Sulfuric Acid Medium Research Articles

Determination of pioglitazone hydrochloride by flow injection chemiluminescence tris(2,2'-bipyridyl)ruthenium (II)-silver (III) complex system.

A novel flow injection-chemiluminescence (FI-CL) approach is proposed for the assay of pioglitazone hydrochloride (PG-HCl) based on its enhancing influence on the tris(2,2'-bipyridyl)ruthenium (II)-silver (III) complex (Ru (bipy)3 2+ -DPA) CL system in sulfuric acid medium. The possible CL reaction mechanism is discussed with CL and UV spectra. The optimum experimental conditions were found as: Ru (bipy)3 2+ , 5.0×10-5 M; H2 SO4 , 1.0×10-3 M; DPA, 1.0×10-4 M; KOH, 1.0×10-3 M; flow rate 4.0 mL min-1 for each flow stream and sample loop volume, 180 μL. The CL intensity of PG-HCl was linear in the range of 1.0×10-3 -5.0 mg L-1 (R2 = 0.9998, n = 10) with limit of detection (LOD, S/N = 3) of 2.2×10-4 mg L-1 , limit of quantification (LOQ, S/N = 10) of 6.7×10-4 mg L-1 , relative standard deviation (RSD) of 1.0-3.3% and sampling rate of 106 h-1 . The methodology was satisfactorily used to quantify PG-HCl in pharmaceutical tablets with recoveries ranging from 93.17 to 102.77 and RSD from 1.9 to 2.8%.

Corrosion Behavior of EN18 Steel and Copper in the Sulfuric Acid Medium for As-Bought and Annealed Materials

EN18 steel and copper are used as materials for oil and gas industries for chemical storage, which come in contact with the sulfuric acid medium during the pickling process. In such instances cleaning of impurities and oxide layer removal, leads to excessive corrosion. Thus, the improvement in the microstructure through annealing treatment and its effect on the corrosion behavior of EN18 steel and copper are studied by immersing in 0.5 M H2SO4 for as-bought and 0.5, 0.25, 0.1 M H2SO4 medium solutions after annealing treatment. The metal specimens were heated to 900 °C for EN18 steel and 600 °C for copper and then both were furnace cooled and the change in the microstructure of annealed and as-received metal specimens was analyzed using Scanning Electron microscopy (SEM). The Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic polarization (PDP) measurement showed that there is a decrease in the corrosion rate for both metals after annealing treatment. The effect of corrosion rate at the temperature range of 30-50 °C was analyzed and activation parameters were described using Arrhenius and transition state theories. Suitable corrosion mechanisms for both steel and copper in the H2SO4 medium have been discussed.

Temperature Effect on Corrosion Rate of Metal AA 5052 Using D-Galactose Inhibitors In Sulfuric Acid Media With Electrochemical Method

Aluminum Alloy 5052 (AA 5052) is a metal that can be used as a biopolar plate in proton exchange membrane fuel cell (PEMFC), because it has the advantages of being resistant to corrosion, high conductivity, easy shape and light weight. PEMFC produces electrical energy and the rest of the process in the form of hot water and steam. In a bipolar plate PEMFC environment corrosion can easily occur due to an acidic environment and high operating temperature around 40°C-80°C. For this reason, a treatment is needed to strengthen the corrosion-resistant properties of AA 5052. The coating of the material can be done using the technique of electrophoretic deposition (EPD) using green inhibitor to reduce the corrosion rate. The electrochemical method was carried out to see how much influence temperature had on the corrosion rate of AA 5052. In this study, d-galactose green inhibitor with a concentration of 0.5 g, EPD time of 20 minutes was used, in a PEMFC environmental simulation in 0.5 M H2SO4 sulfuric acid medium, with test temperatures of 25°C (room temperature), 40°C, 60°C, and 80°C. From the results of the analysis using the electrochemical method, there was an effect of temperature on the corrosion rate of AA 5052 without an inhibitor layer of 0.3610 mmpy at room temperature and increased at 80°C 3.9527 mmpy. While AA 5052 which was coated with a d-galactose inhibitor, had a corrosion rate of 0.1678 mmpy at room temperature and continued to increase at a temperature of 80°C 3.7745 mmpy. Inhibitor efficiency was 53.51% at room temperature and decreased with increasing temperature to 4.5% at 80°C.

