Acid Solution In Presence Research Articles

Recovery of rare earth elements from coal samples from the Sohagpur coalfield, Madhya Pradesh, India

ABSTRACT REEs play a pivotal role in the manufacturing of numerous industrial, defense, consumer, and aviation-related gadgets. As many primary sources of REEs are either exhausted or depleted, coal can be a good secondary source of REEs in the near future. The traditional thermochemical processes to extract REEs are expensive and detrimental to the environment, and thus exploration of more environment friendly and sustainable recovery methods are of the utmost necessity at the present time. In this study, we present in-depth investigation of REEs extraction from the coal samples from the Sohagpur coalfield, Madhya Pradesh. We conducted multiple experiments mainly focusing on rotational movement with the help of a laboratory shaker, magnetic stirrer with hot plate, and a flocculator jar test apparatus in the presence of acidic solutions. Our study highlights that the flocculator jar test apparatus exhibits the maximum recovery of REEs (Ce- 95%, Nd- 83%, La- 82%, Eu- 82%, Pr- 76%, Sm- 74%, Gd- 69%, and Tb- 69%) from coal in the presence of 2 M HNO3. This technique of REEs recovery from coal is easy to use, effective, has little environmental impact, and can be applied on an industrial scale with only minor adjustments to the machinery.

Fenton-like photocatalyzed degradation of dibutyl phthalate with goethite and carboxylic acids

Detailed investigation of photocatalyzed degradation of dibutyl phthalate (DBP), an endocrine disrupter, in the presence of α-FeOOH (goethite) and different carboxylic acids is the focus of this study. To get a better insight into the efficiency of the degradation, the influence of different parameters, such as concentration of total Fe and Fe(II), dissolved oxygen, DBP concentration, pH and salinity is investigated. The reaction mechanism consists of several interrelationship steps. The first step is the chemical reaction of carboxylic acid groups of the organic acids with hydroxyl groups of the α-FeOOH and a charge transfer upon illumination generating Fe(II). The second step is the release of Fe(II) into the solution followed by H2O2 oxidation to form highly photoactive hydroxyl complex of iron(III) and ˙OH. Simultaneously, the superoxide radical O2˙− and hydroperoxyl radical is formed in acidic solutions in presence of carboxylic acids as well. This mechanism explains the genesis of different reactive species oxidizing DBP. From the variety of the studied carboxylic acids (oxalic, citric, salicylic, pyruvic, maleic, and fumaric), oxalic acid is the best Fe-ligand for the photoreductive dissolution of goethite. Concentrations of the total amount of Fe and its dissociated forms Fe(II) as well as oxygen and hydroxyl radicals play a fundamental role in efficiency of DBP degradation. The photodegradation of DBP with goethite and the use of suitable carboxylic acids under optimized reaction conditions could be an efficient process for decontamination of polluted waters.

Saussurea obvallatta leaves extract as a potential eco-friendly corrosion inhibitor for mild steel in 1 M HCl

The extract of saussurea obvallatta leaves (SOLE) has been examined for corrosion inhibition studies for mild steel (MS) in 1 M HCl solution by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and traditional mass change measurements. SOLE controlled maximum of 90 % corrosion rate of MS in 1 M HCl solution at 200 ppm of SOLE. SEM-EDX, AFM and Contact angle images revealed that, MS surface was least affected by the acid solution in presence of SOLE. FT-IR and UV–Visible absorption spectral values established the set of a corrosion defensive layer over the MS surface. Potentiodynamic measurement revealed that SOLE act as a both anodic and cathodic type of inhibitor. Quantum chemical calculations shows that, the EHOMO as an electron donor of SOLE donate electrons to appropriate acceptor molecules to the vacant d orbital of Fe atoms of MS. Un-filled 3d orbital of MS could bind with HOMO of the inhibitors. On the other hand filled 4s orbital could donate the electron to LUMO of the inhibitor as oftenly ELUMO indicates the ability of molecules to accept electrons. Variation of experimental temperature studies revealed that the stability of the protective layer decreased at higher temperature and corrosion activation energies increased in the addition of SOLE.

