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1.
Chemosphere ; : 132650, 2021 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-34699876

RESUMO

Chlorophenol is a widely used organic compound, and the environmental and health problems caused by it have being worsened in recent years. This study used 2,4,6-trichlorophenol (2,4,6-TCP) as the target pollutant, and employed ultrasound (US) enhanced zero-valent iron (Fe0)/EDTA/air system (FEA), namely US/FEA, to remove 2,4,6-TCP. The influence of single factor experimental conditions such as EDTA concentration, Fe0 dosage, US power, pH and pollutant concentration on the removal efficiency of 2,4,6-TCP was investigated, and the optimal reaction conditions were determined. The mechanism of reactive oxygen species (ROS) produced by US/FEA was explored. The degradation process and removal mechanism of 2,4,6-TCP in the US/FEA were discussed through the determination and analysis of intermediate products. The results showed that US could continuously activate and renew the Fe0 surface, accelerate its oxidation and corrosion process, and then continuously and stably produce sufficient amounts of Fe2+ and Fe3+. Ultrasonic cavitation effect could reduce the difficulty of O2 activation reaction, and promote the production of sufficient H2O2. The addition of EDTA made the system have a wide range of pH applications, and its performance under neutral and alkaline conditions was also superior. The ROS of US/FEA included ·OH, O2·- and Fe(IV), where Fe(IV) was the main contributor to the removal of 2,4,6-TCP. In addition, the degradation of 2,4,6-TCP had two processes including dechlorination and benzene ring opening. First, 2,4,6-TCP was dechlorinated and degraded into phenol. And then, phenol was degraded into small molecular acids by ring-opening, and finally it was mineralized into CO2 and H2O completely. US/FEA is a promising technology for high-efficiency degradation of organic matter and deep environmental purification.

2.
Adv Mater ; : e2105951, 2021 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-34617348

RESUMO

Zn metal anode has garnered growing scientific and industrial interest owing to its appropriate redox potential, low cost, and high safety. Nevertheless, the instability of Zn anode caused by dendrite formation, hydrogen evolution, and side reactions has greatly hampered its commercialization. Herein, an in situ grown ZnSe overlayer is crafted over one side of commercial Zn foil via chemical vapor deposition in a scalable manner, aiming to achieve optimized electrolyte/Zn interfaces with large-scale viability. Impressively, thus-derived ZnSe coating functions as a cultivator to guide oriented growth of Zn (002) plane at the infancy stage of stripping/plating cycles, thereby inhibiting the formation of Zn dendrites and the occurrence of side reactions. As a result, high cyclic stability (1530 h at 1.0 mA cm-2 /1.0 mAh cm-2 ; 172 h at 30.0 mA cm-2 /10.0 mAh cm-2 ) in symmetric cells is harvested. Meanwhile, when paired with V2 O5 based cathode, assembled full cell achieves an outstanding capacity (194.5 mAh g-1 ) and elongated lifespan (a capacity retention of 84% after 1000 cycles) at 5.0 A g-1 . The reversible Zn anode enabled by the interfacial manipulation strategy via ZnSe cultivator is anticipated to satisfy the demand of commercial use.

3.
Sci Adv ; 7(31)2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34330700

RESUMO

Van der Waals epitaxy provides a fertile playground for the monolithic integration of various materials for advanced electronics and optoelectronics. Here, a previously unidentified nanorod-assisted van der Waals epitaxy is developed and nearly single-crystalline GaN films are first grown on amorphous silica glass substrates using a graphene interfacial layer. The epitaxial GaN-based light-emitting diode structures, with a record internal quantum efficiency, can be readily lifted off, becoming large-size flexible devices. Without the effects of the potential field from a single-crystalline substrate, we expect this approach to be equally applicable for high-quality growth of nitrides on arbitrary substrates. Our work provides a revolutionary technology for the growth of high-quality semiconductors, thus enabling the hetero-integration of highly mismatched material systems.

