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1.
Sci Total Environ ; 952: 175998, 2024 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-39233067

RESUMO

Knowledge of antibiotic desorption from high-temperature biochar is essential for assessing their environmental risks, and for the successful application of biochar to remove antibiotics. In previous studies, irreversible pore deformation, formation of charge-assisted hydrogen bonds or amide bonds were individually proposed to explain the desorption hysteresis of antibiotics on biochars, leading to a debate on hysteresis mechanism. In this study, desorption of sulfamethoxazole (SMX), ciprofloxacin (CFX) and tetracycline (TET) on a wood chip biochar produced at 700 °C (WBC700) and its oxidized product (O-WBC700) was investigated to explore the underlying hysteresis mechanism. Significant desorption hysteresis was observed for SMX, CFX and TET on WBC700 and O-WBC700. Hysteresis index (HI) of each antibiotic was higher on O-WBC700 with more oxygen-containing groups than WBC700, and was higher at lower equilibrium concentration. HI of antibiotics on WBC700 (or O-WBC700) increased in the order of SMX < CFX < TET. The calculated adsorption enthalpy of each antibiotic on WBC700 was positive, indicating an endothermic process. These phenomena together with FTIR, XPS spectra confirmed that the desorption hysteresis mechanism of antibiotics on high-temperature biochar is the formation of amide bonds by amidation reaction, but not the pore deformation or the hydrogen bond. Moreover, antibiotic can form amide bonds with WBC700 only if the amine group with pKa > 4.0, and the HI values were positively correlated with their pKa values. Amine group of antibiotics with higher pKa value show more nucleophilicity and could form stronger amide bonds with carboxyl group of biochar. The obtained results could help to solve the debate on desorption hysteresis mechanism of antibiotics on high-temperature biochars, and provide a new insight into the role of amine groups and amidation reaction on the hysteresis.


Assuntos
Antibacterianos , Carvão Vegetal , Carvão Vegetal/química , Antibacterianos/química , Adsorção , Temperatura Alta , Aminas/química , Ciprofloxacina/química , Sulfametoxazol/química , Modelos Químicos , Tetraciclina/química
2.
ACS Appl Bio Mater ; 7(8): 5290-5307, 2024 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-39047188

RESUMO

The single-step synthesis of nitro-derivatized SG using dimethyldichlorosilane in an aprotic solvent dichloromethane at 300 K is efficient and straightforward. Reduction and diazotization effectively functionalize the material for enzyme coupling at the O-carbon of the enzyme's tyrosine. The high extraction efficiency of protonated dichromate ions with a breakthrough capacity of 480 µmol·g-1 is notable. Eco-friendly elution using distilled water achieves a significant enrichment factor of 23.2. Excellent reusability (up to 900 cycles) and stable sorption efficiency (ζ ≥ 0.9) highlight the material's potential for practical applications and future research.


Assuntos
Teste de Materiais , Papaína , Propriedades de Superfície , Papaína/química , Papaína/metabolismo , Aminas/química , Tamanho da Partícula , Estrutura Molecular , Materiais Biocompatíveis/química , Materiais Biocompatíveis/síntese química , Prótons
3.
Artigo em Inglês | MEDLINE | ID: mdl-38858287

RESUMO

Growing concern about global warming and greenhouse effects has led to persistent demands for increased energy efficiency and reduced carbon dioxide emissions. As a result, energy-intensive processing of carbon dioxide separation became imperative. Accordingly, energy-efficient, economically viable carbon dioxide separation technologies are sought as carbon dioxide capture options for future industrial process schemes. The article provides an overview of current technology for the separation of carbon dioxide, specifically focusing on adsorption. In this study, amine-loaded Zeolite-Y adsorbents were evaluated to enhance carbon dioxide adsorption capacity through synthesis, characterization, and the adsorption of carbon dioxide, within the context of current trends in separation technology. This study aims to study the ability of amine-loaded Zeolite-Y to adsorb carbon dioxide using three different loadings ethanolamine, diethanolamine, and triethanolamine. The amine-loaded materials were characterized by various technologies, including X-ray diffraction pattern (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET), and field emission scanning electron microscope (FESEM) studies. The study suggests that monoethanolamine-loaded Zeolite-Y is a promising and cost-effective adsorbent for carbon dioxide adsorption in comparison to other synthesized amine-loaded adsorbents. The adsorbent has been able to adsorb carbon dioxide in the range of 1.14-2.26 mmol g-1 at 303 K and 1 bar for a loading of 1, 5, and 10 wt.% amine groups.