Thermal hazards analysis of styrene in contact with impurities

Styrene is a reactive monomer commonly used to produce polystyrene and other copolymers. Unintended thermal runaway polymerization reactions of styrene keep reoccurring and have led to catastrophic consequences. One of the possible causes of these runaway incidents involves the contamination of the styrene monomer by incompatible species, which was not adequately investigated and documented. This study focuses on the quantification of thermal runaway hazards of styrene in contact with a series of contamination substances by adopting calorimetric analysis. Both Differential Scanning Calorimeter (DSC) and Advanced Reactive System Screening Tool (ARSST) were employed to examine the exothermic characteristics of styrene mixed with contaminating substances at different concentration levels and mixing conditions. Key safety parameters of the exothermic reaction, such as the onset temperature, the overall heat release, the maximum self-heating rate, as well as the activation energy, were obtained. The results indicated that the thermal runaway polymerization of purified styrene was significantly altered by the presence of contaminant species. Water effectively retarded and quenched the runaway polymerization at a higher temperature range. Alkaline had no substantial effect on the thermal runaway characteristics. The presence of acid solution under both static contact and vigorous mixing condition significantly promoted the thermal polymerization of styrene. A trace amount of concentrated acid initiated violent exothermic activity even at room temperature; and the severity of the reaction was profoundly impacted by the mass-transfer. Our study demonstrates significant implications in the prevention of runaway incidents during transportation and storage of styrene.

NEW APPLICATIONS FOR AMOXICILLIN DETERMINATION IN PURE FORM AND PHARMACEUTICALS BASED ON IODATE-IODIDE MIXTURE: TITRIMETRY AND SPECTROSCOPY STUDIES

Three simple methods are described for the determination of amoxicillin (AMX) in bulk drug and dosage forms using iodate-iodide mixture reagent. These methods employed the well-known analytical reaction between iodate-iodide mixture in the presence of acid solution. The iodide oxidized by iodate to iodine in an amount equivalent to the -COOH group present in amoxicillin (AMX) and the liberated iodine determined by titrimetry and spectrophotometry. In the titrimetric method (method A), the liberated iodine was reacted with a measured excess of thiosulphate and the residual thiosulphate was determined by titration with a standard iodine solution using starch indicator, the method was applicable over 2 - 16 mg of AMX. In the second and third methods, the absorbance of the liberated iodine was measured at 370 nm (method B) and also iodine was reacted with starch and starch-iodine complex was measured at 570 nm (method C). In spectrophotometric methods (B and C), Beer’s law was obeyed over the concentration range of 5 - 50 and 5 - 60 µg mL-1 AMX with a molar absorptivity values of 5.55×103 L mol-1 cm-1 and 4.76×103 L mol-1 cm-1 for the method A and method B, respectively. The limits of detection (LOD) and quantification (LOQ) were calculated for method B and method C. The proposed methods were found to yield reliable results when applied to bulk drug and dosage forms analysis, and hence they can be applied in quality control laboratories.

New insight into electropolymerization of melamine. I: Chloride promoted growth of polymelamine in different pH medium

Electropolymerization of melamine, 1,3,5-triazine-2,4,6-triamine, has been investigated here in aqueous solutions in a very wide pH range, which formerly was believed to be confined only in an acidic medium. We report here for the first time the polymerization can take place in neutral and alkaline besides acidic solution in presence of Cl− ions. The key effects of the acidity of solution, potential window and concentration of Cl− ions and melamine monomer on the polymelamine (pMel) deposition have been further confirmed one by one, respectively. We proved that presence of Cl− ions is the necessary condition rather than H+. The electropolymerization of melamine is very sensitive to Cl− (even in 1 mM), and in situ electrogeneration of active chlorine effectively promote the growth of pMel film in separate solutions with different pH. Based on the relevant reactions during the process of electropolymerization, a tentative mechanism is given here. With this knowledge, a better control of the electrochemical synthesis can be envisioned, thus making pMel film suitable for the construction of multifunctional platforms.

