Low Distribution Coefficients Research Articles

Removal of 17α‐ethinylestradiol, salicylic acid, trimethoprim, carbamazepine and nonylphenol through biological carbon and nitrogen removal processes

AbstractThis study investigated five different trace organic contaminants (TOrCs) (one hormone: 17α‐ethinylestradiol (EE2), two pharmaceuticals: salicylic acid (SA) and trimethoprim (TMP), one analgesic drug: carbamazepine (CBZ), and one surfactant metabolite: nonylphenol (NP)) removal efficiency at a full‐scale Advanced Wastewater Treatment Plant (AWTP). The AWTP achieved average EE2, SA and NP removal over 80% at the biological carbon removal stages. The results also showed a 66% removal of TMP at the nitrogen removal stages. CBZ was recalcitrant throughout the plant, due to its high solubility and low distribution coefficient between wastewater and sludge. Batch experiments were conducted on active and inactive secondary, nitrification and denitrification sludge by adding TOrCs to understand the removal mechanism through sorption and biodegradation. Sorption was the dominant mechanism to remove EE2, SA and NP in secondary treatment processes. In nitrification and denitrification processes, higher percentage of TOrCs removal through biodegradation were observed compared to removal through sorption.

Cu and Zn adsorption to a terrestrial sediment: Influence of solid-to-solution ratio

Laboratory batch adsorption experiments are commonly used to quantify contaminant adsorption to natural sediments. The distribution coefficients (KD) determined via these experiments are often incorporated into reactive transport models to predict contaminant movement in groundwater. The solid-to-solution ratio (SSR) in most laboratory experiments is much lower in comparison to that in aquifers, therefore it is questionable if distribution coefficients thus obtained can accurately quantify contaminant adsorption in the natural environment. SSR may also influence the leaching of multivalent cations and organic matters from natural sediments, which in turn could alter contaminant adsorption. The objective of this study is to determine how SSR influences heavy metal adsorption to a heterogeneous natural sediment. Cu and Zn adsorption was examined at SSRs of 250 and 25 g/L in the pH range of 3–8 using both batch experiments and surface complexation modelling. Results indicated that Ca, Mg, and DOC leaching depended on SSR, with higher SSR generally resulting in greater leaching. Conversely, Al and Fe leaching was less dependent on SSR. Cu distribution coefficients in the low pH range (3–6) and Zn distribution coefficients across the pH range (3–8) were not very sensitive to the SSR, despite higher leached concentrations of competing cations at a higher SSR. In contrast, Cu distribution coefficients at high pH (6–8) were more SSR-dependent, likely due to formation of non-adsorbing aqueous Cu-DOC complexes. This study demonstrates that cautions must be taken when distribution coefficients measured by laboratory batch experiments are used to predict contaminant transport in aquifers.

Extraction of acetic acid, glycolaldehyde and acetol from aqueous solutions mimicking pyrolysis oil cuts using ionic liquids

Value-added oxygenates, such as acetic acid (HAc), glycolaldehyde and acetol, are present in pyrolysis oil and its cuts in substantial amounts. This work describes the separation of these value-added oxygenates from artificial aqueous fractions of pyrolysis oil via liquid-liquid extraction. Three phosphonium ionic liquids (ILs), two imidazolium ILs and one benchmark organic mixture (40 wt% tri-n-octylamine in 1-octanol: TOA/1-octanol) were applied as solvents. Although suited as solvent for HAc and glycolaldehyde, the benchmark TOA/1-octanol showed a low acetol distribution coefficient (0.05), which makes it less suitable for use in an integrated oxygenates extraction process. Phosphonium ILs showed the highest affinities for HAc and glycolaldehyde, and reasonable affinity for acetol. However, none of these solvents could be applied to remove all oxygenates from the aqueous solution in a single extraction step, because of the difficulty of oxygenates evaporation from phosphonium ILs and the reactivity of glycolaldehyde with P666,14[N(CN)2] in the presence of HAc, as was confirmed by NMR. Based on the good affinity of the imidazolium ILs for acetol, a two-step extraction process was proposed where Hmim[B(CN)4] may be used to extract acetol and HAc in the first step and be regenerated by evaporation of the solutes, and P666,14[Phos] may be applied to extract glycolaldehyde in the second step and be regenerated by back-extraction with water.