4.
Mikrochim Acta ; 191(4): 181, 2024 03 06.
Artigo em Inglês | MEDLINE | ID: mdl-38446252

RESUMO

Silica nanoparticles (SiNPs) with a chemically modified surface typically have a complicated chemical composition, which can significantly differ from their intended design. In this study, we systematically studied the effects of two surface modification methods on active-targeting of intracellular organelles of SiNPs: (1) the widely used step-by-step approach, which involves modifying SiNPs in two steps, i.e., the outer surface of SiNPs was firstly modified with amino groups and then these amino groups were linked with targeting groups, and (2) a newly developed one-step approach in which the ligand-silane complex is initially synthesized, followed by chemically immobilizing the complex on the surface of SiNPs. In the one-step approach, the molar ratio of reactants was precisely tuned so that there are no reactive groups left on the outer surface of SiNPs. Two essential organelles, mitochondria and the nucleus, were selected to compare the targeting performances of SiNPs synthesized via these two approaches. By characterizing physicochemical properties, including structural properties, the number of amino groups, surface charge, polydispersity, and cell colocalization, we demonstrated that SiNPs synthesized via the one-step approach with no residual linkage groups on their surface showed significantly improved mitochondria- and nucleus-targeting performances. This precise control of surface properties allows for optimized biological behavior and active-targeting efficiency of SiNPs. We anticipate that such simple and efficient synthetic strategies will enable the synthesis of effective SiNPs for active-targeting organelles in various biological applications.


Assuntos
Mitocôndrias , Nanopartículas , Corantes , Silanos , Dióxido de Silício
5.
Nanomaterials (Basel) ; 14(1)2024 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-38202578

RESUMO

Nitrogen-doped graphene-based materials are of utmost importance in sensing and energy conversion devices due to their unique physicochemical properties. However, the presence of defects such as pyrrolic nitrogen and oxygenated functional groups reduces their electrical conductivity. Herein, a two-step approach based on the electrochemical exfoliation of graphite foils in aqueous mixed electrolytes followed by thermal reduction at 900 °C is used to prepare high-quality few layers of N-doped graphene-based materials. The exfoliations were conducted in 0.1 M (NH4)2SO4 or H2SO4 and HNO3 (5 mM or 0.1 M) electrolytes mixtures and the HNO3 vol% varied. Chemical analysis demonstrated that the as-prepared graphene oxides contain nitro and amine groups. Thermal reduction is needed for substitutional N-doping. Nitrogen and oxygen surface concentrations vary between 0.23-0.96% and 3-8%, respectively. Exfoliation in (NH4)2SO4 and/or 5 mM HNO3 favors the formation of pyridinic-N (10-40% of the total N), whereas 1 M HNO3 favors the formation of graphitic-N (≈60%). The electrical conductivity ranges between 166-2705 Scm-1. Raman spectroscopy revealed a low density of defects (ID/IG ratio between 0.1 and 0.7) and that most samples are composed of mono-to-bilayer graphene-based materials (IG/I2D integrated intensities ratio). Structural and compositional stability of selected samples after storage in air for three months is demonstrated. These results confirm the high quality of the synthesized undoped and N-doped graphene-type materials.