Selective elimination of natural radionuclides during the processing of high grade monazite concentrates by caustic conversion method

This work is directed for removal of the nondesired species (228Ra, 226Ra, 223Ra, 210Pb, Th(IV) and Fe(III)) in the rare earth chloride (RECl3) liquor before separation of Ln(III). The different factors affecting elimination of radium-isotopes, lead (210Pb), Th(IV) and Fe(III) from the RECl3 liquor, have been investigated and optimized. The results indicated that the activity concentration of radionuclides in RECl3 liquor was above the safe limits required during the separation process of Ln(III). Adjustment of pH 3±0.1 leads to eliminate 14±1% of radionuclides and Th(IV), and 40±3% of Fe(III), while 12±1% of Ln(III) was lost. The developed method shows that more than 95% of the nondesired species was selectively removed when the liquor was eliminated by potassium sulfate or sulfuric acid solutions in presence of Ba/Pb-carrier (1: 1). About 20-83% of Ln(III) was lost when the non-desired species removed by sodium or ammonium sulfate or potassium chromate solutions. Fe(III) interfered with Ln(III) when radionuclides and Th(IV) were eliminated by 2.6M H2SO4 in presence of Ba/Pb-carrier. Finally, use of 0.23M K2SO4 or 2.6M H2SO4 was efficient to reduce level of 228Ra, 226Ra, 223Ra and 210Pb to the safe limits in viewpoint of radiation protection. In addition, the interfered Th(IV) and Fe(III) were also eliminated efficiently from RECl3 liquor before the chemical processing of Ln(III).

Electrochemical Characterization of Natural Chalcopyrite Dissolution in Sulfuric Acid Solution in Presence of Peroxydisulfate

In this study, the effect of peroxydisulfate ion on electrochemical behavior of natural chalcopyrite in 0.5M H2SO4 was investigated by means of AC/DC electrochemical tests and atomic force microscopy (AFM). Regarding potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS), increase in peroxydisulfate ion concentration accelerates the electrochemical dissolution of the chalcopyrite electrode. Also, Mott-Schottky measurements proved that peroxydisulfate ion decreases n-type semiconducting properties of the chalcopyrite passive layer. Finally, atomic force microscopy showed directly that in presence of peroxydisulfate ion, chalcopyrite more severely corrodes compared with the blank sulfuric solution.

Synthesis and properties of a green and self-cleaning hard protective coating

Abstract Polysiloxane coatings prepared by pre-hydrolysis/condensation of methyltrimethoxysilane (MTMS), etraethoxysilane (TEOS), methyltriethoxysilane (MTES) and polydimethylsiloxane (PDMS) in the presence of acid solution were presented in this paper in order to explore their potential use as protective and self-cleaning agents for car surface. The hardness and adhesion on the substrate properties of coatings were thoroughly examined by pencil hardness tester and adhesion tester. Contact angle meter was used to measure the hydrophobic angle properties of coatings. All the properties of coatings were related closely to the composition of coating and the hydrolysis degree of organoalkoxysilane. We found that the Scratch hardness can be improved by the controlling of TEOS quality ratio and acidity conditions, while more dosage of MTMS, MTES and PDMS favor raising the hydrophobic angle. Excellent adhesion property of paint coat was obtained with the presence of γ-(2,3-epoxypropoxy) propytrimethoxysilane (KH-560). Whatever, the best self-cleaning coatings with excellent hardness and adhesion on the substrate was sample A4 synthesized by a sol–gel process of low-cost organoalkoxysilane, prepared at the quality ratio of (MTMS):(TEOS):(MTES):(PDMS):(KH-560) of 8:7:4:4:4 and water-to-precursor quality ratio of 1:7. Finally, ambient-curable self-cleaning coating suitable for large area application was obtained. The scratch hardness and adhesion strength of the coatings was 3H and 0 after hardening with a high speed, respectively. The contact angle after UV aging of the coating was 92°. The transmittance of the coating exceeded 98.5%. Meanwhile, the coating has good resistance to solvent and weather resistance.