4.
Environ Sci Pollut Res Int ; 28(37): 51865-51878, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-33990923

RESUMO

Flocculation is one of the commonly used sludge conditioning methods in water supply plants, which can improve the sludge dewatering performance by reducing the specific resistance of sludge (SRF), decreasing the amount of sludge, and finally lowering the transportation cost and subsequent disposal cost of sludge. Therefore, it is particularly important to develop new and efficient flocculants. In this paper, the template copolymer of acryloxy trimethylammonium chloride (DAC) and acrylamide (AM) was successfully synthesized by microwave-template copolymerization (MV-TP) using sodium polyacrylate (NaPAA) as template. The template copolymer was analyzed by infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance hydrogen spectroscopy (1H NMR), and scanning electron microscopy (SEM). It was found that this template copolymer had obvious cationic microblock structure. In addition, the test results of association constant (KM) and polymerization kinetics showed that the MW-TP was assigned to free radical initiated polymerization and the polymerization mechanism was I Zip-up (ZIP). It confirmed the formation of cation fragment structure again. Due to its dense positive charges in this new cationic microblock structure, it greatly improved the functions of electric neutralization, electrical patching, and adsorption bridging. The cationic fragment structure in the template copolymer could help to generate large and dense floc structure and form stable drainage channels. Under external pressure, these large and compact floc structures had greater compressive resistance, which avoided deformation and blockage of drainage channels and voids. It was beneficial to reduce SRF and evidently enhanced sludge dewatering performance.


Assuntos
Esgotos , Eliminação de Resíduos Líquidos , Resinas Acrílicas , Cátions , Floculação , Espectroscopia de Infravermelho com Transformada de Fourier , Água
5.
Small ; 17(19): e2100098, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33788402

RESUMO

The nitride films with high indium (In) composition play a crucial role in the fabrication of In-rich InGaN-based optoelectronic devices. However, a major limitation is In incorporation requiring a low temperature during growth at the expense of nitride dissociation. Here, to overcome this limitation, a strain-modulated growth method, namely the graphene (Gr)-nanorod (NR) enhanced quasi-van der Waals epitaxy, is proposed to increase the In composition in InGaN alloy. The lattice transparency of Gr enables constraint of in-plane orientation of nitride film and epitaxial relationships at the heterointerface. The Gr interlayer together with NRs buffer layer substantially reduces the stress of the GaN film by 74.4%, from 0.9 to 0.23 GPa, and thus increases the In incorporation by 30.7%. The first principles calculations confirm that the release of strain accounts for the dramatic improvement. The photoluminescence peak of multiple quantum wells shifts from 461 to 497 nm and the functionally small-sized cyan light-emitting diodes of 7 × 9 mil2 are demonstrated. These findings provide an efficient approach for the growth of In-rich InGaN film and extend the applications of nitrides in advanced optoelectronic, photovoltaic, and thermoelectric devices.

6.
Environ Sci Pollut Res Int ; 28(2): 1933-1947, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32862344

RESUMO

In this study, a novel anionic template polymer (TPAS) with microblock structure was prepared by ultraviolet light (UV)-assisted template copolymerization (UV-TP). Acrylamide (AM) and sodium styrene sulfonate (SSS) were selected as monomers and polypropylene ammonium chloride (PAAC) was chosen as the template. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), nuclear magnetic resonance hydrogen spectroscopy (1H NMR), and thermogravimetry/differential scanning calorimetry (TG/DSC) were used to characterize the polymer chemical structure. The results showed that the attractive anionic microblock structure was formed in TPAS. Besides, the association constant (KM) and template reaction kinetics analysis results indicated that the polymerization reaction followed I (ZIP) template copolymerization mechanism. It proved the microblock structure formation again. The anionic microblock structure in TPAM could greatly improve the ability of charge neutralization, electrical patching, and bridging. After the hematite wastewater was conditioned by TPAS with this novel anionic microblock structure, the generated hematite flocs had larger particle size and denser structure. It was favorable for the reduction of turbidity, and the turbidity removal rate could reach 97.8%. TPAS showed excellent flocculation performance for hematite wastewater and had a broad market application prospect.


