclei for polar stratospheric clouds. Internally mixed black carbon is a measurable but very small component of the stratospheric aerosol by mass. Despite their importance for heterogeneous chemistry, there are few quantitative measurements of halogens in stratospheric particles.

GERMINAÇÃO DE SEMENTES DE Bauhinia spp.

O presente trabalho teve como objetivo caracterizar e estudar o comportamento germinativo das sementes de Bauhinia variegata L. var. candida e variegata, e Bauhinia forficata Link var. forficata. O delineamento foi inteiramente casualizado, com 4 repetições. Os tratamentos utilizados em Bauhinia variegata foram: água a 97 ºC até esfriar, água a 70 ºC durante 1 e 2 minutos, ácido sulfúrico durante 1, 2 e 3 minutos, escarificação mecânica e sementes intactas (controle); e em Bauhinia forficata, escarificação mecânica, imersão em ácido sulfúrico durante 5 e 10 minutos, armazenamento de sementes intactas durante seis meses, ácido sulfúrico durante 5 minutos e sementes recém-colhidas (controle). Tratamento com escarificação mecânica reduz a dormência das sementes de Bauhinia forficata e aumenta a porcentagem de germinação de Bauhinia variegata var. cândida e a velocidade de germinação das sementes Bauhinia variegata var. variegata. Tratamentos com ácido sulfúrico durante um minuto aumentam a velocidade de germinação das sementes Bauhinia variegata var. variegata e, por 10 minutos, reduzem os mecanismos de dormência das sementes de Bauhinia forficata. O armazenamento e a imersão das sementes de Bauhinia forficata Link var. forficata em ácido sulfúrico aumentam a germinação. A termoterapia a 97 ºC determina a morte das sementes de Bauhinia variegata var. variegata.

Influence of the electrolyte composition on the kinetics of the oxygen evolution reaction and ozone production processes

The influence of electrolyte composition (pure sulphuric or perchloric acid and their mixtures) on the kinetics of the oxygen evolution reaction (OER) and the electrochemical ozone production (EOP) on beta-PbO2 electrodes was investigated by electrochemical impedance spectroscopy and quasi-stationary polarisation curves. Analysis of the impedance spectra revealed a dependency of the electric double layer capacity and the adsorption pseudocapacitance, due to reaction intermediates, on electrolyte composition. The pseudocapacitance is a function of electrode potential and electrolyte composition, indicating the surface coverage by the reaction intermediates depends on these parameters. Tafel slope data support primary water discharge as rate determining step of the OER and EOP electrode processes. EOP current efficiency data (phiEOP) show pure electrolytes lead to maximum O3 production when compared to mixed electrolytes. According to the theoretical analysis of the electrode mechanism, this behaviour is a consequence of the reduction in surface concentration of the active centres leading to EOP caused by anion adsorption.

Oxygen reduction on platinum in aqueous sulphuric acid in the presence of ammonium

The oxygen reduction reaction (ORR) was studied using a rotating disk electrode. The kinetic current density (cd) at 0.7 V RHE was reduced by more than a factor of 10 on pre-reduced Pt and a factor of 2.5 on pre-oxidised Pt when comparing ORR rate for pure sulphuric acid to that in 0.18 M H 2SO 4 + 0.1 M NH 3 solution which was the highest ammonium concentration studied. The Tafel slope at low cd on pre-reduced Pt is about − 90 mV/decade in the presence of ammonium compared to about − 74 mV/decade in pure acidic solution. The Tafel slopes at high cd is not affected by ammonium. The Tafel slope of ORR on pre-oxidised Pt surface is not significantly affected by ammonium. The exchange cd is lower in the presence of ammonium both for pre-reduced and pre-oxidised Pt. The direct origin of the loss of ORR activity has not been firmly resolved. Adsorption and oxidation of ammonium including intermediate species as well as nitrogen–oxygen species formed at high potentials may be involved.

Carbon supported Pt–Co alloys as methanol-resistant oxygen-reduction electrocatalysts for direct methanol fuel cells

The electrocatalysis of the oxygen reduction reaction on carbon supported Pt and Pt–Co (Pt/C and Pt–Co/C) alloy electrocatalysts was investigated in sulphuric acid (both in the absence and in the presence of methanol) and in direct methanol fuel cells (DMFCs). In pure sulphuric acid Pt–Co/C alloys showed improved specific activity towards the oxygen reduction compared to pure platinum. In the methanol containing electrolyte a higher methanol tolerance of the binary electrocatalysts than Pt/C was observed. The onset potential for methanol oxidation at Pt–Co/C was shifted to more positive potentials. Accordingly, Pt–Co/C electrocatalyts showed an improved performance as cathode materials in DMFCs.