Effect of calcium-oxide on the removal of calcium during industrial directional solidification of upgraded metallurgical-grade silicon

Directional solidification is often used to remove metallic impurity in the photovoltaic industry for the low equilibrium distribution coefficient between solid and melt. However, in our present experiments, compared with other impurities, the removal of calcium is variable at the low height of ingot, which is caused by the existence of insoluble CaO particle. CaO exists as insoluble particle in the feedstock. During directional solidification stage, CaO motions with the melt convection, and it is likely to envelop in solid. Consequently, the content of calcium is relatively high if many CaO particles are just contained, which is verified by the analysis of SEM-EDS. In a word, the removal efficiency depends upon the chemical state of calcium. The reason why CaO exists is studied, and the envelopment of the particle is mainly discussed by means of thermodynamics, especially on gravitational force, repulsive force, and drag force.

Investigation of extraction of vanadium(V) with di-2-ethylhexylphosphoric acid

to the formation of hydrogen bond between the dioxonium ion and the phosphoryl group P=O. It indicates that di-2-ethylhexylphosphoric acid extracts vanadium(V) with the formation of ionic associates. For the evaluation of the number of extractant molecules solvating the dioxonium ion the method of molar ratios was used. It follows from the extraction isotherm that one molecule of di-2-ethylhexylphosphoric acid corresponds to 10 vanadium ions. Considering our previous data on the ionic state of vanadium(V) in the range under study this means that one molecule of extractant corresponds to one decavanadate anion [8]. Hence, the method of saturation of organic phase permits not only to establish the number of solvating molecules of extractant in the composition of complex, but also to make the preliminary conclusion that vanadium(V) enters the composition of extracted complex as decavanadate anion. It is confirmed by the results of studies of the IR spectra of extracts of vanadium(V) with di-2-ethylhexylphosphoric acid. At high concentrations of vanadium(V) a broadening of absorption band at 1030 cm –1 is observed at the side of low frequencies and two shoulders at ~970 cm –1 and ~920 cm –1 appear. The comparative analysis of IR spectra of the extract of vanadium(V) with di-2ethylhexylphosphoric acid and the reported data on the IR spectra of vanadium(V) dioxocation and decavanadate anions [8] permits to attribute the low intensity bands at ~960 cm –1 and ~920 cm –1 to two types of binding of vanadium with terminal oxygen atoms of f- and g-type of decavanadate anion. Hence, the method of saturation and the results of IR studies of the extracts of vanadium(V) with di-2DOI: 10.1134/S1070363213060261 Di-2-ethylhexylphosphoric acid is known as the cation-exchanging extractant. It is widely used for the extraction of vanadium(IV) [1-5]. The extraction of vanadium(V) in a form of dioxocation with this substance proceeds with the very low distribution coefficient, and due to that it is not utilized [6]. We have worked up the conditions under which the change in the extraction mechanism from the cationexchanging to the solvate one takes place in the course of extraction what permits to extract vanadium(V) with di-2-ethylhexylphosphoric acid with high distribution coefficient. In this work we present the results of study of extraction of vanadium(V) with di-2-ethylhexylphosphoric acid. The investigation of extraction of vanadium(V) with di-2-ethylhexylphosphoric acid was carried out by means of IR and electronic spectroscopy. For the evaluation of the composition of extracted complex IR spectra of pure di-2-ethylhexylphosphoric acid and the vanadium(V) extract were recorded. In the IR spectra of the extract together with the absorption bands of di2-ethylhexylphosphoric acid the bands at 1650, 1750, 2140, and 3390 cm –1 are present which are characteristic of dioxonium ion [7]. The bands at 1170, 1370, and 2900 cm –1 which are also characteristic of H5O2 + ion are partially overlapped with more intense bands of di-2-ethylhexylphosphoric acid. The absorption band of P=O bond (νP=O) in the vanadium(V) extract has the frequency 1210 cm –1 . In the IR spectrum of pure di-2ethylhexylphosphoric acid the band of P=O bond (νP=O) has a maximum at 1225 cm –1 . As it was shown above, in the vanadium(V) extracts the dioxonium ion is presented. Due to that the shift of the band of P=O bond to the side of low frequencies may be attributed as

Evaluation of the interfacial compatibility in wood flour/polypropylene composites with the dielectric approach

