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1.
Food Chem ; 340: 128100, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33059268

RESUMO

A strongly basic ion-exchange resin catalyst was reported to exhibit a high catalytic activity in transesterification to produce a bio-based surfactant, sugar ester under mild condition. However, the side-reactions to decompose the reactant and the product were found to occur. This study was aimed to improve the selectivity of sugar ester synthesis by newly focusing on the basicity of the resin. A weakly basic resin (Diaion WA20) with a lower mass transfer resistance suppressed the decompositions while maintaining synthesis rate. Controlling molar ratio of the reactants in the intraparticle reaction field also increased the reaction selectivity, 72.1% and product yield, 57.5%. Both values were drastically increased compared to the reported values with the strongly basic resin (selectivity 50.9%, yield 14.3%). This is the first knowledge to show a high catalytic activity of weakly basic resin. These results suggest that a more efficient continuous production process would be possible.


Assuntos
Ésteres/química , Ácidos Graxos/química , Resinas de Troca Iônica/química , Açúcares/química , Catálise , Esterificação
2.
J Chromatogr A ; 1633: 461627, 2020 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-33128970

RESUMO

A Poly (3,4-ethylenedioxothiophene) (PEDOT)/UiO-66 composite was electrodeposited on an etched stainless-steel wire as head-space solid-phase microextraction (HS-SPME) coating. A robust, well controlled thickness, and uniform coating of metal organic framework composites can be realized by the electrodeposited strategy. The incorporated UiO-66 not only enhanced the uniformity and stability of the composite coating, but also effectively decreased the stacking phenomenon of PEDOT and improved its extraction efficiency, which was over 100 times higher than that of the PEDOT coating without UiO-66. The composite coating was used to enrich seven types of volatile organic compounds (VOCs) in ion-exchange resins, including methyl cyclohexane, benzene, toluene, ortho-xylene, styrene, para-xylene and divinyl-benzene. The results of adsorption isotherm analysis showed that π stacking effect played dominant role between the composite coating and VOCs in the extraction process. The composite coating was characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared and thermogravimetric analysis, respectively. A determination method for seven kinds of VOCs was established by HS-SPME coupled with gas chromatography-flame ionization detection (GC-FID). Under the optimal experimental conditions, the detection linear range (LRs) was 0.09-100 ng mL-1, and the detection limit (LODs) was 0.03-0.06 ng mL-1 (S/N = 3). The method was applied for the migration detection of VOCs in four types of ion-exchange resin, which showed satisfactory recovery (84.5-117.2%).


Assuntos
Técnicas de Química Analítica/métodos , Estruturas Metalorgânicas/química , Polímeros/química , Tiofenos/química , Compostos Orgânicos Voláteis/isolamento & purificação , Adsorção , Benzeno/análise , Benzeno/isolamento & purificação , Cromatografia Gasosa , Ionização de Chama , Resinas de Troca Iônica/química , Limite de Detecção , Microextração em Fase Sólida , Aço Inoxidável/química , Tolueno/análise , Tolueno/isolamento & purificação , Compostos Orgânicos Voláteis/análise , Xilenos/análise , Xilenos/isolamento & purificação
3.
Proc Natl Acad Sci U S A ; 117(13): 7004-7010, 2020 03 31.
Artigo em Inglês | MEDLINE | ID: mdl-32179691

RESUMO

Protein mobility at solid-liquid interfaces can affect the performance of applications such as bioseparations and biosensors by facilitating reorganization of adsorbed protein, accelerating molecular recognition, and informing the fundamentals of adsorption. In the case of ion-exchange chromatographic beads with small, tortuous pores, where the existence of surface diffusion is often not recognized, slow mass transfer can result in lower resin capacity utilization. We demonstrate that accounting for and exploiting protein surface diffusion can alleviate the mass-transfer limitations on multiple significant length scales. Although the surface diffusivity has previously been shown to correlate with ionic strength (IS) and binding affinity, we show that the dependence is solely on the binding affinity, irrespective of pH, IS, and resin ligand density. Different surface diffusivities give rise to different protein distributions within the resin, as characterized using confocal microscopy and small-angle neutron scattering (length scales of micrometer and nanometer, respectively). The binding dependence of surface diffusion inspired a protein-loading approach in which the binding affinity, and hence the surface diffusivity, is modulated by varying IS. Such gradient loading increased the protein uptake efficiency by up to 43%, corroborating the importance of protein surface diffusion in protein transport in ion-exchange chromatography.


