Fabrication of silane-modified magnetic nano sorbent for enhanced ultrasonic wave driven removal of methylene blue from aqueous media: Isotherms,kinetics, and thermodynamic mechanistic studies

In this study, we report a simple and economic one-pot synthesis of magnetite (Fe₃O₄) nanostructure and its modification with tetraethyl orthosilicate by coprecipitation method. The synthesized (Fe₃O₄@SiO₂) nano sorbent was applied for enhanced adsorptive removal of methylene blue by ultrasonic wave driven batch experiments. After successful synthesis, the nanostructure was characterized for their physical structure by FT-IR, VSM, TEM, and XRD. For the maximum adsorptive performance of nano sorbent, various parameters were optimized, such as dose, pH, time, concentration, and temperature. The adsorption mechanism was best fitted by Langmuir isotherm with a maximum capacity of 148.69 mg/g, while kinetics best fitted by pseudo-second-order kinetic. The synthesized nano sorbent was successfully applied for enhanced adsorptive removal of toxic methylene blue from aqueous media. The proposed method is promising and effective in terms of simplicity, cost operation, green energy consumption, reproducible, excellent reusability, and magnetically separability with fast kinetic.     

Rapid magnetic solid-phase extraction based on magnetite/silica/poly(methacrylic acid–co–ethylene glycol dimethacrylate) composite microspheres for the determination of sulfonamide in milk samples

A novel magnetic solid-phase extraction (MSPE) sorbent, magnetite/silica/poly (methacrylic acid–co-ethylene glycol dimethacrylate) (Fe₃O₄/SiO₂/P(MAA-co-EGDMA)), was developed. This MSPE material was prepared by distillation–precipitation polymerization of MAA and EGDMA in the presence of Fe₃O₄/SiO₂ microspheres with the surface containing abundant reactive double bonds. The resultant sorbent material was characterized by elemental analysis, electron microscopy, X-ray diffraction and Fourier-transformed infrared spectroscopy. In this work, eleven sulfonamides (SAs) were selected as model analytes to validate the extraction performance of this new MSPE sorbent. Noticeably, the extraction can be carried out quickly, the extraction time for the SAs onto Fe₃O₄/SiO₂/P(MAA-co-EGDMA) sorbent can be clearly shortened to 0.5 min. The desorption solution of SAs was analyzed by LC–MS/MS, and the results showed that the recoveries of these compounds were in the range of 87.6–115.6%, with relative standard deviations ranging between 0.9% and 10.8%; the limit of detection were in the range of 0.5–49.5 ng/L.     

Properties and Application of a Chelating Sorbent Prepared by Modification of LiChroprep-NH<Subscript>2</Subscript> with Calcon

A new chelating sorbent for metal ions was prepared by modification of chemically modified silica – LiChroprep-NH₂ with Calcon. The molecular mechanism of binding this reagent to the surface of the applied carrier is presented. The properties of this sorbent were compared to analogous sorbents with a plain silica carrier and chemically modified silicas – LiChroprep-RP containing Calcon. The advantages of the new sorbent compared to the silica and LiChroprep-RP chelating sorbents are demonstrated. The sorbent obtained was applied as stationary phase in solid-phase extraction (SPE) for separations of some chosen mixtures of metal ions and for additional purification of aqueous solutions of salts of alkali metals from trace amounts of heavy metals. The multiple use of the sorbent based on LiChroprep-NH₂ in sorption-desorption processes of metal ions without deterioration of its sorption capacity is demonstrated.     

Trace analysis of Pt (IV) metal ions in roadside soil and water samples by Fe3O4/graphene/polypyrrole nanocomposite as a solid-phase extraction sorbent followed by atomic absorption spectrometry

A novel Fe₃O₄/graphene/polypyrrole nanocomposite has been successfully synthesised via a simple chemical method and applied as a new magnetic solid-phase extraction (MSPE) sorbent for the separation and pre-concentration of trace amounts of Pt (IV) in environmental samples followed by flame atomic absorption spectrometric (FAAS) detection. The nanocomposite has been characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. Seven important parameters, affecting the extraction efficiency of Pt (IV), including pH, adsorption time, desorption solvent type and concentration, desorption time, elution volume and sample volume, were investigated. Under the optimised conditions, the calibration graph was linear in the range of 50–1500 μg L^?1 (R = 0.993). The detection limit and pre-concentration factor (PF) for Pt (IV) were found to be 16 μg L^?1 and 112.5, respectively. Under the optimised solid-phase extraction (SPE) conditions, the adsorption isotherm and the adsorption capacity of the nanocomposite for Pt (IV) were studied. Pt (IV) adsorption equilibrium data were fitted well to the Langmuir isotherm and the maximum adsorption capacity of the magnetic sorbent was calculated from the Langmuir isotherm model as 416.7 mg g^?1. The precision of the method was studied as intraday and interday variations. A relative standard deviation percentage (RSD%) value less than 3.0 indicates that the method is precise. Also, the accuracy of the method was tested by the analysis of the standard reference material (NIST SRM 2556) and by recovery measurements on spiked real samples. It was also shown that the optimised method was suitable for the analysis of trace amounts of Pt (IV) in roadside soil, tap water and wastewater samples.     