AbstractTo clarify the interaction between the wood and polymer in wood flour/polymer composites, the dielectric constant and dielectric loss factor values were measured for poplar (Populus tomentasa Carr.) wood flour/polypropylene (PP) composites with different wood contents. The dielectric relaxation strength, distribution of relaxation time, and activation thermodynamic quantities of the dielectric relaxation caused by the reorientation of the methylol groups (CH2OH) in the amorphous region of the wood cell wall were then calculated. The results show that the dielectric relaxation strength changed very little below a wood content of 40% and began to increase above that value; this was due to the strong hindrance of PP to the reorientation of methylol groups and, therefore, suggests a close interaction between the wood and PP below a wood content of 40%. The low distribution coefficient of the relaxation time at extremely low temperatures below a 40% wood content was also found; this indicated that some groups in the wood could not move because of the influence of PP. The apparent activation energy increased with wood contents below 40% and then decreased; this further confirmed the optimal interfacial compatibility at a 40% wood content in the wood flour/PP composites in the absence of additives. This result was consistent with the results we obtained by a stress‐relaxation approach. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Influence of temperature and background electrolyte on the sorption of neptunium(V) on Opalinus Clay

The temperature dependence of the sorption of 8μM neptunium(V) on Opalinus Clay (OPA, Mont Terri, Switzerland) was investigated between 40 and 80°C and compared to previous results for 20°C. The batch experiments were performed under ambient air conditions in synthetic pore water (pH=7.6, I=0.4M) under variation of the solid-to-liquid ratio between 2 and 20g/L. Under these conditions the sorption of Np(V) on OPA was found to be an endothermic process as the average distribution coefficient (Kd) increases continuously with increasing temperature from 23±4L/kg at 40°C to 678±254L/kg at 80°C. In the temperature range of 40-80°C, the plot of log(Kd) vs. 1/T could be fitted to the Van't Hoff equation delivering an apparent sorption enthalpy of 80±16kJ/mol and an apparent sorption entropy of 278±48J/K·mol.Since pore water consists of several constituents (mainly NaCl, CaCl2, and MgCl2), additional batch experiments were performed at room temperature to investigate the influence of 0.1 and 0.4M NaClO4, NaCl, CaCl2, and MgCl2 electrolytes on the sorption of Np(V) on OPA at pH 7.6. The results showed significant differences between monovalent (Na+) and divalent (Mg2+, Ca2+) electrolytes. While the sorption isotherms in sodium electrolytes (I=0.4M) provided Kd values of 231±13 (NaClO4) and 224±17L/kg (NaCl), low distribution coefficients of 54±6L/kg (MgCl2, I=0.1M) and less were determined in magnesium and calcium electrolytes. A weak dependence on ionic strength was observed only in the batch experiments using NaClO4 as electrolyte. In all other electrolytes the influence of ionic strength on the sorption of Np(V) was negligible between I=0.1 and 0.4M.

Design and evaluation of enteric-coated tablets for rifampicin and isoniazid combinations

In order to improve the bioavailability of rifampicin (RIF) from rifampicin and isoniazid (INH) combination formulations, the physicochemical characteristics of RIF, stability of RIF in different pH buffers in the presence of INH, as well as the effect of particle size of RIF materials on the dissolution rate were investigated. On the basis of the above examinations, enteric-coated tablets for RIF and INH combinations were designed and prepared. RIF showed low solubility and high apparent distribution coefficient in the intestinal pH (pH 4.0–7.4). With the decrease in pH, the degradation of RIF increase and the presence of INH deepen the degradation. Enteric-coated tablets were prepared after grinding the RIF materials by dry granulation technique. The pharmacokinetics of RIF and INH of self-made enteric-coated tablets in dogs were studied by comparing with the reference tablets. The AUC0–48 of RIF in both reference and test tablets were 304.77 ± 42.27 and 353.79 ± 31.63 µg·h·mL−1, respectively. The AUC0–48 of INH in both reference and test tablets were 17.14 ± 8.59 and 19.62 ± 10.57 µg·h·mL−1, respectively. Enteric-coated tablets may minimize the decomposition of RIF in gastrointestinal tract and improve the bioavailability.