Assuntos
Resinas de Troca Iônica/química , Modelos Químicos , Proteínas/química , Difusão
4.
Chemosphere ; 244: 125589, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32050353

RESUMO

Radioactive Cs ions are extremely harmful to the human body, causing cancers and other diseases. Treatments were performed on radioactive Cs present in wastewater after use in industrial or medical fields. Prussian blue (PB) has been widely used for the removal of Cs ions from water but its colloidal structure hinders reuse, making it problematic for practical use. To solve this problem, we used a commercial macroporous polymer resin as a PB matrix. To provide an efficient anchor for PB, the surface of the polymer resin was decorated with sodium dodecylbenzenesulfonate to produce a negatively charged surface. The successful chemical binding between the polymer resin and PB prevented leakage of the latter during adsorption and crosslinked structure of the matrix provided regeneration of the adsorbent. The adsorbent maintained its removal efficiency after five repeats of the regeneration process. The PB-based, Cs ion-exchange resin showed excellent selectivity toward Cs ions and good reusability, maintaining its high adsorption capacity.


Assuntos
Benzenossulfonatos/química , Césio/química , Ferrocianetos/química , Resinas de Troca Iônica/química , Poluentes Químicos da Água/química , Adsorção , Humanos , Águas Residuárias/química , Purificação da Água
5.
Chemosphere ; 241: 125090, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31683451

RESUMO

It is essential to mitigate the risk of exposure to effluent organic matter (EfOM) in aquatic environments to ensure safe wastewater recycling. Magnetic ion-exchange (MIEX) resin adsorption combined with ozonation could provide EfOM removal. However, the poor understanding of the influences of the parameters and mechanisms in the hybrid process has restricted the applications. In this study, the response surface methodology was used to reveal the interactions of the major operation parameters. The degradation behaviour of the EfOM was investigated by using spectroscopy combined with mathematical methods. The effect of the pH on the EfOM removal was also analysed. The maximum efficiency of the removal of dissolved organic carbon (DOC) was 59.77% at the optimal MIEX resin dosage of 7.97 mL/L, ozone concentration of 8 mg/L, agitation speed of 199.84 r/min, and pH of 9.98. The ozonation was superior to resin adsorption in the removal of 1054-Da compounds, while the resin adsorption was advantageous in the removal of 4168-Da compounds. Three fluorescent components (C1, C2, and C3) were more easily subjected to external perturbation than the DOC and ultraviolet absorbance at 254 nm in the oxidation processes. The MIEX resin exhibited low efficiencies of removal of the fluorescent substances. A synchronous fluorescence analysis coupled with a two-dimensional correlation analysis revealed that the variation in EfOM followed the order of fulvic-to humic-like substances in the hybrid process of MIEX and the following ozonation. The pH was the most significant influencing factor in the hybrid process.


Assuntos
Resinas de Troca Iônica/química , Ozônio/química , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Adsorção , Carbono/isolamento & purificação , Concentração de Íons de Hidrogênio , Fenômenos Magnéticos , Oxirredução , Eliminação de Resíduos Líquidos/instrumentação , Poluentes Químicos da Água/química
6.
J Chromatogr A ; 1614: 460732, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31836308

RESUMO

Differences in the characteristics of seventeen commercial C-30 liquid chromatographic columns were studied for the separation of carotenoid isomers. A mixture consisting of nine xanthophyll and hydrocarbon carotenoids were separated under conditions carefully chosen to reveal changes in selectivity. The influence of the mobile phase composition, column temperature, and mobile phase flow rate were evaluated. Shape selectivity was characterized with Standard Reference Material (SRM) 869b Column Selectivity Test Mixture, for correlation with carotenoid retention behavior. Regular changes were observed across a broad spectrum of shape selectivity characteristics as indicated by SRM 869b. Better separations of carotenoid isomers were achieved with C-30 columns than were possible with C-18 columns, even after optimization of separation conditions.