D2EHPA treated resin for the extraction of rare earth elements

ABSTRACT Resin-based separation techniques are utilised for the extraction of metals. However, separation of rare earth elements in ultrapure form by using resins is difficult due to similarity in chemical properties of rare earth elements. An attempt has been made to improve the selectivity of resin for the extraction of rare earth elements by using di-2-ethylhexyl phosphoric acid (D2EHPA). D2EHPA treated macroporous chloromethylated styrene divinyl benzene resin has been prepared and its potential to extract rare earth elements such as praseodymium and neodymium has been investigated. The extraction of neodymium was marginally higher than praseodymium. However, stripping of neodymium was significantly higher as compared to stripping of praseodymium in both hydrochloric acid and sulphuric acid media. The properties of the resins have also been studied by using various instrumental techniques such as thermogravimetry-differential thermal analysis, scanning electron microscopy and Fourier transform infra-red spectroscopy.

Correction: Selective extraction of Hf over Zr by a novel extractant (n-octyl)(2,4,4′-trimethylpentyl)phosphinic acid (INET-1) from sulfuric acid media

Correction: Selective extraction of Hf over Zr by a novel extractant (n-octyl)(2,4,4′-trimethylpentyl)phosphinic acid (INET-1) from sulfuric acid media

Correction to: Selective extraction of Hf over Zr by a novel extractant (n-octyl) (2,4,4′-trimethylpentyl)phosphinic acid (INET-1) from sulfuric acid media

Correction to: Selective extraction of Hf over Zr by a novel extractant (n-octyl) (2,4,4′-trimethylpentyl)phosphinic acid (INET-1) from sulfuric acid media

A Simple and Rapid Spectrophotometric method for the determination of Iodate in table salt samples using Pyrogallol red dye

A simple and rapid spectrophotometric method for the determination of iodate in table salt samples has been standardized using the oxidation reaction of iodate with pyrogallol red dye in sulphuric acid medium. The determination of iodate was done by measuring the decrease in absorbance of pyrogallol red dye at 470 nm. A standard calibration curve was prepared, for iodate concentrations in the range of 0.05 µg mL-1 to5 µg mL-1. The effect of NaCl and Iinterference on iodate determination has been studied. The kinetics of the reaction between pyrogallol red and iodate has also been studied. The oxidation reaction was found to be first order with respect to iodate concentration. The method has been used for the determination of iodate in 10 different brands of locally available common salt samples.

A Simple and Rapid Spectrophotometric method for the determination of Iodate in table salt samples using Pyrogallol red dye

A simple and rapid spectrophotometric method for the determination of iodate in table salt samples has been standardized using the oxidation reaction of iodate with pyrogallol red dye in sulphuric acid medium. The determination of iodate was done by measuring the decrease in absorbance of pyrogallol red dye at 470 nm. A standard calibration curve was prepared, for iodate concentrations in the range of 0.05 µg mL-1 to5 µg mL-1. The effect of NaCl and Iinterference on iodate determination has been studied. The kinetics of the reaction between pyrogallol red and iodate has also been studied. The oxidation reaction was found to be first order with respect to iodate concentration. The method has been used for the determination of iodate in 10 different brands of locally available common salt samples. Key Words: Iodate, Table salt, Pyrogallol

A Simple and Rapid Spectrophotometric method for the determination of Iodate in table salt samples using Pyrogallol red dye

A simple and rapid spectrophotometric method for the determination of iodate in table salt samples has been standardized using the oxidation reaction of iodate with pyrogallol red dye in sulphuric acid medium. The determination of iodate was done by measuring the decrease in absorbance of pyrogallol red dye at 470 nm. A standard calibration curve was prepared, for iodate concentrations in the range of 0.05 μg mL-1 to5 μg mL-1. The effect of NaCl and Iinterference on iodate determination has been studied. The kinetics of the reaction between pyrogallol red and iodate has also been studied. The oxidation reaction was found to be first order with respect to iodate concentration. The method has been used for the determination of iodate in 10 different brands of locally available common salt samples

