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1.
Environ Sci Technol ; 57(36): 13658-13668, 2023 09 12.
Artigo em Inglês | MEDLINE | ID: mdl-37647171

RESUMO

Ionic contaminants such as Cr(VI) pose a challenge for water purification using membrane-based processes. However, existing membranes have low permeability and selectivity for Cr(VI). Therefore, in this study, we prepared an electrically controlled adsorptive membrane (ECAM-L) by coating a loose Cl--doped polypyrrole layer on a carbon nanotube substrate, and we evaluated the performance of ECAM-L for Cr(VI) separation from water. We also used electrochemical quartz crystal microbalance measurements and molecular dynamics and density functional theory calculations to investigate the separation mechanisms. The adsorption and desorption of Cr(VI) could be modulated by varying the electrostatic interactions between ECAM-L and Cr(VI) via potential control, enabling the cyclic use of the ECAM-L without additional additives. Consequently, the oxidized ECAM-L showed high Cr(VI) removal performance (<50 µg/L) and treatment capacity (>3500 L/m2) at a high water flux (283 L/m2/h), as well as reusability after the application of a potential. Our study demonstrates an efficient membrane design for water decontamination that can selectively separate Cr(VI) through a short electric stimulus.


Assuntos
Polímeros , Pirróis , Adsorção , Água
2.
Environ Sci Technol ; 57(12): 5003-5012, 2023 03 28.
Artigo em Inglês | MEDLINE | ID: mdl-36931868

RESUMO

The adsorption of contaminants by porous carbon has been extensively studied by conventional isotherm and kinetic methods. However, the co-adsorption behavior and sorption sites of multiple contaminants in different-sized pores remain unclear. Herein, the nuclear magnetic resonance (NMR) approach is performed to investigate the adsorption mechanism of toluene and cetane in the confined space of carbon at the molecular level. The ring current effect induces the variation in the NMR chemical shifts of in-pore adsorbed toluene and cetane, realizing the identification of pore-dependent adsorption sites for contaminant removal. Cetane has a slower adsorption kinetic but a higher binding energy than toluene, which could squeeze toluene from micropores to larger pores with increasing adsorption quantity. This leads to a stronger competitive adsorption effect in small micropores than in mesopores. Accordingly, hierarchical porous carbons are determined to be the most effective adsorbents for the adsorption of coexisting contaminants. This study not only provides an effective NMR method to reveal the adsorption mechanism in the confined space of porous carbon at the molecular level but also offers new insights into the pore size-dependent adsorption of activated carbon for petroleum contaminant treatment.


Assuntos
Carvão Vegetal , Tolueno , Tolueno/química , Porosidade , Espectroscopia de Ressonância Magnética , Adsorção , Ácido Ascórbico
3.
Angew Chem Int Ed Engl ; 61(46): e202212706, 2022 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-36138516

RESUMO

Photoreduction of CO2 provides an appealing way to alleviate the energy crisis and manage the global carbon balance but is limited by the high activation energy and the rate-limiting proton transfer. We now develop a dual-site strategy for high-efficiency CO2 conversion through polarizing CO2 molecules at pyridine N vacancies and accelerating the intermediate protonation by protonated pyridine N adjacent to nitrogen vacancies on polymeric carbon nitride. Our photocatalysts with atomic-level engineered active sites manifest a high CO production rate of 1835 µmol g-1 h-1 , 183 times higher than the pristine bulk carbon nitride. Theoretical prediction and experimental studies confirm that such excellent performance is attributed to the synergistic effect between vacant and protonated pyridine N in decreasing the formation energy of the key *COOH intermediates and the efficient electron transfer relay facilitated by the defect-induced shallow trap state and homogeneous charge mediators.

4.
Phys Rev Lett ; 121(13): 131103, 2018 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-30312037

RESUMO

The observed multi-GeV γ-ray emission from the solar disk-sourced by hadronic cosmic rays interacting with gas and affected by complex magnetic fields-is not understood. Utilizing an improved analysis of the Fermi-LAT data that includes the first resolved imaging of the disk, we find strong evidence that this emission is produced by two separate mechanisms. Between 2010 and 2017 (the rise to and fall from solar maximum), the γ-ray emission was dominated by a polar component. Between 2008 and 2009 (solar minimum) this component remained present, but the total emission was instead dominated by a new equatorial component with a brighter flux and harder spectrum. Most strikingly, although six γ rays above 100 GeV were observed during the 1.4 yr of solar minimum, none were observed during the next 7.8 yr. These features, along with a 30-50 GeV spectral dip which will be discussed in a companion paper, were not anticipated by theory. To understand the underlying physics, Fermi-LAT and HAWC observations of the imminent cycle 25 solar minimum are crucial.

