H2SO4 Medium Research Articles

Synthesis, characterization and electrochemical evaluation of anticorrosion property of a tetrapolymer for carbon steel in strong acid media

Abstract A novel tetrapolymer (TP) consisting of carboxylate, sulphonate, phosphonate and sulfur dioxide based co-monomers was synthesized using Butler cyclopoymerization technique. The synthesized tetrapolymer was characterized using FTIR, 1H-NMR, 13C NMR and elemental analysis. The performance of the tetrapolymer as a corrosion inhibitor for St37 carbon steel in 15% HCl and 15% H2SO4 acid media was assessed using electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), potentiodynamic polarization (PDP) and electrochemical frequency modulation (EFM) techniques. The influence of addition of a small amount of KI on the corrosion inhibition efficiency of TP was also assessed. Results obtained showed that the tetrapolymer moderately inhibited the corrosion of St37 steel in the acid media with protection efficiency of 79.5% and 61.1% at the optimum concentration of 1000 mg·L− 1 studied in HCl and H2SO4 media respectively. On addition of 5 mmol·L−1 KI to the optimum tetrapolymer concentration, the protection efficiency was upgraded to 90.6% and 93.5% in HCl and H2SO4 environment, respectively. The enhanced performance of the polymer in the presence of KI is due to synergistic action deduced from synergism parameter (S1) which was found to be greater than unity. The tetrapolymer afforded the corrosion inhibition of St37 steel in the acid media by virtue of adsorption of the polymer molecules on the steel surface which was confirmed by ATR-FTIR analysis of the adsorbed film extracted from the steel surface. TP + KI formed complex with St37 steel surface in H2SO4 solution but not in HCl solution.

Spectrophotometric Determination of Sulphite in Various Water Samples Via Chromium-1,5-Diphenylcarbazide Complex

A simple and rapid spectrophotometric method for the determination of sulphite SO3-2 is described. The method is based on the rapid reduction of known amount of chromate CrO4-2 in the presence of sulphite in acidic medium of 2N H2SO4. The amount of excess of chromate was measured after it reactions with 1,5-diphenylcarbazide which finally gives a pink-violet, water soluble and stable complex, which exhibit a maximum absorption at 542 nm. Beer's law was obeyed in the concentration range from 0.004-6.0 µg of sulphite in a final volume of 25 ml with a molar absorbtivity of 4.64×104 l.mol-1.cm-1, Sandal's sensitivity index of 0.001724 ?g .cm-2 and relative standard deviation of ±0.55 - ±0.83 depending on the concentration level. The present method has been developed for the determination of sulphite in the presence of thiosulphate. Good recoveries of sulphite from various water samples are achieved using the proposed method.

Corrosion and Quantum Studies of Alkyl Substituted Piperidin-4-Ones with Thiosemicarbazone on Mild Steel in an Acidic Medium

The acid corrosion inhibition technique of mild-steel in 1N sulfuric acid by a part of alkyl substituted 2,6-diphenyl piperidin-4-one with thiosemicarbazone has been observed by quantum chemical calculations, electrochemical AC impedance measurements, weight loss process and potentiodynamic polarization studies. Results show that substituted γ-2,c-6-diphenyl piperidin-4-ones with thiosemicarbazone act as perfect corrosion inhibitors and their inhibition efficiency increase with the addition of inhibitors. The potentiodynamic polarization curves pointed the studied inhibitors are mixed type of character and cathodic nature in 1 N H2SO4 media. The impedance spectroscopy shows a change in the value of charge transfer resistance (Rct) and double layer capacitance (Cdl) indicating the adsorption of the some substituted piperidin-4-ones with thiosemicarbazones on the mild steel surface. For all the three types of alkyl substituted 2,6-diphenyl pipieridin-4-one with thiosemicarbazone, the inhibition efficiency raised to increment in the inhibitor concentration and the performance of the three inhibitors are 01TS> 02TS> 03TS. The adsorption of the alkyl substituted 2,6-diphenyl piperidin-4-one with thiosemicarbazone on the mild-steel metallic surface pursued the Langmuir's adsorption isotherm. Quantum chemical calculations were executed by adopting density functional theory (DFT) to conclude whether a clear link exists among the inhibiting outcome of the inhibitor and the electronic characteristics of its main fundamentals.