Polythiophene-coated Fe3O4 superparamagnetic nanocomposite: Synthesis and application as a new sorbent for solid-phase extraction

In the present work, a novel type of superparamagnetic nanosorbent, polythiophene-coated Fe₃O₄ nanoparticles (Fe₃O₄@PTh NPs), have been successfully synthesized. The synthesized NPs were characterized by scanning electron microscopy (SEM), Fourier transform-infrared (FT-IR) spectroscopy, and thermal gravimetric analysis (TGA). The synthesized Fe₃O₄@PTh NPs were applied as an efficient sorbent for extraction and preconcentration of several typical plasticizer compounds (di-n-butyl phthalate (DBP), di-(2-ethylhexyl) phthalate (DEHP), and dioctyl adipate (DOA)) from environmental water samples. Separation of Fe₃O₄@PTh NPs from the aqueous solution was simply achieved by applying external magnetic field. Separation and determination of the extracted plasticizers was performed by gas chromatography–flame ionization detection (GC–FID). Several variables affecting the extraction efficiency of the analytes i.e., amount of NPs sorbent, salt concentration, extraction time, and desorption conditions were investigated and optimized. The best working conditions were as follows: amount of sorbent, 100 mg; NaCl concentration, 30% (w/v); sample volume, 45 mL; extraction time, 10 min; and 100 μL of ethyl acetate for desorption of the analytes within 2 min. Under optimized conditions, preconcentration factors for DBP, DEHP, and DOA were obtained as 86, 194, and 213, respectively. The calibration curves were linear (R² > 0.998) in the concentration range of 0.4–100 μg L⁻¹ for both DEHP and DOA and 0.7–100 μg L⁻¹ for DBP. The limits of detection (LODs) were obtained in the range of 0.2–0.4 μg L⁻¹. The intra-day relative standard deviations (RSDs%) based on four replicates were obtained in the range of 4.0–12.3%. The proposed procedure was applied to analysis of water samples including river water, bottled mineral water, and boiling water exposed to polyethylene container (after cooling) and recoveries between 85 and 99% and RSDs lower than 12.8% were obtained.     

Dry Potassium-Based Sorbents for CO<Subscript>2</Subscript> Capture

Dry potassium-based sorbents were prepared by impregnation with potassium carbonate on supports such as activated carbon (AC), TiO₂, Al₂O₃, MgO, CaO, SiO₂ and various zeolites. The CO₂ capture capacity and regeneration property of various sorbents were measured in the presence of H₂O in a fixed bed reactor, during multiple cycles at various temperature conditions (CO₂ absorption at 50–100 °C and regeneration at 130–400 °C). The KAlI30, KCaI30, and KMgI30 sorbents formed new structures such as KAl(CO₃)₂(OH)₂, K₂Ca(CO₃)₂, K₂Mg(CO₃)₂, and K₂Mg(CO₃)₂·4(H₂O), which did not completely convert to the original K₂CO₃ phase at temperatures below 200 °C, during the CO₂ absorption process in the presence of 9 vol.% H₂O. In the case of KACI30, KTiI30, and KZrI30, only a KHCO₃ crystal structure was formed during CO₂ absorption. The formation of active species, K₂CO₃·1.5H₂O, by the pretreatment with water vapor and the formation of the KHCO₃ crystal structure after CO₂ absorption are important factors for absorption and regeneration, respectively, even at low temperatures (130–150 °C). In particular, the KTiI30 sorbent showed excellent characteristics with respect to CO₂ absorption and regeneration in that it satisfies the requirements of a large amount of CO₂ absorption (87 mg CO₂/g sorbent) without the pretreatment with water vapor, unlike KACI30, and a fast and complete regeneration at a low temperature condition (1 atm, 150 °C). In addition, the higher total CO₂ capture capacity of KMgI30 (178.6 mg CO₂/g sorbent) than that of the theoretical value (95 mg CO₂/g sorbent) was explained through the contribution of the absorption ability of MgO support. In this review, we introduce the CO₂ capture capacities and regeneration properties of several potassium-based sorbents, the changes in the physical properties of the sorbents before/after CO₂ absorption, and the role of water vapor and its effects on CO₂ absorption.     