5.
Appl Microbiol Biotechnol ; 100(10): 4617-25, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-26762391

RESUMO

Klebsiella oxytoca GS-4-08 is capable of azo dye reduction, but its quinone respiration and Fe(III) reduction abilities have not been reported so far. In this study, the abilities of this strain were reported in detail for the first time. As the biotic reduction of Fe(III) plays an important role in the biogeochemical cycles, two amorphous Fe(III) oxides were tested as the sole electron acceptor during the anaerobic respiration of strain GS-4-08. For the reduction of goethite and hematite, the biogenic Fe(II) concentrations reached 0.06 and 0.15 mM, respectively. Humic acid analog anthraquinone-2-disulfonate (AQS) was found to serve as an electron shuttle to increase the reduction of both methyl orange (MO) and amorphous Fe(III) oxides, and improve the dye tolerance of the strain. However, the formation of Fe(II) was not accelerated by biologically reduced AQS (B-AH2QS) because of the high bioavailability of soluble Fe(III). For the K. oxytoca strain, high soluble Fe(III) concentrations (above 1 mM) limit its growth and decolorization ability, while lower soluble Fe(III) concentrations produce an electron competition with MO initially, and then stimulate the decolorization after the electron couples of Fe(III)/Fe(II) are formed. With the ability to respire both soluble Fe(III) and insoluble Fe(III) oxides, this formerly known azo-reducer may be used as a promising model organism for the study of the interaction of these potentially competing processes in contaminated environments.


Assuntos
Antraquinonas/química , Compostos Azo/química , Compostos Férricos/química , Compostos de Ferro/química , Klebsiella oxytoca/metabolismo , Minerais/química , Benzoquinonas/química , Meios de Cultura/química , Substâncias Húmicas/análise , Modelos Teóricos , Oxirredução , Óxidos/química
6.
Appl Microbiol Biotechnol ; 99(21): 9277-87, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26175104

RESUMO

Strain CICC 23870 capable of decolorization of various azo dyes under high saline conditions was isolated from saline-alkali soil. The oxygen-insensitive azoreductase in crude extracts exhibited a wide substrate adaptively in the presence of NADH as a cofactor. The decolorization process by free cells followed first-order kinetics, with a high Methyl Orange (MO) tolerance concentration up to 100 mg l(-1) estimated by Haldane model. The average decolorization rate of free cell system was 26.30 mg g(-1) h(-1) at initial MO concentration of 32.7 mg l(-1). However, the values for the systems of immobilized cells (4 mm) in alginate, alginate and nano-TiO2, and alginate and powered activated carbon (PAC) were 6.83, 4.64, and 11.34 mg g(-1) h(-1), respectively. The effective diffusion factors in the tree different matrices were calculated by diffusion-based mathematic model. The diffusion step controls the overall decolorization rate, and the effective diffusion coefficients varied with internal structure of the bead matrices. The diffusion coefficients were increased from 4.98 × 10(-9) to 2.25 × 10(-8) cm(2) s(-1) when PAC was added, but decreased to 6.62 × 10(-10) cm(2) s(-1) when nano-TiO2 was added. The immobilized matrices could be reused for at least three cycles but with a decreased decolorization rate, possibly due to the breakage of beads at the end of each cycle, which led to the loss of immobilized bacteria.


Assuntos
Compostos Azo/metabolismo , Bacillus/isolamento & purificação , Bacillus/metabolismo , Águas Residuárias/química , Poluentes da Água/metabolismo , Bacillus/efeitos dos fármacos , Biodegradação Ambiental , Biotransformação , Cinética , NAD/metabolismo , NADH NADPH Oxirredutases/metabolismo , Nitrorredutases , Sais/metabolismo , Microbiologia do Solo , Especificidade por Substrato
7.
Foods ; 13(9)2024 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-38731763