계분 퇴비화 시설 인근 농경지 토양, 지표수 및 저질토의 계절별 잔류 항생물질 모니터링

본 연구는 강원도 원주 지역의 계분 퇴비화 시설 인근의 농경지 토양, 지표수 및 저질토에 대한 TCs계열 3종(TC, CTC 및 OTC), SAs 계열 3종(SMX, STZ 및 SMT), IPs 계열 3종(LSL, MNS 및 SLM) 및 MLs 계열 1종(TYL) 등 총 4개 계열 10종의 항생물질을 선정하여 영농시기 별 잔류특성을 조사하였다. 토양 시료의 경우 TCs가 다른 계열 항생물질과 비교하여 가장 높은 농도로 검출되었으며 이는 TCs 내 케톤기와 토양 내 2가 양이온이 복합체를 형성, 표토에 강하게 흡착되어 심토까지 이동하지 않고 축적된 것으로 추측된다. 반면 TCs와 비교해 토양 내 SAs 잔류량이 낮은 이유는 적은 사용량과 낮은 흡착계수에서 기인된 것으로 판단되었다. 수질시료의 TCs는 집중강우로 인한 토양유실 및 이후 유량 감소로 인해 6월보다 9월에 높은 농도를 보였다. 저질토 내 TCs 농도 증가 이유가 양이온간의 복합체 형성, 이온교환 및 부식산의 수소결합으로 인해 지표수로 유입된 TCs가 저질토로 흡착, 축적되었기 때문으로 판단된다. 본 연구를 통해 계분퇴비 시용시 주변환경으로 높은 농도의 항생물질이 유입될 가능성이 있으며, 이로 인해 토양 내 내성 박테리아 생성 및 생태계 교란뿐만 아니라 직 간접적으로 인간에게 피해가 우려되는 바 지속적인 모니터링을 통한 관리방안 마련이 필요할 것으로 판단된다. Concentration of antibiotics including a tetracycline group (TCs) of tetracycline (TC), chlortetracycline (CTC), and oxytetracycline (OTC), a sulfonamide group (SAs) of sulfamethoxazole (SMX), sulfathiazole (STZ), and sulfamethazine (SMT), an ionophore group (IPs) of lasalocid (LSL), monensin (MNS), and salinomycin (SLM), and a macrolide group (MLs) of tylosin (TYL) was determined from samples collected from the agricultural soil, stream water, and sediment. For the agricultural soil samples, the concentration of TCs had the highest value among all tested antibiotic's groups due to its high accumulation rate on the surface soils. The lower concentrations of SAs in the agricultural soils may be resulted from its lower usage and lower distribution coefficient (Kd) compared to TCs. The concentration of TCs in stream water was significantly increased through June to September. It would be likely due to soil loss during an intensive rainfall event and a reduction of water level after the monsoon season. A significant amount of TCs in the sediment was also detected due to its accumulation from runoff, which occurred by complexation of divalent cations, ion exchange, and hydrogen bonding among humic acid molecules. To ensure environmental or human safety, continuous monitoring of antibiotics residues in surrounding ecosystems and systematic approach to the occurrence mechanism of antibiotic resistant bacteria are required.

Bioconcentration factor estimates of polycyclic aromatic hydrocarbons in grains of corn plants cultivated in soils treated with sewage sludge

This study presents a model to simulate the organic substance concentrations in corn grains assuming that the substances in soil solution are absorbed via the transpiration stream by plants growing in soils fertilized with sewage sludge (SS). The model was applied and validated using soil and corn grain samples from a long-term field experiment with six successive yearly applications of SS to the soil. The following polycyclic aromatic hydrocarbons (PAHs) were simulated and evaluated in soil and grain samples: acenaphthene, acenaphthylene, anthracene, benz(a)anthracene, benz(a)pyrene, benz(b)fluoranthene, benz(g,h,i)perylene, benz(k)fluoranthene, chrysene, dibenz(a,h)anthracene, fluoranthene, fluorene, indeno(1,2,3-c,d)pyrene, naphthalene, phenanthrene and pyrene. The PAH bioconcentration factors ( BCF) in corn grains ranged from 1.57 to 10.97 L kg − 1 . Polycyclic aromatic hydrocarbons with low soil distribution coefficients and high values of transpiration stream concentration factors ( TSCF) are more likely to be absorbed by corn plants and accumulated in grains. It was possible to estimate and observe that highly lipophilic PAH molecules (heavy PAHs) show lower accumulative potential in corn grains than the less lipophilic ones (light PAHs). Sewage sludges containing significant concentrations of light PAHs with two, three or four benzene rings should be avoided as fertilizers in alimentary field crops.