Assuntos
Carotenoides/isolamento & purificação , Cromatografia Líquida/instrumentação , Resinas de Troca Iônica/química , Resinas de Troca Iônica/normas , Hidrocarbonetos/química , Isomerismo
7.
Molecules ; 24(15)2019 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-31370148

RESUMO

A novel functional ion-exchange/adsorption metal organic resin (MOR), TEBAC-HKUST-1, was prepared and characterized. Ethanedithiol was used as the grafting agent to introduce thiol groups onto HKUST-1, and 4-vinylbenzyl chloride was then grafted onto SH-HKUST-1 using thiol groups. Finally, the quaternary ammonium functional group was immobilized onto the carrier by performing a quaternization reaction. The structure and property of TEBAC-HKUST-1 MOR were characterized by TGA, N2 adsorption-desorption, FTIR, SEM, and XRD. TEBAC-HKUST-1 MOR was used to remove metal cyanide complexes from wastewater. The adsorption was rapid, and the metal cyanide complexes including Pt(CN)42-, Co(CN)63-, Cu(CN)32-, and Fe(CN)63- were removed in 30 min. TEBAC-HKUST-1 MOR exhibited a high stability in neutral and weak basic aqueous solutions. Furthermore, Pt(II) could be efficiently recovered through two-step elution. The recovery rate of Pt(II) for five cycles were over 92.0% in the mixture solution containing Pt(CN)42-, Co(CN)63-, Cu(CN)32-, and Fe(CN)63-. The kinetic data were best fitted with the pseudo second-order model. Moreover, the isothermal data were best fitted with the Langmuir model. The thermodynamic results show that the adsorption is a spontaneous and exothermic process. TEBAC-HKUST-1 MOR not only exhibited excellent ability for the rapid removal of metal cyanide complexes, but also provided a new idea for the extraction of noble metals from cyanide-contaminated water.


Assuntos
Cianetos/isolamento & purificação , Compostos Organometálicos/química , Águas Residuárias/química , Purificação da Água/métodos , Adsorção , Complexos de Coordenação/química , Cianetos/química , Cianetos/toxicidade , Humanos , Concentração de Íons de Hidrogênio , Resinas de Troca Iônica/química , Cinética , Paládio/química , Termodinâmica , Poluentes Químicos da Água
8.
Int J Biol Macromol ; 138: 681-692, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31344414

RESUMO

We develop a technique for the sorption of inulinase from Kluyveromyces marxianus on the KU-2 matrix cation-exchanger. The most appropriate conditions for immobilization are: 25 °C, pH 4.5, incubation time 1.5 h, protein content during immobilization 10 mg/g of carrier. At higher (20-100 mg/g) concentrations, inulinase forms local high-concentration domains on the ion-exchanger surface, the enzyme is adsorbed on the protein, not on the carrier. 62% of the initial catalytic activity of inulinase is immobilized on KU-2 by the adsorption method. Upon the enzyme immobilization on KU-2, the number of unordered structures in the protein is reduced by ~10%, that points to the compaction of the molecule. Hydrogen bonds are formed only between the sulfo groups of carrier and the protein molecule, without affecting other structures of the cation exchanger. The highest activity of the inulinase immobilized on KU-2 was observed at 70 °C (cf. 50 °C for the native enzyme). Heating of the solution for 60 min in the temperature range of 50-80 °C failed to inactivate completely the immobilized enzyme; the complete loss of its ability to hydrolyze inulin was achieved only after more than 1 h incubation at 90 °C.