Assuntos
Águas Residuárias , Ânions , Compostos Férricos , Floculação , Polimerização , Espectroscopia de Infravermelho com Transformada de Fourier
7.
J Hazard Mater ; 409: 124526, 2021 05 05.
Artigo em Inglês | MEDLINE | ID: mdl-33218909

RESUMO

Microbial extracellular polymeric substances (EPS) coating nanoparticles (NPs) surface can form NPs-EPS corona, which significantly affect the adsorption of NPs to toxic substances and alter the ecotoxicological effect of NPs. In this work, the EPS coronas on TiO2 NPs (TNPs) and CeO2 NPs (CNPs) were characterized and the adsorption characteristics of NPs with and without EPS corona to five heavy metals were investigated in single-metal and multiple-metal systems. The results of spectral analysis showed that NPs-EPS corona exhibited new crystalline phases and abundant functional groups. Moreover, 42 and 13 proteins were identified in the TNPs-EPS and CNPs-EPS coronas, respectively. The rates of Cd2+, Pb2+, Cu2+, Ni2+ and Ag+ adsorption by NPs-EPS corona increased to values that were 6.7-7.6, 4.4-5.1, 4.2-5.5, 3.9-4.9 and 8.5-8.8 times those of NPs without EPS corona, respectively, in single-metal system. NPs-EPS coronas are effective in absorbing Ag+, Pb2+ and Cu2+ compared with Cd2+and Ni2+ in multiple metal adsorption. These results indicated that NPs-EPS corona effectively adsorb and remove heavy metals by forming NPs-EPS-metal complexes and inducing precipitation. However, NPs-EPS corona can enhance the toxicity of NPs by accumulating highly-toxic heavy metals in aquatic environments.


Assuntos
Metais Pesados , Nanopartículas , Adsorção , Matriz Extracelular de Substâncias Poliméricas , Metais Pesados/toxicidade , Nanopartículas/toxicidade
8.
Bioresour Technol ; 323: 124569, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33360949

RESUMO

Catalytic hydrothermal liquefaction (HTL) of lignin was examined at various temperature (250-310 °C) and reaction time in the presence of different solvents (water, methanol and ethanol) with different metal supported on MCM-41 mesoporous catalyst. In case of ethanol solvent, the maximum bio-oil yield of 56.2 wt% was obtained with Ni-Al/MCM-41. However in case of water, bio-oil yield was (44.3 wt%); while significantly improves bio-oil yield for methanol solvent (48.1 wt%). It is indicated that alcoholic solvents promoted the lignin decomposition, while in the presence of catalyst; water solvent significantly improves lignin degradation. Loading of Ni and Al on MCM-41, the acid strength of the catalyst increased, which enhanced lignin degradation. From the GC-MS analysis, the main G-type (ca.54%) phenolic compounds were produced with higher percentage of aromatic hydrocarbon compounds. CHNS and GPC analysis showed that catalytic liquefaction encouraged hydrodeoxygenation, which produced lower oxygen content bio-oil with lower molecular weight.


Assuntos
Biocombustíveis , Lignina , Catálise , Solventes , Temperatura , Água
9.
Polymers (Basel) ; 12(11)2020 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-33218149

RESUMO

In the present study, a novel graft modified flocculant CTS-g-PAMD was synthesized and applied to conduct sludge conditioning and dewatering. CTS-g-PAMD was copolymerized with AM, DMC and chitosan (CTS) under UV-H2O2 initiation. In addition, the effects of single factor experiments on the molecular weight (MW) CTS grafting efficiency (GE) of CTS-g-PAMD were determined and the optimal copolymerization conditions were achieved. The GE of CTS-g-PAMD reached 91.1% and the MW was 4.82 × 106 Da. As revealed from the characterized results of Fourier-transform infrared spectra (FT-IR), 1H/ NMR, X-ray diffraction (XRD), scanning electron microscopic (SEM) and X-ray photoelectron spectroscopy (XPS), the successful synthesis of CTS-g-PAMD was confirmed, which is considered to be conducive to explaining sludge dewatering performance. Under the optimal conditions (pH = 7.0, flocculant dosage = 35 mg/L), the best flocculating performance (FCMC: 73.7%; SRF: 4.7 × 1012 m·kg-1, turbidity: 9.4 NTU) and large and dense sludge flocs (floc size d50 = 379.142 µm, floc fractal dimension Df = 1.58) were formed. The DMC and CTS chain segments exhibiting cationic properties significantly improved the positive charge density and enhanced the electrical patching effect of CTS-g-PAMD. The long molecular chain of CTS-g-PAMD exhibited superior extensibility, which enhanced bridging effect on adsorption. Moreover, the sludge floc after undergoing CTS-g-PAMD conditioning exhibited robust shear resistance and regeneration ability. After the sludge floc was crushed and broken, a large and dense sludge floc was formed, helping significantly reduce the sludge specific resistance (SRF), turbidity and cake moisture content (FCMC) and enhance the sludge dewatering effect. The novel CTS-g-PAMD flocculant shows promising practical applications and high market value.