Sorption Recovery of Platinum (IV) from Hydrochloric Acidic Solutions in Presence of Iron (III), Copper (II) and Zinc

The present work is devoted to sorption preconcentration of platinum (II,IV) in the presence of iron (III), copper (II) and zinc from chloride solutions on the samples of CYBBER – new Russian brand of ion exchangers. The initial concentrations of platinum, iron and non-ferrous metal ions were 0.25, 0.5 and 2.0 mmol/L, respectively. The acidity of the investigated solutions was 0.01 – 2 mol/L. It was shown that the ion exchangers possess high sorption ability to the noble metal ions, and allow the quantitative recovery of these ions. It was also found out that platinum can be isolated from the accompanying components by means of separate elution with 0.001 M HCl (iron ions), 0.5 M HNO 3 (non-ferrous metal ions) and thiourea solution (80 g/L) in 0.3 M H 2 SO 4 (platinum ions).

Abrasion and chemical resistance of composite vitreous enamel coatings with hard particles

Vitreous enamels are coatings commonly used to protect aluminium substrates, because of their very good protection properties together with aesthetical ones. The properties of this layer can be optimized changing the chemical composition of the starting frit or with mill additives. The addition of hard particles, very common method with other types of coatings, for this layer has not yet been studied. The aim of this research is to study how the addition of hard particles influences the mechanical and chemical resistance of enamels applied on AA4006 alloy. Deposits with two different kinds of particles [tungsten carbide (WC) and silicon carbide (SiC)] with two concentrations were considered. The enamel layer without particles was considered as reference. Two different kinds of abrasion test (Taber and PEI) were adopted to study the abrasion resistance. Enamel coatings' properties were characterized considering the changes in mass, gloss and roughness values before and during abrasion tests. Moreover, the observation of cross sections and surfaces permitted to evaluate the coatings' quality and to obtain information about the damage mechanisms. The most improved abrasion resistance was achieved using the concentration of 10 vol% for SiC and 5 vol% for WC. Therefore, the adding of hard particles could be a valid solution to improve the abrasion resistance of the vitreous enamels. The chemical resistance behaviour was checked with immersion into acid and basic solutions. The presence in the layer of SiC particles produced a reduction of resistance in presence of acidic solution, while enamel with WC particles resulted more resistant. Copyright © 2015 John Wiley & Sons, Ltd.

Valence Stabilization of Polyvalent Uranium Ions in Presence of Some Organic Additives during Extended Gamma Irradiation of Their Aqueous Acidic Solutions

In gamma irradiated aqueous acidic uranium solutions, tetravalent uranium ions are easily oxidized while U(VI) ions remain unchanged. In general, valence change of polyvalent metallic ions during chemical reprocessing of spent nuclear fuel solutions can lead to undesirable effects under the influence of the existing gamma radiations. Consequently, studies on valence stabilization of Uranium ions during chemical treatment in strong gamma irradiation fields seem to be highly interesting. It has been reported before that some organic compounds proved to be effective in stabilizing the valence of Fe(II) ions during extended gamma irradiation of their acidic solutions. In the present work, valence stabilization of Uranium ions in acidic solutions in presence of different classes of organic compounds has been studied. The results showed that in case of U(IV), methanol or formic acid are capable of providing about 80% protection while ethanol or acetaldehyde can provide about 70% protection. Propanol has the least protective effect i.e. about 54%. On using U(VI) instead of U(IV) in the irradiated solutions, the uranium ions were reduced and the formed U(IV) was protected as follows: formic acid or methanol can provide 69% or 63% protection respectively while ethanol, acetaldehyde or propanol can provide 50%, 35% and 24% respectively. In any case, protection exists as long as the organic additives were not completely consumed.