Effect of Aqueous Media on the Recovery of Scandium by Selective Precipitation

This research presents a novel precipitation method for scandium (Sc) concentrate refining from bauxite residue leachates and the effect of aqueous media on this triple-stage successive precipitation process. The precipitation pattern and the precipitation behavior of the constituent elements was investigated using different precipitation agents in three major mineral acid media, namely, H2SO4, HNO3, and HCl in a comparative manner. Experimental investigations showed behavioral similarities between HNO3 and HCl media, while H2SO4 media was different from them because of the nature of the formed complexes. NH4OH was found to be the best precipitation agent in every leaching media to remove Fe(III) with low Sc co-precipitation. To limit Sc loss from the system, Fe(III) removal was divided into two steps, leading to more than 90% of Fe(III) removal at the end of the process. Phosphate concentrates were produced in the final step of the precipitation process with dibasic phosphates which have a strong affinity towards Sc. Concentrates containing more than 50% of ScPO4 were produced in each case from the solutions after Fe(III) removal, as described. A flow diagram of the selective precipitation process is proposed for these three mineral acid media with their characteristic parameters.

Modeling of liquid–liquid extraction of vanadium with primary amine N1923 in H2SO4 medium

This paper deals with a systematic thermodynamic study on the liquid–liquid extraction of vanadium from aqueous solution (0.001–0.1 mol/kg) using primary amine N1923 (0.004–0.3 mol/kg). Suitable and practical thermodynamic models (Pitzer–Pitzer and Pitzer–Margules) were improved and verified for the first time. Firstly, the Pitzer parameters were correlated based on solid–liquid equilibrium data, and then employed as the initial values in regression progress. Finally, all the interaction parameters (βaq0, βaq1, βRV,RVorg, βR,RVorg, βR,Rorg, ARV,Rorg, Atol,RVorg and Atol,Rorg) were regressed. Liquid–liquid equilibrium data were predicted using those parameters and compared to the experimental results, which confirmed the reliability and suitability of these models for the present system. Furthermore, these models provided excellent predictions of the effect of the initial amine molality and pH value on the extraction, showing great promise for industrial applications.

HDEHP-CMPO/SiO2-P: a promising solid-phase extractant for uranium recovery from different acidic media

A novel macroporous silica-based HDEHP-CMPO impregnated polymeric solid-phase extractant showed an excellent uranium adsorption efficiency from HNO3, HCl, and H2SO4 media with the wide concentration range from the near neutral to high acidic conditions. The adsorption equilibrium data were well described with the Redlich–Peterson isotherm with the relatively high uranium adsorption capacity. Furthermore, the HDEHP-CMPO/SiO2-P showed a significant selectivity for U(VI) among the coexisting elements while the co-extraction of Fe(III) with U(VI) was observed. In desorption process, Fe(III) and U(VI) were separated and desorbed efficiently using the 1 M H2SO4 solution at 55 °C and 1 M NH4HCO3 solution at 25 °C, respectively.

