On-line ionic imprinted polymer selective solid-phase extraction of nickel and lead from seawater and their determination by inductively coupled plasma-optical emission spectrometry

Nickel(II) and lead(II) ionic imprinted 8-hydroxyquinoline polymers were synthesized by a precipitation polymerization technique and were used as selective solid phase extraction supports for the determination of nickel and lead in seawater by flow injection solid phase extraction on-line inductively coupled plasma-optical emission spectrometry. An optimum loading flow rate of 2.25 mL min⁻¹ for 2 min and an elution flow rate of 2.25 mL min⁻¹ for 1 min gave an enrichment factor of 15 for nickel. However, a low dynamic capacity and/or rate for adsorption and desorption was found for lead ionic imprinted polymer and a flow rate of 3.00 mL min⁻¹ for 4-min loading and a flow rate of 2.25 mL min⁻¹ for 1-min elution gave a enrichment factor of 5. The limit of detection was 0.33 μg L⁻¹ for nickel and 1.88 μg L⁻¹ for lead, with a precision (n = 11) of 8% (2.37 μg Ni L⁻¹) for nickel and 11% (8.38 μg Pb L⁻¹) for lead. Accuracy was also assessed by analyzing SLEW-3 (estuarine water) and TM-24 (lake water) certified reference materials, and the values determined were in good agreement with the certified concentrations.     

Separation of acid whey proteins on the preparative scale by hyperdiffusive anion exchange chromatography

Summary The eluent flow through a fixed bed of a strong anion-exchanger Q Hyper D/F packing has been characterized by mean of the residence time distribution and the separation conditions of acid whey proteins have been established. Myoglobin under non-retaining conditions was used as a test protein because its molecular weight was close to that of α-lactalbumin, the target protein of this study. In the interstitial velocity range of 44–350 cm h⁻¹ a constant reduced height equivalent to a theoretical plate of 13 was observed. Nearly pure fractions of the five main acid whey proteins were obtained on the preparative scale for a gradient slope of NaCl 1 mM mL⁻¹, in the pH range of 6–8 and an interstitial velocity of 127 cm h⁻¹ (flow rate of 2 mL min⁻¹). A separation focused on a pure fraction of α-lactalbumin was achieved at pH 7.5 and was effective up to an interstitial velocity of 500 cm h⁻¹ (flow rate of 8 mL min⁻¹). An indepth characterization of α-lactalbumin by electrospray ionization—mass spectrometry showed that 15% of α-lactalbumin was lactosylated both in the collected fraction and in the acid whey protein concentrate used as feed.     

Production of low sulfur diesel fuel via adsorption: an equilibrium and kinetic study on the adsorption of dibenzothiophene onto NaY zeolite

The adsorption of dibenzothiophene (DBT) in hexadecane onto NaY zeolite has been studied by performing equilibrium and kinetic adsorption experiments. The influence of several variables such as contact time, initial concentration of DBT and temperature on the adsorption has been investigated. The results show that the isothermal equilibrium can be represented by the Langmuir equation. The maximum adsorption capacity at different temperatures and the corresponding Langmuir constant (K _L ) have been deduced. The thermodynamic parameters (ΔG ⁰,ΔH ⁰,ΔS ⁰) for the adsorption of DBT have also been calculated from the temperature dependence of K _L using the van’t Hoff equation. The value of ΔH ⁰,ΔS ⁰ are found to be −30.3 kJ mol⁻¹ and −33.2 J mol⁻¹ K⁻¹ respectively. The adsorption is spontaneous and exothermic. The kinetics for the adsorption process can be described by either the Langmuir model or a pseudo-second-order model. It is found that the adsorption capacity and the initial rate of adsorption are dependent on contact time, temperature and the initial DBT concentration. The low apparent activation energy (12.4 kJ mol⁻¹) indicates that adsorption has a low potential barrier suggesting a mass transfer controlled process. In addition, the competitive adsorption between DBT, naphthalene and quinoline on NaY was also investigated.     