6.
Molecules ; 27(19)2022 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-36234830

RESUMO

Organophosphorus ligands are an invaluable family of compounds that continue to underpin important roles in disciplines such as coordination chemistry and catalysis. Their success can routinely be traced back to facile tuneability thus enabling a high degree of control over, for example, electronic and steric properties. Diphosphines, phosphorus compounds bearing two separated PIII donor atoms, are also highly valued and impart their own unique features, for example excellent chelating properties upon metal complexation. In many classical ligands of this type, the backbone connectivity has been based on all carbon spacers only but there is growing interest in embedding other donor atoms such as additional nitrogen (-NH-, -NR-) sites. This review will collate some important examples of ligands in this field, illustrate their role as ligands in coordination chemistry and highlight some of their reactivities and applications. It will be shown that incorporation of a nitrogen-based group can impart unusual reactivities and important catalytic applications.


Assuntos
Quelantes , Nitrogênio , Carbono , Catálise , Quelantes/química , Ligantes , Nitrogênio/química
7.
Bioresour Technol ; 362: 127793, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-35987435

RESUMO

The potential effect of polyethyleneimine as a flocculant on anaerobic digestion of sludge was investigated. Polyethyleneimine above 12 g/kg total suspended solids inhibited the entire anaerobic digestion process including solubilization, hydrolysis, acidification, and methanogenesis. The addition of 24 g/kg total suspended solids polyethyleneimine reduced methane production from 167 ± 5 L/kg volatile suspended solids in the control reactor (without polyethyleneimine) to 141 ± 5 L/kg volatile suspended solids. Polyethyleneimine bound to extracellular polymeric substances, thus enhancing sludge agglomeration and hindering the release of organics. Meanwhile, the reduction of cytochrome C impeded electron transport, consequently curbed direct interspecies electron transfer. The adsorption of carbon dioxide by amine groups also hampered methane conversion. This study elucidated the concept that polyethyleneimine reduces mass transfer in anaerobic digestion, providing new insights into the potential behavior of flocculants in sludge treatment.


Assuntos
Polietilenoimina , Esgotos , Anaerobiose , Reatores Biológicos , Metano/metabolismo
8.
Bioresour Technol ; 356: 127331, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-35580788

RESUMO

The effects and key mechanisms of polydimethyldiallylammonium chloride on anaerobic digestion of waste activated sludge were investigated. Polydimethyldiallylammonium chloride at 38.1 g/kg total solids substantially reduced cumulative methane production from 138.2 ± 5.5 to 49.4 ± 5.0 L CH4/kg volatile solids added, a reduction of 64.3 ± 0.2%. The quaternary ammonium groups on polydimethyldiallylammonium chloride agglomerated sludge flocs by neutralizing negatively charged amino groups in in extracellular polymeric substances, which hindered the release of organic matter. Quaternary ammonium groups induce oxidative stress by inducing the production of reactive oxygen species, thereby inhibiting the activity of anaerobic digestive enzymes. In addition, quaternary amine groups reduced the abundance of hydrolyzing bacteria, acidifying bacteria, and acetylotrophic methanogens. Oxidative stress could be an underappreciated mechanism that quaternary ammonium groups deteriorate anaerobic digestion, which could be transformative for understanding the potential risks of quaternary ammonium cationic flocculants in biological sludge treatment.


Assuntos
Compostos de Amônio , Esgotos , Anaerobiose , Reatores Biológicos , Cloretos , Halogênios , Metano , Estresse Oxidativo , Esgotos/microbiologia , Eliminação de Resíduos Líquidos
9.
Polymers (Basel) ; 13(18)2021 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-34578027

RESUMO

Fluorinated graphene (FGi) is easy to agglomerate, after which it turns into a curly and wavy shape, which results in a great decrease in the properties of the resultant composite materials and coatings. In this study, fluorinated graphene oxide (FGO) modified with p-phenylenediamine (PPD) was prepared, but with a view to avoid its agglomeration and retain a sheet-like structure. Through the reaction between PPD and the epoxy groups of FGO, the modified FGO with an amino group (N-PGO) had a larger interlayer d-spacing than FGO. The stability of N-PGO was also improved, and nitrogen, fluorine, oxygen, and carbon were evenly distributed in the N-PGO sheets. All the results indicate that PPD can act as an effective spacer to separate graphene sheets for good anti-agglomeration properties. This method produced modified graphene with fluorine, amino, and carbonyl groups. It shows potential in introducing N-PGO as a reactive modifier in composite materials and coatings for a variety of industrial applications including waterborne epoxy materials.