Assuntos
Enzimas Imobilizadas , Glicosídeo Hidrolases/química , Resinas de Troca Iônica/química , Adsorção , Biocatálise , Ativação Enzimática , Estabilidade Enzimática , Concentração de Íons de Hidrogênio , Hidrólise , Kluyveromyces/enzimologia , Modelos Moleculares , Conformação Proteica , Análise Espectral , Temperatura
9.
Int J Mol Sci ; 20(14)2019 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-31336637

RESUMO

Electrodialysis and electrodeionization are separation processes whose performance depends on the quality and properties of ion-exchange membranes. One of the features that largely affects these properties is heterogeneity of the membranes both on the macroscopic and microscopic level. Macroscopic heterogeneity is an intrinsic property of heterogeneous ion-exchange membranes. In these membranes, the functional ion-exchange component is dispersed in a non-conductive binder. The functional component is finely ground ion-exchange resin particles. The understanding of the effect of structure on the heterogeneous membrane properties and behavior is thus of utmost importance since it does not only affect the actual performance but also the cost and therefore competitiveness of the aforementioned separation processes. Here we study the electrokinetic behavior of cation-exchange resin particle systems with well-defined geometrical structure. This approach can be understood as a bottom up approach regarding the membrane preparation. We prepare a structured cation-exchange membrane by using its fundamental component, which is the ion exchange resin. We then perform an experimental study with four different experimental systems in which the number of used cation-exchange particles changes from 1 to 4. These systems are studied by means of basic electrochemical characterization measurements, such as measurement of current-voltage curves and direct optical observation of phenomena that occur at the interface between the ion-exchange system and the adjacent electrolyte. Our work aims at better understanding of the relation between the structure and the membrane properties and of how structure affects electrokinetic behavior of these systems.


Assuntos
Cátions/química , Eletricidade , Resinas de Troca Iônica/química , Troca Iônica , Eletroquímica , Concentração de Íons de Hidrogênio , Membranas Artificiais
10.
Environ Pollut ; 252(Pt B): 1042-1050, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31252101

RESUMO

Aiming at realizing heavy metal recycling and resource utilization, a carbon-based iron catalyst (Fe@C) was synthesized through a resin carbonization method, and adopted for peroxymonosulfate (PMS) activation to remove bisphenol S (BPS), an emerging aquatic contaminant. This study demonstrated that Fe@C exhibited excellent catalytic potential for BPS degradation with a relatively low activation energy (Ea = 29.90 kJ/mol). Kinetic factors affecting the activation performance were thoroughly investigated. The obtained results indicated that Fe@C composite exhibited the superior uniformity with carbon as the framework and granular iron oxide as the coverage. pH increase could cause the inhibitive effect on BPS degradation, while the increasing catalyst loading (0.05-0.5 g/L) was conducive for the catalytic performance of Fe@C, with an optimal PMS concentration at 1.0 mM. A negative influence on BPS degradation was obtained in the presence of SO42-, HCO3- and lower concentration of Cl- (0-20 mM), compared to the promotion at higher concentration of Cl- (>50 mM). Based on the electron spin resonance (ESR) monitoring and radical scavenging results, it is demonstrated that singlet oxygen, a non-radical species, emerged together with ·SO4- and ·OH for BPS degradation. A three-channel catalytic mechanism was verified through typical characterizations. Furthermore, the degradation pathway of BPS was proposed based on the identified intermediates. This novel carbon-based activator for PMS showed notable potential for the waste resin recycling and water decontamination. A novel Fe-based activator carbonized from a saturated resin exhibits excellent performance for Bisphenol S degradation with activated peroxymonosulfate.


Assuntos
Carbono/química , Compostos Férricos/química , Peróxidos/química , Fenóis/análise , Sulfonas/análise , Poluentes Químicos da Água/análise , Catálise , Resinas de Troca Iônica/química , Cinética , Reciclagem
11.
J Chromatogr A ; 1603: 130-140, 2019 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-31235330

