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1.
Nat Commun ; 11(1): 5062, 2020 10 08.
Artigo em Inglês | MEDLINE | ID: mdl-33033254

RESUMO

Septins are GTP-binding proteins involved in diverse cellular processes including division and membrane remodeling. Septins form linear, palindromic heteromeric complexes that can assemble in filaments and higher-order structures. Structural studies revealed various septin architectures, but questions concerning assembly-dynamics and -pathways persist. Here we used high-speed atomic force microscopy (HS-AFM) and kinetic modeling which allowed us to determine that septin filament assembly was a diffusion-driven process, while formation of higher-order structures was complex and involved self-templating. Slightly acidic pH and increased monovalent ion concentrations favor filament-assembly, -alignment and -pairing. Filament-alignment and -pairing further favored diffusion-driven assembly. Pairing is mediated by the septin N-termini face, and may occur symmetrically or staggered, likely important for the formation of higher-order structures of different shapes. Multilayered structures are templated by the morphology of the underlying layers. The septin C-termini face, namely the C-terminal extension of Cdc12, may be involved in membrane binding.


Assuntos
Microscopia de Força Atômica , Septinas/metabolismo , Simulação por Computador , Difusão , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Cinética , Lipídeos/química , Domínios Proteicos , Septinas/ultraestrutura , Eletricidade Estática
2.
Nat Commun ; 11(1): 5066, 2020 10 08.
Artigo em Inglês | MEDLINE | ID: mdl-33033255

RESUMO

The inducible co-stimulator (ICOS) is a member of the CD28/B7 superfamily, and delivers a positive co-stimulatory signal to activated T cells upon binding to its ligand (ICOS-L). Dysregulation of this pathway has been implicated in autoimmune diseases and cancer, and is currently under clinical investigation as an immune checkpoint blockade. Here, we describe the molecular interactions of the ICOS/ICOS-L immune complex at 3.3 Å resolution. A central FDPPPF motif and residues within the CC' loop of ICOS are responsible for the specificity of the interaction with ICOS-L, with a distinct receptor binding orientation in comparison to other family members. Furthermore, our structure and binding data reveal that the ICOS N110 N-linked glycan participates in ICOS-L binding. In addition, we report crystal structures of ICOS and ICOS-L in complex with monoclonal antibodies under clinical evaluation in immunotherapy. Strikingly, antibody paratopes closely mimic receptor-ligand binding core interactions, in addition to contacting peripheral residues to confer high binding affinities. Our results uncover key molecular interactions of an immune complex central to human adaptive immunity and have direct implications for the ongoing development of therapeutic interventions targeting immune checkpoint receptors.


Assuntos
Anticorpos/uso terapêutico , Complexo Antígeno-Anticorpo/química , Ligante Coestimulador de Linfócitos T Induzíveis/química , Proteína Coestimuladora de Linfócitos T Induzíveis/química , Mimetismo Molecular/imunologia , Sequência de Aminoácidos , Complexo Antígeno-Anticorpo/metabolismo , Antígenos CD28/metabolismo , Humanos , Interações Hidrofóbicas e Hidrofílicas , Ligante Coestimulador de Linfócitos T Induzíveis/metabolismo , Proteína Coestimuladora de Linfócitos T Induzíveis/metabolismo , Cinética , Ligantes , Modelos Moleculares , Ligação Proteica , Multimerização Proteica
3.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2235-2238, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018452

RESUMO

Electroporation is a well-established technique used to stimulate cells, enhancing membrane permeability. Although the biological phenomena occurring after the poration process have been widely studied, the physical mechanisms of pore formation are not clearly understood. In this work we investigated by means of molecular dynamics simulations the kinetics of pore formation, linking the different stages of poration to specific arrangements of lipid membrane domains.Clinical Relevance-The approach followed in this study aims to shed light on the molecular mechanisms at the basis of the electroporation technique, nowadays used to enhance the entrance of poorly permeant anticancer drugs into tumor cells, for gene electrotransfer and all the other applications exploiting the modulation of cell membrane properties.


