Inorganic Acid Solutions Research Articles

Separation and determination of lead in human urine and water samples based on thiol functionalized mesoporous silica nanoparticles packed on cartridges by micro column fast micro solid-phase extraction

An efficient method based on thiol functionalized mesoporous silica nanoparticles (HS-MSNPs) was used for extraction of lead ions (PbII) from urine and water samples by packed column micro solid phase extraction (PC-MSPE). By procedure, 15 mg of HS-MSNPs packed in syringe cartridges (SC, 5 mL) with cellulose membrane and pH adjusting at 5.5-6.5. Then, the lead of urine and water sample was efficiently extracted on HS-MSNPs after pushing the plunger of a syringe. Finally, the Pb (II) was back-extracted with inorganic acid solution and the remained solution determined by electrothermal atomic absorption spectrometry (ET-AAS). By optimization conditions, the enrichment factor, LOD, linear range and RSD% was obtained 24.8, 0.04 μg L-1, 0.12-5.5 μg L-1 and less than 5%, respectively for 5 mL of urine samples. The validation was confirmed by spiking of real samples and using certified reference material (CRM, NIST) in water and urine sample.

Comparative Studies of Combined Influence of Variables on the Esterification Degree of Pectin Extracted by Sulfuric Acid and Citric Acid

The influence of extraction variables on degree of esterification (DE) of pectin was studied due to the significant effects of DE on the properties of the pectin-based functional biomaterials. The extracting agents (sulfuric acid and citric acid), pH value of extraction solution, extraction time, and temperature were selected to study the hydrolysis reaction of carboxylic acid ester by response surface methodology (RSM). The hydrolysis reaction occurred more violently in the weak organic acid solution than that in the strong inorganic acid solution. The DE was significantly influenced by pH of extraction solution, extraction time, and temperature through the analysis of variance. In addition, the values of DE reduced with the increasing of extraction temperature, lapse of time, and decreasing of pH value. What is more, the effects of extraction conditions on the yield, monosaccharide composition, content of protein, and ferulic acid were also studied. It is evident that the lower pH value contributed to higher extraction yield. The content of Total CH and GalA of pectin extracted by sulfuric acid were higher than that of pectin extracted by citric acid, and the content of monosaccharide showed an opposite trend.

Mechanisms of potassium release from calcareous soils to different salt, organic acid and inorganic acid solutions

Mechanisms of potassium (K) release and fixation in calcareous soils may differ from non-calcareous soils. In the current investigation, four soils with different properties were extracted three and 10 times (45 and 150min, defined as short- and long-term respectively) with 0.025molL−1 CaCl2, HCl and oxalic and citric acid solutions and the contents of calcium (Ca), magnesium (Mg), aluminium (Al) and K in the extracts were determined. Immediately after K extraction, 500mg kg–1 of K (as KCl) was added to the remaining soils and shaken for 24h and K-fixation capacity was determined. No significant difference was observed between CaCl2 and HCl solutions in K extraction from soils in the short- and long-term experiments; the concentrations of Ca, Mg and Al in the extractants showed that HCl was not able to dissolve soil minerals and the soils released K via exchange reaction of Ca (originated from CaCO3 dissolution by HCl) with interlayer K. The organic acids had similar behaviour to each other in the short-term experiment; however, partial dissolution of minerals by citric acid was observed. Oxalic acid extracted less K than other solutions in the short-term experiment due to precipitation of soluble Ca as oxalate salt and thereby less exchange of soluble Ca with non-exchangeable K. Oxalic and citric acids dissolved K-bearing minerals and released K in the long-term experiment, but oxalic acid was more effective. The K-fixation capacity of soils was lower when treated with organic acids than with CaCl2 and HCl, possibly due to the dissolution of K-fixing minerals like smectite and illite by oxalate and citrate. Long-term treatment of soils with different solutions decreased K-fixation capacity of soils due to dissolution of K-fixing minerals or flocculation of minerals by Ca and slower K diffusion to the interlayer. With respect to the highly calcareous nature of the studied soils, the soluble cations in calcareous soils (predominantly Ca and Mg) may have been exchanged with non-exchangeable K of clay minerals and buffered soluble K as well as organic acids produced by plant roots and microorganisms.