Description of the Hg/[H<Subscript>2</Subscript>O + <Emphasis Type="Italic">mc</Emphasis> KCl + (1 − <Emphasis Type="Italic">m</Emphasis>)<Emphasis Type="Italic">c</Emphasis> KF] system in terms of the modified model of electrical double layer

Specific adsorption of anion Cl⁻ at the Hg/H₂O interface from mixed solutions mc KCl + (1 − m)c KF is analyzed in terms of a recently put forward modified model of electrical double layer. The calculations showed that the modified model of electrical double layer not only adequately gives the form of experiment curves of differential capacitance but also allows explaining the deviation from linearity of the dependence of the adsorption energy on the electrode charge. Of importance is a decrease in the dense layer capacitance when passing from KF to KCl under the condition of constant surface coverage with the Cl⁻ ions. The results of calculations in terms of the modified model of electrical double layer are compared with those obtained in terms of the Sanz-Gonzalez model.     

Sorption behavior of germanium(IV) on titanium dioxide nanoparticles

Titanium dioxide nanoparticles were employed for the sorption of Ge(IV) ions from aqueous solution. The process was studied in detail by varying the sorption time, pH, and temperature. The sorption process was found to be fast, equilibrium was reached within 3 min. A maximum sorption could be achieved from solution when the pH ranges between 4.0 and 11.0. Sorbed Ge(IV) ions can be completely desorbed with 2 mL of 0.3 mol L⁻¹ K₃PO₄-1.0 mol L⁻¹ H₂SO₄ mixture solution. The kinetic experimental data properly correlate with the second-order kinetic model (k ₂ = 0.88 g mg⁻¹ min⁻¹ (25°C)), Reichenberg equation and Morris-Weber model. The estimated E _a for Ge(IV) adsorption on nano-TiO₂ was 19.66 kJ mol⁻¹. The overall rate process appears to be influenced by intra-particle diffusion. The sorption data could be well interpreted with the Langmuir and Dubinin-Radushkevich (D-R) type sorption isotherms. The D-R parameters were calculated to be K = −0.00321 mol₂ kJ⁻², q _m = 0.59 mmol g⁻¹ and E = 12.48 kJ mol⁻¹ at room temperature. Furthermore, the thermodynamic parameters were also determined, and the ΔH ⁰ and ΔG ⁰ values indicated a spontaneous exothermic behavior.     

Catanionic surfactant ambient cloud point extraction and high-performance liquid chromatography for simultaneous analysis of organophosphorus pesticide residues in water and fruit juice samples

A mixed anionic–cationic surfactant cloud point extraction (CPE) has been developed using sodium dodecyl sulfate (SDS) and tetrabutylammonium bromide (TBABr) for the extraction and preconcentration of organophosphorus pesticides (OPPs) at ambient temperature before analysis by high-performance liquid chromatography. The studied OPPs were azinphos-methyl, parathion-methyl, fenitrothion, diazinon, chlorpyrifos, and prothiophos. The optimum conditions of the mixed anionic–cationic CPE were 50 mmol L⁻¹ SDS, 100 mmol L⁻¹ TBABr, and 10% (w/v) NaCl. The extracted OPPs were successfully separated within 11 min using the conditions of a Waters Symmetry C8 column, a flow rate of 0.8 mL min⁻¹, a gradient elution of methanol and water, and detection at 210 nm. Linearity was found over the range 0.05–5 μg mL⁻¹, with the correlation coefficients higher than 0.996. The enrichment factor of the target analytes was in the range 6–11, which corresponds to their limits of detection from 1 to 30 ng mL⁻¹. High precisions (intra-day and inter-day) were obtained with relative standard deviation <1.5% (t _R) and 10% (peak area). Accuracies (% recovery) of the different spiked OPP concentrations were 82.7–109.1% (water samples) and 80.3–113.3% (fruit juice samples). No contamination by the OPPs was observed in any studied samples.     