Liquid Phase Equilibria for Mixtures of (Water + Morpholine + Ethyl Nonanoate, Dimethyl Phthalate, or Isoamyl Alcohol) at 298.15 K

This work reports liquid−liquid equilibrium (LLE) data for the mixtures {water (1) + morpholine (2) + ethyl nonanoate, dimethyl phthalate, or isoamyl alcohol (3)} at 298.15 K and 101.3 kPa. The solubility curves and tie-line end compositions were examined for the related mixtures. The reliability of the experimental tie-line data was verified by using the Othmer−Tobias correlation. Distribution coefficients and separation factors were evaluated for the immiscibility region. Although all of the proposed solvents show low distribution coefficients, they can be served as convenient agents for extracting morpholine from aqueous medium, since they exhibit high separation factors. The experimental tie-line data were correlated by universal quasichemical activity coefficient (UNIQUAC) model representing the LLE data for these systems with respect to tie-line slopes only.

Electrical and structural properties of p ‐type nanocrystalline silicon grown by LEPECVD for photovoltaic applications

Abstractp‐doped hydrogenated nanocrystalline silicon (p‐nc‐Si:H) is one of the most critical layers in thin film silicon solar cells. LEPECVD is a new technique for the growth of nc‐Si at high growth rate without compromising the layer quality, using a dense but low energy plasma. Thin p‐nc‐Si:H layers are grown on glass and ZnO:Al coated glass and their structural and electrical properties are investigated as a function of the silane dilution (d) and of the doping ratio (DR). The influence of the substrate on the structural properties is investigated and discussed. The incubation layer is clearly observed on both substrate types and its thickness is estimated. LEPECVD distinguishes itself from other high growth rate methods by a very low impurity distribution coefficient to obtain a comparable conductivity and boron density. The conduction path is shown to be dependent on the density of boron in the layer while a significant decrease of conductivity at high DR is not observed in the studied range (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Interaction of 6,6′′-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2′:6′,2′′-terpyridine (CyMe4-BTTP) with some trivalent ions such as lanthanide(iii) ions and americium(iii)

The new ligand 6,6''-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2':6',2''-terpyridine (CyMe4-BTTP) has been synthesized in 4 steps from 2,2':6',2''-terpyridine. Detailed NMR and mass spectrometry studies indicate that the ligand forms 1:2 complexes with lanthanide(III) perchlorates where the aliphatic rings are conformationally constrained whereas 1:1 complexes are formed with lanthanide(III) nitrates where the rings are conformationally mobile. An optimized structure of the 1:2 solution complex with Yb(III) was obtained from the relative magnitude of the induced paramagnetic shifts. X-Ray crystallographic structures of the ligand and of its 1:1 complex with Y(III) were also obtained. The NMR and mass spectra of [Pd(CyMe4-BTTP)]n(2n+) are consistent with a dinuclear double helical structure (n = 2). In the absence of a phase-modifier, CyMe4-BTTP in n-octanol showed a maximum distribution coefficient of Am(III) of 0.039 (±20%) and a maximum separation factor of Am(III) over Eu(III) of 12.0 from nitric acid. The metal(III) cations are extracted as the 1:1 complex from nitric acid. The generally low distribution coefficients observed compared with the BTBPs arise because the 1:1 complex of CyMe4-BTTP is considerably less hydrophobic than the 1:2 complexes formed by the BTBPs. In M(BTTP)(3+) complexes, there is a competition between the nitrate ions and the ligand for the complexation of the metal.

Extraction Equilibrium of Ethanol for Bioethanol Production — Solvent Selection and Liquid-liquid Equilibrium Measurement —