RESUMO

Zwitterionic chiral ion-exchange selectors (ZWIX) obtained by conjugation of quinine and 2-aminocyclohexanesulfonic acid via a carbamate bond were immobilized on three different silica particle types, viz. 120 Š3 µm fully porous particles (FPP), 200 Š3 µm FPP and 160 Š2.7 µm superficially porous particles (SPP). Selector densities were determined by elemental analysis and the porosities of packed columns measured by inverse size exclusion chromatography with polystyrene standards. Liquid chromatographic tests with a set of chiral zwitterionic, acidic and basic analytes showed that the surface chemistry was successfully transferred to the distinct particle morphologies. The chromatographic performance of the three columns was evaluated by acquiring van Deemter curves. The results showed that the column packed with the SPP particles gives the best performance and kinetic plots further demonstrated that they represent the most favorable compromise in terms of speed, efficiency and pressure drop. Sub-minute separations could be accomplished at much lower pressure drop on the core-shell column, e.g. 2-amino-2-phenylbutyric acid was baseline separated in less than 15 s on a 5 cm long column. The Maxwell effective medium theory with second order approximation was applied to calculate effective diffusion in the mesoporous zones of SPP and FPP, which allowed eventually to deconvolute the individual peak dispersion contributions (ha, hb, hc,m, hc,s, hc,ads). The efficiency gain of the 160 ŠSPP column compared to the 120 ŠFPP (benchmark) column was mainly due to lower eddies (ha), smaller c-term accounting for slow adsorption-desorption kinetics in enantioselective chromatography (hc,ads), and also due to lower stationary mass transfer resistance (hc,s). Enhanced effective diffusion (Deff) in the SPP column contributed to a lower longitudinal diffusion (hb). In contrast, the mobile phase mass transfer coefficient was similar in the two columns leading to comparable hc,m contributions. This study discloses some options for improvement of the efficiency of ZWIX-type chiral columns such as replacing narrow pore (120 Å) by wide pore (200 Å) particles, substituting FPP by SPP and reducing the selector density on the surface.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Resinas de Troca Iônica/química , Adsorção , Cinética , Porosidade , Estereoisomerismo , Temperatura
12.
Sci Total Environ ; 683: 709-718, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31150891

RESUMO

Over the past century, atmospheric nitrogen deposition (Ndep) has increased across the western United States due to agricultural and urban development, resulting in degraded ecosystem quality. Regional patterns of Ndep are often estimated by coupling direct measurements from large-scale monitoring networks and atmospheric chemistry models, but such efforts can be problematic in the western US because of complex terrain and sparse sampling. This study aimed not only to understand Ndep patterns in mountainous ecosystems but also to investigate whether isotope values of lichens and throughfall deposition can be used to determine Ndep sources, and serve as an additional tool in ecosystem health assessments. We measured Ndep amounts and δ15N in montane conifer forests of the Greater Yellowstone Ecosystem using canopy throughfall and bulk monitors and lichens. In addition, we examined patterns of C:N ratios in lichens as a possible indicator of lichen physiological condition. The isotopic signature of δ15N of Ndep helps to discern emission sources, because δ15N of NOx from combustion tends to be high (-5 to +25‰) while NHx from agricultural sources tends to be comparatively low (-40 to -10‰). Summertime Ndep increased with elevation and ranged from 0.26 to 1.66 kg ha-1. Ndep was higher than expected in remote areas. The δ15N values of lichens were typically -15.3 to -10‰ suggesting agriculture as a primary emission source of deposition. Lichen %N, δ15N and C:N ratios can provide important information about Ndep sources and patterns over small spatial scales in complex terrain.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental/métodos , Nitrogênio/análise , Parques Recreativos , Ecossistema , Monitoramento Ambiental/instrumentação , Florestas , Resinas de Troca Iônica/química , Líquens
13.
Int J Mol Sci ; 20(10)2019 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-31091791