Adsorption properties of BEA zeolites and their aluminum phosphate extrudates for purification of isomaltose

The disaccharide isomaltose is produced via an enzymatic reaction and is adsorbed to BEA zeolite. This reaction integrated adsorption can be achieved as fluidized bed as well as fixed bed. We investigated isotherms, adsorption enthalpies and sorption kinetics of BEA zeolite and extrudates with a novel aluminum phosphate sintermatrix. These extrudates contain 50% (w/w) of BEA 150 zeolites (Si/Al = 75) as primary crystals. BET-surface for extrudates is 245 m²⋅g⁻¹ and 487 m²⋅g⁻¹ for zeolite. Extrudates show a monomodal macropore structure with a maximum at 90 nm. All isotherms show a type I shape. For lower equilibrium concentrations, which occur during the enzymatic reaction, Henry’s law is applied and compared to a Langmuir model. Adsorption equilibrium constant K _i,L calculated from Langmuir for extrudates at 4 °C is 64.7 mL⋅g⁻¹ and more than twice as high as obtained from Henry’s law with K _i is 26.8 mL⋅g⁻¹. Adsorption on extrudates at 4 °C is much stronger than on zeolite crystals where the Henry coefficient K _i is 17.1 mL⋅g⁻¹. Adsorption enthalpy Δh _Ad calculated from van’t Hoff plot with the Henry equation is −44.3 kJ⋅mol⁻¹ for extrudates and −29.6 kJ⋅mol⁻¹ for zeolite crystals. Finally, the kinetics for ad- and desorption were calculated from the initial slope. The diffusion rate for ad- and desorption on extrudates were in the same range while adsorption on zeolites is three orders of magnitudes faster than desorption.     

Modified model of electrical double layer for mixed solutions of constant ionic strength

A model is suggested, which generalized the Alekseev-Popov-Kolotyrkin model for the case of mixed solutions of constant ionic strength of the type mc KA_*⁻ + (1 − m)c KA, where A_*⁻ is the surface-active anion that lowers the electrical double layer capacitance as compared with that observed in the presence of surface-inactive anion A⁻. Calculations made for a real system mc NaNO₃ + (1 − m)c NaF showed that at 0.2 ≤ m ≤ 1 a transition occurred from quadratic to linear dependence of adsorption energy on the electrode potential (or charge). The conclusions are in agreement with experimental data obtained for the studied system.     

Flow injection on-line determination of uranium after preconcentration on XAD-4 resin impregnated with dibenzoylmethane

A flow injection on-line determination of uranium(VI) after preconcentration in a minicolumn having amberlite XAD-4 resin impregnated with dibenzoylmethane (DBM) is described. Uranium(VI) is selectively adsorbed from aqueous solution of pH 5.5 in the minicolumn (5.5 cm long with 5.0 mm i.d.) at a flow rate of 13.6 mL min⁻¹. The uranium(VI) complex was desorbed from the resin by 0.1 mol dm⁻³ HCl at a flow rate of 4.2 mL min⁻¹ and mixed with arsenazo-III solution (0.05% solution in 0.1 mol dm⁻³ HCl, 4.2 mL min⁻¹), and taken to the flow through cell of spectrophotometer where its absorbance was measured at 651 nm. Various parameters affecting the complex formation and its elution were optimized. Peak height (absorbance) was used for data analyses. The preconcentration factors of 36 and 143, detection limits of 0.9 and 0.232 μg L⁻¹, sample throughputs of 40 and 10 were obtained for preconcentration time of 60 and 300 s, respectively. The tolerance limits of many interfering cations like Th(IV) and rare-earth elements were improved. The proposed method was applied on different water (spiked tap, well and sea water) and biological samples and good recovery was obtained. The method was also validated on mocked uranium ore sample and the results were in good agreement with the reported value.     

First results on Fe solid-phase extraction from coastal seawater using anatase TiO2 nano-particles

