Acid In Aqueous Phase Research Articles

Thermal behaviour of Peracetic Acid for the epoxydation of vegetable oils in the presence of catalyst

Abstract Peroxyacids are commonly used in chemical processing, synthesis and bleaching. Recently, they have been demonstrated to be very versatile for the epoxidation of unsaturated oil, aiming at the synthesis of polyepoxides (plasticizer, resins and adhesives). These processes are characterized by high yields and selectivity. However, due to their hazard and instability, the peroxy reactants are often obtained from the corresponding organic acid in situ by combination with Hydrogen Peroxide, in the presence of a mineral (Sulphuric or Phosphoric) acid as catalyst. The aim of this study is to analyse the thermal stability of the catalytic system used for vegetable oil peroxidation with the purpose of operating under safety conditions and then identify the safety parameters necessary to prevent the runaway reaction. This paper presents the study of the decomposition of peroxyacetic acid in aqueous phase by using a Thermal Screening Unit. Also, the effect of the presence of the acid catalysts was analysed.

Complexation of Eu(III) in a Completely Incinerable Ionic Liquid System: A Luminescence Spectroscopy Approach

AbstractLuminescence study of europium(III) ion has been carried out in a completely incenerable (CHON based) ionic liquid system. The ionic liquid used in the study was trioctylmethylammonium nitrate ([N1888][NO3] while the extractant used was N,N‐dioctyl‐2‐hydroxyacetamide (DOHyA). The complexation of europium(III) in such type of ionic liquid system and its elaboration by luminescence study is highlighted for the first time in this paper. The luminescence behaviour of europium(III) was ascertained as a function of various parameters, such as aqueous phase acidity, extractant concentration, initial metal ion concentration, types of ionic liquid diluents etc. The luminescence intensity of Eu(III) was remarkably high in the ionic liquid medium at all aqueous phase acidity (0.1 M to 5 M HNO3) as compared to that of in aqueous phase. The luminescence lifetime of Eu(III) in this complex is in the range of 360 μs – 550 μs which is quite higher than that of aqueous phase (107 μs ‐ 130 μs), suggesting the luminescence enhancement is a result of reduction in non‐radiative decay channels in ionic liquid medium. The emission peak of Eu(III) in DOHyA was compared with that of DOMeA (N,N‐dioctyl‐2‐methoxyacetamide) in ionic liquid medium in order to highlight the presence of –OH group in DOHyA. The luminescence spectra of Eu(III) was also investigated by changing the type of aqueous phase acidity from nitrate ion to chloride ion and the results are detailed in the paper.

An automated continuous homogeneous microextraction for the determination of selenium and arsenic by hydride generation atomic fluorescence spectrometry

An automated continuous homogeneous microextraction approach based on a flow system has been developed and coupled with a hydride generation atomic fluorescence spectrometry system (HG-AFS). The developed approach was applied for the determination of trace arsenic and selenium in environmental water and liver samples. The nonanoic acid was investigated as a switchable hydrophilicity solvent (SHS) for homogeneous microextraction of As(III) and Se(IV) complexes with pyrrolidinedithiocarbamate (PDC). The procedure involved on-line mixing ammonium PDC (aqueous phase), sodium nonanoate (aqueous phase) and acid sample solution resulting in the formation of SHS (nonanoic acid) dispersed into the acid aqueous phase. By this continuous process, analytes complexes with PDC were formed and extracted into the fine SHS droplets followed by retention into a monolithic column packed with block of porous PTFE. Finally, the retained complexes were eluted with NaOH solution and delivered to the HG-AFS system. The limits of detection, calculated from a blank test based on 3σ, were 0.01μgL−1 for both analytes.

N-Alkyl calix[4]azacrowns for the selective extraction of uranium.