10.
ACS Nano ; 15(8): 13871-13890, 2021 Aug 24.
Artigo em Inglês | MEDLINE | ID: mdl-34379407

RESUMO

Polydopamine (PDA)-coated nanoparticles (NPs) are emerging carriers of therapeutic agents for nanomedicine applications due to their biocompatibility and abundant entry to various cell types, yet it remains unknown whether their cellular entry engages cell-surface receptors. As monomeric dopamine (DA) is an endogenous ligand of dopamine receptor and raw ingredient of PDA, we elucidate the interaction between polyethylene glycol-stabilized, PDA-coated gold NPs (Au@PDA@PEG NPs) and dopamine receptors, particularly D2 (D2DR). After proving the binding of Au@PDA@PEG NPs to recombinant and cellular D2DR, we employ antibody blocking, gene knockdown, and gene overexpression to establish the role of D2DR in the cellular uptake of Au@PDA@PEG NPs in vitro. By preparing a series of PEG-coated AuNPs that contain different structural analogues of DA (Au@PEG-X NPs), we demonstrate that catechol and amine groups collectively enhance the binding of NPs to D2DR and their cellular uptake. By intravenously injecting Au@PDA@PEG NPs to Balb/c mice, we reveal their in vivo binding to D2DR in the liver by competitive inhibition and immunohistochemistry together with their preferential association to D2DR-rich resident Kupffer cells by flow cytometry, a result consistent with the profuse expression of D2DR by resident Kupffer cells. Catechol and amine groups jointly contribute to the preferential association of NPs to D2DR-rich Kupffer cells. Our data highlight the importance of D2DR expression and DA-related functional groups in mediating the cell-nano interactions of PDA-based nanomedicines.


Assuntos
Nanopartículas Metálicas , Nanopartículas , Camundongos , Animais , Ouro/química , Nanopartículas Metálicas/química , Nanopartículas/química , Dopamina/química , Receptores Dopaminérgicos
11.
Membranes (Basel) ; 11(3)2021 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-33805589

RESUMO

Delignified lignocellulosic biomass was functionalized with amine groups. Then, the pretreated lignin-free date pits cellulose and the amine-functionalized-date pits cellulose (0-5 wt%) were incorporated into a polysulfone polymer matrix to fabricate composite membranes. The amine groups give additional hydrogen bonding to those existing from the hydroxyl groups in the date pits cellulose. The approach gives an efficient avenue to enhance the CO2 molecules' transport pathways through the membrane matrix. The interactions between phases were investigated via Fourier transformed infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), whereas pure gases (CO2 and N2) were used to evaluate the gas separation performances. Additionally, the thermal and mechanical properties of the fabricated composites were tested. The pure polysulfone membrane achieved an optimum separation performance at 4 Bar. The optimum separation performance for the composite membranes is achieved at 2 wt%. About 32% and 33% increments of the ideal CO2/N2 selectivity is achieved for the lignin-free date pits cellulose composite membrane and the amine-functionalized-date pits cellulose composite membrane, respectively.

12.
Biomed Microdevices ; 22(3): 44, 2020 06 22.
Artigo em Inglês | MEDLINE | ID: mdl-32572586

RESUMO

We present a disposable polymeric microfluidic device capable of reversibly binding and purifying Salmonella DNA through solid phase extraction (SPE). The microfluidic channels are first oxygen plasma treated and simultaneously micro-nanotextured, and then functionalized with amine groups via modification with L-histidine or poly-L-histidine. L-Histidine and poly-L-histidine bind on the plasma treated chip surface, and are not detached when rinsing with DNA purification protocol buffers. A pH-dependent protocol is applied on-chip to purify Salmonella DNA, which is first bound on the protonated amines at a pH (5.0) lower than their pKa of surface amine-groups which is 6.0 and then released at a pH higher than the pKa value (10.5). It was found that modification with poly-L-histidine resulted in higher surface density of amine groups onto microfluidic channel. Using the chip modified with poly-L-histidine, high recovery efficiency of at least 550 ng of isolated Salmonella DNA as well as DNA purification from Salmonella cell lysates corresponding to less than 5000 cells or 0.026 ng of Salmonella DNA was achieved. The protocol developed does not require ethanol or chaotropic solutions typically used in DNA purification, which are known inhibitors for downstream operations such as polymerase chain reactions (PCR) and which can also attack some polymeric microfluidic materials. Therefore, the microfluidic device and the related protocol hold promise for facile incorporation in microfluidics and Lab-on-a-chip (LOC) platforms for pathogen detection or in general for DNA purification.