Ethanol distributions between selected organic and aqueous phases were measured for recovery and concentration of bioethanol from fermented solution. The strategy of solvent selection was based on the background of biofuel production, and m-xylene was selected as the primary solvent and capric acid, 1-hexanol and 2-ethyl hexanol secondary solvents were utilized to enhance the ethanol solubility. The extraction performance was evaluated through the liquid-liquid equilibrium. m-Xylene showed low distribution coefficient of ethanol and high separation selectivity of ethanol relative to water. All secondary solvents increased the distribution coefficient. The separation selectivity was greatly reduced by capric acid, but was similar for 1-hexanol and 2-ethyl hexanol. The two phase region was smaller for 1-hexanol than for 2-ethyl hexanol, chosen as the best secondary solvent. Examination of the effects of 2-ethyl hexanol concentration in the solvent found that a small amount of 2-ethyl hexanol could enhance the distribution coefficient and maintain the separation selectivity constant. The measured liquid-liquid equilibria were estimated with the ordinary and modified UNIFAC methods. Both methods could predict the liquid-liquid equilibrium behaviors of the measured systems, but the modified UNIFAC method could show a better correlation. However, the water concentrations in the organic phases were estimated to be larger than the measured values if the measured concentrations were very low.

Regulation of sevoflurane on immune factors

Sevoflurane is a potent non-explosive inhalational anesthetic agent which provides rapid anesthetic induction and recovery consistent with its low distribution coefficient and high efficacy. Recently, the immune responses to sevoflurane and immune regulation have attracted sufficient attention, mainly focusing on its anti-inflammatory effects, attenuation of the stress response and relief of the ischemia-reperfusion injury. This review briefly demonstrates the immune responses and the immuno-mechanism of red blood cell, lymphocyte and cytokines when exposed to sevoflurane. Since the regulation of sevoflurane is precise and complex, the diversification deserves further experimental and clinical evidences. Key words: Sevoflurane; Regulation; Immune factors

Pathways of advanced oxidation of phenol by Fenton's reagent—Identification of oxidative coupling intermediates by extractive acetylation

Homogeneous Fenton reaction (H 2O 2/Fe 2+ system) using significantly substoichiometric concentrations of H 2O 2 oxidant to oxidize phenol was characterized focusing on the formation of stable aromatic intermediates. Beyond the most abundant benzenediols, the pattern of aromatic intermediates was chiefly characterized by hydroxylated biphenyls and diphenyl ethers with different degrees of hydroxylation. Hydroxylated dibenzofurans (DBF), p,p′-dioxins, as well as highly condensed aromatic intermediates including polyols of polycyclic aromatic hydrocarbons (PAHs), could also be detected, but in lower concentrations. The formation of aromatic intermediates could be predicted on the basis of oxidative coupling reactions of resonance-stabilized radicals generated by the attack of the highly reactive hydroxyl radicals (OH*) on phenol. GC/MS identification of oxidative coupling intermediates was performed after derivatization of the solvent extracts. Derivatization reactions included silylation to give TMS (trimethylsilyl) ethers, as well as single-step extractive acetylation using acetic anhydride in alkaline aqueous solutions (pH 10.5) to give acetates. Solvent extraction of aqueous solutions, a prerequisite to generate TMS ethers, caused strong discrimination of polyols due to their low distribution coefficients in non-polar solvents. This discrimination could be overcome by extracting the in-situ formed acetates of the intermediates. Extractive acetylation allowed the detection of tri-, tetra-, and penta-hydroxylated aromatic intermediates generated by Fenton oxidation processes, which have been overlooked upto now. Thus, extractive acetylation to detect stable aromatic intermediates covering a wide range of hydroxylation degrees can foster the understanding, monitoring, and management of advanced oxidation processes, especially in the field of wastewater treatment.

Extractant screening and selection for methyl tert-butyl ether removal from aqueous streams

Recovery of low concentration methyl tert-butyl ether (MTBE) from aqueous solutions is difficult. Activated carbon adsorption or air stripping suffer from low capacity and high energy input. Liquid–liquid extraction is suggested as an alternative separation technique, but requires a suitable extractant. Based on molecular considerations, an extractant screening with COSMO-RS gives a good qualitative trend. Halogenated phenols provide the highest MTBE capacity. This is confirmed by liquid–liquid equilibrium experiments. 3-Iodophenol is selected as the MTBE extractant, because it combines comparatively low toxicity and high distribution coefficient K D. Propylbenzene is selected as the diluent. The K D of MTBE extraction with 3-iodophenol/propylbenzene is 270 at high extractant concentrations and low MTBE concentrations. Water solubility of 3-iodophenol can possibly be minimized by additional branched alkyl chains, preferably in para position at the aromatic ring to avoid steric hindrance during hydrogen bonding. In this study, reactive extraction of MTBE is successfully performed for the first time.