The selective extraction of uranium by N-octylcalix[4]azacrown (NOCAC) and N-ethylhexylcalix[4]azacrown (NEHCAC) was investigated. The ligands were synthesised in three steps through the functionalisation of t-butyl calix[4]arene at the distal-1,3-positions of the lower rim with ethyl acetate groups followed by cyclisation with (imino)bis(ethane-2,1-diyl)diamide. A detailed investigation on the effect of various parameters, such as the aqueous phase acidity (sulfuric acid), the ionic strength, and ligand concentration, on the extraction of uranium(vi) has been conducted. The effect of the H2SO4 concentration has been studied from 0.02 to 3 M. Preliminary studies carried out on NOCAC in dodecane/octanol diluents showed that the uranium extraction from sulfuric acid is more efficient at a low H2SO4 concentrations. The stoichiometry of complexation was estimated from the slope method, NMR titration, and electrospray ionisation-mass spectrometry analysis. Both ligands were found to be highly selective for uranium(vi) over other competitive cations present in a simulated leach solution containing seven competitive cations. The successful recovery of the uranium from the organic phase has been performed thanks to stripping steps involving ammonium oxalate, ammonium carbonate, and sodium carbonate as stripping agents.

Ethyl acetate fraction of Cymbopogon citratus as a potential source of antioxidant compounds

New fraction from a lemongrass acidic aqueous phase as a source of compounds with remarkable antioxidant properties by different in vitro mechanisms.

Extraction and recovery of soft metal ion by porous silica coated by hydrophilic polymer gel with hexavalent nitrogen-donor ligand

ABSTRACTA hydrophilic N-isopropylacrylamide (NIPA) gel copolymerized with a hexavalent nitrogen donor ligand, N,N,N’,N’-tetrakis(4-propenyloxy-2-pyridylmethyl)ethylenediamine (TPPEN), adsorbs soft metals selectively from the acidic aqueous phase. We are developing porous silica particles coating the TPPEN-NIPA gel with high TPPEN content thinly on the pore surface of porous silica by a new gel-coating method using surface tension. Half of the pore volume of the silica particles remained by the coating of the TPPEN-NIPA gel with the high TPPEN content of 30 mol%. A large separation factor (SF) of Cd(II)/Eu(III) of 60 was observed at pH 2. The proposed chromatographic agent with the high TPPEN content is applicable for practical use.

Dynamic Light Scattering and FTIR Spectroscopic Investigations on the Reverse Micelles Produced During the Extraction of Nd(III) and Nitric Acid in Tetra Ethylhexyl Diglycolamide

AbstractThe aggregation behaviour of reverse micelles, formed during the extraction of neodymium nitrate and nitric acid, in an organic phase composed of tetra‐bis(2‐ethylhexyl) diglycolamide (TEHDGA) in n‐dodecane (n‐DD) was studied, at various temperatures. The organic phase, 0.2 M TEHDGA/n‐DD was equilibrated with aqueous solutions of nitric acid in the presence and absence of neodymium nitrate. At certain nitric acid and Nd(III) concentration in aqueous phase, the organic phase underwent splitting into two phases, with top phase known as “diluent rich phase”, the other one known as “third phase” or “metal ion rich phase”. Dynamic light scattering, attenuated total reflectance (ATR) ‐Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopic methods were employed for probing the size and distribution of aggregates present in the organic phase before and after splitting. The investigations revealed that the aggregates, formed in organic phase, interact efficiently with the extracted metal ions and these interactions increased with increase in the concentration of nitric acid and neodymium nitrate in organic phase. In addition, the interaction among the reverse micelles in third phase appear to be very strong as compared to that observed in the organic phase before third phase formation, and such strong interactions resulted in a merger and narrow distribution of reverse micelles in third phase.

NdFeB magnet recycling: Dysprosium recovery by non-dispersive solvent extraction employing hollow fibre membrane contactor

Hollow Fibre Membrane (HFM) operation in non-dispersive solvent extraction (NDSX) mode has been successfully employed for the separation of dysprosium from NdFeB magnetic scrap material using EHEHPA as an extractant. Effect of various hydrodynamic parameters including aqueous phase acidity, extractant concentration, Dy concentration in feed, phase ratio and flow rate were investigated to optimize the condition for quantitative recovery of dysprosium from the leach liquor obtained by the dissolution of hard disk drive (HDD) in nitric acid media. 0.5 M EHEHPA, 0.3 M HNO3 as aqueous feed phase, 100 ml/min flow rate and phase ratio of 1:1 were found to be optimum for both the cycle test runs. Taking the advantage of fast extraction kinetics of dysprosium, two cycle HFM-NDSX approach was adopted to concentrate Dy from 20 to 83% in first cycle while raising its purity >97% in the second cycle. The overall process also yielded neodymium rich by-product for its further purification.