The Electrochemical and Microstructure Effects of TiB2 and SiC Addition to AA5052/Al2O3 Surface Composite Coatings in 0.5 M H2SO4 Solution

In this work, Al2O3, SiC, and TiB2 ceramic coatings with different formulations were produced on the surface of AA5052 matrix by gas tungsten arc welding (GTAW). The corrosion behavior of the composites and the base metal (BM) was evaluated in a solution of 0.5 M H2SO4 with electrochemical techniques such as open circuit potential (OCP) monitoring, potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS). The morphology of the cladded surfaces was monitored by scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS). Based on the PDP and EIS results, BM had the lowest corrosion rate in the 0.5 M H2SO4 solution. All composite coatings shifted to higher corrosion rate values than that of BM, indicating that AA5052 composites had lower corrosion resistance compared to the BM. SEM images of the corroded surface of BM exhibit minimum pitting corrosion in sulfuric acid media. According to electrochemical studies, AA5052/Al2O3 + SiC + TiB2 composite had the lowest corrosion resistance due to the formation of micro-galvanic sites on the aluminum matrix surface. However, the AA5052/Al2O3 + TiB2 composite showed the best corrosion performance compared to other composites. In general, by adding SiC and TiB2 ceramics to Al2O3 and fabricating binary composites, the corrosion resistance of AA5052/Al2O3 composite is improved. Although the corrosion resistance of AA5052 composites is lower than the BM, their higher surface hardness makes their use justified in applications where high mechanical properties are required if the environment is not too aggressive.Graphical Abstract

Kinetic Fluorimetric Determination of Formaldehyde by Oxidation of Rhodamine B with Potassium Bromate

Based on the H2SO4-Rhodamine B-KBrO3 system, the kinetic fluorescence method was used to determine formaldehyde. The experimental results show that in the sulfuric acid medium, the fading process of oxidized rhodamine B by potassium bromate is inhibited by the catalytic action of formaldehyde. The results showed that the formaldehyde concentration in the range of 0.4 to 4.4 μmol/L had a good linear relationship with lg (IF/I0F) = 0.01385 c (μmol/L) + 0.02353, the correlation coefficient was 0.9974, and the method detection limit was 0.3027 μmol/L. In the determination of formaldehyde in the synthetical water sample and laundry water, the recoveries were 98.68% and 103.20%. The results were consistent with the certified value.

Liquid-liquid extraction of zirconium(IV) from sulphuric acid medium using a binary mixture of tri-n-octylamine and Cyanex923 in kerosene

The extraction behaviour of zirconium(IV) from sulfuric acid medium has been studied with a binary mixture of tri-n-octyl amine (TOA) and Cyanex923 (a mixture of four trialkyl phosphine oxides) in kerosene using a novel liquid-liquid extraction method. Quantitative extraction of zirconium(IV) with binary mixture of Cyanex923 and TOA in kerosene was studied by changing different parameters such as acid variation, extractant variation, effect of chloride ion concentration, effect of temperature, metal concentration variation, diluent effect, and pH effect. The percentage of extraction of zirconium(IV) decreased when the concentration of Cyanex923 and TOA increased. The percentage of zirconium(IV) was observed as 97.56% in a binary mixture of 0.007 M Cyanex923 and 0.06 M TOA. Kerosene was found to be an effective diluent for the extraction of zirconium(IV) with 97.56% extraction using a binary mixture of Cyanex923 and TOA. In addition, the stripping of the zirconium(IV) metal ion in the organic phase was also examined.

Spectrophotometric determination of nitrite in curing meat samples basing on the nitrosation reaction

A new Spectrophotometric method for the determination of nitrite ion was studied. The method is based on the nitrosation reaction of nitrite ion with tryptophan in sulphuric acid medium. During it's reaction with nitrite, an intensively yellow-coloured substance is formed, having maximum absorption at 440nm. The calibration curve showed that Beer s law obeyed over the range of 0.05-3.0μg/ml of nitrite, with a detection limit of 0.00μg/ml. The molar absorptivity and Sandell index were 1.3887*104 L/mol.cm and 0.00331μg/cm2 respectively. The optimum conditions affecting and interferences of the foreign ions were studied. The results obtained of the proposed method for determination of nitrite in meat samples were agreed with those obtained by the Naphthyl ethylene diamine NEDA standard method.