Assuntos
DNA Bacteriano/isolamento & purificação , Histidina/química , Dispositivos Lab-On-A-Chip , Extração em Fase Sólida/instrumentação , Aminas/química , DNA Bacteriano/química , Salmonella/citologia , Salmonella/genética
13.
Ultrason Sonochem ; 66: 105068, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32224449

RESUMO

This study presents the production of a novel natural blue colorant obtained from the cross-linking between milk proteins and genipin assisted by low-frequency and high-power ultrasound technology. Genipin was extracted from unripe Genipa americana L. using milk as a solvent. Also, milk colloidal system was used as a reaction medium and carrier for the blue color compounds. The effects of ultrasound nominal power (100, 200, 300, and 400 W) on the blue color formation kinetics in milk samples were evaluated at 2, 24, and 48 h of cold storage in relation to their free-genipin content and color parameters. In addition, Fourier transform infrared (FTIR) spectrum, droplet size distribution, microstructure, and kinetic stability of the blue colorant-loaded milk samples were assessed. Our results have demonstrated that the ultrasound technology was a promising and efficient technique to obtain blue colorant-loaded milk samples. One-step acoustic cavitation assisted the genipin extraction and its diffusion into the milk colloidal system favoring its cross-linking with milk proteins. Ultrasound process intensification by increasing the nominal power promoted higher genipin recovery resulting in bluer milk samples. However, the application of high temperatures associated with intensified acoustic cavitation processing favored the occurrence of non-enzymatic browning due to the formation of complex melanin substances from the Maillard reaction. Also, the blue milk samples were chemically stable since their functional groups were not modified after ultrasound processing. Likewise, all blue colorant-loaded milk samples were kinetically stable during their cold storage. Therefore, a novel natural blue colorant with high-potential application in food products like ice creams, dairy beverages, bakery products, and candies was produced.


Assuntos
Produtos Biológicos/química , Corantes/química , Leite/química , Rubiaceae/química , Ondas Ultrassônicas , Animais , Cinética , Solventes/química
15.
ACS Appl Mater Interfaces ; 10(21): 17662-17671, 2018 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-29733574

RESUMO

A quaternized reverse thermal gel (RTG) aimed at replacing current surgical incision drapes (SIDs) was designed and characterized. The antimicrobial efficacy of the quaternized RTG was analyzed using both in vitro and in vivo models and was compared to standard SIDs. Polymer characterization was completed using both nuclear magnetic resonance (1H NMR) and lower critical solution temperature (LCST) analysis. Biocompatibility was assessed using a standard cell viability assay. The in vitro antimicrobial efficacy of the polymer was analyzed against four common bacteria species using a time-kill test. The in vivo antimicrobial efficacy of the polymer and standard SIDs were compared using a murine model aimed at mimicking surgical conditions. NMR confirmed the polymer structure and presence of quaternized groups and alkyl chains. The polymer displayed a LCST of 34 °C and a rapid rate of gelation, allowing stable gel formation when applied to skin. Once quaternized, the polymer displayed an increase in kill-rate of bacteria compared to unquaternized polymer. In experiments aimed at mimicking surgical conditions, the quaternized polymer showed statistically comparable bacteria-killing capacity to the standard SID and even surpassed the SID for killing capacity at various time points. A novel approach to replacing current SIDs was developed using an antimicrobial polymer system with RTG properties. The RTG properties of this polymer maintain a liquid state at low temperatures and a gel upon heating, allowing this polymer to form a tight coating when applied to skin. Furthermore, this polymer achieved excellent antimicrobial properties in both in vitro and in vivo models. With further optimization, this polymer system has the potential to replace and streamline presurgical patient preparations through its easy application and beneficial antimicrobial properties.