Tannic acid functionalized graphene hydrogel for organic dye adsorption

Water purification provides a feasible way to relieve the pressure of water shortage and water pollution which we are facing and adsorption is one of the most effective ways to turn polluted water into clean water. Here, we prepared graphene-tannic acid hydrogel using graphene oxide and tannic acid, a natural green reducer and adsorbent, through one-step hydrothermal method. The composition, structure, and morphology of the compounds were systematically examined. The adsorption of dyes was mainly influenced by the morphology and chemical properties of gel. The addition of tannic acid, a molecule rich in oxygen containing functional groups, changed the surface chemistry of graphene sheets and microstructures of gels, which was beneficial for contaminate adsorption. Compared with reduced graphene oxide hydrogel, the graphene-tannic acid hydrogel showed an outstanding adsorption capacity for organic dye methylene blue, more than 500 mg/g at pH 10 and the maximum adsorption capacity was up to 714 mg/g. After adsorption, ethanol and inorganic acid solution can be used as desorption agent and there was no significant adsorption capacity loss after 5 cycles.

A clinical and histopathological comparison of the effectiveness of salicylic acid to a compound of inorganic acids for the treatment of digital dermatitis in cattle

Bovine digital dermatitis (DD) is a painful infectious disease, causing lameness, reduced animal welfare, and production losses in dairy herds. The main factors contributing to DD are an infection with Treponema spp. and poor hygiene. Topical treatment has primarily consisted of antibiotics; however, the demand for effective nonantibiotic alternatives is increasing. The objective was to evaluate the performance of 3 nonantibiotic topical treatments (salicylic acid and a compound of inorganic acids in a 20% solution and in a dry form) on DD in a commercial dairy herd. Within the 30-d test period, 42 DD lesions on 33 Holstein cows were assigned to receive 1 of the 3 treatments. Lesions were biopsied before and after treatment and were clinically evaluated 5 times. Improved lesions were clinically defined as either healed (regeneration of the skin) or healing (dry lesions covered by a scab). Unhealed lesions were defined as either active [with a raw, moist, strawberry-like (granulating) surface] or mature (with a raised papillomatous appearance). The effectiveness of treatment was evaluated histopathologically using the following scores: 0 (no spirochetes present), 1 (small number of spirochetes present in the epidermis), 2 (moderate number of spirochetes present and reaching an intermediary level in the epidermis), and 3 (large number of spirochetes present and reaching the deepest part of the epidermis or the superficial dermis). The improvement rate was 10/14 (71%) for salicylic acid, 11/15 (73%) for the inorganic acid solution, and 8/13 (62%) for the inorganic acid powder. The analysis showed no difference among treatments. The association between clinical score and histopathological score was determined by an odds ratio. The odds ratio of a healed lesion having spirochetes in the epidermis was 0.58 and that of an active DD lesion having spirochetes in the epidermis was 26.5.

Traitement Des Phosphates Naturels De Tahoua (Niger) Par Quelques Acides Conventionnels

Within the framework of upgrading natural phosphate of Tahoua, a study was carried out on the dissolution of ore by inorganic acid (sulfuric acid, nitric acid) and organic acid (citric acid) solutions according to pH and attack time. The obtained results show a sudden drop of dissolution rate at pH above 2 and a dissolution almost zero beyond pH 4. The kinetic study shows fast dissolution of ore one hour after the attack. However, this dissolution is slow beyond one hour with few dissolved phosphorus during a relatively high period of time. Furthermore, the sulfuric acid solutions dissolve the ore better than those of citric and nitric acid: 41.07%; 37.03% and 35.64% of dissolved phosphorus respectively for sulfuric, citric and nitric acid solutions at the concentration of 1mol/L.