Assuntos
Fenômenos Biológicos , Bicamadas Lipídicas , Eletroporação , Cinética , Simulação de Dinâmica Molecular
4.
Water Sci Technol ; 82(7): 1404-1415, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-33079719

RESUMO

In this study, peroxydisulfate (PDS) was successfully activated by UV-irradiation for the degradation of paracetamol (PCT) frequently detected in the environment. Results showed that increasing the initial PDS concentration from 5 to 20 mM promote the removal of PCT from 49.3% to 97.5% after 240 min of reaction time. As the initial PCT concentration increased from 0.066 to 0.132 mM, the degradation efficiency of PCT decreased from 98% to 73% after 240 min of reaction time, while the optimal pH was found to be 6. It is apparent that the degradation rate of PCT was favored by the lamp power regardless of the initial PCT concentration, for 0.132 mM of PCT, the degradation efficiency increased from 73% to 95% when the lamp power increased from 9 to 30 W, respectively. The kinetic of degradation of the PCT was described by a pseudo-second order kinetic model. The model obtained by central composite design led to the following optimal conditions for PCT degradation: 0.132 mM initial PCT concentration, 20 mM PDS dose, pH solution 6 and lamp power 30 W led to the removal of 92% of PCT at 25 °C within 240 min of reaction time.


Assuntos
Acetaminofen , Poluentes Químicos da Água , Cinética , Sulfatos , Raios Ultravioleta , Poluentes Químicos da Água/análise
5.
J Environ Qual ; 49(3): 640-653, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-33016407

RESUMO

Parameter estimation is needed for process management, design, and reactor scaling when values from the literature vary tremendously or are unavailable. A Bayesian approach, implemented via Markov chain Monte Carlo (MCMC) simulations using SAS software, was used to estimate the kinetic parameters of toluene and trichloroethylene (TCE) biodegradation by the microorganism Pseudomonas putida F1 in batch cultures. The prediction capabilities of Bayesian estimation were illustrated by comparing predicted and observed data and reported in goodness-of-fit statistics. The sensitivity analysis showed that the parameters obtained using this approach were consistent under the designated toluene and TCE concentration range. Moreover, the impact of TCE on toluene degradation kinetics was numerically exhibited, verifying the fact that TCE was able to stimulate toluene degradation; hence, TCE's presence increased the apparent maximum toluene-specific rate. Various kinetic models were explored at different degrees of complexity. At a low TCE concentration range (e.g., <2 mg L-1 ), a simplified Michaelis-Menten model (i.e., substrate half-saturation parameters approximated the inhibition parameters) was adequate to describe the reaction kinetics. However, at a higher TCE range (e.g., 5 mg L-1 ), a full-scale Michaelis-Menten model was needed to discriminate among the inhibition parameters in the model. The results demonstrated that a Bayesian estimation method is particularly useful for determining complex bioreaction kinetic parameters in the presence of a small volume of experimental data.


Assuntos
Tricloroetileno , Teorema de Bayes , Biodegradação Ambiental , Cinética , Tolueno
6.
J Environ Manage ; 263: 110415, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32883481

RESUMO

Drinking water containing excess fluoride is a major health concern across the globe. The present study reports the feasibility of zirconium impregnated hybrid anion exchange resin (HAIX-Zr) for treating fluoride contaminated groundwater. The HAIX-Zr resin was prepared by impregnating ZrO2 nanoparticles on polymeric anion exchanger resin. Fluoride uptake by HAIX-Zr was quite rapid, 60% removal was obtained within 30 min. Kinetics of fluoride uptake by HAIX-Zr resin followed the pseudo-second-order kinetic model and adsorption data fitted best to Freundlich adsorption isotherm model. Maximum fluoride uptake capacity was observed as 12.0 mg/g. The defluoridation capacity of the resin decreases with increase in solution pH. The co-existing anions like chloride, phosphate, bicarbonate, nitrate, and sulphate at 100 mg/L concentration significantly affected fluoride removal and bicarbonate showed the highest interference. Continuous flow packed bed experiments were performed with real groundwater. To maintain a lower pH, weak acid cation exchange resin (INDION-236) was used before HAIX-Zr. It was observed that reducing the pH of the sample water to 4-4.5, increased the number of treated bed volumes fifteen times. Regeneration of fluoride-containing resin was done by passing 3% NaOH and 3% NaCl solution through an exhausted resin bed. The results revealed that HAIX-Zr can effectively remove fluoride from groundwater.