Simple and Rapid Dual-Dispersive Liquid-Liquid Microextraction as an Innovative Extraction Method for Uranium in Real Water Samples Prior to the Determination of Uranium by a Spectrophotometric Technique.

An innovative, rapid, and simple dual-dispersive liquid-liquid microextraction (DDLL-ME) approach was used to extract uranium from real samples for the first time. The main objective of this study was to disperse extraction solvent by using an air-agitated syringe system to overcome matrix effects and avoid dispersion of hazardous dispersive organic solvents by using heat. The DDLL-ME method consisted of two dispersive liquid-liquid extraction steps with chloroform as the extracting solvent. Uranium formed complexes with 4-(2-thiazolylazo) resorcinol in the aqueous phase and was extracted in extracting solvent (chloroform) after the first dispersive liquid-liquid process. Uranium was then back-extracted in the acidic aqueous phase in a second dispersive liquid-liquid process. Finally, uranium was determined by a spectrophotometric detection technique. The variables that played a key role in the proposed method were studied and optimized. The LOD and sensitivity enhancement factor for uranium were found to be 0.60 µg/L and 45, respectively, under optimized conditions. Calibration graphs were found to be linear in the range of 5.0-600 µg/L. The RSD was 2.5%. Reliability of the proposed method was verified by analyzing certified reference material TM-28.3.

Capillary-Driven Sensor Fabrication of Polydiacetylene-on-Silica Plate in 30 Seconds: Facile Utilization of π-Monomers with C18- to C25-Long Alkyl Chain.

By utilizing the capillary-force-driven action, a novel polydiacetylene-based sensor on the porous silica plate was developed within 30 s for π-diacetylene monomers with variable chain lengths. This method enables one to utilize diacetylene monomers even with the shorter alkyl chain length of C18–C21, which has not been possible with conventional methods. The invented sensor platform employing shorter monomers was found to perform better, as was demonstrated for gaseous and aqueous analytes, i.e., ammonia gas and nucleic acids in aqueous phase. This new polydiacetylene platform opens up the development of quick and easy fabrication and the use of chemical and biochemical chips.

Tuning aggregation-induced emission properties with the number of cyano and ester groups in the same dibenzo[b,d]thiophene skeleton for effective detection of explosives

Three aggregation-induced emission (AIE) active molecules were designed and synthesized where they have the same dibenzo[b,d]thiophene skeleton but the different number of cyano and ester groups. Aggregation-induced fluorescence experiments reveal that compounds 1–3 show a remarkable bathochromic-shift and AIE phenomenon. With the enhancement of water volume fractions, the intensity of emission band presents a step-by-step increase when fw=0–70% in compound 1, where the maximum emission wavelength is 564nm in the aggregated state and the peak area when fw=90% is 5-fold more than that when fw=0%. Furthermore, fluorescence titration results demonstate that this family of dibenzothiophene derivatives 1–3 is one of potential selective chemosensors for picric acid in aqueous phase and the obvious color change of the cellulose-based dibenzothiophene mixtures is illustrated with the addition of different explosives. In addition, theoretic computational studies on related luminogens have been carried out. To the best of our knowledge, this is the first fabrication of cellulose-based dibenzothiophene composites exhibiting AIE properties for effective detection of explosives.