Assuntos
Antibacterianos/química , Animais , Bactérias , Camundongos , Compostos Organofosforados , Polímeros , Ferida Cirúrgica
16.
Environ Sci Pollut Res Int ; 25(18): 17457-17472, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29656356

RESUMO

The performance of synthesized cast and electrospun polyvinyl alcohol/chitosan/zinc oxide/aminopropyltriethoxylsilane (PVA/chitosan/ZnO-APTES) nano-adsorbents were compared in removal of Cd(II) and Ni(II) ions from wastewater. The adsorbents were characterized by SEM, BET, FTIR and TGA analyses. Furthermore, the swelling investigations were carried out to study the adsorbent stability in aqueous solution. The effect of several parameters such as contents of ZnO-NH2, contact time, initial Cd(II) and Ni(II) concentration and temperature on the adsorption capacity was investigated in a batch mode. In comparison with cast adsorbent, nanofiber adsorbent indicated the better adsorption performance. The experimental data well fitted the double-exponential kinetic model. In single metal ion system, the maximum adsorption capacity of nanofiber for Cd(II) and Ni(II) ions is estimated to be 1.239 and 0.851 mmol/g, respectively, much higher than qm of cast adsorbent for Cd(II) (0.625 mmol/g) and Ni(II) (0.474 mmol/g) ions. Thermodynamic parameters were investigated to identify the nature of adsorption process. In binary system of Cd(II)-Ni(II) ions, the inhibitory effect of competitive Cd(II) ion on the Ni(II) adsorption was greater than the inhibitory effect of competitive on the Cd(II) adsorption. The selectivity adsorption of both nanofiber and cast adsorbents was in order of Cd(II) > Ni(II).


Assuntos
Cádmio/metabolismo , Quitosana/química , Íons/química , Níquel/metabolismo , Óxido de Zinco/química , Adsorção , Cinética , Metais , Nanofibras , Termodinâmica , Águas Residuárias , Água
17.
Materials (Basel) ; 11(4)2018 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-29597288

RESUMO

Amine groups play significant roles in polymeric composites for heavy metals removal. However, generating a composite with a large number of functional and stable amine groups based on clay is still a challenge. In this work, a new amine-functionalized adsorbent based on acid-activated vermiculite (a-Verm) was prepared by organic modification of silane coupling agent as bridge, followed by in situ polymerization of acrylamide (AM) and further grafting of triethylene tetramine (TETA). The obtained polymeric composite g-PAM/OVerm was characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), Fourier transform infrared (FTIR), thermal analysis (TG/DTG), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) analyses, confirming that amine groups were successfully grafted onto the surface of Verm. The efficacy g-PAM/OVerm for removing Pb(II) was tested. The adsorption equilibrium data on g-PAM/OVerm was in good accordance with the Langmuir adsorption isotherms, and the adsorption maximal value of Pb(II) was 219.4 mg·g-1. The adsorption kinetic data fit the pseudo-second-order kinetic model well. Additionally, g-PAM/OVerm has better selectivity for Pb(II) ion in comparison with Zn(II), Cd(II) and Cu(II) ions. The present work shows that g-PAM/OVerm holds great potential for removing Pb(II) from wastewater, and provides a new and efficient method for the removal of heavy metal ions from industrial wastewater.