Assuntos
Água Subterrânea , Poluentes Químicos da Água/análise , Purificação da Água , Adsorção , Resinas de Troca de Ânions , Fluoretos , Concentração de Íons de Hidrogênio , Cinética , Zircônio
7.
Am J Vet Res ; 81(10): 804-809, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32969728

RESUMO

OBJECTIVE: To investigate whether an actual improvement in gait could be differentiated from physiologic differences or habituation effects during gait analysis of dogs. ANIMALS: 11 healthy dogs. PROCEDURES: On 4 examination days, kinetic parameters were measured while dogs were walking on a treadmill. Differences in mean parameter values and habituation effects (ie, effect sizes) were quantified and compared among examination days. Coefficients of variation for repeated measurements were calculated to determine measurement reproducibility, and minimum differences were calculated to distinguish between physiologic fluctuation and an actual change in gait pattern. RESULTS: Among the 4 examination days, mean absolute differences in peak vertical force and vertical impulse (VI) varied from 1.5% to 5.3% of body weight (BW) and 0.9% to 1.8% of BW·s, respectively. Mean absolute differences in the percentage of stance-phase duration (%SPD) and relative stride length (RSL) varied from 0.9% to 3.2% and 1.7% to 3.0%, respectively. Reproducibility of parameter measurements was good. Values for %SPD had the lowest amount of dispersion and largest effect size, suggesting a habituation effect for this parameter. Calculated minimum differences among the days for peak vertical force, VI, %SPD, and RSL did not exceed 9.9% of BW, 3.3% of BW·s, 5.8 percentage points, and 5.2 percentage points, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: The %SPD of healthy dogs walking on a treadmill was the most sensitive and diagnostically reliable of the measured kinetic parameters, in contrast to VI and RSL. Findings suggested that actual changes can be distinguished from random physiologic fluctuations during gait analysis of dogs.


Assuntos
Teste de Esforço/veterinária , Caminhada , Animais , Fenômenos Biomecânicos , Cães , Marcha , Cinética , Reprodutibilidade dos Testes
8.
Am J Vet Res ; 81(10): 790-795, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32969729

RESUMO

OBJECTIVE: To use the small data approach of the Clinical and Laboratory Standards Institute (CLSI) to evaluate the transferability of reference intervals (RIs) for kinetic variables obtained with instrumented gait analysis (IGA) in dogs from an RI-originator laboratory to another laboratory that used the same data acquisition and analytic techniques for IGA in walking dogs. ANIMALS: 27 adult client-owned dogs without evidence of lameness. PROCEDURES: Dogs were individually walked at their preferred velocity on a pressure-sensing walkway for IGA at the Colorado State University Animal Gait Laboratory (CSU-AGL), and 6 valid trials were analyzed for each dog. The small data approach of the CLSI was then used to evaluate transferability of RIs previously established at the Purdue University Animal Gait Laboratory (PU-AGL). A linear model was used to establish weight-dependent RIs for peak vertical force (PVF). RESULTS: Results indicated that RIs of dynamic weight distribution (DWD), DWD symmetry index, DWD coefficient of variation, PVF symmetry index, and PVF coefficient of variation were transferable from PU-AGL to CSU-AGL, whereas the weight-dependent RIs for PVF were not. Regression slopes for PVF versus body weight were greater for all limbs in dogs tested at the CSU-AGL, compared with historic results for dogs tested at the PU-AGL. CONCLUSIONS AND CLINICAL RELEVANCE: Use of the small data approach method of the CLSI to validate transference of RIs for IGA kinetic variables in walking dogs was simple and efficient to perform and may help facilitate clinical and research collaborations on gait analysis.