Oxygen reduction at Pt and Pt 70Ni 30 in H 2SO 4/CH 3OH solution

The electrochemical oxygen reduction reaction (ORR) was studied at Pt and Pt alloyed with 30 atom% Ni in 1 M H 2SO 4 and in 1 M H 2SO 4/0.5 M CH 3OH by means of rotating disc electrode. In pure sulphuric acid, the overpotential of ORR at 1 mA cm −2 is about 80 mV lower at Pt 70Ni 30 than at pure Pt. It was found that in methanol containing electrolyte solution the onset potential for oxygen reduction at PtNi is shifted to more positive potentials and the alloy catalyst has an 11 times higher limiting current density for oxygen reduction than Pt. Thus, PtNi as cathode catalyst should have a higher methanol tolerance for fuel cell applications. On the other hand, no significant differences in the methanol oxidation on both electrodes was found using cycling voltammetry, especially regarding the onset potential for methanol oxidation. During all the measurements no significant electrochemical activity loss was observed at Pt 0.7Ni 0.3. Ex-situ XPS investigations before and after the electrochemical experiments have revealed Pt enrichment in the first surface layers of the PtNi.

Electrochemical dissolution of tin in methanesulphonic acid solutions

High-rate electroplating of tin on a moving steel strip is generally carried out in cells with dimensionally stable anodes. To obtain a matt tin deposit a concentrated acidic tin methanesulphonate solution containing a small concentration of sulphuric acid is used. The concentrated tin methanesulphonate solution is prepared by dissolution of tin particles with oxygen in a special column. To describe this dissolution process electrode reactions (namely, reduction of oxygen, hydrogen peroxide and hydrogen ions on a tin electrode and oxidation of tin) were studied using electrochemical techniques. It was concluded that on tin, oxygen is almost entirely reduced to water and that H2O2 cannot corrode tin directly, but its decomposition products, for instance oxygen, can. The exchange current density and the charge transfer coefficient for the investigated electrode reactions are estimated. The dissolution of tin by oxygen is determined by the kinetic parameters of the oxygen reduction reaction and by the mass transfer of (i) dissolved oxygen to and (ii) Sn2+ ions from the tin electrode surface. Hydrogen evolution can be neglected during the dissolution of tin in the presence of oxygen. Moreover, it was found that the rate of tin corrosion increases with (i) increasing H+ concentration, (ii) oxygen concentration, (iii) convection intensity and (iv) temperature. It is likely that the tin surface is not covered with oxygen during corrosion in pure methanesulphonic acid solutions, but an oxide layer may be present on the tin surface during oxygen corrosion in pure sulphuric acid solutions. This oxide layer may hinder the oxygen corrosion of tin.

Preparation and properties of new acid catalysts obtained by grafting alkoxides and derivatives on the most common supports. Part III – grafting titanium alkoxides and sulphate derivatives on silica

Some catalysts have been prepared by grafting different amounts of titanium isopropoxide dissolved in toluene on a silica support and by steaming and calcinating the products obtained. A catalyst has been prepared also by first treating with pure sulphuric acid titanium isopropoxide, grafting the titanium alkoxide sulphate on silica and again by steaming and calcinating the product obtained. All the catalysts prepared have been characterized using different techniques such as: electrochemical potentiometric titrations to evaluate the PZC (point of zero charge), the hydroxyl densities and the surface dissociation equilibrium constants; TGA (thermal gravimetric analyses) to evaluate the hydroxyl densities; TPD (thermal programmed desorption) of organic bases such as pyridine and lutidine; and XPS (X-ray photoemission spectroscopy). All catalysts have also been tested by determining the performances in three different reactions: dehydration of methanol, epoxidation of cyclooctene with cumene hydroperoxide and isomerization of 1-butene to 2-butene. The behaviour of the catalysts prepared shows that grafting titanium on silica strongly modifies the original surface and the catalysts obtained with the mentioned grafting techniques are different from those obtained by impregnation and coprecipitation.

Preparation and properties of new acid catalysts obtained by grafting alkoxides and derivatives on the most common supports note I — grafting aluminium and zirconium alkoxides and related sulphates on silica

In this paper we will show that it is possible to modify the acid properties of a surface, rich of hydroxyl groups by grafting in suitable conditions metal alkoxides, such as aluminium and zirconium alkoxide. Depending on the amount of metal alkoxide it is possible to obtain, after steaming of the surface and calcination, different coverage degree up to the monolayer. Iteration of the grafting technique gives a multilayer, completely modifying the orginal surface. Grafting aluminium and zirconium alkoxides pre-treated in homogeneous phase with pure sulphuric acid leads to catalysts with very strong acid sites on the surface. The acidic properties of the catalysts obtained by grafting aluminium and zirconium alkoxides and their sulphate derivatives on silica have been characterized by different techniques such as: potentiometric titrations, Temperature Programmed Desorption of organic bases and differential calorimetry to evaluate the density of the active sites and their strength. Prepared catalysts were proven in test reactions such as methanol dehydration and hydrocarbon isomerization and cracking. We have shown that sulphated catalysts have very strong acid sites of both the Brönsted and Lewis type, able to promote hydrocarbon isomerization and cracking at the relatively low temperature of 250°C.