10.
Ultrason Sonochem ; 69: 105259, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32738455

RESUMO

Petroleum is a continuous and dynamically stable colloidal system. In the process of oil extraction, transportation, and post-treatment, the stability of the petroleum sol system is easily destroyed, resulting in asphaltenes precipitation that can make pore throat, oil wells, and pipelines blocked, thereby damaging the reservoir and reducing oil recovery. In this paper, removing near-well plugging caused by asphaltene deposition with high-power ultrasound is investigated. Six PZT transducers with different parameters were used to carry out the experimental study. Results show that ultrasonic frequency is one important factor for removing colloidal precipitation plugging in cores, it could not be too high nor too low. The optimum ultrasonic frequency is 25 kHz; Selecting transducers with a higher power is an effective way to improve the removal efficiency. The optimum ultrasonic power is 1000 W. With the increase of ultrasonic treatment time, the recovery rate reaches the maximum and tends to be stable. ultrasonic processing time should be controlled within 120 min. Besides, three methods - ultrasonic treatment alone, chemical injection alone, and ultrasound-chemical method - for removing colloidal precipitation plugging are compared. Results indicate that the ultrasound-assisted chemical method is better than chemical injection alone or ultrasonic treatment alone to remove colloidal sediment in the core. Finally, the mechanism of the ultrasonic deplugging technique is analyzed from three aspects: cavitation effect, the thermal effect, and mechanical vibration.

11.
Bioresour Technol ; 314: 123758, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32629379

RESUMO

Pyrolysis of Spirulina Platensis (SP) microalgae was carried out under different reaction environment such as nitrogen (N2) and carbon dioxide (CO2) at different reaction temperatures of 300, 350, 400, 450 and 500 °C. Catalytic upgradations were examined over solid acid (ZSM-5) and solid base (MgO) catalyst, and with ZSM-5-MgO catalysts mixtures. Results showed, pyrolysis of non-catalytic biomass yielded maximum bio-oil of 43.6% under N2. However catalytic upgradation in CO2 environment produced lower bio-oil due to the coke formation. Maximum bio-oil (46.2 wt%) was obtained with basic metal MgO catalyst in N2 environment compared to other catalyst and environments. Mixture of MgO-ZSM-5 catalyst improved the bio-oil yield (37.8-48.6 wt%) compared to individual catalytic reaction under N2 and CO2. Higher high heating value (HHV) was observed in catalytic bio-oil 36.8 MJ/Kg. Bio-oil (catalytic) analysis revealed that 64-70% of compounds are in hydrocarbon range. Bio-oil was rich in hydrocarbons of C7-C18 range with less oxygenated compounds.