Assuntos
Análise da Marcha , Caminhada , Animais , Fenômenos Biomecânicos , Cães , Marcha , Cinética
9.
Water Sci Technol ; 82(4): 651-662, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32970618

RESUMO

The adsorption isotherms of Reactive Red 120 (RR-120) on Brazilian pine-fruit shell activated carbon, at six temperatures (298, 303, 308, 313, 318 and 323 K) and pH = 6, were determined and interpreted using a double layer model with one energy. A statistical physics treatment established the formulation of this model. Steric and energetic parameters related to the adsorption process, such as the number of adsorbed molecules per site, the receptor sites density and the concentration at half-saturation, have been considered. Thermodynamic potential functions such as entropy, internal energy and Gibbs free enthalpy are analyzed, and the choice of the models is based on assumptions in correlation with experimental conditions. By numerical fitting, the investigated parameters were deduced. The theoretical expressions provide a good understanding and interpretation of the adsorption isotherms at the microscopic level. We believe that our work contributes to new theoretical insights on the dye adsorption in order to know the physical nature of the adsorption process.


Assuntos
Carvão Vegetal , Triazinas , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Termodinâmica
10.
Water Sci Technol ; 82(4): 673-682, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32970620

RESUMO

Loess is a typical natural mineral particle distributed widely around the world, and it is inexpensive, readily accessible, and harmless to the environment. In this study, loess was modified by surface grafting copolymerization of functional monomers, such as acrylic acid, N-vinyl pyrrolidone, and N,N-methylenebisacrylamide as a cross-linking agent, which afforded a novel loess-based grafting copolymer (LC-PAVP). After being characterized by scanning electron microscopy, thermal gravimetric analysis and Fourier-transform infrared spectroscopy, its adsorption capacity and mechanism of removing lead ions (Pb2+) were investigated. With the study of the optimal experimental conditions, it was demonstrated that the removal rate of Pb2+ by LC-PAVP can reach up to 99.49% in 60 min at room temperature. It was also found that the kinetic characteristics of the adsorption capacity due to the pseudo-second-order kinetic model and the thermodynamics conformed well with the Freundlich model. In summary, as a lost-cost and eco-friendly loess-based adsorbent, LC-PAVP is a good potential material for wastewater treatment.


Assuntos
Acrilatos , Poluentes Químicos da Água/análise , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Polímeros , Espectroscopia de Infravermelho com Transformada de Fourier , Termodinâmica , Águas Residuárias
11.
Water Sci Technol ; 82(4): 695-703, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32970622

RESUMO

The current work investigates the removal of two hazardous macrolide molecules, spiramycin and tylosin, by photodegradation under external UV-light irradiation conditions in a slurry photoreactor using titanium dioxide as a catalyst. The kinetics of degradation and effects of main process parameters such as catalyst dosage, initial macrolide concentration, light intensity and stirring rate on the degradation rate of pollutants have been examined in detail in order to obtain the optimum operational conditions. It was found that the process followed a pseudo first-order kinetics according to the Langmuir-Hinshelwood model. The optimum conditions for the degradation of spiramycin and tylosin were low compound concentration, 1 g L-1 of catalyst dosage, 100 W m-2 light intensity and 560 rpm stirring rate. Then, a maximum removal (more than 90%) was obtained after 300 min of irradiation time. Furthermore, results show that the selection of optimized operational parameters leads to satisfactory total organic carbon removal rate (up to 51%) and biochemical oxygen demand to chemical oxygen demand ratio (∼1) confirming the good potential of this technique to remove complex macrolides from aqueous solutions.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Catálise , Cinética , Macrolídeos , Fotólise , Titânio , Raios Ultravioleta
12.
Water Sci Technol ; 82(4): 715-731, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32970624

RESUMO

In the present work, native chitosan (Ch) along with its chemically and physico-chemically modified versions, namely sulphate cross-linked chitosan (SCC) and sulphate cross-linked chitosan-bentonite composite (SCC-B), were employed as potential adsorbents for the removal of an anionic dye, Alizarin Red S (ARS) from aqueous solutions. All three adsorbents were extensively characterized using techniques such as Fourier-transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, Brunauer-Emmett-Teller analysis, thermogravimetric-differential thermal analysis, and pH point of zero charge. Various parameters were optimized, including pH of dye solution, contact time, adsorbent dose, initial adsorbate concentration and temperature of adsorption. Four adsorption isotherm models were studied and it was found that the Freundlich model was best-fit for all three systems. Maximum adsorption capacities towards adsorption of ARS were found to be 42.48, 109.12 and 131.58 mg g-1 for Ch, SCC and SCC-B, respectively. Kinetics of adsorption was examined by employing three well-known models in order to deduce the mechanism of adsorption. Thermodynamic studies show that the process is spontaneous and exothermic for all adsorbents employed. Furthermore, it was observed that for large sample volumes, the column adsorption method was more effective compared to the batch method.