RESUMO

Ratoon rice, the cultivation of a second crop from the stubble after the main harvest, is recognized as an eco-friendly and resource-saving method for rice production. Here, a field experiment was carried out in the Yangtze River region to investigate the impact of varying stubble heights on the grain quality of ratoon rice, as well as to compare the grain quality between the main and ratoon season. This study, which focused on 12 commonly cultivated rice varieties, conducted a comprehensive analysis assessing milling characteristics, appearance, and cooking quality. The results show that ratoon rice crops exhibited a higher milled rice rate and head rice rate compared to the main rice crops. Conversely, chalky rice percentage, chalkiness degree, and amylose content were lower in ratoon rice crops. Principal component analysis grouped eight relevant quality indicators of rice quality which were concentrated into three categories, with amylose content identified as the key indicator of rice quality for distinguishing between different stubble heights. Random forest results reveal a robust and significant correlation between appearance quality index and amylose content. Subordinate function analysis indicated that a stubble height of 30 cm resulted in optimal rice quality, with Lingliangyou 211 exhibiting the highest quality and Xiangzao Xian 32 the lowest. Overall, our study suggests that ratoon rice crops generally outperform main rice crops in terms of quality, with the optimal measurement at a stubble height of 30 cm. This study holds substantial importance for selecting appropriate stubble heights for ratoon rice crops and enhancing overall rice quality.

8.
Sci Adv ; 10(21): eadn8696, 2024 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-38787943

RESUMO

Drinking water with micropollutants is a notable environmental concern worldwide. Membrane separation is one of the few methods capable of removing micropollutants from water. However, existing membranes face challenges in the simultaneous and efficient treatment of small-molecular and ionic contaminants because of their limited permselectivity. Here, we propose a high-efficiency water purification method using a low-pressure Janus membrane with electro-induced multi-affinity. By virtue of hydrophobic and electrostatic interactions between the functional interfaces and contaminants, the Janus membrane achieves simultaneous separation of diverse types of organics and heavy metals from water via single-pass filtration, with an approximately 100% removal efficiency, high water flux (>680 liters m-2 hour-1), and 98% lower energy consumption compared with commercial nanofiltration membranes. The electro-induced switching of interfacial affinity enables 100% regeneration of membrane performance; thus, our work paves a sustainable avenue for drinking water purification by regulating the interfacial affinity of membranes.

9.
Ann Med Surg (Lond) ; 85(8): 3783-3790, 2023 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-37554899

RESUMO

Some studies have reported the efficacy and safety of the Atlas stent and the Leo Baby stent-assisted coiling (SAC) of intracranial aneurysms arising from small cerebral vessels. The authors aimed to compare the clinical performance of the Atlas and the Leo Baby stents in small parent arteries. Methods and materials: Between January 2019 and November 2022, 56 patients at our centre were treated using either Atlas or Leo Baby SAC of intracranial aneurysms arising from small parent vessels (<2 mm). The clinical and angiographic imaging data of the two cohorts were retrospectively collected and comparatively analyzed. Results: A total of 56 patients were included in this study. Thirty-two patients were treated with the Atlas SAC, and 24 patients were treated with the Leo Baby SAC. The mean age of the Atlas stent cohort was older, and the mean aneurysm size was smaller than the Leo Baby stent. The immediate complete occlusion rate was 68.6% in the Atlas stent cohort and 62.5% in the Leo Baby stent cohort. The mean angiographic follow-up time for Atlas stent cohort was 8.9±2.5 months, and the final aneurysm complete occlusion rate was 81.0%. The mean follow-up time for Leo Baby stent cohort was 18.9±6.0 months, and the final aneurysm complete occlusion rate was 83.3%. Conclusions: At the final follow-up, the Atlas or the Leo baby stent SAC of intracranial aneurysms with small parent vessels resulted in favourable angiographic results and clinical outcomes, with a low rate of associated complications.

10.
J Colloid Interface Sci ; 615: 456-464, 2022 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-35150953

RESUMO

Designing non-precious electrocatalysts with multiple active centers and durability toward overall water splitting is of great significance for storing renewable energy. This study reports a low-cost Mo, Fe codoped NiCoPx electrocatalysts derived from Co-Fe Prussian blue analogue and following phosphorization process. Benefitted from the optimized electronic configuration, hierarchical structure and abundant active sites, the Mo,Fe-NiCoPx/NF electrode has shown competitive oxygen evolution reaction (ƞ10 = 197 mV) and hydrogen evolution reaction performance (ƞ10 = 99 mV) when the current density is 10 mA cm-2 in 1 M KOH solution. Moreover, the integrated water splitting device assembled by Mo,Fe-NiCoPx/NF as both anode and cathode only needs a voltage of 1.545 V to reach 10 mA cm-2. Density functional theory results further confirm that the Mo, Fe codoped heterostructure can synergistically optimize the d-band center and Gibbs free energy during electrocatalytic processes, thus accelerating the kinetics of electrochemical water splitting. This work demonstrates the importance of rational combination of metal doping and interface engineering for advanced catalytic materials.