Coupling dispersive liquid-liquid microextraction to inductively coupled plasma atomic emission spectrometry: An oxymoron?

Coupling dispersive liquid-liquid micro-extraction (DLLME) to inductively coupled plasma atomic emission spectrometry (ICP-AES) is usually troublesome due to the limited plasma tolerance to the organic solvents usually employed for metal extraction. This work explores different coupling strategies allowing the multi-element determination by ICP-AES of the solutions obtained after DLLME procedures. To this end, three of the most common extractant solvents in DLLME procedures (1-undecanol, 1-butyl-3-methyl-imidazolium hexafluorophosphate and chloroform) have been selected to face most of the main problems reported in DLLME-ICP-AES coupling (i.e., those arising from the high solvent viscosity and volatility). Results demonstrate that DLLME can be successfully coupled to ICP-AES after a careful optimization of the experimental conditions. Thus, elemental analysis in 1-undecanol and 1-butyl-3-methyl-imidazolium hexafluorophosphate extracts can be achieved by ICP-AES after a simple dilution step with methanol (1:0.5). Chloroform can be directly introduced into the plasma with minimum changes in the ICP-AES configuration usually employed when operating with aqueous solutions. Diluted inorganic acid solutions (1% w w−1 either nitric or hydrochloric acids) have been successfully tested for the first time as a carrier for the introduction of organic extractants in ICP-AES. The coupling strategies proposed have been successfully applied to the multi-element analysis (Al, Cu, Fe, Mn, Ni and Zn) of different water samples (i.e. marine, tap and river) by DLLME-ICP-AES.

Corrosion protection by organic coatings containing polyaniline salts prepared by oxidative polymerization

The aim of this work was to describe polyaniline salts synthesized and to assess the mechanical and anticorrosion properties of alkyd resin-based coating materials pigmented with them, in dependence on the pigment volume concentration and type. Polyaniline salts were prepared by oxidative polymerization in the solutions of inorganic (hydrochloric, phosphoric, and sulfuric) and organic (p-toluenesulfonic and 5-sulfosalicylic) acids. Polyaniline salts were characterized by thermal analysis and spectroscopic methods. Electrical conductivity was also measured by the van der Pauw method, and the molecular weight of the polyaniline was determined by gel permeation chromatography. Furthermore, the particle size of the solid salts was measured, and the morphology was studied by scanning electron microscopy. Subsequently, the parameters required to formulate pigmented organic coatings, i.e., density and critical pigment volume concentration were determined. A soybean oil-based fast drying alkyd resin of medium oil length was used as the binder for the organic coating material. Organic coatings containing the polyaniline salts at pigment volume concentrations 0%, 1%, 5%, 10%, and 15% were formulated and subjected to a standard accelerated cyclic corrosion tests. The organic coatings (paint films) were also subjected to mechanical tests and to the electrochemical test by potentiodynamic polarization studies.

The effect of monoethanolamine on conductivity and efficiency of electrodialysis of acid and salt solutions

Experimental studies of the specific conductivity (SC) are carried out for aqueous solutions of organic and inorganic acids and salts including those containing different amounts of monoethanolamine (MEA), which model the absorption solutions used in purification of gas mixtures from carbon dioxide and containing heatstable salts (HSS). It is shown that the addition of MEA to binary aqueous electrolyte solutions gives rise to changes in the SC: in the MEA concentration range from 0 to ∼1.5 M, the SC of the resulting ternary solutions increases but decreases again with the further increase in MEA concentration. This behavior of SC is typical also of aqueous binary amine solutions. It is shown that in the presence of MEA, the quantitative removal of dissolved acids and salts proceeds faster with the simultaneous increase in the specific energy consumption by a factor of 7–9 (up to 85.7–93.6 kJ/dm3). It is assumed that the reason for the decrease in SC and the enhancement of energy consumption at electrodialysis of mixed solutions is the probable existence of monoethanolamine both as free solvated ions and neutral molecules and as self-assembled associated structures (ion pairs and more complex particles) which involve also the ions of salts dissolved in amine-containing solutions.