Liquid-Solid Extraction of Vitamin D3 Metabolites from Plasma for Analysis by HPLC,GC/MS and Protein Binding Techniques

Abstract

Liquid-solid extraction of vitamin D₃ metabolites from human plasma using octadecylsilane bonded silica has been studied. Steroid-protein interactions were minimized by diluting the plasma (or serum) with two volumes of saline and passing the solution through the sorbent at 64°C. Highly purified secosteroid fractions were obtained by washing with aqueous methanol, drying the sorbent in situ with a stream of nitrogen for one minute and eluting with mixtures of hexane/chloroform. Recoveries of vitamin D₃ metabolites were essentially quantitative. Applications to the rapid analysis of 25-hydroxy- and 1α, 25-dihydroxy-vitamin D in plasma by high-performance liquid chromatography, gas chromatography-mass spectrometry or by a receptor protein assay are reported.     

High Efficiency Annular Denuder for Formaldehyde Monitoring

Abstract

A practical and correct methodology for evaluating CH₂O in air without sampling artifact formation is presented. Formaldehyde is collected on an annular denuder coated with bisulfite-triethanolamine. The sorbent layer is extracted with water and the solution analyzed by the chromotropic acid (CTA) procedure. Sorption efficiency and loading capacity have been investigated along with storage stability.

Results of laboratory validation studies have indicated that a small annular denuder was able to sample about 300 μg CH₂O without an appreciable decrease in the initial collection efficiency (99% at 2.5 1 min^?1).

Tests on storage stability before and after exposure have also demonstrated that both oxidation of bisulfite and release of CH₂O did not occur for time periods as long as 1 month.     

In-tube magnetic solid phase microextraction of some fluoroquinolones based on the use of sodium dodecyl sulfate coated Fe3O4 nanoparticles packed tube

In-tube magnetic solid phase microextraction (in-tube MSPME) of fluoroquinolones from water and urine samples based on the use of sodium dodecyl sulfate (SDS) coated Fe₃O₄ nanoparticles packed tube has been reported. After the preparation of Fe₃O₄ nanoparticles (NPs) by a batch synthesis, these NPs were introduced into a stainless steel tube by a syringe and then a strong magnet was placed around the tube, so that the Fe₃O₄ NPs were remained in the tube and the tube was used in the in-tube SPME-HPLC/UV for the analysis of fluoroquinolones in water and urine samples. Plackett–Burman design was employed for screening the variables significantly affecting the extraction efficiency. Then, the significant factors were more investigated by Box–Behnken design. Calibration curves were linear (R² > 0.990) in the range of 0.1–1000 μg L⁻¹ for ciprofloxacin (CIP) and 0.5–500 μg L⁻¹ for enrofloxacin (ENR) and ofloxacin (OFL), respectively. LODs for all studied fluoroquinolones ranged from 0.01 to 0.05 μg L⁻¹. The main advantages of this method were rapid and easy automation and analysis, short extraction time, high sensitivity, possibility of fully sorbent collection after analysis, wide linear range and no need to organic solvents in extraction.     

New adsorbent based on zeolite modified with hyperbranched polyesterpolybenzoylthiocarbamate

A new hybrid adsorbent based on zeolite modified with hyperbranched polyesterpolybenzoylthiocarbamate is presented. The structure and morphology of the sorbent are characterized by potentiometric titration, IR, ¹H and ¹³C NMR spectroscopy, and electron microscopy. The fundamental possibility of extracting transition metal ions has been demonstrated using the examples of Cu^II and Co^II ions. It is shown that the sorption capacity of the adsorbent to Cu_II salt is 25.34 mg g^?1. A method of sorbent regeneration is proposed.

     

Use of Sulfonated Cation-Exchange Resin Based on Hypercrosslinked Polystyrene for the Separation of Organic Acids

The use of sulfonated cation-exchange resins based on hypercrosslinked polystyrene (HCPS) and highly cross-linked polystyrene–divinylbenzene (80% divinylbenzene) for the separation of organic acids was studied. The influence of the concentration of the eluent, temperature of the chromatographic column, and concentration of acetonitrile in the eluent on the retention of aliphatic carboxylic acids in ion-exclusion chromatography was examined. The optimal separation of organic acids on the HCPS sorbent is attained at 65°C with the use of 10 mM H₂SO₄with or without acetonitrile addition as the eluent. The sorbent based on HCPS in combination with spectrophotometric detection is promising for the determination of organic acids and other weakly ionized and neutral compounds with low molecular mass in samples of complex composition (juices and beer).     