Electroplated Zn–Ni nanocrystalline alloys as an efficient electrocatalyst cathode for the generation of hydrogen fuel in acid medium

Energy conversion and renewable energy are the valuable research fields for the future of the energy. Synthesis of electroplated thin film of low cost elements and their alloys is promising nanomaterials for energy conversion. Electroplating of Zn–Ni alloys were performed using natural products such as cysteine and gluconate under direct current and ultrasound waves. The morphological and crystalline structures of the electroplated Zn–Ni alloys were examined using scanning electron microscopy, SEM, and X-ray diffraction techniques, XRD. The chemical composition of the electroplated Zn–Ni alloys was determined using energy dispersive X-ray analysis, EDX. The morphological structures of electroplated Zn–Ni alloys changed from smooth to coral reef-like and granular structures with the increase of Zn wt%. Electrocatalysis of the hydrogen evolution reaction using the electroplated Zn–Ni alloys was studied in 0.5 M H2SO4 medium by the cathodic polarization and electrochemical impedance spectroscopy, EIS. The electroplated Zn–9.5Ni cathode of cubic γ-brass arrangement exhibits the highest rate of hydrogen evolution reaction.

Investigation of hydride generation from arsenosugars - Is it feasible for speciation analysis?

Hydride generation (HG) from arsenosugars (dimethylarsinoylribosides) in batch and flow injection modes was studied. Its efficiency was found higher in H2SO4 medium than in HCl and higher in the batch mode than in the flow injection mode. To increase the efficiency in the flow injection mode a new generator with two inlets of NaBH4 solution was designed. This modified generator was interfaced between a HPLC column and an atomic fluorescence detector. The arsenosugars studied yielded HG efficiencies in the range 13–30% most probably due to a complicated mechanism of HG. While the mechanism included a formation of two structures of the analyte-borane-complexes, only one of them can lead to a formation of volatile arsanes (dimethylarsane, methylarsane, and arsane were identified).

A bimetallic oxide Fe1.89Mo4.11O7 electrocatalyst with highly efficient hydrogen evolution reaction activity in alkaline and acidic media.

Transition-metal Mo-based materials have been considered to be among the most effective hydrogen evolution reaction (HER) electrocatalysts. Regulating the electronic structure of Mo atoms with guest metal atoms is considered as one of the important strategies to improve their HER activity. However, introduction of guest metal elements in the vicinity of Mo sites with atomic-level hybridization is difficult to realize, resulting in the failure of the modified electronic structure of Mo sites. Herein, an Fe1.89Mo4.11O7/MoO2 material is prepared through the thermal treatment of a ferrimolybdate precursor. It exhibits a Tafel slope of 79 mV dec-1 and an exchange current density of 0.069 mA cm-2 in 1 M KOH medium, as well as a Tafel slope of 47 mV dec-1 and an exchange current density of 0.072 mA cm-2 in 0.5 M H2SO4 medium. Compared to original Mo-based oxides, Fe1.89Mo4.11O7 with the regulated Mo electronic structure shows a more suitable Mo-H bond strength for the fast kinetics of the HER process. Density functional theory (DFT) calculations also indicate that the Mo-H bond strength in Fe1.89Mo4.11O7 is similar to the Pt-H bond strength, resulting in the high kinetic activity of Mo-based HER electrocatalysts in alkaline and acidic media.

Spectrophotometric Determination of Sulphite in Various Water Samples Via Chromium-1,5-Diphenylcarbazide Complex

A simple and rapid spectrophotometric method for the determination of sulphite SO3-2 is described. The method is based on the rapid reduction of known amount of chromate CrO4-2 in the presence of sulphite in acidic medium of 2N H2SO4. The amount of excess of chromate was measured after it reactions with 1,5-diphenylcarbazide which finally gives a pink-violet, water soluble and stable complex, which exhibit a maximum absorption at 542 nm. Beer's law was obeyed in the concentration range from 0.004-6.0 µg of sulphite in a final volume of 25 ml with a molar absorbtivity of 4.64×104 l.mol-1.cm-1, Sandal's sensitivity index of 0.001724 ?g .cm-2 and relative standard deviation of ±0.55 - ±0.83 depending on the concentration level. The present method has been developed for the determination of sulphite in the presence of thiosulphate. Good recoveries of sulphite from various water samples are achieved using the proposed method.