Experimental Study of Montmorillonite Structure and Transformation of Its Properties under Treatment with Inorganic Acid Solutions

This paper discusses the mechanism of montmorillonite structural alteration and modification of bentonites’ properties (based on samples from clay deposits Taganskoye, Kazakhstan and Mukhortala, Buriatia) under thermochemical treatment (treatment with inorganic acid solutions at different temperatures, concentrations and reaction times). Treatment conditions were chosen according to those accepted in chemical industry for obtaining acid modified clays as catalysts or sorbents. Also, more intense treatment was carried out to simulate possible influence at the liquid radioactive site repositories. A series of methods was used: XRD, FTIR, ICP-AES, TEM, nitrogen adsorption, and particle size analysis. It allowed revealing certain processes: transformation of montmorillonite structure which appears in the leaching of interlayer and octahedral cations and protonation of the interlayer and –OH groups at octahedral sheets. In turn, changes in the structure of the 2:1 layer of montmorillonite and its interlayer result in significant alterations in the properties: reduction of cation exchange capacity and an increase of specific surface area. Acid treatment also leads to a redistribution of particle sizes and changes the pore system. The results of the work showed that bentonite clays retain a significant portion of their adsorption properties even after a prolonged and intense thermochemical treatment (1 M HNO3, 60 °C, 108 h).

Corrosion Properties of Titanium Obtained by the Method of Powder Metallurgy

We study the corrosion rate of titanium obtained by the method of powder metallurgy in aqueous solutions of inorganic acids. It is shown that the addition of titanium hydride to the original powder mixture increases the density of the material, decreases the actual contact area with aggressive media, and hence, enhances its corrosion resistance. However, we did not establish any clear relationship between the content of titanium hydride in the original powder mixture and the corrosion rate of the compacted material.

ASSESSMENT OF METAL RECOVERY FROM RAW SPENT HYDRODESULFURIZATION CATALYST THROUGH BIOLEACHING AND CHEMICAL LEACHING

The aim of this work is to evaluate the recovery of metals from a spent catalyst of diesel hydrodesulfurization (HDS), without any chemical, thermal, or physical pre-treatment, using the Acidithiobacillus thiooxidans FG-01 strain and chemical leaching. The spent catalyst is a hazardous waste due to the presence of organochlorine compounds, petroleum hydrocarbons, and heavy metals. Chemical leaching tests were performed with solutions of citric acid (20 g L-1), oxalic acid (20 g L-1), citric and oxalic acid mixture (1:1, 20 g L-1), and sulfuric acid (10 g L-1). The best results of metals recovery through chemical reaction were obtained when using the inorganic acid solution. The two-step bioleaching assays were conducted in 500 mL Erlenmeyer flasks, with a pulp density of 27.5 g L-1, and a sulfuric acid concentration of 20 g L-1. There were no differences between chemical and microbial leaching results. The A. thiooxidans FG-01 is a promising strain due to the recovery of Al (~65%), V (~25%), and Mo (~25%) from the raw solid residue.

The Phosphochlorinated Polymeric Sorbents for Sorption of Gold (III)

This study evaluated the simple methods to improve the sorptional capability of polymeric sorbent to gold (III) ions. The polymeric sorbents have been synthesized by a chemical modification of dithizone phosphorchlorinated PB. The structure and composition of functional polymers are studied by IR spectroscopy, X-ray fluorescence analysis, the diffusion of optical spectroscopy, scanning electron microscopy, thermogravimetric and elemental analysis. It found that the obtained sorbents had porous crosslinked structure and did not dissolve in any organic solvents, solutions of inorganic acids and alkalines. The sorption properties of the syntesized polymer sorbents onto gold (III) ion in aqueous solutions have been studied. It is found that the adsorption effect of gold makes 85% - 90% and the equilibrium sorption capacity of polymer sorbent is 137 mg/g in acidic media. In order to improve sorption efficiency of sorbents to gold ions, the non-covalent immobilization of organic sulfur containing compound to the polymer matrix was carried out. The gold embedded polymer matrix was characterized by SEM, EDX, XRD and visible absorption spectroscopy. The obtained results indicated that the polymeric sorbent contained metallic form of zero-valent gold. It was found that the average particle size of elemental gold crystals was 28.31 nm.