RESUMO

The electro-kinetic instability in a pressure driven shear flow near an ion exchange membrane is considered. The electrochemical system, through which an electrical potential drop is applied, consists in a polarization layer in contact with the membrane and a bulk. The numerical investigation contained two aspects: analysis of the instability modes and description of the Lagrangian transport of fluid and ions. Regarding the first aspect, the modes were analyzed as a function of the potential drop. The analysis revealed how the spatial distribution of forces controls the dynamics of vortex association and dissociation. In particular, the birth of a counter-clockwise vortex between two clockwise vortices, and the initiation of clusters constituting one or two envelopes wrapping a vortex group, were examined. In regards to the second aspect, the trajectories were computed with the fourth order Runge Kutta scheme for the time integration and with the biquadratric upstream scheme for the spatial and time interpolation of the fluid velocity and the ion flux. The results for the periodic mode showed two kinds of trajectories: the trochoidal motion and the longitudinal one coupled with a periodic transverse motion. For the aperiodic modes, other mechanisms appeared, such as ejection from the mixing layer, trapping by a growing vortex or merging vortices. The analysis of the local velocity field, the vortices' shape, the spatial distribution of the forces and the ion flux components explained these trajectories.


Assuntos
Técnicas Eletroquímicas , Resinas de Troca Iônica/química , Membranas Artificiais , Modelos Teóricos
14.
Methods Mol Biol ; 1985: 251-277, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31069739

RESUMO

For the early 2000s, chromatographic methods applying chiral stationary phases (CSPs) became the most effective techniques for the resolution of chiral compounds on both analytical and preparative scales. High-performance liquid chromatography (HPLC) employing various types of chiral selectors covalently bonded to silica-based supports offers a state-of-the-art methodology for "chiral analysis." Although a large number of CSPs are available nowadays, the design and development of new "chiral columns" are still needed since it is obvious that in practice one needs a good portfolio of different columns to face the challenging task of enantiomeric resolutions. The development of the unique chiral anion, cation, and zwitterion exchangers achieved by Lindner and his partners serves as an expansion of the range of the efficiently applicable CSPs.In this context this overview chapter discusses and summarizes direct enantiomer separations of chiral acids and ampholytes applying zwitterionic ion exchangers derived from Cinchona alkaloids. Our aim is to provide comprehensive information on practical solutions with focus on the molecular recognition and methodological variables.


Assuntos
Cromatografia Líquida/métodos , Alcaloides de Cinchona/química , Alcaloides de Cinchona/isolamento & purificação , Resinas de Troca Iônica/química , Modelos Químicos , Estereoisomerismo , Água/química
15.
Food Chem ; 292: 260-266, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31054674

RESUMO

The presence of 2-acetyl-4(5)-(1,2,3,4-tetrahydroxybutyl)-imidazole (THI) in beverages has raised several concerns regarding its toxicity to humans. The sample preparation and detection of THI in complex matrices is challenging owing to its high water solubility. Here we reported a rapid sample preparation method based on dispersive micro-solid phase extraction (D-µ-SPE) using polymer cation exchange sorbent as sorbent for the extraction of THI from beverage samples. THI was detected by high performance anion exchange chromatography-pulsed amperometric detector (HPAEC-PAD) and high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The experimental parameters of D-µ-SPE on extraction efficiency were carefully optimized. Under the optimized conditions, high recoveries (83.4-96.1%) and good reproducibility (%RSD ≤ 8.7%) were obtained using D-µ-SPE-HPAEC-PAD and D-µ-SPE-HPLC-MS/MS. Limit of quantification was 75 ng/mL for HPAEC-PAD and 5 ng/mL for HPLC-MS/MS. This work proves the potential application the newly developed method for the quantification of THI in beverages containing caramel color.


Assuntos
Bebidas/análise , Imidazóis/análise , Resinas de Troca Iônica/química , Polímeros/química , Carboidratos/análise , Cromatografia Líquida de Alta Pressão/métodos , Humanos , Imidazóis/isolamento & purificação , Limite de Detecção , Reprodutibilidade dos Testes , Microextração em Fase Sólida , Espectrometria de Massas em Tandem/métodos
16.
Water Sci Technol ; 79(5): 820-832, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31025960