One-step coelectrodeposition-assisted layer-by-layer assembly of gold nanoparticles and reduced graphene oxide and its self-healing three-dimensional nanohybrid for an ultrasensitive DNA sensor.

A layer-by-layer (LBL) assembly was employed for preparing multilayer thin films with a controlled architecture and composition. In this study, we report the one-step coelectrodeposition-assisted LBL assembly of both gold nanoparticles (AuNPs) and reduced graphene oxide (rGO) on the surface of a glassy carbon electrode (GCE) for the ultrasensitive electrochemical impedance sensing of DNA hybridization. A self-healable nanohybrid thin film with a three-dimensional (3D) alternate-layered nanoarchitecture was obtained by the one-step simultaneous electro-reduction of both graphene oxide and gold chloride in a high acidic medium of H2SO4 using cyclic voltammetry and was confirmed by different characterization techniques. The DNA bioelectrode was prepared by immobilizing the capture DNA onto the surface of the as-obtained self-healable AuNP/rGO/AuNP/GCE with a 3D LBL nanoarchitecture via gold-thiol interactions, which then served as an impedance sensing platform for the label-free ultrasensitive electrochemical detection of DNA hybridization over a wide range from 1.0 × 10-9 to 1.0 × 10-13 g ml-1, a low limit of detection of 3.9 × 10-14 g ml-1 (S/N = 3), ultrahigh sensitivity, and excellent selectivity. This study presents a promising electrochemical sensing platform for the label-free ultrasensitive detection of DNA hybridization with potential application in cancer diagnostics and the preparation of a self-healable nanohybrid thin film with a 3D alternate-layered nanoarchitecture via a one-step coelectrodeposition-assisted LBL assembly.

Spathodea Campanulata as a Corrosion Inhibitor for Mild Steel in 1N H2SO4 Media

Corrosion inhibition efficiency of dry Spathodea Campanulata (Sc) leaves in 1N H2SO4 medium was investigated by weight loss and temperature studies. Effect of temperature (35-75°C) on the corrosion behaviour of mild steel in the presence of plant extract was studied. Inhibition was found to increase with increase in concentration of the extract. Adsorption of extract molecules on mild steel surface obeyed the Langmuir, Temkin, Freundlich adsorption isotherms.Polarization studies showed that the extract of Sc behaved as a very good mixed type inhibitor inhibiting both anodic and cathodic reaction. The results obtained prove that the leaves of Spathodea Campanulata act as a good corrosion inhibitor having efficiency of 82.74% at 1.5% inhibitor concentration.Surface analysis was done by scanning electron microscope technology (SEM) to study the nature of adsorption.

Electrochemical measurements and semi-empirical calculations for understanding adsorption of novel cationic Gemini surfactant on carbon steel in H2SO4 solution

A novel imidazolium-based cationic Gemini surfactant (GS) was synthesized, characterized and evaluated as a corrosion inhibitor for carbon steel in 0.5 M H2SO4 using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. The results revealed that this Gemini surfactant can act as an effective mixed-type inhibitor (ηp ∼ 90%) for carbon steel via adsorption of its molecules on the metal surface according to Langmuir adsorption isotherm. The synthesized GS showed a good synergistic inhibitory action with Ce3+cations and Iˉ anions in 0.5 M H2SO4 medium (ηp ∼ 93% and 95%, respectively). Thermodynamic activation parameters for the dissolution process of carbon steel in blank and inhibited sulfuric acid solution were calculated and discussed. A suitable equivalent circuit was used to analyze the experimental EIS data and modeling the inhibition process. Quantum chemical calculations have revealed that the tested Gemini surfactant can interact with Fe surface through electron transfer from the metal atom to surfactant molecule.