Assuntos
Microalgas , Pirólise , Biocombustíveis , Biomassa , Dióxido de Carbono , Catálise , Temperatura Alta , Hidrocarbonetos , Nitrogênio , Óleos Vegetais , Polifenóis
12.
Small ; 16(4): e1905485, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31894647

RESUMO

Direct growth of graphene on glass can bring an innovative revolution by coupling the complementary properties of traditional glass and modern graphene (such as transparency and conductivity), offering brand new daily-life related applications. However, preparation of high-quality graphene on nonmetallic glass is still challenging. Herein, the direct route of low sheet resistance graphene on glass is reported by using in situ-introduced water as a mild etchant and methane as a carbon precursor via chemical vapor deposition. The derived graphene features with large domain sizes and few amorphous carbon impurities. Intriguingly, the sheet resistance of graphene on glass is dramatically lowered down to ≈1170 Ω sq-1 at the optical transmittance ≈93%, ≈20% of that derived without the water etchant. Based on the highly conductive and optical transparent graphene on glass, a see-through thermochromic display is thus fabricated with transparent graphene glass as a heater. This work can motivate further investigations of the direct synthesis of high-quality graphene on functional glass and its versatile applications in transparent electronic devices or displays.

13.
Bioorg Med Chem Lett ; 30(4): 126901, 2020 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-31882299

RESUMO

Early studies demonstrated that over expression of indoleamine 2,3-dioxygenase (IDO1) in tumor microenvironment results in tumor immune escape. Herein, in order to simplify the structure of two kinds of IDO1 inhibitors from marine alkaloid, Exiguamine A and Tsitsikammamines, we designed, synthesized a series of 1H-indole-4,7-dione derivatives and evaluated their inhibitory activity in IDO1 enzyme and in IFN-γ stimulated Hela cells in vitro. The structure-activity relationship demonstrated that 5-(pyridin-3-yl)-1H-indole-4,7-dione is a promising scaffold for IDO1 inhibitors and most compounds with this core showed moderate inhibition potency at micromole level. Our further enzyme kinetics experiments reveal that these new developed compounds might act as reversible competitive inhibitors of IDO1.


Assuntos
Inibidores Enzimáticos/química , Indolamina-Pirrol 2,3,-Dioxigenase/antagonistas & inibidores , Indóis/química , Sítios de Ligação , Avaliação Pré-Clínica de Medicamentos , Inibidores Enzimáticos/metabolismo , Células HeLa , Humanos , Indolamina-Pirrol 2,3,-Dioxigenase/metabolismo , Indóis/metabolismo , Concentração Inibidora 50 , Cinética , Simulação de Acoplamento Molecular , Estrutura Terciária de Proteína , Relação Estrutura-Atividade
14.
Sci Total Environ ; 689: 546-556, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31279201

RESUMO

As one of the core technologies employed in the field of sludge conditioning, flocculation has the ability to improve the sludge dewatering performance and reduce its volume and amount, which can accordingly result in lower costs in sludge transportation as well as subsequent disposal. Therefore, the development of new and high-efficiency flocculants is a hot topic in this field. The template copolymer (TPAD) of acryloyloxyethyl trimethyl ammonium chloride (DAC) and acrylamide (AM) was successfully synthesized through ultrasonic-template copolymerization using sodium-polyacrylate (NaPAA) as a template. The analysis of FTIR, 1H (13C) NMR, TG/DSC and SEM revealed that TPAD had a conspicuously significant cationic segmental structure. In addition, the results obtained from the analysis on the association constant (KM) and the kinetics of the template reaction indicated that the ultrasonic-template was a free radical initiated polymerization and the polymerization mechanism was I Zip-up (ZIP), and which once again confirmed the formation of the cationic fragment structure. This novel cationic fragment structure in TPAD greatly enhanced the ability of charge neutralization, electric patching, adsorption and bridging, thus improving the active sludge conditioning and dewatering performance (FCMC: 72.9%, SRF: 4.0 × 1012 m·kg-1, d50: 228.604 µm, Df: 2.02 at 400 r/min). The floc breakage and regeneration experiments showed that the cationic fragment structure in TPAD could make great contribution to the formation of large and dense floc structures, and these flocs were able to regenerate rapidly after breakage. Finally, it was also known that these large and compact floc structures were beneficial to the creation of more channels and voids, thereby decreasing sludge resistance (SRF) and improving sludge dewatering performance.