18.
J Hazard Mater ; 352: 47-56, 2018 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-29573729

RESUMO

Coadsorption of Cu(II) and two dihydroxybenzene isomers (hydroquinone, HQ and catechol, CAT) onto a multi-amine modified resin (CEAD) were comparatively studied. The presence of Cu(II) promoted adsorption of both HQ and CAT by a maximum of 25.8% and 41.6%, respectively. However, two diphenols exerted a very different influence on Cu(II) uptake. Higher concentrations of HQ consistently suppressed Cu(II) adsorption while the coexistence of CAT facilitated it, especially at lower CAT concentrations. The interactions among solutes and adsorbents were revealed by means of kinetic tracking, sequential adsorption experiments, and characterizations/calculations (FTIR, XPS, MINTEQ and DFT). Cu(II) and HQ/CAT competed for amine sites with the order of adsorption affinity as HQ > Cu(II) > CAT. The bridging effect of Cu(II) forming ternary complexes (amine-Cu-CAT/HQ) on the resin phase was the dominant mechanism for the enhanced adsorption of diphenols. The [Cu-CAT] complex species showed a lower affinity to bind directly to amine sites compared with free Cu2+. Instead, the complex could be attracted by the polyphenyl matrix of CEAD, contributing to the increase of Cu(II) adsorption. Additionally, Cu(II) and diphenols were successively recovered, and CEAD could be stably reused. The findings will guide adsorbent applications and the environmental fate of concurrent heavy metals and phenolic compounds.

19.
Bioprocess Biosyst Eng ; 41(6): 749-756, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29417222

RESUMO

In this study, we synthesized super magnetic Fe(OH)3@Fe3O4 nanoparticles (SPIONs) by the co-precipitation method and introduction of amine groups via chemisorption of L-aspartic acid (LAA) on the surface of SPIONs. Penaeus vannamei protease (PVP) was immobilized onto amine-functionalized supermagnetic nanoparticles (ASPIONs), and conditions affecting PVP immobilization were investigated. PVP immobilized onto ASPIONs exhibited shifts in both working optimum pH and temperature with an increase from pH 7 to pH 8, and increased optimum temperature by 10 °C compared to free enzyme. Similarly, the thermal, pH, and storage stabilities of the immobilized PVP were superior to those of free form of the enzyme. In comparison to the free enzyme, the immobilized enzyme was reusable for 15 cycles while retaining 73% of its initial activity. The Michaelis-Menten kinetic constant (Km) and maximum reaction velocity (Vmax) for free PVP were 2.3 µM and 88 µM min-1, respectively, whereas Km and Vmax values of immobilized enzyme were 2.5 µM and 85 µM min-1, respectively. These results indicated that immobilized PVP was efficient in terms of catalytic activity and can be applied to continuous casein processing applications in the different industries.


Assuntos
Proteínas de Artrópodes/química , Ácido Aspártico/química , Enzimas Imobilizadas/química , Compostos Férricos/química , Nanopartículas de Magnetita/química , Penaeidae/enzimologia , Peptídeo Hidrolases/química , Animais , Propriedades de Superfície
20.
J Colloid Interface Sci ; 505: 593-604, 2017 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-28647572

RESUMO

Mesoporous carbon of cubic structure was functionalized with ethylamine, ethylenediamine, diethylenetriamine and triethylenetetramine at 40°C for 8h. The mesostructure and textural parameters of the new materials were determined by X-ray diffraction and low-temperature nitrogen sorption techniques. The functional groups present on the surface of the samples were identified by FT-IR and thermogravimetric studies. Functionalization of the mesoporous carbon led to reduction of the surface area and pore volume as well as to an increase in the mean pore diameter. The micropores/small mesopores can be blocked by the attached surface amino groups. We found that after functionalization the mesostructural regularity was still maintained. A key element of the study was a series of adsorption tests of solophenyl red 3BL polyazo dye onto amine-functionalized mesoporous carbons from aqueous solutions. The influence of the process time, concentration of adsorbate, pH and temperature on the efficiency of the adsorption process was analyzed. The samples modified with amine groups were found to show much higher sorption capacities towards solophenyl red 3BL than pure carbon. It is a results of formation of a large number of positive surface sites that interact with anionic adsorbate. The adsorption kinetics was found to follow closely the pseudo-second-order kinetic model. The results of the intraparticle diffusion model suggested that intraparticle diffusion was not the only one rate-controlling step. The adsorption of the dye was a spontaneous and endothermic process.

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