Hydrogen consuming anodes for energy saving in sodium sulphate electrolysis

AbstractGas diffusion electrodes, made of PTFE‐bonded carbon with precious metal catalysts, were investigated as hydrogen consuming anodes in sodium sulphate electrolysis. The catalysts used were platinum and palladium and mixtures of both metals, prepared by two different methods. Various metal meshes were used as current collector. The electrodes performed well in pure sulphuric acid (5–15 wt‐%) and in mixtures with sodium sulphate (10 wt‐%) at temperatures of 30 to 70°C and current densities up to 5 kA/m2. In long‐term experiments, at a current density of 2.6 kA/m2, the electrodes were stable over three months. The electrodes were characterised by stationary current density/potential curves and by galvanostatic current interruption measurements.

Separation of Metal Pairs using Bis (2-Ethylhexyl) Phosphoric Acid (HDEHP); Separation of Cerium from Uranium and from Thorium

A systematic study was performed on the extraction and separation of uranium-cerium and thorium-cerium pairs for HDEHP from pure hydrochloric and sulphuric acid solutions as well as from their binary mixtures. The effect of water miscible alcohols and actone on the separation of these elements was also investigated. The separation of uranium and thorium from macroamounts of cerium can be best achieved from. 2.4 M HCl in presence of 50% isopropyl alcohol. There are other media plausible for the separation of trace cerium from uranium and thorium matrices.

Adaptation of characteristic vector analysis to pKBH+calculations of very weak bases from incomplete ultraviolet spectral data

An adaptation of characteristic vector analysis has been applied to incomplete u.v. spectral data of a very weak base only partially protonated in pure sulphuric acid, 3-cyano-5,5-dimethylcyclohex-2-en-1-one (1). The estimated pKBH+ value, –5.29, obtained from the HA acidity function is in very good agreement with those calculated from linear free energy relationships: pKBH+vs.σ+(–4.96) or pKBH+vs.σI, σR+(–4.93) and the extra-thermodynamic relationship of pKBH+vs.ΔHBF3°(–5.32) for a series of 3-substituted-5,5-dimethylcyclohex-2-en-1-ones. This statistical method can be generalized for compounds in which the protonation is very incomplete even in pure sulphuric acid and for which the u.v.–visible spectral data are limited.

Study of the methanol oxidation reaction on platinum using the potential-step technique

Anodic potential steps were applied to a smooth platinum electrode in pure and methanolic sulphuric acid solutions. Rising current against time transients were observed in the potential range 0.6–0.8 V against the normal hydrogen electrode (NHE), corresponding to the methanol oxidation reaction. The bifunctional role of platinum electrocatalysts, encouraging the simultaneous adsorption of water and methanol, is clearly demonstrated. The rising current against time data are fitted to a mathematical model previously proposed for a nucleation and growth process in which the current is controlled by charge transfer and diffusion processes before being finally limited by an increasing oxide film.

Comparison of acidities in molten hydrogenosulphates and their eutectics

Acidity in pure hydrogenosulphates NaHSO 4 , KHSO 4 , NH 4 HSO 4 and in their eutectics (Na-K)HSO 4 , (K-NH 4 )HSO 4 and (NH 4 -Na)HSO 4 , was studied, at t =200°C and P (H 2 O) =0.03 atm, by using an indicator glass-electrode. The values of the constants of autoprotolysis and of the solubilities of alkaline and ammonium sulphates have been determined for each of the molten salts considered. The acidity ranges available in these solvents were then compared by means of a single acidity scale referring to pure sulphuric acid. This comparison was made possible by mearusing, with a transference method, the vapour pressures of the sulphuric acid above its solutions in hydrogenosulphates and their eutectics. So, it demonstrated that the more acidic media are obtained in the eutectic (Na-K)HSO 4 , and the more basic ones in NH 4 HSO 4 . Moreover, various thermodynamic functions, and especially, the standard entropies of the pure hydrogenosulphates, have been determined

Comparison of acidities in molten hydrogenosulphates and their eutectics

Acidity in pure hydrogenosulphates NaHSO 4, KHSO 4, NH 4HSO 4 and in their eutectics (Na-K)HSO 4, (K-NH 4)HSO 4 and (NH 4-Na)HSO 4, was studied, at t=200°C and P(H 2O) =0.03 atm, by using an indicator glass-electrode. The values of the constants of autoprotolysis and of the solubilities of alkaline and ammonium sulphates have been determined for each of the molten salts considered. The acidity ranges available in these solvents were then compared by means of a single acidity scale referring to pure sulphuric acid. This comparison was made possible by mearusing, with a transference method, the vapour pressures of the sulphuric acid above its solutions in hydrogenosulphates and their eutectics. So, it demonstrated that the more acidic media are obtained in the eutectic (Na-K)HSO 4, and the more basic ones in NH 4HSO 4. Moreover, various thermodynamic functions, and especially, the standard entropies of the pure hydrogenosulphates, have been determined