Facile synthesis of a boronate affinity sorbent from mesoporous nanomagnetic polyhedral oligomeric silsesquioxanes composite and its application for enrichment of catecholamines in human urine

A boronate-decorated nanomagnetic organic-inorganic hybrid material was facilely synthesized by utilizing the nanomagnetic polyhedral oligomeric silsesquioxanes (POSS) composite (Fe₃O₄@POSS) as the base platform. A simple copolymerization occurred between 3-acrylamidophenylboronic acid (AAPBA) and the residual end vinyl groups supplied by the substrate. Here the special emphasis was placed on the octavinyl POSS, which not only acted as the building blocks for a hybrid architecture but also facilitated the process of grafting boronate groups onto the surface of POSS based nanomagnetic composite (Fe₃O₄@POSS). The successful immobilization of affinity ligand-AAPBA on the Fe₃O₄@POSS was confirmed by Fourier transform infrared (FT-IR), elemental analysis, inductively coupled plasma atomic emission spectrometer (ICP-AES), field emission scanning electron microscope. A magnetic solid-phase extraction (MSPE) for cis-diols enrichment was developed using the as-prepared Fe₃O₄@POSS-AAPBA material as an affinity sorbent and three catecholamines (CAs), namely noradrenaline, epinephrine and isoprenaline, as model analytes. Under the optimal extraction conditions, sensitive and simultaneous analysis of three CAs from the urine sample was achieved by high-performance liquid chromatography with UV detection (HPLC-UV). The limits of detection (LOD, S/N = 3) and the limits of quantitation (LOQ, S/N = 10) for the target analytes were 0.81–1.32 ng mL⁻¹ and 2.70–4.40 ng mL⁻¹, respectively. Also good recoveries (85.5–101.7%) and repeatability (RSD≤10.1%) were obtained by this method. This work not only showed a facility for the utilization of Fe₃O₄@POSS as a substrate for constructing a boronate functionalized nanomagnetic sorbent, but also demonstrated the capability of the derived material for recognition of trace amount of cis-diols biomolecules presented in complicated biological matrices.     

Multiwavelength Spectrophotometric Determination of Acid Dissociation Constants. Deconvolution of Binary Mixtures of Ionizable Compounds

ABSTRACT

A spectral deconvolution method based on target factor analysis has been developed to determine pK_a values of binary mixtures of monoprotic and/or diprotic ionizable compounds. The technique makes use of the approach of Frans and Harris, which has been implemented previously for mixtures of monoprotic compounds (Anal. Chem. 1985, 57, 1718-1721), to extract the unknown pK_a values. The method has been illustrated by using the multiwavelength spectrophotometrictitation data of binary mixtures of: I. benzoic acid and phenol, 2. benzoic acid and nicotinic acid, 3. p-aminosalicylic acid and phthalic acid. It was demonstrated that the pK_a values as determined in this study are in good agreement with the literature.     

Determination of Pyrethroid Pesticides in Environmental Waters Based on Magnetic Titanium Dioxide Nanoparticles Extraction Followed by HPLC Analysis

A simple and fast method based on magnetic separation for extraction of pyrethroid pesticides including beta-cyfluthrin, cyhalothrin and cyphenothrin from environmental water samples has been established. Magnetic titanium dioxide was used as sorbent, which was synthesized by coating TiO₂ on Fe₃O₄ in liquid-state co-precipitation method. The sorbent has been characterized by scanning electron microscopy and Fourier-transform infrared spectrometry, and the magnetic properties were investigated with physical property measurement system. Various parameters affecting the extraction efficiency were evaluated to achieve optimal condition and decrease ambiguous interactions. The analytes desorbed from the sorbent were detected by high performance liquid chromatography. Under the optimal condition, the linearity of the method is in the range of 25–2,500 ng L^?1. The detection limits and quantification limits of pyrethroid pesticides are in the range of 2.8–6.1 ng L^?1 and 9.3–20.3 ng L^?1, respectively. The relative standard deviations of intra- and inter-day tests ranging from 2.5 to 7.2 % and from 3.6 to 9.1 % were obtained. In all three spiked levels (25, 250 and 2,500 ng L^?1), the recoveries of pyrethroid pesticides were in the range of 84.5–94.1 %. The proposed method was successfully applied to determine pyrethroids in three water samples. Cyphenothrin was found in one river water near farmlands, and its concentration was 52 ng L^?1.     