11.
Front Neurosci ; 16: 825859, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35360156

RESUMO

The neutrophil-to-lymphocyte ratio (NLR) plays an important role in the progression of intracerebral hemorrhage (ICH). An increasing number of studies have reported that a high NLR is correlated with poor clinical outcomes among patients with ICH. Here, we conducted a systematic review and meta-analysis to evaluate the prognostic value of NLR in the setting of ICH. We performed a comprehensive search of electronic literature databases to identify all relevant studies evaluating the prognostic role of NLR in patients with ICH. Two researchers independently screened the studies and extracted relevant data. We extracted, pooled, and weighted odds ratio (OR) and 95% confidence interval (CI) values using a generic inverse-variance method, and then evaluated the heterogeneity among studies using Q test and I 2 statistic. Finally, we selected a total of 26 studies including 7,317 patients for the current study. Overall, our results indicated that a high NLR was significantly associated with a poor outcome (OR, 1.32; 95% CI, 1.19-1.46; P < 0.00001), mortality (OR, 1.05; 95% CI, 1.01-1.09; P = 0.02), and neurological deterioration (OR, 1.65; 95% CI, 1.08-2.52; P = 0.02). We did not observe a significant association between NLR and hematoma expansion (OR, 1.04; 95% CI, 0.99-1.08; P = 0.09). Our study indicated that a high NLR is significantly associated with poor clinical outcomes in patients with ICH. As NLR is a simple and easily available biomarker, future studies should focus on exploring its application in the prognostic evaluation of patients with ICH.

12.
Front Neurol ; 13: 974354, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36570460

RESUMO

Background: The study was designed to assess the clinical performance of a tubridge flow diverter (TFD) in the treatment of intracranial aneurysms and to compare the efficacy and safety between intracranial aneurysms treated with TFD alone and TFD combined with coiling. Methods: In this retrospective study, patients treated with the TFD alone or TFD combined with coiling between June 2018 to November 2022 were included. The patient demographics, the characteristics of the aneurysm, and the treatment outcomes between the two groups were compared. Propensity score matching was performed to match the variables with a significant difference between groups. Results: In the current study, data from 93 consecutive patients including 104 aneurysms treated with TFD were analyzed. In total, 43 patients with 49 aneurysms were treated with TFD alone, and 50 patients with 55 aneurysms were treated with TFD combined with coiling. Aneurysms in the TFD combined with the coiling group were larger (12.9 ± 8.6 vs. 8.7 ± 8.8 mm, P = 0.016) and more likely to be saccular (92.7% vs. 75.5%, P = 0.027) than in the TFD alone group. No significant difference was observed between the two groups in terms of perioperative complication rate. During the follow-up period, the complete occlusion rate in the TFD combined with the coiling group was higher (80.0% vs. 43.8%, P = 0.001) than in the TFD alone group. These results were further confirmed using a propensity score matching analysis. Conclusion: TFD combined with coiling can be a safe and effective alternative option for the treatment of complex aneurysms. Given the potential risks of these therapeutic modalities, thus very careful consideration is required on an individual patient basis.