Effect of Sodium Hydroxide on the Fast Synthesis of Superhydro-phobic Powder from Polymethylhydrosiloxane

The paper reports the role of sodium hydroxide in the synthesis of a superhydrophobic powder from polymethylhydrosiloxane (PMHS) in the presence of ethanol and water. The effects of other basic and acidic solutions as well as the absence of water were also investigated. PMHS exhibited rapid gelation (from 8 h to 2 h) by increasing the concentration of sodium hydroxide in the presence of ethanol and water. In contrast, gelation did not occur in the absence of sodium hydroxide or water or in the presence of acidic solutions. Delayed gelation (96 h to 120 h) occurred as a result of the introduction of dipotassium hydrogen phosphate trihydrate. Superhydrophobic powder was obtained by the evaporation of solvents from the gelated sol at 150 °C. The surface properties of the superhydrophobic powder were examined by scanning electron microscopy, high resolution transmission electron microscopy, N2 sorption isotherm, and X-ray diffraction. The particle size, functional groups and thermal stability of the powder were analyzed by dynamic light scattering spectroscopy, Fourier transform infrared spectroscopy, 29Si cross polarization magic angle spinning nuclear magnetic resonance spectroscopy, and thermogravimetric analysis. The surface properties of the powder were also assessed by contact angle measurements. The results showed that increasing the concentration of sodium hydroxide added to PMHS or increasing the drying temperature of the gelated sol resulted in the more rapid formation of superhydrophobic powder.

Graphene /TiO2 Composite Electrode: Synthesis and Application towards the Oxygen Reduction Reaction

A graphene oxide (GO) was prepared from a commercial graphite nano-crystals using Hummers’ method. Later, GO powder was reduced either by placing it under a H2 gas flow in a controlled gas reactor at 450 oC or using a hydrazine hydrate solution (HH) in a 1000-Watt microwave oven. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction patterns (XRD) confirmed that both of the oxidation and reduction processes of graphite and GO powders, respectively, were incomplete. Also, the surface area of the H2 gas - reduced GO powder was found to be higher than the case where HH was used to reduce the same powder. Fourier transform infrared spectroscopy (FT-IR) and XPS have revealed that GO surface consists mainly of hydroxyl, epoxy, carbonyl and carboxylic groups. The electrocatalytic properties of (i) glassy carbon (GC), (ii) commercial TiO2 (P25-TiO2/GC), (iii) TiO2-supported GO (GO/TiO2/GC), (iv) TiO2 – supported HH – reduced GO (HHRGO/TiO2/GC) and (v) TiO2 – supported H2 gas – reduced GO (H2RGO/TiO2/GC) electrodes towards the oxygen reduction reaction (ORR) in acidic solution in presence and absence of UV radiation were examined. The results have shown that the H2RGO/TiO2/GC electrode has the best electrocatalytic activity in terms of current at a certain potential but glassy carbon electrode (GC) was found to be the best in terms of the onset potential of the ORR.

Corrosion Behaviour of Aluminium and AA5754 Alloy in 1% Acetic Acid Solution in Presence of Laurel Oil

Corrosion Behaviour of Aluminium and AA5754 Alloy in 1% Acetic Acid Solution in Presence of Laurel Oil

Co-Dispersion Behavior of ZrB₂-SiC-B₄C-C Powders with Polyethyleneimine.

The aqueous dispersion behavior of ZrB2, SiC powders with B4C and C as sintering aids was investigated. Well co-dispersed suspension can be obtained in acidic solutions in presence of polyethyleneimine (PEI). The adsorption of PEI on the powder surface was measured by thermal gravimetric (TG) analysis. Rheological measurements displayed the effect of dispersant on the flow behavior of as-prepared slurries. An optimum condition was obtained with 1 wt % PEI. The viscosity of 40 vol % ZrB2–SiC–B4C–C (ZSBC) suspension at 100 s−1 was as low as 0.74 Pa·s, which was suitable for aqueous processing.

Electrodeposition of Ni-Zn Alloys on Steel from Acidic Solution in Presence of Boric Acid

The electrode position of nickel with zinc in presence of boric acid was studied in order to determine the influence of the composition of the deposition solution on the properties of the obtained electrodeposits. The Ni / Zn concentrations ratio in solution determines the deposition mechanism and thus, the chemical composition and the electrochemical activity of the electrodeposited alloys. Boric acid decreases current density which minimizes anomalous deposition. The typical results from these acidic media are the formation of Ni-rich alloys (%Ni > 90) by a normal code position mechanism with a better electrochemical activity than Ni for the hydrogen evolution reaction HER reaction. Results show that it is possible to obtain alloys rich in either zinc or nickel, from an acidic solution containing boric acid. For Ni / Zn concentration ratios in the range of 1-3, Zn-rich alloys are obtained despite Zn is the less noble element and even when it is present at lower concentrations than Ni, confirming that at these conditions alloys are deposited by an anomalous deposition mechanism as reported by many researchers1,2,3