This paper describes the application of TiO₂ nano-particles (anatase form) for the solid-phase extraction of iron from coastal seawater samples. We investigated the adsorption processes by infra-red spectroscopy. We compared in batch and on-(mini)column extraction approaches (0.1 and 0.05 g TiO₂ per sample, respectively), combined to external calibration and detection by inductively coupled plasma mass spectrometry at medium mass resolution. Globally, this titania phase was slightly more efficient with seawater than with ultra-pure water, although between pH 2 and pH 7, the Fe retention efficiency progressed more in ultra-pure water than in seawater (6.9 versus 4.8 times improvement). Different reaction schemes are proposed between Fe(III) species and the two main categories of titania sites at pH 2 (adsorption of [FeL _x ]^{(3 − x)+} via possibly the mediation of chlorides) and at pH 7 (adsorption of [Fe(OH)₂]⁺ and precipitation of [Fe(OH)₃]⁰). Under optimised conditions, the inlet system was pre-cleaned by pumping 6% HCl for ∼2 h, and the column was conditioned by aspirating ultra-pure water (1.7 g min⁻¹) and 0.05% ammonia (0.6 g min⁻¹) for 1 min. Then 3 g seawater sample was loaded at the same flow rate while being mixed on-line with 0.05% ammonia at 0.6 g min⁻¹ to adjust the pH to 7. The iron retained on the oxide powder was then eluted with 3 g 6% HCl (<0.002% residual salinity in the separated samples). The overall procedural blank was 220 ± 46 (2 s, n = 16) ng Fe kg⁻¹ (the titania was renewed in the column every 20 samples, with 2-min rinsing in between samples with 6% HCl at 1.5 g min⁻¹). The recovery estimated from the Canadian certified reference material CASS-2 was 69.5 ± 7.6% (2 s, n = 4). Typically, the relative combined uncertainty (k = 2) estimated for the measurement of ∼1 μg Fe kg⁻¹ (0.45 μm filtered and acidified to pH 1.5) of seawater was ∼12%. We applied our method to a similar sample, from the coastal region of the North Sea. The agreement well within stated uncertainties of our result with the value obtained independently by isotope dilution mass spectrometry further validated our method.     

Investigation of technical characteristics of chemical adsorbent “mercerized wood”

Investigations on the influence of the velocity (flow) of gas on the surface integrity of the layer of adsorbent “mercerized wood” were carried out, the data on the aerodynamic resistance of the layer depending on the specific consumption of the air and value of the residual pressure of gases above dried adsorbent were obtained. At density of the adsorbent within 0.25 to 0.35 g cm⁻³ the consumption of gas can vary up to the value of 1.4 l cm⁻³ min⁻¹. It is shown that the aerodynamic resistance of the layer is insignificant at the density of the layer of the adsorbent no more than 0.35 g cm⁻³. Functional dependences of aerodynamic resistance on the specific consumption of gas for different densities of the layer of the adsorbent were obtained. The empirical equation of Shilov-Dubinin for calculation of the process of absorption of HF is illustrated.     

Thermal behavior study and decomposition kinetics of salbutamol under isothermal and non-isothermal conditions

The thermal decomposition of salbutamol (β₂ — selective adrenoreceptor) was studied using differential scanning calorimetry (DSC) and thermogravimetry/derivative thermogravimetry (TG/DTG). It was observed that the commercial sample showed a different thermal profile than the standard sample caused by the presence of excipients. These compounds increase the thermal stability of the drug. Moreover, higher activation energy was calculated for the pharmaceutical sample, which was estimated by isothermal and non-isothermal methods for the first stage of the thermal decomposition process. For isothermal experiments the average values were E _act=130 kJ mol⁻¹ (for standard sample) and E _act=252 kJ mol⁻¹ (for pharmaceutical sample) in a dynamic nitrogen atmosphere (50 mL min⁻¹). For non-isothermal method, activation energy was obtained from the plot of log heating rates vs. 1/T in dynamic air atmosphere (50 mL min⁻¹). The calculated values were E _act=134 kJ mol⁻¹ (for standard sample) and E _act=139 kJ mol⁻¹ (for pharmaceutical sample).     

Sorption behavior of Am(III) onto granite

Sorption behavior of Am(III) onto granite was investigated. The distribution coefficient (K _d ) of Am(III) onto granite was determined in the solution of which pH was ranged from 2.9 to 11.4 and ionic strength was set at 10⁻² and 10⁻¹. TheK _d values were found to increase with increasing pH and with decreasing ionic strength. The obtained data were successfully analyzed by applying an electrical double layer model. The optimum parameter values of the double layer electrostatics and adsorption reactions were obtained, and the selective adsorption behavior of Am(III) onto the granite was discussed.     