Assuntos
Quitosana , Poluentes Químicos da Água , Adsorção , Antraquinonas , Humanos , Concentração de Íons de Hidrogênio , Cinética , Deficiência Energética Relativa no Esporte , Espectroscopia de Infravermelho com Transformada de Fourier , Termodinâmica
13.
Water Sci Technol ; 82(4): 732-746, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32970625

RESUMO

The application of activated carbon fiber supported nanoscale zero-valent iron (ACF-nZVI) in the continuous removal of Cr(VI) and methyl orange (MO) from aqueous solution was studied in depth. The breakthrough curves of Cr(VI) in a fixed bed with ACF-nZVI were measured, and compared with those in the fixed bed with ACF. The catalytic wet peroxide oxidation (CWPO) process for MO was also carried out using ACF-nZVI after reacting with Cr(VI) in the same fixed bed. The results showed that the breakthrough time of ACF-nZVI was significantly longer than that of ACF. Higher pH values were unfavorable for the Cr(VI) removal. The breakthrough time increased with decreasing inlet Cr(VI) concentration or increasing bed height. The Yoon-Nelson and bed depth service time (BDST) models were found to show good agreement with the experimental data. The Cr(VI) removal capacity when using ACF-nZVI was two times higher than that when using ACF. Under the optimal empty bed contact time of 1.256 min, the fixed bed displayed high MO conversion (99.2%) and chemical oxygen demand removal ratio (55.7%) with low Fe leaching concentration (<5 mg/L) after continuous running for 240 min. After three cycles, the conversion of MO remained largely unchanged.


Assuntos
Carvão Vegetal , Poluentes Químicos da Água/análise , Adsorção , Compostos Azo , Fibra de Carbono , Cromo/análise , Ferro , Cinética
14.
Water Sci Technol ; 82(4): 747-758, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32970626

RESUMO

The eco-friendly and non-toxic natural organic substance, insolubilized humic acid (IHA), was used to remove Mn(II) from aqueous solutions. The adsorption characteristics were studied through a series of static adsorption tests. The results show that conditions such as the dose, the pH of the solution and the initial concentration of Mn(II) all affect removal efficiency, and the optimal pH value was 5.5. The sorption process for Mn(II) on IHA conforms to the pseudo-second-order adsorption kinetic model and intra-particle diffusion is not the only factor affecting the adsorption rate. Both Langmuir and Freundlich models can describe this adsorption behavior, and the experimental maximum adsorption capacity of IHA was 52.87 mg/g under optimal conditions. The thermodynamic analysis of adsorption shows that the adsorption process is a non-spontaneous endothermic physical reaction. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were used to characterize the samples, it was found that as IHA successfully adsorbed Mn(II), the surface morphology of IHA changed after the adsorption reaction. The adsorption mechanism for Mn(II) on IHA is to provide electron pairs for carboxyl, phenolic hydroxyl and other functional groups to form stable complexes with Mn(II).