Recovery of Metal Values from Spent Zinc–Carbon Dry Cell Batteries

Spent zinc–carbon dry cell batteries were characterized in the process of recovery of metal values. Zinc, manganese and steel were the major metallic materials constituting 63 % of the weight of spent batteries. Different components of the spent batteries were separately processed to extract the metallic values. A maximum of 92 % of total amount of zinc contained in the anodes could be extracted with a purity of over 99.0 % from the anodes by heating at 600 °C for 10 min in presence of 12 % NH4Cl flux. Spent electrolyte paste containing manganese and zinc as major metallic elements, was leached in sulfuric acid solution in presence of hydrogen peroxide as a reducing agent. The optimum condition for leaching was found to be concentration of sulfuric acid: 2.5 M, concentration of hydrogen peroxide: 10 %, temperature: 60 °C, stirring speed: 600 rpm and solid/liquid ratio 1:12. A maximum of 88 % manganese contained in the paste could be dissolved within 27 min of leaching under the optimized conditions. Dissolution of zinc under the same conditions was 97 %. A maximum of 69.89 % of manganese and 83.29 % of zinc contained in the leach liquor could be precipitated in the form of manganese carbonate and zinc oxalate.

Solution thermodynamics of aqueous nicotinic acid solutions in presence of tetrabutylammonium hydrogen sulphate

In this study we investigated the effects of tetrabutylammonium hydrogen sulphate (Bu4NHSO4) on the solute-solute and solute-solvent interactions in the aqueous solutions of nicotinic acid in terms of apparent molar volumes (?V), standard partial molar volumes (?V0) and viscosity B-coefficients at 298.15, 308.15, and 318.15 K under ambient pressure. These interactions are further discussed in terms of ion-dipolar, hydrophobic- hydrophobic, hydrophilic-hydrophobic group interactions. The activation parameters of viscous flow for Bu4NHSO4 in the aqueous solutions of nicotinic acid were discussed in terms of transition state theory. The overall results indicated that ion-hydrophilic and hydrophilic-hydrophilic group interactions are predominant in the aqueous solutions of nicotinic acid and Bu4NHSO4 has a dehydration effect on the hydrated nicotinic acid.

Iodometric determination of milligram and microgram amounts of levocetirizine in pharmaceuticals

Four simple, selective and sensitive methods are described for the determination of levocetirizine dihydrochloride (LCT) in bulk drug and in tablets. The methods exploit the well-known analytical reaction between iodide and iodate in the presence of acid solution. Iodide present is oxidized by iodate in an amount equivalent to the HCl present in LCT to iodine and the liberated iodine is determined by four different procedures which inturn quantify LCT at varying detection range and sensitiveness. Two direct titrimetric procedures involve titration of iodine by thiosulphate either towards starch end point (method A) or potentiometrically (method B). Both the methods have a reaction stiochiometry of 1: 1 (LCT: liberated iodine) and have quantification ranges of 2–20 mg LCT for method A and method B. The liberated iodine is also measured spectrophotometrically at 350 nm (method C) or the iodine-starch complex measured at 570 nm (method D). In both the methods, the absorbance is found to be linearly dependent on the concentration of iodine which in turn is related to LCT concentration. The calibration curves are linear over 5–40 and 1.25–12.5 mg mL−1 LCT for method C and method D, respectively. The calculated molar absorptivity and Sandel sensitivity values are 1.0 × 104 L mol−1 cm−1 and 0.0435 mg cm−2, respectively for method C, and their respective values for method D are 2.9 × 104 L mol−1 cm−1 and 0.0156 mg cm−2. The intra-day and inter-day accuracy and precision studies were carried according to the ICH guidelines. The method was successfully applied to the analysis of two brands of tablets LCT. The accuracy was also checked by placebo blank and synthetic mixture analyses besides recovery study via standard addition procedure.