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1.
Small ; : e2404885, 2024 Sep 23.
Article in English | MEDLINE | ID: mdl-39308232

ABSTRACT

The overall maximization of photocatalytic H2O2 production efficiency urgently requires the comprehensive optimization of each step in multiplex photocatalysis. Despite numerous endeavors, isolated researches focusing on single efficiencies hinder further advancements in overall catalytic activity. In this work, a series of imine-linked COFs (TT-COF-X), incorporating electronically tunable functional groups (X = ─H, ─OMe, ─OH, ─Br), are rationally fabricated for visible-light-driven H2O2 production via a dual-channel pathway involving 2e- water oxidation and 2e- oxygen reduction. Combined simulations and characterizations reveal that the synergistic modification of functional groups for electronic conjugation and locally intramolecular polarity collectively enhanced light absorption, charge separation and transfer, and interface water-oxygen affinity efficiency. Notably, femtosecond time-resolved transient absorption (fs-TA) reveals that the polarity-induced built-in electric field play a crucial role in facilitating exciton dissociation by reacting BIEF-mediated shallow trapping state. The simultaneously optimal tri-efficiency ultimately results in the highest H2O2 production rate of 3406.25 µmol h-1 g-1 and apparent quantum yields of 8.1% of TT-COF-OH. This study offers an emerging strategy to rational design of photocatalysts from the comprehensive tri-efficiency-oriented perspective.

2.
Small ; : e2406319, 2024 Sep 02.
Article in English | MEDLINE | ID: mdl-39221550

ABSTRACT

In the domain of heterogeneous catalytic activation of peroxymonosulfate (PMS), high-valent metal-oxo (HVMO) species are widely recognized as potent oxidants for the abatement of organic pollutants. However, the generation selectivity and efficiency of HVMO are often constrained by stringent requirements for catalyst adsorption sites and electron transfer efficiency. In this study, a single-atom catalyst, CuSA/CNP&S, is synthesized featuring multiple types (planar/axial) of heteroatom coordination via an H-bond-assisted self-assembly strategy. It is confirmed that CuN3 active centers with axial S coordination are uniformly distributed in a carbon matrix modified by planar P atoms. CuSA/CNP&S activated PMS to selectively generate Cu(III)═OH species as the primary reactive oxygen species (ROS). The pseudo-first-order kinetic rate for bisphenol A degradation reached 1.51 min-1, a 17.57-fold increase compared to the unmodified CuSA/CN catalyst. Additionally, the CuSA/CNP&S catalyst demonstrates high efficiency and durability in removing contaminants from various aqueous matrices. Theoretical calculations and experimental results indicate that the intrinsic electric field generated by distal planar P atoms enhances electron transfer efficiency within the carbon matrix. Meanwhile, axial S coordination elevates the d-band center and tunes the eg * band broadening of Cu, thereby enhancing the adsorption selectivity for the terminal oxygen of PMS. This multitype coordination synergistically mitigates the issues of low selectivity and yield of HVMO species.

3.
Chemosphere ; 324: 138220, 2023 May.
Article in English | MEDLINE | ID: mdl-36842559

ABSTRACT

Photocatalytic 2e- ORR paves a promising avenue for hydrogen peroxide (H2O2) production. However, the obscure structure-activity relationship between a specific structure and photocatalytic 2e- ORR restricts the understanding of its intrinsic mechanism. In this work, Metal-Organic Frameworks (MOFs) with missing linker-cluster domain (MLCD) defects were employed as a model to shed new light on the effect of MLCD defect on photocatalytic 2e- ORR, which mainly focused on the radical reaction and electron behavior. Experiments and theoretical calculations revealed that incorporating MLCD defects significantly lowered the contribution rate of reactive superoxide radical (·O2-). Meanwhile, the retarded interfacial charge transfer via "Ti-O″ bridge was caused by the undesirable electron dissipation and augmented orbital-limited resistance induced by electron spin polarization. Therefore, the photocatalytic 2e- ORR activity was decreased to 30% of its origin by construction MLCD defects. This study provides insights into the internal mechanism of photocatalytic 2e- ORR for designing and optimizing excellent defective nanomaterials.