Assuntos
Poluentes Químicos da Água/análise , Adsorção , Substâncias Húmicas , Concentração de Íons de Hidrogênio , Cinética , Espectroscopia de Infravermelho com Transformada de Fourier , Termodinâmica
15.
Water Sci Technol ; 82(4): 759-772, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32970627

RESUMO

In recent years, carbon tetrachloride (CT) has been frequently detected in surface water and groundwater around the world; it is necessary to find an effective way to treat wastewater contaminated with it. In this study, Ni/Fe bimetallic nanoparticles were immobilized on reduced graphene oxide (NF@rGO), and used to dechlorinate CT in aqueous solution. Scanning electron microscopy (SEM) demonstrated that the two-dimensional structure of rGO could disperse nanoparticles commendably. The results of batch experiments showed that the 4N4F@rGO (Fe/GO = 4 wt./wt., and Ni/Fe = 4 wt.%) could reach a higher reduction capacity (143.2 mgCT/gcatalyst) compared with Ni/Fe bimetallic nanoparticles (91.7 mgCT/gcatalyst) and Fe0 nanoparticles (49.8 mgCT/gcatalyst) respectively. That benefited from the nickel metal as a co-catalyst, which could reduce the reaction activation energy of 6.59 kJ/mol, and rGO as an electrical conductivity supporting material could further reduce the reaction activation energy of 4.73 kJ/mol as presented in the conceptual model. More complete dechlorination products were generated with the use of 4N4F@rGO. Based on the above results, the reductive pathway of CT and the catalytic reaction mechanism have been discussed.


Assuntos
Ferro , Níquel , Tetracloreto de Carbono , Grafite , Cinética
16.
Water Sci Technol ; 82(4): 773-786, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32970628

RESUMO

Petrochemical wastewater is difficult to process because of various types of pollutants with high toxicity. With the improvement in the national discharge standard, traditional biochemical treatment methods may not meet the standards and further advanced treatment techniques would be required. In this study, electrochemical oxidation with boron doped diamond (BDD) anode as post-treatment was carried out for the treatment of real biotreated petrochemical wastewater. The effects of current density, pH value, agitation rate, and anode materials on chemical oxygen demand (COD) removal and current efficiency were studied. The results revealed the appropriate conditions to be a current density of 10 mA·cm-2, a pH value of 3, and an agitation rate of 400 rpm. Moreover, as compared with the graphite electrode, the BDD electrode had a higher oxidation efficiency and COD removal efficiency. Furthermore, GC-MS was used to analyze the final degradation products, in which ammonium chloride, formic acid, acetic acid, and malonic acid were detected. Finally, the energy consumption was estimated to be 6.24 kWh·m-3 with a final COD of 30.2 mg·L-1 at a current density of 10 mA·cm-2 without the addition of extra substances. This study provides an alternative for the upgrading of petrochemical wastewater treatment plants.


Assuntos
Diamante , Poluentes Químicos da Água , Boro , Eletrodos , Cinética , Oxirredução , Águas Residuárias/análise
17.
Water Sci Technol ; 82(2): 242-254, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32941166

RESUMO

Using waste pomelo peel as raw material, pomelo peel-based biochar (BC) was prepared by pyrolysis at 400 °C, and the pomelo peel-based biochar was prepared by loading γ-Fe2O3 onto the surface of the pomelo peel-based biochar by unlimited oxygen chemical precipitation. The results showed that the pomelo peel biochar loaded with γ-Fe2O3 had higher specific surface area and larger pore volume. The load of γ-Fe2O3 gives γ-Fe2O3@BC excellent magnetic separation ability, and its magnetic saturation intensity is as high as 30.60 emu/g. BC and γ-Fe2O3@BC were applied to remove norfloxacin (NOR) from a water body. It was found that the adsorption of NOR by both of them followed the pseudo-second-order kinetic model. The adsorption isotherm mainly conforms to the Sips model, and the adsorption process of NOR is a spontaneous endothermic reaction. The pH and ionic strength have a great influence on the adsorption of NOR by BC and γ-Fe2O3@BC, and they play a role mainly by influencing the morphology of NOR in water. The adsorption mechanism showed that cation exchange and hydrogen bonding were the main forces for BC to adsorb NOR. Moreover, the γ-Fe2O3 particles enhanced the hydrophobicity of the pomelo peel-based biochar, making the hydrophobicity become the main force for the adsorption of NOR by the γ-Fe2O3@BC. The adsorption-desorption experiment showed that after four cycles of recycling, the adsorption capacity of γ-Fe2O3@BC for NOR was still up to 61.43% of the initial adsorption capacity, and it had a good recycling property.