Nanostructured hard coatings: the key to safe operation of equipment in extreme conditions

Two main classes of hard coatings based on tungsten and tungsten carbides prepared by chemical gas-phase sedimentation are considered in this work. The coatings possess high hardness (11–40 GPa) and thickness (12–100 µm). Results on abrasive and corrosion resistance in solutions of hydrogen sulfide, inorganic acids, and other aggressive environment are presented. All these coatings are promising for use in extremely severe conditions of abrasive, corrosion, and erosive wear owing to a unique combination of chemical stability, hardness, viscosity, and crackand impact-resistance.

Study on the Electrochemical Characteristics of Multiwalled CNTs Decorated By Various Oxygen Functional Groups (Non-Aqueous and Aqueous based Electrolytes)

Functionalized nano carbon have been reported as promising cathode materials for Li ion battery (LIB).[1-2] Unlike the conventional Li intercalation into host material, the Li storage mechanism on this materials was thought to be the Faradaic reaction between surface functional groups and Li, C=O + Li+ + e- = C-O-Li.[1-2] Introducing functional groups on few walled carbon nanotubes (CNTs) by acid treatment resulted in Li storage capacity up to 120 mAh/g.[2] However, the origin of which functional groups is responsible for such reaction still elusive. A better understanding on the electrochemical characteristics of functionalized nano carbon is not only important for LIB storage but also aqueous based electrochemical systems. It is known that there are two major dominant surface groups present on functionalized CNTs; they are carboxyl and carbonyls.[3] To be able to study the electrochemical characteristics of different oxygen functional groups, controlling the type of surface groups on CNTs is obligatory. Here, different kind of functional groups are introduced onto multiwalled CNTs (VGCFX) by varying different oxidizing agent, such as reflux under inorganic acid solution or reacting with organic acid (i.e. citric acid). Furthermore, by annealing at certain temperatures, we also could selectively attain the functional groups present on the surface of CNTs. The electrochemical studies of oxygen functional groups are carried out in non-aqueous (organic) and aqueous based electrolytes, to obtain comprehensive knowledge on the functional groups reactivity. On the other hand, X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD) are extensively used to examine the type and amount of surface groups. Fig. 1 shows the C1s XPS spectra of two of different samples, they are acid treated CNTs (HA) and citric acid treated HA (HA-CA). Briefly, acid treated CNTs was derived from refluxing pristine CNTs in the mixture of H2SO4/HNO3, while citric acid treatment was conducted by mixing the HA with citric acid, followed by annealing in air at 300 oC. It can be seen from XPS scan, that HA-CA has an appeared peak relating to the carboxyl group (288.9 eV) than HA. This suggests that citric acid treatment is plausible to introduce carboxyl groups on the surface of multiwalled CNTs. The roles of the oxygen functional groups play in the electrochemical characteristics will be discussed in the presentation.