Evaluation of CO2 adsorption capacity of solid sorbents

The CO₂ adsorption capacity of the low-cost solid sorbents of waste tire char (TC) and chicken waste char (CW) was compared with commercial active carbon (AC) and 5 ? zeolite (ZA) using thermogravimetric analysis (TG), pressurized TG, and differential scanning calorimetry (DSC). The sorbents were degassed in a TG up to 150 °C to release all gases on the surface of the sample, then cooled down to the designed temperature for adsorption. TG results indicated that the CO₂ adsorption capacity of TC was higher than that of CW, but lower than those of AC and ZA. The maximum adsorption rate of TC at 50 °C was 0.61% min⁻¹, lower than that of AC, but higher than that of CW, 0.44% min⁻¹. The maximum adsorption rate of ZA at 50 °C was 3.1% min⁻¹. When the pressure was over 4 bar, the adsorption rate of ZA was lower than that of TC and AC. At 30 bar, the total CO₂ uptake of TC was 20 wt%, higher than that of CW and ZA but lower than that of AC. The temperature, nitrogen concentration, and water content also influenced the CO₂ adsorption capacity of sorbents to some extent. DSC results showed that adsorption was an exothermic process. The heat of CO₂ adsorption per mole of CO₂ of TC at 50 °C was 24 kJ mol⁻¹ while the ZA had the largest heat of adsorption at 38 kJ mol⁻¹. Comparing the characteristics of TC and CW, TC may be a promising sorbent for removal of CO₂.     

Degradation of 4-chlorophenol in aqueous solution by γ-radiation and ozone oxidation

The degradation of 4-chlorophenol (4-CP) by using gamma rays generated by a ⁶⁰Co source in the presence of O₃ was investigated. The radiolysis of 4-CP and the kinetics of 4-CP mineralization were analyzed based on the determination of total organic carbon (TOC). The influence of initial 4-CP concentration and the free radicals scavengers (such as NaHCO₃ and t-butanol) on the 4-CP degradation was also studied. The results showed that when the radiation rate was 336 Gy·min⁻¹, 4-chlorophenol at concentration of 10 mg·L⁻¹ could be completely degraded at the radiation dose of 2 kGy. The degradation of 4-chlorophenol could be described by a first-order reaction model, the rate constant of 4-CP degradation by combined ozonation and radiation was 0.1016 min⁻¹, which was 2.4 times higher than the sum of radiation (0.0294 min⁻¹) and ozonation (0.0137 min⁻¹). It revealed that the combination of radiation and ozonation resulted in synergistic effect, which can remarkably increase the degradation efficiency of 4-CP.     

Electrochemical deposition of silicate–cetyltrimethylammonium bromide nanocomposite film on glassy carbon electrode for sensing of methyl parathion

A novel electrochemical sensor for methyl parathion based on silicate– cetyltrimethylammonium bromide nanocomposite film has been fabricated by electro-assisted deposition onto glassy carbon electrode in one-step via an electrochemical modulation of pH at the electrode/solution interface to promote controlled gelification of tetraethylorthosilicate sol, and was characterized with scanning electron microscopy, X-ray diffraction, and electrochemical impedance spectroscopy. The electrochemical sensing of methyl parathion on the film-modified electrode was investigated applying cyclic voltammetry and square wave voltammetry. Compared to the unmodified electrode, the shapes of the redox peaks were improved and the peak currents significantly increased. Experimental parameters such as deposition time, pH value, and accumulation conditions have been optimized. A linear relationship between the peak current and methyl parathion concentration was obtained in the range from 1.0 × 10⁻⁷ to 1.0 × 10⁻⁴ mol L⁻¹ with a detection limit of 1.04 × 10 ⁻⁸ mol L⁻¹ (S/N = 3) after accumulation at 0 V for 120 s. The film electrode shows great promise for determination of methyl parathion in real samples.      