Phase and composition controllable synthesis of nickel phosphide-based nanoparticles via a low-temperature process for efficient electrocatalytic hydrogen evolution

Nickel phosphide has been shown to be active toward hydrogen evolution reaction (HER). In this paper, we demonstrate the phase and composition controllable synthesis of nickel phosphide-based nanoparticles (NiP-based NPs) via a low-temperature phosphidation reaction (250 °C) using NaH2PO2 as the phosphorus source and the as-prepared Ni(OH)2 precursor as the nickel source. Interestingly, by changing the NaOH concentration and nickel source used to fabricate Ni(OH)2 precursors, we could adjust the phases and compositions of as-synthesized NiP-based nanocatalysts from Ni5P4, Ni2P to Ni12P5. The different steric hindrance and the electrostatic repulsion of synthesized β-Ni(OH)2 precursors result in the formation of three NiP phases with various Ni:P ratios. Electrochemical characterizations reveal that the NiP-based NPs with P-rich phase (Ni5P4+Ni2P) exhibit remarkable electrocatalytic HER property, with low overpotential (η) of 111 mV to reach a current density of 10 mA cm−2 in a 0.5 M H2SO4 media, which is superior than those of pure Ni2P (η = 118 mV) and the Ni-rich NiP-based counterpart (Ni12P5+Ni2P) (η = 131 mV). This is attributed to the stronger ensemble effect of P and more active sites provided by P-rich NiP-based NPs. Our results demonstrate that by tailoring the surface properties of Ni(OH)2 precursors, the phases and compositions of NiP-based nanoparticles could be easily tuned, which provides a simple, economic, and green strategy to optimize the HER performance of transition metal phosphide-based electrocatalysts.

Synthesis of new pyrrolo[3,2-l]acridinones and pyrrolo[3,2-c][1,8]naphthyridinones by condensation of methoxybenzenes or phenols with isobutyric aldehyde and o-aminonitriles

A reaction of methoxybenzenes or phenols with isobutyric aldehyde and 2-amino-5-nitro- or 2-amino-4-chlorobenzonitriles in concentrated H2SO4 medium was used for the preparation of new pyrrolo[3,2-l]acridinone derivatives. Analogous reactions using 2-amino-3-pyridinecarbonitrile enabled the synthesis of previously unknown benzo[b]pyrrolo[3,2-c][1,8]naphthyridinones.

Leaching of Metals from Spent Lithium-Ion Batteries

The recycling of valuable metals from spent lithium-ion batteries (LIBs) is becoming increasingly important due to the depletion of natural resources and potential pollution from the spent batteries. In this work, different types of acids (2 M citric (C6H8O7), 1 M oxalic (C2H2O4), 2 M sulfuric (H2SO4), 4 M hydrochloric (HCl), and 1 M nitric (HNO3) acid)) and reducing agents (hydrogen peroxide (H2O2), glucose (C6H12O6) and ascorbic acid (C6H8O6)) were selected for investigating the recovery of valuable metals from waste LIBs. The crushed and sieved material contained on average 23% (w/w) cobalt, 3% (w/w) lithium, and 1–5% (w/w) nickel, copper, manganese, aluminum, and iron. Results indicated that mineral acids (4 M HCl and 2 M H2SO4 with 1% (v/v) H2O2) produced generally higher yields compared with organic acids, with a nearly complete dissolution of lithium, cobalt, and nickel at 25 °C with a slurry density of 5% (w/v). Further leaching experiments carried out with H2SO4 media and different reducing agents with a slurry density of 10% (w/v) show that nearly all of the cobalt and lithium can be leached out in sulfuric acid (2 M) when using C6H8O6 as a reducing agent (10% g/gscraps) at 80 °C.