Fabrication of Channel Type Mixing Devices for Efficient Solvent Extraction for High Purity Silica Production

As one of the most cost-effective methods to produce solar-grade silicon (SOG-Si), purification of silica solution by extracting its impurities through wet chemical processes has been proposed. This paper reports on the design of channel type reactor for liquid-liquid extraction to purify silica solution, focusing particularly on the extraction of B (boric acid) in aqueous phase with 2,2,4-trimethyl-1,3-pentanediol (TMPD) in organic phase. The reactor fabricated by 3D printing technology was designed to have two characteristic structures: (i) a throat structure that shows gradually diverging part after converging near Y shaped inlets and (ii) obstacles structure on downstream. Two solutions were made to contact with each other by turbulent mixing around the throat structure, causing small droplets formation that was dispersed and retained efficiently even on downstream by obstacles structure. This droplet dispersion shortens diffusion distance of boric acid to meet TMPD at the liquid-liquid interface, providing efficient mass transfer. At higher flow rate i.e., 380 ml/min, the extraction efficiency was 97.43% after the multi stage process. The results suggest that the channel type reactor designed here is profitable for elimination of impurities, such as B or P, in silica solution to produce SOG-Si.

Application of dual cloud point extraction for the enrichment of zinc in serum samples of psychiatric patients prior to analysis by FAAS

It is reported in literature that zinc (Zn2+) has antidepressant activity. In present study Zn2+ was analyzed in blood serum of male patients having various psychiatric disorders (schizophrenia, depression, bipolar). As it is usually present in trace levels. Hence a novel, environmental friendly, dual-cloud point extraction (d-CPE) method was developed for the enrichment of its trace levels in acid digested serum samples. In the first step of d-CPE, Zn2+ was complexed with 1-(2-pyridylazo)-2-naphthol (PAN), and the complex was entrapped in a nonionic surfactant (Triton X-114). After achieving cloud point by heating, the mixture was separated into two layers i.e. aqueous and surfactant-rich by centrifugation. In second step of d-CPE, the analyte complex in the surfactant-rich phase was treated wih acid to extract back the metal analytes in acidic aqueous phase, the mixture was again heated upto cloud point and the whole procedure was repeated. This time the aqueous phase, having the metals, was taken and subjected to FAAS using conventional nebulization. The accuracy of the developed methodologies (conventional and d-CPE), were verified by their application to certified reference material of serum (CRM). Reliability of the method was checked by relative standard deviation (%RSD), which was found to be <5%. The limit of detection and limit of quantification were calculated for the proposed method as 1.09μg/L, and 3.63 respectively and enhancement factor was found to be 40. The developed procedure was successfully applied to the serum samples of patients (male) having different psychiatric disorders and non-psychiatric control subjects for the determination of Zn2+.

On-line Preconcentration of Pd(II) Using Polyamine Silica Gel Filled Mini Column for Flame Atomic Absorption Spectrometric Determination

In this study, a novel method for determination of Pd(II) ions at trace level was developed using on-line preconcentration onto polyamine group bonded silica (PA-SG) with flame atomic absorption spectrometric determination. Pd(II) uptake dynamics of PA-SG was studied batchwise by investigating acidity and chloride concentration of aqueous phase, contact time and initial concentration of Pd(II) ions. The Pd(II) adsorption capacity of PA-SG was found to be 158.7 mg g−1 from aqueous phase containing 0.1 M HCl. The on-line preconcentration procedure of Pd(II) was optimized with main analytical parameters including sample and eluent flow rate, eluent type and volume and matrix ions. The optimum eluent type and flow rate of sample and eluent were found to be 1.0% thiourea in 1.0 mol L−1 HCl and 7.5 mL min−1, respectively. The preconcentration factor and sampling frequency were calculated to be 23.9 and 20 h−1, respectively. The calibration graph was linear over the range 10–200 µg L−1. The limits of detection (3σ) and quantification (10σ) values were computed to be 3 µg L−1 and 10 µg L−1, respectively. The RSD, % was found to be 4.6% for five measurement of 25 µg L−1 of Pd(II) ions. The accuracy of the developed method was successfully checked by determination of Pd(II) level of certified reference material platinum ore (SARM 7B). The proposed method was successfully applied for Pd(II) determination in various environmental water samples such as river, lake, sea and tap water, and spent auto catalyst.