Pressure Leaching of Copper Slag Flotation Tailings in Oxygenated Sulfuric Acid Media.

In this study, a hydrometallurgical method for the recovery of copper, cobalt, and zinc from copper slag flotation tailings (SFT) was investigated. SFT contains large amounts of valuable metallic compounds, such as copper, cobalt, and zinc. A representative SFT sample containing 0.50% Cu, 0.148% Co, 3.93% Zn, and 39.50% Fe was used in experimental studies. High-pressure oxidative acid leaching of SFT was carried out to assess the effects of sulfuric acid concentration, oxygen partial pressure, reaction time, solid/liquid ratio, and temperature on the extraction of copper, cobalt, zinc, and iron. The dissolution of metals from the SFT sample increased with temperature and sulfuric acid concentration. However, high acid concentrations and high solid/liquid (S/L) ratios led to gel formation that caused filtration problems and inhibited metal dissolution. The optimum leaching conditions were found to be a leaching time of 90 min, an acid concentration of 250 kg/t, a temperature of 220 °C, an S/L ratio of 1:5, and an oxygen partial pressure of 0.7 MPa. Under these conditions, 93.1 ± 1.1% Cu, 96.3 ± 1.8% Co, and 92.3 ± 1.7% Zn were extracted. Iron dissolution was only 0.5 ± 0.1%. This hydrometallurgical process almost completely recovers valuable metals. In particular, cobalt, which is of great importance in the production of lithium-ion batteries, has been declared a critical metal by the United States, Canada, and the EU and was taken into solution with very high extraction efficiency (>95%). Additionally, oxygen partial pressure enhanced copper, cobalt, and zinc dissolution. When O2 was not introduced into the leaching system, the extraction efficiencies of Co, Cu, and Zn were approximately 24.5, 5.3, and 26.3%, respectively, after 2 h of leaching treatment.

Natural Sweet Almond Oil as an Effective Green Inhibitor for Aluminum Corrosion in Sulfuric Acid Medium

Natural Sweet Almond Oil as an Effective Green Inhibitor for Aluminum Corrosion in Sulfuric Acid Medium

Selective extraction of Hf over Zr by a novel extractant (n-octyl)(2,4,4′-trimethylpentyl)phosphinic acid (INET-1) from sulfuric acid media

Selective extraction of Hf over Zr by a novel extractant (n-octyl)(2,4,4′-trimethylpentyl)phosphinic acid (INET-1) from sulfuric acid media

Study of the Corrosion of Nickel-Chromium Alloy in an Acidic Solution Protected by Nickel Nanoparticles.

This study uses nickel nanoparticles coated on the nickel–chromium (Ni–Cr) alloy by the electrodeposition technique to protect the alloy against corrosion. An open-circuit potential and potentiodynamic and linear polarization resistance in a 1 M H2SO4 solution saturated with carbon dioxide were used to study the anticorrosion performance of nanoparticle coatings. When coated with nanomaterials, the corrosion rate of Ni–Cr alloy was lower than when it was bare, and the potential for corrosion increased from −0.433 V for uncoated Ni–Cr alloy to −0.103 V when the electrodes were exposed to saturated calomel. Electrochemical experiments show that nickel-coated Ni–Cr alloy corrosion in sulfuric acid media has high protective characteristics, with an efficiency of 83.69% at 0.165 mA/cm2 current density when pH = 1 is used. As demonstrated by the results of this research, the nickel–chromium alloy can be protected from corrosion in acidic media by a low-acidity bath coating layer. Surface morphologies have shown that coatings at different acidic scales may be able to resist an acid attack because of their excellent adherence to the nickel–chromium alloy surface. Measures for determining and studying the composition of the alloy surface’s protective covering were improved using X-ray diffraction (XRD).

Determination of 93Mo in Radioactive Samples of Sulfuric Acid Media from Nuclear Facilities.