The effect of copper contamination at the cathode of Cu-Cl/HCl electrolyzers

In this work, the concentration of cathodic copper is carefully controlled by employing a “proton-pump” configuration in a H2SO4 media, preventing complications from anodic reactions or speciation. When run in the proton-pump mode 0.5 M H2SO4 was used as the catholyte while the anolyte was humidified hydrogen gas. The catholyte was then spiked with various amounts of Cu2+ and the effects of copper concentration were investigated using a variety of electrochemical tests including cyclic voltammetry (CV), linear sweep voltammetry (LSV) and potential stair-step voltammetry. Galvanostatic tests were performed at a constant current density of 300 mA/cm2 to determine the effect of copper concentration on the voltage and hydrogen production efficiency. Our results show that the presence of copper does in fact impact the system, by decreasing the voltage efficiency. However, the coulombic hydrogen production efficiency was unaffected by increasing catholyte copper concentration.

Gum Arabic-silver nanoparticles composite as a green anticorrosive formulation for steel corrosion in strong acid media

A green anticorrosive composite (GA-AgNPs) has been formulated for steel in 15% HCl and 15% H2SO4 media. Characterization of GA-AgNPs is achieved via FTIR, UV-vis, EDAX, and SEM. Gravimetric, electrochemical (EIS, EFM, DEIS, & TP), and surface assessment (SEM, EDAX, AFM, & XPS) techniques have been deployed in the anticorrosion studies. Results from all applied methods potray GA-AgNPs as effective anticorrosive agent. Inhibition is by adsorption mechanism and follows Langmuir isotherm. GA-AgNPs acts as mixed type inhibitor in 15% H2SO4 solution but as anodic type in 15% HCl solution. Results from surface techniques confirm adsorption of GA-AgNPs molecules on specimen surface. Oxides, hydroxides, carbonates, and sulphates (H2SO4 medium) or chlorides (HCl medium) are the corrosion products in the free corrodent according to XPS results. In the presence of composite, both ionic and neutral forms of GA-AgNPS are adsorbed. AgNPs are present on the surface in the form: Ag°, Ag2O, and AgO.

Synthesis, stability, and electrocatalysis by Cu(II) and Zn(II) complexes of meso-bridged isomeric porphyrinoid tetraphenylporphycene

Spectral characteristics (electronic absorption spectra, fluorescence emission spectra, 1H NMR) of prepared Cu(II) and Zn(II) complexes of 2,7,12,17-tetraphenylporphycene {H2(β-Ph)4Por}, their thermal stability, and persistence toward acids, as well as electrochemical and electrocatalytic properties have been discussed. It has been found by cyclic voltammetry that the electrocatalytic activity of metalloporphycenes M(β-Ph)4Por in the reaction of molecular oxygen reduction is close to that of metalloporphyrins M(ms-Ph)4P. Thermal stability and persistence of M(β-Ph)4Por in acidic medium are considerably lower than those of porphyrin analogs. Thus, the kinetic stability of copper(II) complex of 2,7,12,17-tetraphenylporphycene in HOAc–H2SO4 medium as compared with Cu(ms-Ph)4P is lower by more than an order of magnitude, while its thermal stability is almost 200°С lower, which is caused by sterically unfavorable change in the shape of coordination center of ligand H2(β-Ph)4Por upon complexation.

Corrosion inhibition of mildsteel in sulphuric acid by methanol extract of Luffa aegyptiaca leaves – electrochemical and statistical view

An electrochemical and statistical view of methanol extract of Luffa aegyptiaca leaves (MLA) on the corrosion inhibition of mild steel (MS) in 0.5 M H2SO4 medium were investigated by potentiodynamic polarisation and electrochemical impedance spectroscopy. Polarization studies showed that the MLA acts as mixed type inhibitor with predominant cathodic behaviour. The percentage inhibition efficiency was found to increase with MLA concentration and decreased with the temperature. Thermodynamic parameter such as free energy value was negative, that indicates spontaneous adsorption of inhibitor on MS surface. Adsorption of MLA was found to obey Langmuir isotherm. The analysis of variance studies showed that the inhibition efficiencies calculated from the different electrochemical parameters are statistically significant. Surface studies were performed by Fourier transform infrared spectroscopy and atomic force microscopy.