Investigation of some factors contributing to negative food effects

A drug is defined as exhibiting negative food effects, if the co-administration of food statistically decreases its area under the curve, AUC, when compared with its administration on a fasted stomach. In this study, the role of biopharmaceutical factors that contribute to negative food effects was studied using furosemide, nadolol, tacrine and atenolol (as model compounds exhibiting negative food effects), and prednisolone, hydrochlorothiazide and ibuprofen (as model compounds that do not show any food effects). The physiological pH of the upper intestinal tract is lower, at pH 5, in the postprandial state when compared with the preprandial state, pH 6.5. Drugs that exhibited negative food effects had low apical to basolateral Caco-2 permeabilities, low pKa/pKb and Log P values of less than 1. The drugs exhibiting negative food effects had low distribution coefficients at the pH conditions of the fed and fasted states. Furosemide, being a hydrophilic, poorly soluble acidic drug showed lower solubility in the fed state when compared with the fasted state. Basic drugs, atenolol, nadolol and tacrine, are ionized to a higher extent in the fed state and exhibit lower permeability and lower absorption when compared with the fasted state. Thus, drugs were found to exhibit negative food effects owing to their decrease in solubility or permeability in the upper intestinal tract of the fed state when compared with the fasted state.

Quantitative aspects of Mn‐activated cathodoluminescence of natural and synthetic aragonite

AbstractThe cathodoluminescence analyses of the trigonal carbonates calcite and dolomite have been applied intensively in sedimentary petrology for a long time and the properties of these minerals are well‐known, but much less attention has been paid to aragonite. In this study, the cathodoluminescence behaviour and the trace element composition of natural and synthetic aragonite have been studied employing trace element analyses (proton induced X‐ray emission) and luminescence spectroscopy. Aragonite doped with Mn2+ has been synthesized in a NH4+–Mg2+–Ca2+–Cl− solution in contact with a CO2–H2O–NH3 atmosphere. The low effective distribution coefficients indicate a rapid growth of the crystals of millimetre size which occurred within hours or days. The natural aragonite samples contain Mn, Fe and Sr in different concentrations. The Mn‐bearing aragonites exhibit a bright green luminescence which is caused by a strong emission band at 575 nm with a half‐width of about 84 nm. The luminescence intensity shows a strong positive correlation with Mn in aragonite when Fe and Mn do not exceed 2000 p.p.m. The intensity is depressed if the concentration of these elements exceeds the critical values. In the shell of a recent Unio sp., the luminescence intensity deviates from the linear correlation, although the trace element contents are not too high; this is probably an effect of quenching by organic material between the crystallites of the biogenic aragonite.

Chromatographic Separations of Traces 134Cs, 60Co, and 152,154Eu Using Silico-, Molybdo-, and Chromotitanates as Inorganic Ion Exchangers

Silicotitanate, molybdotitanate, and chromotitanate as inorganic ion exchange materials were synthesized with Si/Ti, Mo/Ti, and Cr/Ti ratios equal to 1.0, 1.33, and 0.5, respectively. The chemical composition of the synthesized materials were determined and found to SiTiO4·9.52H2O, Mo4Ti3O16·10.2H2O, and Cr2Ti4O11·5.65H2O for silicotitanate, molybdotitanate, and chromotitanate, respectively. Schematic illustrations of these materials were achieved according to the related structures. The stability of these synthesized materials in different media showed high resistance toward chemical attack. Batch adsorption technique was used for the investigation of the distribution coefficients of 134Cs, 60Co, and 152,154Eu from synthetic mixture solutions on the three inorganic ion exchangers. The effect of the medium composition (pH) on the distribution coefficients was studied, and the data obtained indicated that 60Co had a very low distribution coefficient on the three ion exchangers in 0.1 M HNO3 and a mixed system of 0.1 M HNO3 + 0.1 M NaNO3. 134Cs and 152,154Eu are highly adsorbed on molybdotitanate and chromotitanate in 0.1 M HNO3 medium; on the other hand, these ions have high distribution coefficients on silicotitanate in 0.1 M HNO3 + 0.1 M NaNO3 medium. Based on the batch distribution coefficient data achieved, chromatographic column separations of 134Cs−60Co, 134Cs−152,154Eu, and 60Co−152,154Eu were carried out using different eluants such as 0.01 M HNO3, 0.1 M HNO3, 0.1 M NH4Cl, and 0.1 M NH4OH.