Studies on the uptake of Am(III) and Eu(III) on ionic liquid modified polystyrene-divinyl benzene

Abstract Imidazolium bis(2-ethylhexyl)phosphate ionic liquid was anchored on a polystyrene-divinylbenzene (PS-DVB) copolymer and the product (R-Im-DEHP) was studied for the extraction of Am(III) and Eu(III) from dilute nitric acid medium to examine the feasibility using the anchored adsorbent for their mutual separation. The effect of various parameters such as the duration of equilibration, concentration of nitric acid, europium ion, and diethylenetriaminepentaacetic acid (DTPA) in aqueous phase on the distribution coefficient (K d) of Am(III) and Eu(III) was studied. The distribution coefficient of Am(III) and Eu(III) decreased with increase in the concentration of nitric acid. Rapid extraction of metal ions in the initial stages of equilibration followed by the establishment of equilibrium occurred within 4 h. The data on the rate of uptake of Am(III) and Eu(III) were fitted into pseudo-first order and pseudo-second order rate equation. The extraction isotherm was fitted to Langmuir and Freundlich adsorption models and the apparent europium extraction capacity was determined. The mechanism of extraction was elucidated and the conditions needed for efficient separation of Am(III) from Eu(III) was optimized using DTPA. The study indicated the possibility of using R-Im-DEHP for the separation of Eu(III) from Am(III) with high separation factors.

Ultrasonically Dispersed Ionic Liquid-Based Microextraction of Lead in Biological Samples of Malnourished Children Prior to Analysis by Flame Atomic Absorption Spectrometry.

In the present study, a simple ultrasonically dispersed modified liquid-phase microextraction method was developed for the extraction of lead (Pb) from blood and scalp hair samples of malnourished children (MNC). The complexation of Pb was executed by means of the complexing agent, ammonium pyrrolidinedithiocarbamate (APDC), whereas extraction was carried out through the ionic liquid (IL), 1-butyl-3-methylimidazolium hexafluorophosphate. Ultrasound energy was used for the dispersion and extraction of the metal complex into an IL because it enhances the extraction of the metal complex into infinite IL drops at a temperature range of 40-80°C for 1-5 min. After sonication, the enriched analyte phase was separated by centrifugation. Nitric acid (HNO3; 0.5-2 mol/L) was added to the IL-enriched phase to back-extract the analyte into the acidic aqueous phase and analyzed by flame atomic absorption spectrometry. Various experimental parameters that affect the efficiency of the proposed method, such as volume of IL, concentration of the complexing agent, pH, ultrasonication time and temperature, and concentration of HNO3, were optimized. The enhancement factor was calculated as 70. The LOD for Pb ions was found to be 0.19 μg/L, with an RSD of <5%. Accuracy was ensured by applying the procedure to a certified reference material for whole blood and scalp hair. The developed procedure was successfully applied for the analysis of the concentration of Pb ion in whole-blood and scalp hair samples of MNC from different areas of Sindh, Pakistan. The concentration of Pb among MNC was 2-fold higher than the referent.

Application of Turbiscan in the homoaggregation and heteroaggregation of copper nanoparticles

With the development of industries, copper nanoparticles (Cu NPs) have been abundantly discharged into natural water and may threaten the safety of aquatic environments. The stability (such as homoaggregation and heteroaggregation) of Cu NPs in aqueous phase may affect their toxicity. Turbiscan, including three kinds of data processing methods (transmitted intensity (T), variation of average transmitted intensity (ΔT) and Turbiscan stability index (TSI), were used to investigate the homoaggregation and heteroaggregation of Cu NPs with humic acid (HA) and kaolin in aqueous phase. T and TSI were used to analyze Cu NPs-kaolin and Cu NPs-HA-kaolin systems, respectively, whereas T and ΔT were used to analyze Cu NPs and Cu NPs-HA systems. Results showed that the stability of the system is influenced by the dissolution and sedimentation of Cu NPs, and the aggregation and sedimentation of Cu NPs, HA and kaolin. When pH is 4, the dissolution of Cu NPs is the main factor affecting the system stability. Kaolin may reduce the stability of system by sedimentation or impeding the dissolution of Cu NPs. When pH is 8, the aggregation and sedimentation of Cu NPs mainly affect the system stability. Kaolin renders the system unstable by promoting the aggregation of Cu NPs. In addition, HA improves the stability of the system by inhibiting the aggregation of Cu NPs and kaolin when pH=4 and 8. Ionic strength reduces the stability of system by condensing electric double layer. Therefore, Turbiscan can be used to study both homoaggregation and heteroaggregation in a relatively long period (12h), and three kinds of data processing methods can be applied based on the properties of the samples.