Radiochemical determination of Mo in pure tungsten

A radiochemical neutron activation technique for Mo determination in high purity tungsten, based on some specific properties of Mo and W radionuclides has been developed. Al₂O₃ powder has been used as a sorbent. An estimation of the Mo content was carried out via the selectively separated^99mTc daughter radionuclide. Limit of detection was 10 ng g^–1.     

Removal of uranium(VI) and thorium(IV) ions from aqueous solutions by functionalized silica: kinetic and thermodynamic studies

Adsorption behavior of uranyl and thorium ions from synthetic radioactive solutions onto functionalized silica as sorbent has been investigated. The effect of contact time, initial concentration of radioactive solutions, sorbent mass, pH value and temperature on the adsorption capacity of the sorbent was investigated. Negative values of Gibbs free energy of adsorption suggested the spontaneity of the adsorption process on both functionalized silica with –NH₂ groups and with –SH groups. Positive values obtained for ΔH° indicates that the adsorption is an endothermic process. The adsorption isotherms were better fitted by Freundlich model and the adsorption kinetic was well described by the pseudo-second order equation. Desorption studies indicated that the most favorable desorptive reagents for UO₂ ²⁺ is HNO₃ 1 M and for Th⁴⁺ is EDTA 1 M solutions.     

GC-MS Analysis of Contaminants in Breathing Oxygen

Abstract

Oxygen used for flight crews and for extra-hospital therapies is kept in vacuum containers and maintained as liquid phase (LOX) until use; by using this procedure, the weight of the breathing apparatus is reduced, thus extending breathing oxygen availability and improving safety by using atmosphere pressure sampler.

On the other hand, because of its low boiling point (?183°C), during storage and distribution, LOX shows continuous evaporation with a constant increase in pollutant concentration obtained in the LOX production.

Therefore, LOX is subjected to a strict quality control to evaluate the contamination levels from production until its use.

In this study, an analytical procedure has been optimised to measure the main LOX contaminants (freon, chlorinated solvents, light hydrocarbons, CO₂, CO, and N₂O) based on a single technique (GC-MS) and two chromatographic columns (Poraplot Q/HT and HP-Plot molecular sieve 5 A). The proposed method is an improvement in terms of time as well cost of analysis and selectivity with respect to the present methods based on three chromatographic techniques (GC-ECD, GC-FID, GC-HID) and four different columns.     

Formation of lead pyrophosphate glass and the role of anion disproportionation

Thermal, spectroscopic and electrical properties of lead pyrophosphate glass prepared by melt quenching have been examined. A model based on the structural disproportionation of the P₂O ₇ ⁴⁻ ions has been proposed and is shown to consistently explain all the observations. The equilibrium of various anionic species has been discussed on the basis of their electronegativities which are in turn related to their basicities. Communication No. 129 from the Materials Research Centre     

An Interfacial Solar Heating Assisted Liquid Sorbent Atmospheric Water Generator

Harvesting water from air is a promising strategy for fresh‐water production, and it is particularly desirable for areas that lack direct access to clean water. While high‐concentration liquid sorbent is well‐known for high sorption, it has not been widely used for atmospheric water collection, being primarily limited by the difficulty in desorption. Interfacial solar heating based on a salt‐resistant GO‐based aerogel is now shown to enable a high‐concentration liquid sorbent (CaCl₂ 50 wt % solution) based atmospheric water generator. Fresh water (2.89 kg m^?2 day^?1) can be produced at about 70 % relative humidity, with only solar energy input and energy efficiency of desorption as high as 66.9 %. This low‐cost and effective approach provides an attractive pathway to extract water from air, to relieve the thirst of arid, land‐locked, and other areas where fresh water is scarce.     

Solvatochromic Solvent Polarity Measurements In Analytical Chemistry: Synthesiss And Applications Of Et-30

Abstract

The E_T(30) scale of solvent polarity has been shown to be useful in examining many diverse analytical processes. It is based on the charge transfer absorption of 2,6-diphenyl-4-(2,4,6-triphenyl-N-pyridinio)phenolate (referred to as ET-30 in this paper). Unfortunately, use of the E_T(30) scale has been hindered by (a) the lack of a commercial source of the ET-30 dye and (b) the lack of an English language synthetic procedure. Here we discuss recent applications of the E_T(30) scale to analytical techniques, as well as a simplified procedure for the synthesis of ET-30.