13.
Front Neurosci ; 15: 786513, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34955733

RESUMO

The use of adjuvant corticosteroids with surgery for chronic subdural hematoma (CSDH) has received considerable attention in recent years. However, there is no conclusive evidence regarding its effectiveness and safety for CSDH. Therefore, we performed a meta-analysis and systematic review to evaluate the effectiveness and safety of corticosteroids as an adjuvant treatment for the treatment of CSDH. We comprehensively searched electronic databases (PubMed, EMBASE, Cochrane Library, and Web of Science) to identify relevant trials that investigated the efficacy and safety of adjuvant corticosteroids with surgery for CSDH, published from inception until May 2021. Outcome measures included recurrence rate, all-cause mortality, good functional outcome, length of hospitalization, and adverse events. We used the Cochrane risk of bias method to evaluate the quality of randomized controlled trials (RCTs), and the Newcastle Ottawa Scale to evaluate the quality of observational studies. We included nine studies, consisting of three RCTs and six observational studies, that compared corticosteroids as an adjuvant treatment to surgery with surgery alone. Pooled results revealed that the risk of recurrence was significantly reduced in patients who received adjuvant corticosteroids with surgery compared to those who underwent surgery alone (relative risk [RR] = 0.52, 95% confidence interval [CI] = 0.39-0.69, p < 0.00001). However, no statistically significant difference was observed between these groups in all-cause mortality (RR = 0.91, 95% CI = 0.37-2.23, p = 0.83), good functional outcome (RR = 1.03, 95% CI = 0.96-1.10, p = 0.47), length of hospitalization (MD = 0.35, 95% CI = -2.23 to 1.67, p = 0.83), and infection rates (RR = 0.99, 95% CI = 0.64-1.53, p = 0.95). Adjuvant corticosteroids with surgery reduce the risk of recurrence of CDSH, but do not improve the all-cause mortality or functional outcome, as compared to surgery alone. These findings support the use of adjuvant corticosteroids with surgery for CSDH patients. Further high-quality RCTs are required to confirm the efficacy and safety of adjuvant corticosteroids in the treatment of CSDH patients.

14.
Water Res ; 200: 117207, 2021 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-34020332

RESUMO

Membrane separation is a promising technology that can effectively remove various existing contaminants from water with low energy consumption and small carbon footprint. The critical issue of membrane technology development is to obtain a low-cost, stable, tunable and multifunctional material for membrane fabrication. Graphitic carbon nitride (g-C3N4) has emerged as a promising membrane material, owing to the unique structure characteristics and outstanding catalytic activity. This review paper outlined the advanced material strategies used to regulate the molecule structure of g-C3N4 for membrane separation. The presentative progresses on the applications of g-C3N4-based membranes for water purification have been elaborated. Essentially, we highlighted the innovation integration of physical separation, catalysis and energy conversion during water purification, which was of great importance for the sustainability of water treatment techniques. Finally, the continuing challenges of g-C3N4-based membranes and the possible breakthrough directions in the future research was prospected.


Assuntos
Grafite , Purificação da Água , Catálise , Compostos de Nitrogênio
15.
Front Neurol ; 12: 745560, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34867727

RESUMO

The neutrophil-to-lymphocyte ratio (NLR), as an essential systemic inflammation factor, has been widely used as a prognostic indicator in various diseases, such as malignant tumors, cardiovascular disease, and intracranial hemorrhage. An increasing number of studies have believed that NLR is a valuable predictor of prognosis for patients with aneurysmal subarachnoid hemorrhage (aSAH). However, these results remain controversial. In the current study, we planned to carry out a systematic review and meta-analysis to investigate the association between NLR and poor outcome, and the occurrence of delayed cerebral ischemia (DCI). We carried out a comprehensive search for published literatures on PubMed, EMBASE, Cochrane Library, and Web of Science databases from inception to April 1, 2021. We conducted an assessment of all included studies based on the principles proposed in the Newcastle-Ottawa Quality Assessment Scale (NOS). Poor outcome and the occurrence of DCI were considered as the main outcome measure. We calculated the pooled odds ratio (OR) and corresponding 95% confidence interval (CI) to examine the strength of the association of NLR with poor outcome or the occurrence of DCI. We strictly selected a total of 10 studies comprising 4,989 patients. Nine studies reported the association between NLR and poor outcome, and five studies reported the association between NLR and the occurrence of DCI. The pooled results indicated higher NLR was significantly associated with both poorer outcomes (OR = 1.32, 95%CI 1.11-1.57; P = 0.002, I 2 = 87%), and the occurrence of DCI (OR = 1.72, 95%CI 1.22-2.41; P = 0.002, I 2 = 82%) in aSAH patients. The NLR is a valuable indicator of inflammation to independently predict poor outcome and occurrence of DCI after aSAH, where a higher NLR is significantly associated with poor outcomes and occurrence of DCI. These findings suggest that the NLR can help clinicians evaluate the prognosis and identify potentially severe patients early, which may contribute to better management and improve poor prognosis of aSAH patients.