SECM study of hydrogen photogeneration in a 1,2-dichloroethane | water biphasic system with decamethylruthenocene electron donor regeneration

This paper reports light driven hydrogen evolution reaction (HER) at 1,2-dichloroethane|water (DCE|W) interface using photoexcited decamethylruthenocene (DMRc) as electron donor. DMRc is in situ regenerated by electroreduction of its oxidized form (DMRc+) formed during HER as a by-product. This enables continuous HER using small amount of DMRc. Proton transfer from the acidic aqueous phase to the DCE phase is ensured by negative chemical polarization of the liquid|liquid interface. The reduction of protons in DCE occurs only after excitation of DMRc by light. Voltammetry performed with the organic droplet-modified glassy carbon electrode immersed in the aqueous electrolyte solution of various anions, indicated that oxidation of DMRc is followed by an anion insertion from water into the organic phase. We demonstrate that DMRc can be electrochemically regenerated at the microelectrode positioned close to the interface between two immiscible electrolyte solutions (ITIES) by the scanning electrochemical microscopy. Regeneration of the electron donor allows further development of biphasic system towards continuous hydrogen generation platform.

Separation of Am(III) from nitric acid medium by phosphonium ionic liquid–hydroxyacetamide mixture

A strongly hydrophobic phosphonium ionic liquid, trihexyltet radecylphosphonium bis(trifluoromethanesulfonyl)imide ([P66614][NTf2]) was employed as the diluent for the extraction behavior of Am(III) using N,N-dihexyl-2-hydroxyacetamide(DHHy) as extractant. The extractibility of americium(III) in [P66614][NTf2] phase was measured as a function of various parameters such as aqueous phase acidity (0.1–8 M), extractant concentration (0.01–0.15 M), equilibration time (5–120 min) and temperature (298–333 K). The extraction performance observed in DHHy/[P66614][NTf2] was compared with those observed in N,N-dihexyloctamide (DHOA) in [P66614][NTf2] and DHHy in other diluents such as [C4mim][NTf2] and n-dodecane. The effect of temperature on D Am(III) in ionic liquid system and recovery of Am(III) from the loaded phase were ascertained in detail.

Recovery of cobalt from spent lithium ion batteries by using acidic and basic extractants in solvent extraction process

Solvent extraction studies of cobalt from aqueous chloride solution have been focused on using three acidic (Cyanex301, D2EHPA, Cyanex272) and two basic (Alamine336, TOA) extractants. The effects of operating variables, such as time, chloride or sulfate ions, aqueous phase acidity, concentration of the extractant, temperature and various acid solutions in the metal stripping from the loaded organic phase were studied. The values of the stoichiometric coefficients for reactive extraction of cobalt from aqueous chloride solution were calculated by using the relationship between log D and equilibrium concentration of the five extractants. According to the results, Cyanex301 extraction system led to an increase in extraction efficiency of cobalt from aqueous solution in the low concentration range (0.1 M) from the diluted chloride solution (pH = 6–7), while, TOA extractant was an appropriate extractant for cobalt extraction in chloride acidic aqueous solution (6 M HCl). The results illustrate that the increase in temperature was favorable for the extraction cobalt with the five extractants. In addition, the useful data for recovery of cobalt from the synthetic leach liquor of the spent lithium ion batteries were obtained from the experimental data.