Assuntos
Norfloxacino , Poluentes Químicos da Água/análise , Adsorção , Carvão Vegetal , Cinética , Água
18.
Water Sci Technol ; 82(3): 427-439, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32960789

RESUMO

The occurrence of organic micropollutants such as pharmaceutical drugs and hormones in the environment reflects the inefficiency of traditional wastewater treatment technologies. Biosorption is a promising alternative from a technical-economic point of view, so understanding the mechanisms of adsorption in new biosorbents is vital for application and process optimization. Within this context, this study aims to evaluate the mechanisms of adsorption and removal of synthetic and natural hormones by Pinus elliottii bark biosorbent (PS) compared to commercial granular activated carbon (GAC) through kinetic models, isotherm models, and thermodynamic models. The adsorbents were also characterized by morphology, chemical composition, functional groups, and point of zero charge. Characterization of the adsorbents highlights the heterogeneous and fibrous morphology and broader range of functional groups found for PS. Kinetic adjustments showed high accuracy for pseudo-second-order, Elovich, and intraparticle diffusion models, presenting multilinearity and evidencing multi-stage adsorption. The isotherms for PS followed high-affinity models, predominantly chemisorption, while those for GAC followed the Langmuir model, where physisorption predominates. These mechanisms were confirmed by thermodynamic models, which also indicated a higher dependence on temperature in the adsorption process. In the fortified water removal test, PS showed removal values higher than GAC, highlighting the advantages of this adsorbent.


Assuntos
Poluentes Químicos da Água/análise , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Lignina , Termodinâmica
19.
Water Sci Technol ; 82(3): 440-453, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32960790

RESUMO

A polyamine functionalized polystyrene resin (PSATA) was prepared via condensation reaction of acetylated polystyrene resin with triethylenetetramine, which, upon NaBH4 reduction, produced PSATAR. In comparison with the PSATA, the PSATAR with more flexible amine groups shows improved structural properties, and the equilibrium adsorption capacities of phenol, 2-nitrophenol (ONP) and 2,4-dinitrophenol (DNP) in wastewater were up to 1.073, 1.832 and 1.901 mmol/g, respectively. Their adsorption isotherms fit well with the Freundlich model, indicating a multilayer, heterogeneous adsorption nature. Kinetic studies indicated that the adsorption of phenolic compounds conforms to the pseudo-second-order kinetics with the adsorption rate controlled by film diffusion for ONP and DNP, and intra-particle diffusion in the later stage for phenol.


Assuntos
Poluentes Químicos da Água/análise , Purificação da Água , Adsorção , Cinética , Fenóis , Poliestirenos , Trientina , Águas Residuárias
20.
Water Sci Technol ; 82(3): 468-480, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32960792

RESUMO

In this work, a biosorbent was prepared by the ultrasound-acid treatment of Merremia vitifolia plant and tested for the removal of 2,4-dichlorophenoxyacetic acid (2,4-D), a phenoxy herbicide. Optimal values of five batch biosorption parameters namely stirring speed, contact time, biosorbent dosage, initial pH and initial adsorbate concentration were experimentally obtained in sequential manner for an enhanced biosorption capacity. The kinetics of the biosorption of 2,4-D were best described by the pseudo first order kinetic model (R2 = 0.99) and the biosorption equilibrium data were successfully fitted to the Langmuir adsorption isotherm (R2 = 0.99) with a maximum biosorption capacity of 66.93 mg g-1. The mechanism of biosorption was investigated using two intraparticle diffusion models (Weber and Boyd), Dubinin-Radushkevich isotherm model and electrostatic interactions. The presence of intraparticle and film diffusion limitations for the biosorption was confirmed along with the physical and chemical nature of the biosorption. The thermodynamic parameters of the biosorption were calculated using the equilibrium data obtained at four different temperatures. The entropy change for biosorption was found to be negative indicating the decreased randomness at the interface. Desorption studies were carried out using different solvents and the percentages of desorption were compared.


Assuntos
Convolvulaceae , Herbicidas , Poluentes Químicos da Água , Ácido 2,4-Diclorofenoxiacético , Adsorção , Biomassa , Concentração de Íons de Hidrogênio , Cinética , Termodinâmica
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