An improved extraction method of rapeseed oil sample preparation for the subsequent determination in it of azole class fungicides by gas chromatography

The distribution of 19 azole class pesticides in hexane/aqueous–organic mixtures systems and rapeseed oil (or oil solution in hexane)/organic solvents has been studied at 20±1°C. The distribution constants (P) and coefficients (D) between hydrocarbon and polar phase are calculated. It is found that all the studied pesticides are hydrophobic, i.e., in hexane–water system logP≫0. Replacement of water by organic solvents results in sharp logP falling, and their values become negative. It is revealed that solutions of strong inorganic acids in anhydrous acetonitrile extract azole class pesticides from hexane and vegetable oils most fully and selectively. In particular, the acidification of acetonitrile causes a drop of D values in 50–2000 times for the majority of the studied pesticides. This phenomenon was used for the development of the improved technique for the quantitative analysis of a widely used azole class pesticides, which can be presented at trace levels in rapeseed oil. The proposed methodology is based on dissociation extraction (DE) of azoles using perchloric acid in anhydrous acetonitrile, with following clean-up of acetonitrile extract from organic impurities by hexane and aqueous solution of dipotassium hydrogen orthophosphate, and final GC–ECD (gas chromatography with electron capture detection) determination of azole fungicides. The values of obtained recoveries were between 85% and 115% with RSD values below 10%. The obtained limits of quantitation, ranged from 3.0 to 300μgkg−1, are below the maximum residue levels (MRLs) set by the European Union for the majority of pesticides. The developed method was successfully applied to different rapeseed oil samples.

Automatic potentiometric determination of uranium in the presence of vanadium in mixed solutions of inorganic acids and ethanol

The effect of V on quantitative determination of U in solutions in the presence of phosphoric and sulfuric acids and of ethanol was studied. The nonexcludable component of the systematic error and Student’s test were chosen as criteria of the result validity. In phosphoric acid solutions, the presence of V leads to overestimation of the analysis results due to joint titration of V and U. The addition of Fe(III) in the course of sample preparation eliminates this effect. The underestimation of the analysis results, appearing in this case, is eliminated by adding sulfuric acid and ethanol in a definite ratio. For U determination in the presence of V, the media can be ranked in the following order with respect to analysis efficiency: phosphoric acid < phosphoric acid + ethanol < phosphoric acid + sulfuric acid < phosphoric acid + sulfuric acid + ethanol. The optimum medium for the U determination in the presence of V, allowing the permissible U/V weight ratio to be increased from 1 : 0.5 to 1 : 10, was determined.

Extraction Equilibrium of Dysprosium from Inorganic Acid Solutions with 2-Ethylhexylphosphonic Acid Mono-2-Ethylhexyl Ester

Extraction Equilibrium of Dysprosium from Inorganic Acid Solutions with 2-Ethylhexylphosphonic Acid Mono-2-Ethylhexyl Ester

The discharge current effect on the electrolyte nonequilibrium mass transfer rate under the action of an atmospheric glow discharge

The mass transfer rates obtained from experiments for aqueous solutions of inorganic acids and alkali are presented. It is shown that the nonequilibrium evaporation rate versus the discharge current characteristic has an S-shaped form. It is suggested that the break area in the current curve corresponds to the change of the mass transfer mechanism.

Middle-Phase Microemulsions Formed by n-Dodecyl Polyglucoside and Lauric-N-methylglucamide

The three-phase behaviors for the quaternary system of n-dodecyl polyglucoside or lauric-N-methylglucamide (MEGA-12)/n-alcohol/alkane/water have been studied with ϵ-β fishlike phase diagram. The increase of ϵ at constant β causes a series of phase inversions Winsor I(2) → III(3) → II . The physicochemical parameters, such as the mass fraction of n-butanol in the hydrophile-lipophile balanced interfacial layer (AS), the coordinates of the start and end points of the middle-phase microemulsion, and the solubilities of surfactant and n-butanol in alkane phase were calculated. The effects of different oils and aqueous media on the phase behavior, the composition of the interfacial layer, and the solubilizing power were investigated. It was found that the oil with small molecular volume increases the solubilizing power. In inorganic salt (NaCl) and acid (HCl) solutions, less n-butanol is needed than that in alkali (NaOH) solution to form middle- and single-phase microemulsions. The middle-phase microemulsions formed by n-dodecyl polyglucoside and lauric-N-methylglucamide were compared.