16.
J Colloid Interface Sci ; 579: 455-462, 2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-32622094

RESUMO

Two-dimensional (2-D) exfoliated nanomaterials have attracted tremendous attentions because of the unique surface structures and increased reactive sites for various applications. Herein, a one-step pyrolysis method was used to fabricate ultrathin C3N4 photocatalysts, which had significant advantages over conventional post-exfoliation strategies with labor-intensive and time-consuming procedures. We found that oxygen doping by atmospheric air could effectively break the interlayer and intralayer interactions in polymeric C3N4, forming 2-D ultrathin nanocatalysts with high activity for persulfate activation. The integration of photocatalysis and persulfate oxidation resulted in 21- and 15-fold enhancement in the degradation of Bisphenol A pollutants compared to the individual reactions. The significant contributions of atmospheric oxygen doping to the charge separation and surface reactions were fundamentally investigated. This work not only provides a facile strategy to exfoliate polymeric semiconductor into ultrathin nanostructures, but also reveals valuable insight into the exploration of high-performance catalysts for the synergistic removal of environmental contaminants.

17.
R Soc Open Sci ; 7(7): 192029, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32874608

RESUMO

A novel fabrication method of uniform porous structures on the glass surface is proposed. The hydrofluoric acid fog formed by air-jet atomization etches the glass surface to fabricate nanoporous structure (NPS) on glass surface. This NPS shows the enhanced average light transmittance of approximately 92.9% and the superhydrophilic property with a contact angle less than 1° which presents an excellent anti-fog property. Passivated by fluorosilane, the NPS shows nearly the superhydrophobic property with a contact angle of 141.2°. This fabrication method has shown promising application prospects due to its simplicity, low cost and efficiency, which can be easily applied to large-scale industrial production.

18.
Huan Jing Ke Xue ; 40(7): 3146-3153, 2019 Jul 08.
Artigo em Zh | MEDLINE | ID: mdl-31854712

RESUMO

In recent years, improving the performance of catalysts through defect modulation has attracted extensive attention. However, the impact of defect rearrangement on Fenton-like photocatalytic reactions has not been studied. In this study, Fe-containing polyoxometalate molecules were grafted onto the surface of defective TiO2.The influence of oxygen vacancy formation and the defect arrangement process on the catalytic activity was investigated. The results indicated that the calcination of cyanamide modified defective TiO2 is beneficial for the spatial reconstruction of oxygen vacancies generated by H2 atmosphere treatment. With rearranged structural defects, photo-generated electrons were prone to transfer from the surface of P25 to Fe-POM nanoparticles. Due to the enhanced charge separation in TiO2 and the increased reactive sites on the Fenton-like reagent, Fenton-like photocatalysts with rearranged defects showed a 13-fold increase in catalytic activity during the degradation of dye molecules.

19.
Sci Rep ; 6: 34980, 2016 10 07.
Artigo em Inglês | MEDLINE | ID: mdl-27713559

RESUMO

In this work, the effect of cultivation factors on the flocculation efficiency (FE) of bioflocculant P-GS408 from Klebsiella oxytoca was optimized by the response surface methodology. The most significant factor, i.e. culture time, was determined by gray relational analysis. A total of 240 mg of purified P-GS408 was prepared from 1 liter of culture solution under the optimal conditions. GC-MS analysis results indicated that the polysaccharide of P-GS408 mainly contains Rhamnose and Galactose, and the existence of abundant hydroxyl, carboxyl and amino groups was evidenced by FTIR and XPS analyses. With the aid of Fe3+, the FE of kaolin solution by P-GS408 could achieve 99.48% in ten minutes. Functional groups of polysaccharide were involved in the first adsorption step and the zeta potential of kaolin solution changed from -39.0 mV to 43.4 mV in the presence of Fe3+ and P-GS408. Three-dimensional excitation-emission (EEM) fluorescence spectra demonstrates that the trivalent Fe3+ and Al3+ can bind efficiently with P-GS408, while those univalent and divalent cations cannot. With the help of SEM images, FTIR, zeta potential and EEM spectra, we proposed the P-GS408 flocculation mechanism, which consists of coordination bond combination, charge neutrality, adsorption and bridging, and net catching.


Assuntos
Klebsiella oxytoca/metabolismo , Polissacarídeos Bacterianos/metabolismo , Técnicas Bacteriológicas , Meios de Cultura , Compostos Férricos/metabolismo , Floculação , Concentração de Íons de Hidrogênio , Caulim , Klebsiella oxytoca/crescimento & desenvolvimento , Polissacarídeos Bacterianos/química , Espectrometria por Raios X , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura
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