RESUMO

This study investigated the applicability of fluorescence excitation-emission matrix spectroscopy (EEMS) to assess total trihalomethane formation potentials (TTHMFPs) and the ability of magnetic ion exchange (MIEX®) resin to reduce TTHMFP. We treated a surface water and secondary wastewater effluent with MIEX mimicking full-scale operation by repeatedly exposing the same resin batch to additional feed water, with batches ranging from 500 to 5,000 resin bed volumes. Results showed that MIEX was more effective at removing or reducing ultraviolet absorbance (UVA254), dissolved organic carbon (DOC), and TTHMFP in surface water than in secondary effluent. The greater UVA254, DOC and TTHMFP removal for surface waters was explained by the stronger affinity of MIEX for terrestrial dissolved organic matter (DOM) compared to microbial DOM. Fluorescence EEMS results showed that the ratio between terrestrial and microbial fluorescent signals of DOM was significantly greater in surface water than in secondary effluent. Fluorescence surrogate parameters were strongly correlated with TTHMFP, namely, fluorescence intensity of humic-like peak C (R2 = 0.98, p < 0.01), protein-like peak T (R2 = 0.96, p < 0.01), and fulvic-like peak A (R2 = 0.87, p < 0.01). Correlations between fluorescence surrogate parameters and TTHMFP were substantially stronger than correlations between DOC and TTHMFP. Overall, the results indicate that fluorescent parameters extracted from EEMS data can be used as quick surrogate parameters to monitor TTHMFP for a diverse group of raw and MIEX-treated waters.


Assuntos
Resinas de Troca Iônica/química , Trialometanos/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Troca Iônica , Compostos Orgânicos , Espectrometria de Fluorescência , Trialometanos/análise , Poluentes Químicos da Água/análise
17.
J Vis Exp ; (146)2019 04 06.
Artigo em Inglês | MEDLINE | ID: mdl-31009012

RESUMO

This method allows the separation of trypanosomes, parasites responsible for animal and human African trypanosomiasis (HAT), from infected blood. This is the best method for diagnosis of first stage HAT and furthermore this parasite purification method permits serological and research investigations. HAT is caused by Tsetse fly transmitted Trypanosoma brucei gambiense and T. b. rhodesiense. Related trypanosomes are the causative agents of animal trypanosomiasis. Trypanosome detection is essential for HAT diagnosis, treatment and follow-up. The technique described here is the most sensitive parasite detection technique, adapted to field conditions for the diagnosis of T. b. gambiense HAT and can be completed within one hour. Blood is layered onto an anion-exchanger column (DEAE cellulose) previously adjusted to pH 8, and elution buffer is added. Highly negatively charged blood cells are adsorbed onto the column whereas the less negatively charged trypanosomes pass through. Collected trypanosomes are pelleted by centrifugation and observed by microscopy. Moreover, parasites are prepared without cellular damage whilst maintaining their infectivity. Purified trypanosomes are required for immunological testing; they are used in the trypanolysis assay, the gold standard in HAT serology. Stained parasites are utilized in the card agglutination test (CATT) for field serology. Antigens from purified trypanosomes, such as variant surface glycoprotein, exoantigens, are also used in various immunoassays. The procedure described here is designed for African trypanosomes; consequently, chromatography conditions have to be adapted to each trypanosome strain, and more generally, to the blood of each species of host mammal. These fascinating pathogens are easily purified and available to use in biochemical, molecular and cell biology studies including co-culture with host cells to investigate host-parasite relationships at the level of membrane receptors, signaling, and gene expression; drug testing in vitro; investigation of gene deletion, mutation, or overexpression on metabolic processes, cytoskeletal biogenesis and parasite survival.


Assuntos
DEAE-Celulose/química , Resinas de Troca Iônica/química , Trypanosoma/isolamento & purificação , Animais , Ânions , Arginase/metabolismo , Sangue/parasitologia , Cromatografia , Feminino , Glucose/metabolismo , Macrófagos/efeitos dos fármacos , Macrófagos/enzimologia , Camundongos , Pentamidina/farmacologia , Treonina/metabolismo , Trypanosoma/efeitos dos fármacos , Trypanosoma brucei brucei/efeitos dos fármacos
18.
Int J Pharm ; 561: 206-218, 2019 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-30822506