Subject(s)
Metal-Organic Frameworks , Nanostructures , Electrons , Hydrogen Peroxide , Software
4.
J Colloid Interface Sci ; 630(Pt A): 430-442, 2023 Jan 15.
Article in English | MEDLINE | ID: mdl-36265344

ABSTRACT

Solar energy is becoming the most promising option to mitigate the energy crisis in the future and can be applied in renewable and economical technologies such as water splitting and pollutants degradation. The promotion of the electronic energetic level is considered an efficient method to enhance the photocatalytic performance of semiconductor materials for solar energy conversion. The highly energetic electrons exhibit a remarkable reduction ability by virtue of the electronic spin polarization, which is associated with the conduction band (CB) position. Thus, the regulation of the CB position due to the redistribution of electrons by means of defect engineering presents potential. Here, a series of titanium-based metal-organic frameworks (Ti-based MOFs) named MIL-125-m% containing different extents of defects are reported to enable photocatalytic activity under simulated sunlight and visible light illumination for remarkably enhanced photocatalytic hydrogen evolution and pollutant degradation. The experimental results illustrated that MIL-125-5 % exhibited a superior photocatalytic hydrogen evolution rate (16507.27 µmol·g-1·h-1), much higher than that of MIL-125-0 % (1.444 µmol·g-1·h-1). The excellent photocatalytic performance was attributed to upshift of d-band center, which strengthened the adsorption of H*, facilitating the H2 evolution reaction. In addition, the degradation rate of MIL-125-5 % was up to twice the original rate, for the highly energetic electrons induced by the CB flexibility alleviated the photoinduced electron recombination in defective MIL-125. The strategy of defect engineering provides a new path to control the flexibility of the CB position by electronic spin polarization on adjustable metal-organic frameworks (MOFs), and the photocatalytic effect is changed accordingly.

5.
Sci Total Environ ; 859(Pt 2): 160334, 2023 Feb 10.
Article in English | MEDLINE | ID: mdl-36410488

ABSTRACT

The design of high-performance porous adsorbents for phosphorus removal is a persistently hot topic to maintain a sustainable aquatic ecosystem. In the present study, a self-templating strategy using LaFe cyanometallates (CMs) as precursors was adopted to prepare porous LaFe bimetal oxides with optimizable structure and composition for phosphate adsorption. The results showed that a high supplied LaIII/FeII ratio enabled an adequate coordination polymerization in the preparation of LaFe CM precursor and led to a striking three-dimensional (3D) structure of "twin lotus flower" with high coordinated water content, which resulted in a 3D flower-like LaFe oxide with high surface area and high porosity (mainly in mesopore). The LaFe oxide of LaFe15T possessing the optimal La/Fe ratio (1.5: 1) exhibited the most superior performance of phosphate adsorption, where La was confirmed to be the main active site for phosphate capture via ligand exchange mechanism. The batch and column tests of phosphate adsorption showed that the 3D flower-like LaFe oxides are effective adsorbents for phosphate removal. Therefore, the structure optimization in the template preparation stage is an effective strategy to design porous LaFe bimetal oxides as high-performance phosphorus removal materials.


Subject(s)
Oxides , Phosphorus , Oxides/chemistry , Catalytic Domain , Ecosystem , Adsorption , Phosphates/chemistry
6.
J Hazard Mater ; 444(Pt B): 130428, 2023 02 15.
Article in English | MEDLINE | ID: mdl-36435039

ABSTRACT

Simultaneous regulation of adsorption and photocatalytic performance of covalent triazine frameworks (CTFs) to achieve efficient control of organic pollution in water is a promising strategy, but remains a formidable challenge. Herein, pyridine linkers were innovatively introduced into pristine CTF (p-CTF) and the bidirectional electron donor-acceptor (EDA) system of contaminant-to-pyridine and pyridine-to-triazine was constructed inside. Experimental results combined with theoretical calculations revealed that pyridine units with π-deficient properties performed as electron acceptors and electron donors in the adsorption and photocatalytic processes, respectively. This special structure provided a directional pathway for electron transfer, which endowed CTFs with excellent adsorption and photocatalytic properties. Compared to p-CTF, pyridine-linked CTF (M-CTF) showed a 16-fold increase in adsorption capacity for naphthalene (973.4 µmol·g-1). Benefiting from the optimized light absorption and electron transfer form (n → π*transition), M-CTF exhibited high regeneration efficiency after adsorption of both bisphenol A (94 % after 4 cycles) and naphthalene (95 % after 4 cycles). Besides, the removal performance of organic micropollutants from natural water showed a great advantage thanks to the bidirectional EDA system. Overall, the present study provides new insights into the optimization of electronic structures for carbon-based environmental functional materials applied to organic pollution control in water.