15.
ACS Appl Mater Interfaces ; 10(38): 32622-32630, 2018 Sep 26.
Artigo em Inglês | MEDLINE | ID: mdl-30170490

RESUMO

The direct synthesis of low sheet resistance graphene on glass can promote the applications of such intriguing hybrid materials in transparent electronics and energy-related fields. Chemical doping is efficient for tailoring the carrier concentration and the electronic properties of graphene that previously derived from metal substrates. Herein, we report the direct synthesis of 5 in. uniform nitrogen-doped (N-doped) graphene on the quartz glass through a designed low-pressure chemical vapor deposition (LPCVD) route. Ethanol and methylamine were selected respectively as precursor and dopant for acquiring predominantly graphitic-N-doped graphene. We reveal that by a precise control of growth temperature and thus the doping level the sheet resistance of graphene on glass can be as low as one-half that of nondoped graphene, accompanied by relative high crystal quality and transparency. Significantly, we demonstrate that this scalable, 5 in. uniform N-doped graphene glass can serve as excellent electrode materials for fabricating high performance electrochromic smart windows, featured with a much simplified device structure. This work should pave ways for the direct synthesis and application of the new type graphene-based hybrid material.

16.
Sci Total Environ ; 640-641: 107-115, 2018 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-29859427

RESUMO

Due to the complexity of contaminants, the effectiveness of traditional flocculants toward water purification is insufficient. To break the limitation, a novel polymer flocculant [chitosan grafted poly (acrylamide-itaconic acid), CS-g-P(AM-IA)] was synthesized via ultraviolet-initiated graft copolymerization reaction. Characterization results revealed that the graft copolymers were successfully synthesized and with rougher surface structure. The solubility of CS-g-P(AM-IA) and chitosan grafted polyacrylamide (CS-g-PAM) were greatly improved and they can dissolve in the wide pH range of 2.0-12.0. CaCl2 was used as a source of cation bridge to enhance the flocculation of kaolin particles, and its optimum dosage was 150 mg·L-1. At dosage of 30 mg·L-1 and pH of 5.0, the turbidity removal efficiency of CS-g-P(AM-IA) reached the maximum of 93.8%, whereas those of CS-g-PAM and CS were 96.7% and 76.9%, respectively. The patchwise adsorption of ionic groups embedded in the molecular chain on Ca2+-clay complexes took effect to generate flocs with larger particle size. Besides, the decolorization ability of cationic dyes by CS-g-P(AM-IA) was greatly enhanced due to the role of abundant carboxyl groups. In the crystal violet (CV) adsorption experiment, the maximum CV dye removal efficiency for CS-g-P(AM-IA) reached the maximum of 81.6% at dosage of 0.7 mg·mL-1 and pH of 9.0, while those for CS-g-PAM and CS were 51.7% and 36.5%, respectively.

17.
ACS Nano ; 12(7): 6443-6451, 2018 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-29787229

RESUMO

The photonic reflection of a cholesteric liquid crystal (ChLC) device depends on the spatial distribution of the orientations of their helical axes, and many orientation techniques have been developed so far. In this study, we select the hybrids of graphene directly grown on quartz glass as platforms to construct ChLC-based devices. This special design makes graphene serve as both an alignment layer and a conductive layer, thus affording a more simplified device fabrication route. We reveal that multidomain structures can be evolved for ChLCs on polycrystalline monolayer graphene on quartz glass, as evidenced by polarized optical microscope characterizations. The disparate orientations of the helical axes of ChLCs and the formation of multidomain structures are proposed to be induced by the different domain orientations of graphene, leading to a wide viewing angle of the ChLC-based devices. Moreover, the pitch of ChLCs is also observed to play a key role in the relative orientations of ChLCs. A wide viewing angle of the ChLC-based device is also detected especially in the infrared spectrum region. Briefly, this work should provoke the application of graphene glass as a perfect transparent electrode in the fabrication of liquid-crystal-based devices showing broad application potentials in intelligent laser protection and energy-saving smart windows.