RESUMO

We employed a new dry coating process with mild-intensity vibration to prepare a 100-µm-sized microparticle capable of prolonged release of a drug. To accomplish this without using a binder, a series of laboratory-made acrylic latexes with different glass transition temperatures (Tg) ranging from 30 °C to 80 °C were employed as coating agents, and the effects of Tg and powdering method of the coating agents on coating performance were investigated. The laboratory-made acrylic latexes were powdered by spray-drying (SD) or freeze-drying (FD). Diclofenac sodium (DS)-loaded ion-exchange-resin with particle size ∼100 µm was used as a core particle. The process utilized vibrations with amplitude of 0.5 mm and frequency of 90 Hz to form an ordered mixture composed of the core particles with the loosely-layered coating agents. Subsequently, the coating agents were fixed mechanically on the core particle by impaction of zirconia beads. The coating agents powdered by FD showed higher coating efficiencies than those powdered by SD, irrespective of the differences in Tg values. Among the coating agents powdered by FD, the particles coated at Tg = 60 °C exhibited the most prolonged drug-release, although the coating efficiency was not the highest. In our proposed process utilizing mild vibration, we demonstrated that adjusting the Tg of the coating agents is crucial to the formation of binder-free multiple coating layers for prolonged drug release.


Assuntos
Composição de Medicamentos/métodos , Polímeros/química , Pós/química , Temperatura de Transição , Vibração , Preparações de Ação Retardada/química , Dessecação/métodos , Diclofenaco/química , Liberação Controlada de Fármacos , Resinas de Troca Iônica/química , Látex/química , Tamanho da Partícula , Zircônio/química
19.
Chemosphere ; 224: 494-501, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30831501

RESUMO

Conventional sorption media are inefficient for phosphorus removal from wastewater due to preference for competing species such as sulphate, nitrate and organics. This work investigates whether the use of hybrid ion exchange resins effectively negates such concerns. Trials were conducted with a hybrid anion exchange (HAIX) media which was preloaded with different background constituents and operated over multiple regeneration cycles to ascertain the likely impacts. The work revealed that whilst the impact of the other constituents was seen in regards to direct competition, the major impact was on reduction of the rate of intraparticle mass transfer through sorption of the constituents onto the base resin thereby reducing the Donnan membrane effect. Comparison of the impact of the background water constituents on the individual components (hybrid resin, base resin, nanoparticles) revealed the importance of the nanoparticle whereby they effectively transform the ion exchange media into a mono component absorber for phosphorus that enables sustained removal even in complex wastewaters.


Assuntos
Resinas de Troca Iônica/química , Fósforo/isolamento & purificação , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Fósforo/análise , Poluentes Químicos da Água/análise , Purificação da Água
20.
J Chromatogr B Analyt Technol Biomed Life Sci ; 1110-1111: 108-115, 2019 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-30798071

RESUMO

Methionine is an essential sulfur-containing amino acid for organisms. The separation and purification are important for the production of l-methionine from fermentation broth. In this work, the adsorption properties for l-methionine separation of ten macroporous resins were firstly evaluated. Macroporous cation resin D72 showed the best adsorption capacity (52.37 mg/g) and desorption rate (99.12%). The adsorption kinetics of l-methionine on D72 resin followed the pseudo second-order model and adsorption isotherm fitted well to the Sips model, the adsorption process mainly followed a physisorption mechanism. D72 resin packed columns were then used in the batch separation of fermentation broth, the operation parameters were optimized during the dynamic adsorption and desorption experiments. Under the optimized conditions: fermentation broth adjusted to pH = 2, loading flow rate at 2 BV/h, loading volume 55 mL, 1 mol/L NH3·H2O as eluent, elution flow rate at 2 BV/h, column height-diameter ratio at 14:1, excellent recovery and purity of l-methionine (82.37% and 85.69%, respectively) could be achieved.


Assuntos
Cromatografia por Troca Iônica/métodos , Escherichia coli/metabolismo , Resinas de Troca Iônica/química , Metionina/isolamento & purificação , Adsorção , Reatores Biológicos , Fermentação , Metionina/análise , Metionina/química
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