Subject(s)
Electrons , Triazines , Pyridines , Oxidants , Naphthalenes , Water
7.
J Colloid Interface Sci ; 622: 390-401, 2022 Sep 15.
Article in English | MEDLINE | ID: mdl-35525142

ABSTRACT

Two well-defined CoFe bimetal oxides are prepared from Prussian blue analogues (PBAs) as precursors with designable structures, which are further explored for phosphate removal. A speed-controlled coordination strategy is used to fabricate two CoFe PBA microcrystals with different morphologies, then two regular CoFe oxides are obtained via an intermediate-temperature calcination. CoFeS, a slow-speed coordination product with truncated microcube structure, contains less coordinated water and Fe3+ in its framework, but can create more mesopores and Fe3+ in its oxidative product of CoFeST300. CoFeST300 has been demonstrated to have higher adsorption capacity and affinity for phosphate adsorption compared to that of the fast-speed coordination product, due to its more Fe3+ as effective adsorption sites via ligand exchange. Besides, the inner-sphere complexation mechanism makes CoFeST300 high selectivity for phosphate removal compared to other co-existing anions. The application performance of CoFeST300 is examined by multiple continuous treatment of actual sewage, and the result of all effluent concentrations below 0.5 mg P/L verifies a promising potential of the fabricated adsorbent for phosphorus removal. Thus, design or regulation of the precursors is an efficiency method to fabricate an ideal metal oxide for phosphate adsorption.


Subject(s)
Oxides , Water Pollutants, Chemical , Adsorption , Catalytic Domain , Ferrocyanides , Oxides/chemistry , Phosphates , Water Pollutants, Chemical/chemistry
8.
Environ Sci Technol ; 56(10): 6699-6709, 2022 05 17.
Article in English | MEDLINE | ID: mdl-35475353

ABSTRACT

The water shortage crisis, characterized by organic micropollutants (OMPs), urgently requires new materials and methods to deal with it. Although heteroatom doping has been developed into an effective method to modify carbon nanomaterials for various heterogeneous adsorption and catalytic oxidation systems, the active source regulated by intrinsic electron and spin structures is still obscure. Here, a series of nonmetallic element-doped (such as P, S, and Se) covalent triazine frameworks (CTFs) were constructed and applied to remove organic pollutants using the adsorption-photocatalysis process. The external mass transfer model (EMTM) and the homogeneous surface diffusion model (HSDM) were employed to describe the adsorption process. It was found that sulfur-doped CTF (S-CTF-1) showed a 25.6-fold increase in saturated adsorption capacity (554.7 µmol/g) and a 169.0-fold surge in photocatalytic kinetics (5.07 h-1), respectively, compared with the pristine CTF-1. A positive correlation between electron accumulation at the active site (N1 atom) and adsorption energy was further demonstrated with experimental results and theoretical calculations. Meanwhile, the photocatalytic degradation rates were greatly enhanced by forming a built-in electric field driven by spin polarization. In addition, S-CTF-1 still maintained a 98.3% removal of 2,2',4,4'-tetrahydroxybenzophenone (BP-2) micropollutants and 97.6% regeneration after six-cycle sequencing batch treatment in real water matrices. This work established a relation between electron and spin structures for adsorption and photocatalysis, paving a new way to design modified carbon nanomaterials to control OMPs.


Subject(s)
Electrons , Triazines , Adsorption , Carbon , Triazines/chemistry , Water
9.
J Hazard Mater ; 423(Pt A): 127004, 2022 02 05.
Article in English | MEDLINE | ID: mdl-34482074

ABSTRACT

Focusing on the emergence of organic pollutants in aqueous environments, attempts to assemble two-dimensional (2D) materials into three-dimensional (3D) structures are expected to improve their pollution control performance. However, most 3D heterostructural nanomaterials are constructed by mechanical mixing methods, which result in structures that are randomly arranged and prone to collapse. Two typical 2D carbon materials, reduced graphene oxide (rGO) and covalent triazine frameworks (CTFs), have exhibited excellent effects in the fields of contaminant adsorption and photocatalysis, respectively. However, their regular packing structure could not provide an interconnected pore network suitable for the diffusion or adsorption of pollutants. In this study, a series of heterostructures named rGCs were fabricated by direct growth of 2D CTFs with different ratios on the surface of rGO layers. The rGCs were designed to remove trace concentrations of naphthalene (NAP) and benzophenone (BP) from water, which can be regenerated under sunlight. rGC-20, in which nanocubicle-like 3D heterostructures were successfully constructed, not only adsorbed NAP and BP with superb normalized adsorption capacities (5000-5300 µmol/g) but also could be regenerated with an exceptional percentage recovery of 90-95% in the 4th cycle. The microenvironment created in nanocubicle-like 3D heterostructures enhances the adsorption of pollutants, the excitation of electrons and utilization of radicals, which further promotes the adsorption and photocatalysis of rGCs. This work provides a promising adsorbent with outstanding adsorption-regeneration ability for aromatic contaminant removal from water. DATA AVAILABILITY: The main data that support the findings of this study are available from the article and its Supplementary Information. Extra data are available from the corresponding author on request.