A cellulose-based carboxyl cotton chelator having citric acid as an anchored ligand: preparation and application as solid phase extractant for copper determination by flame atomic absorption spectrometry

Citric acid was thermochemically esterified onto defatted cotton fibre to produce a carboxyl cotton chelator (CCC), which had been used for extraction of copper prior to its determination by flame atomic absorption spectrometry. The extraction of copper has been studied under both batch and column methods. Quantitative extraction of copper was achieved in the pH range 4–7. The time needed to extract each sample was less than 30 min by the batch method. The copper extraction capacity of CCC was found to be 22.7 mg g⁻¹ at optimal pH value. The elution was quantitative with 1 mol L⁻¹ hydrochloric acid. The feasible flow rate of copper-containing solution for quantitative extraction onto the column packed with CCC was 0.5–4.0 mL min⁻¹, whereas for elution it was less than 1.5 mL min⁻¹. A 100-fold extraction factor could be achieved under the optimal column conditions. The tolerance limits for common metal ions on the extraction of copper and the time of column reuse were investigated. The proposed method has been successfully applied for extraction and determination of copper in industrial wastewater and natural water samples.     

Determination of the Thermal Degradation Kinetic Parameters of Carbon Fibre Reinforced Epoxy Using TG

In this work, a kinetic study on the thermal degradation of carbon fibre reinforced epoxy is presented. The degradation is investigated by means of dynamic thermogravimetric analysis (TG) in air and inert atmosphere at heating rates from 0.5 to 20°C min⁻¹ . Curves obtained by TG in air are quite different from those obtained in nitrogen. A three-step loss is observed during dynamic TG in air while mass loss proceeded as a two step process in nitrogen at fast heating rate. To elucidate this difference, a kinetic analysis is carried on. A kinetic model described by the Kissinger method or by the Ozawa method gives the kinetic parameters of the composite decomposition. Apparent activation energy calculated by Kissinger method in oxidative atmosphere for each step is between 40–50 kJ mol⁻¹ upper than E _a calculated in inert atmosphere. The thermo-oxidative degradation illustrated by Ozawa method shows a stable apparent activation energy (E _a ≈130 kJ mol⁻¹ ) even though the thermal degradation in nitrogen flow presents a maximum E _a for 15% mass loss (E _a ≈60 kJ mol⁻¹ ). This revised version was published online in July 2006 with corrections to the Cover Date.     

Comparative study of CTAB adsorption on bituminous coal and clay mineral

Adsorption of cetyltrimethylammonium bromide (CTAB) onto bituminous coal (BC) and a clay mineral, montmorillonite (MMT), was studied. Simultaneous measurements of the CTAB adsorption and zeta potential determination of the adsorption suspensions were carried out. The adsorption isotherms were found to be of the typical Langmuir type; values of the CTAB adsorption capacities were calculated (a _m = 0.65 mmol g⁻¹ for coal and a _m = 3.24 mmol g⁻¹ for MMT). The shape of the adsorption isotherms was correlated with zeta potential values at the adsorption equilibrium. The adsorption properties of both sorbents were studied by voltammetry on carbon paste electrodes (CPE) modified with coal-CTAB and MMT-CTAB system, respectively. Open circuit sorption with differential pulse voltammetry was performed in order to compare the sorption properties of the systems with the unmodified sorbents. The Cu²⁺ adsorption on BC and MMT decreased to approximately 50 % and 40 %, respectively. The surface adsorption mechanism of CTAB on coal based on hydrophilic interactions was proposed. In the case of montmorillonite, the CTAB intercalation is expected via ion exchange into the inter-layer space forming a double- or triple-layer arrangement.     

High-Speed Purification of Recombinant Interleukin-11 by IMAC with Rigid Biporous Beads

Rigid biporous beads were prepared and modified by iminodiacetic acid (IDA) for application in immobilized metal affinity chromatography of proteins. The retention behavior of four model proteins on the metal chelate columns loaded with copper (II) and nickel (II) ions were studied. The separation of the four proteins by the Ni-IDA column at 40 cm.min⁻¹ was realized within 2 min. His6-interluekin-11 (His6-IL-11) was also purified by the Ni-IDA column at 40 cm.min⁻¹. The collected His6-IL-11 fraction showed a purity of about 80%. The results indicate that the IMAC with the biporous medium is promising for high-speed protein purification.