18.
Carbohydr Polym ; 181: 327-336, 2018 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-29253979

RESUMO

A multifunctional carboxylate-rich magnetic chitosan flocculant (Mag@PIA-g-CS) was prepared through surface graft copolymerization on magnetite particles. The effect of monomer molar ratio, initiator and pre-neutralized degree on polymerization rate was determined. Various analytical methods were applied to characterize Mag@PIA-g-CS, exhibiting the successful grafting of polymers, good magnetic feature and core-shell structure. The kinetic process of Ni(II) and malachite green (MG) flocculation by Mag@PIA-g-CS reached equilibrium within <60min with the optimal uptake rate of 98.3% and 87.4%, and exhibited satisfactory removal effect in wide pH range (4.0-8.0 for Ni(II), 5.0-10.0 for MG). Mag@PIA-g-CS exhibited superior flocculation performance over chitosan magnetic flocculant (Mag@CS). The pH-dependent behavior, rapid responsiveness and sensitivity to ionic strength in batch flocculation tests indicated the distinct effect of ionic groups. Moreover, sweeping action of linear molecular chains facilitated further flocculation. Mag@PIA-g-CS showed high stability in extreme environments, and can be easily regenerated and separated.

19.
Materials (Basel) ; 10(3)2017 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-28772642

RESUMO

Cationic polyacrylamides have been employed widely to improve sludge dewatering performance, but the cationic units are randomly distributed in the molecular chain, which restricts the further enhancement of dewaterability. Common template technology to prepare block copolymers requiring a huge number of templates reduces the polymer purity and molecular weight. Here, we adopted the surface-active monomer benzyl dimethyl 2-(methacryloyloxy)ethyl ammonium chloride (BDMDAC) to synthesize cationic microblocky polyacrylamide initiated by ultrasound. The reactivity ratio of monomers suggested that novel cationic monomer BDMDAC had higher homopolymerization ability, and was thus more prone to forming a microblock structure. The statistical analysis of sequence-length distribution indicated that the number and length of cationic segments increased in the PAB molecules. In addition, the characteristic results of Fourier transform infrared (FTIR), proton nuclear magnetic resonance (¹H NMR), and thermogravimetric analysis (TGA) provided evidence for the synthesis of copolymer with cationic microblocks. Finally, the results of dewatering tests demonstrated that sludge dewaterability was greatly improved by adding the synthesized novel flocculants, and the sludge-specific resistance to filtration, filter cake moisture content and residual turbidity all reached a minimum (68.7%, 5.4 × 1012 m·kg-1, and 2.6 NTU, respectively) at 40 mg·L-1. The PAB flocs were large, compact, difficult to break, and easy to regrow. Furthermore, PAB was more effective in the removal of protein from soluble extracellular polymeric substances (SEPSs). In summary, this study provides a novel solution to synthesize cationic microblock polyacrylamide for improving sludge dewatering.

20.
J Hazard Mater ; 332: 1-9, 2017 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-28279868

RESUMO

Extracellular organic matter (EOM) is ubiquitous in the algae-polluted water and has a significant impact on the human health and drinking water treatment. We investigate the different characteristics of dissolved extracellular organic matter (dEOM) and bound extracellular organic matter (bEOM) recovered from the various growth period of Microcystis aeruginosa and the interactions of them and polyaluminum chloride (PACl). The roles of the different EOM in the algae-polluted water treatment are also discussed. The functional groups of aromatic, OH, NH, CN and NO in bEOM possessing the stronger interaction with hydroxyl aluminum compared with dEOM is responsible for bEOM and algae removal. Some low molecular weight (MW) organic components and protein-like substances in bEOM are most easily removed. And dEOM weakly reacts with PACl or inhibits coagulation, especially dEOM with the high MW organic components. The main coagulation mechanisms of bEOM are the generation of insoluble Al-bEOM through complexation, the bridge of AlO4Al12(OH)24(H2O)127+ (Al13), the adsorption of Al(OH)3(am) and the entrapment of flocs. The adsorption of Al13 and Al(OH)3(am) mainly contribute to dEOM removal. It is also recommended to treat the algae with dEOM and bEOM at the initial stage.


Assuntos
Hidróxido de Alumínio/química , Microcystis/química , Purificação da Água , Eutrofização , Floculação
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