93Mo is an important radionuclide in view of radioactive waste repository because of its long half-life and high mobility in the environment. 93Mo decays by electron capture without any measurable gamma ray emission. The concentration of 93Mo in most of the radioactive waste is many orders of magnitude lower than the major activation product radionuclides, which makes the accurate determination of 93Mo a big challenge. A new analytical method for the determination of 93Mo in sulfuric acid media from nuclear power reactor was developed. 93Mo was separated from most of the radionuclides by cation exchange chromatography followed by the removal of sulfate by CaSO4 precipitation. A further purification of 93Mo, especially from anion species of 51Cr and 125Sb, was achieved by anion exchange chromatography and a short alumina column separation. The chemical yield of 93Mo in the entire separation procedure reached about 75%, and the decontamination factors for all potential interfering radionuclides were 1.5 × 106-1.6 × 108. The purified 93Mo was measured by liquid scintillation counting through counting its low-energy Auger electrons. A detection limit of 2 mBq/g for 93Mo in 50 g sample was achieved by this method, which enables the quantitative determination of 93Mo in most of the radioactive samples in the decommissioning waste and coolant water of nuclear power reactors. The developed method has been successfully applied to determine 93Mo in coolant water of nuclear power reactors, providing a robust analytical approach of 93Mo for the radiological characterization of radioactive wastes.

Development and Scale-up of Chemical Process for Conversion of Impure Sodium Diuranate to Uranium Peroxide

Abstract Uranium mills following the sulfuric acid leaching route produce Uranium Peroxide (UP) as uranium ore concentrate (yellow cake), which is then refined to produce nuclear grade uranium products. Whereas the mills processing ores by alkaline leaching route generate Sodium Diuranate (SDU) as yellow cake, which commonly contains impurities viz. Zr, SiO2, Mo, Organic Carbon (OC). These impurities form muck, interfacial crud and acid insolubles during digestion and solvent extraction (SX) stages in refining process. Hence, SDU needs to be pre-treated before processing in the uranium refinery. India has substantial U reserves (>50%) hosted in carbonate minerals matrix which obviously need alkaline processing for extraction of U. In the present study, the origin of impurities in a SDU produced in an Indian Uranium mill was traced back to the mineralogical composition of the ore, chemical reactivity of minerals to the reagents,and build-up of impurities in process streams due to existence of multiple recycle streams in the milling process flowsheet. A process scheme has been developed for converting SDU into highly pure Heat Treated Uranium Peroxide (HTUP). The scheme involves digestion of SDU in sulfuric acid medium followed by separation of insolubles from the liquor which is later subjected to pH controlled U-peroxide precipitation process. The U-peroxide formed was heat treated to drive-off active oxygen and water of crystallization. A HTUP product assaying about 91% U3O8 was produced from an impure SDU assaying 74% U3O8. Process has been demonstrated at large scale (about 100 kg/batch) and engineering data and scale up parameters have been generated.

Photoreduction of Copper Ions Using Silica-Surfactant Hybrid and Titanium (IV) Oxide under Sulfuric Acid Conditions.

Photoreduction of Cu2+ ions to Cu metal by titanium(IV) oxide (TiO2) was conducted in the presence of a silica–surfactant hybrid under sulfuric acid conditions. After irradiation, a dark-red color, reflections due to Cu metal in the X-ray diffraction pattern, and peaks due to Cu 2p1/2 and 2p3/2 in the X-ray photoelectron spectrum indicated the precipitation of Cu metal in the product. In addition, an increase in the Brunauer–Emmett–Teller specific surface area from 36 and 45 m2/g for the silica–surfactant and TiO2, respectively, to 591 m2/g for the product, and a decrease in the intensity of the C-H stretching band in the Fourier–transform infra-red spectra implied the removal of surfactant during the reaction. These characteristics were never observed when TiO2 was used solely. Therefore, this study indicated that the photoreduction of Cu2+ ions to Cu metal by TiO2 was facilitated under the sulfuric acid medium, where the surfactants extracted from silica–surfactant hybrids by protons in the acidic condition were successfully photo-oxidized by TiO2. Thus, this study presents a new application of the conversion of a silica–surfactant hybrid into mesoporous silicas.