Subject(s)
Water Pollutants, Chemical , Water , Adsorption , Sunlight , Triazines , Water Pollutants, Chemical/analysis
10.
J Colloid Interface Sci ; 545: 276-281, 2019 Jun 01.
Article in English | MEDLINE | ID: mdl-30897423

ABSTRACT

Graphene oxide (GO) based membranes are widely adopted in molecular separation based on size exclusion effect by stacked GO sheets. Both high flux and efficient rejection of GO-based membranes for long-term operation are highly expected for practical applications. Here, an attapulgite (ATP) nanofibers/ GO composite (ATP/GO) membrane is assembled by filtration of mixed aqueous colloidal suspensions of ATP and GO. Due to the modification of interlayer distance and surface property of GO membrane by ATP, the ATP/GO membrane demonstrates excellent separation performance, with a high water flux of 221.16 Lm-2 h-1bar-1, 7.7 times higher than that of pure GO membrane. Meanwhile, the rejection of ATP/GO is also slightly improved comparing with that of GO membrane. It is also found that increasing the thickness of the membrane is effective to enhance rejection percentage. The ATP/GO membranes reported here show high efficiency for molecular separation, which demonstrates potential applications in water purification and environmental protection.

11.
ACS Appl Mater Interfaces ; 11(11): 10672-10679, 2019 Mar 20.
Article in English | MEDLINE | ID: mdl-30799599

ABSTRACT

Solar steam generation is considered to be a promising strategy for sustainable clean water supply. An easily made and robust solar still can practically meet any contingency in wilderness survival, compared to high-cost and delicate solar thermal materials, for example, plasmonic metals, carbon nanotubes, or graphene-based materials. Inspired by rice plants with high transpiration, we develop a universal solar steam-generation device from wasted rice straw for robust clean water production. The upper leaves of rice straw are carbonized and composited with bacterial cellulose to function as a superior light absorber and the lower culms are designed as excellent water pumps. The unique capillary structures and multilevel geometrical structures of the rice culms contribute to their outstanding water pumping capacity for surface evaporation, resulting in an evaporation rate of 1.2 kg m-2 h-1 with 75.8% conversion efficiency. The rice straw-derived solar still has a daily clean water yield of 6.4-7.9 kg m-2 on sunny days and 4.6-5.6 kg m-2 on cloudy days over 14 days of operation. More attention-grabbing aspect is that this evaporation device is applicable to various water-bearing media, for example, sand, soil, and seawater, to collect clean water with a stable evaporation performance, and the unique multilevel structures of the culms make great contribution to the unimpeded water channels. By turning "waste" to "wealth," this project shines significant light on a facilely fabricated, robust, and efficient solar still, especially designed for urgent priority in wilderness survival.

12.
Nanotechnology ; 28(46): 465401, 2017 11 17.
Article in English | MEDLINE | ID: mdl-29063865

ABSTRACT

A new conductive carbon hybrid combining both reduced graphene nanoscrolls and carbon nanotubes (rGNSs-CNTs) is prepared, and used to host Fe3O4 nanoparticles through an in situ synthesis method. As an anode material for LIBs, the obtained Fe3O4@rGNSs-CNTs shows good electrochemical performance. At a current density of 0.1 A g-1, the anode material shows a high reversible capacity of 1232.9 mAh g-1 after 100 cycles. Even at a current density of 1 A g-1, it still achieves a high reversible capacity of 812.3 mAh g-1 after 200 cycles. Comparing with bare Fe3O4 and Fe3O4/rGO composite anode materials without nanoscroll structure, Fe3O4@rGNSs-CNTs shows much better rate capability with a reversible capacity of 605.0 and 500.0 mAh g-1 at 3 and 5 A g-1, respectively. The excellent electrochemical performance of the Fe3O4@rGNSs-CNTs anode material can be ascribed to the hybrid structure of rGNSs-CNTs, and their strong interaction with Fe3O4 nanoparticles, which on one hand provides more pathways for lithium ions and electrons, on the other hand effectively relieves the volume change of Fe3O4 during the charge-discharge process.

13.
Small ; 13(34)2017 09.
Article in English | MEDLINE | ID: mdl-28692763

ABSTRACT

Macroscopic porous graphene materials composed of graphene sheets have demonstrated their advantageous aspects in diverse application areas. It is essential to maximize their excellent performances by rationally controlling the sheet arrangement and pore structure. Bulk porous graphene materials with oriented pore structure and arrangement of graphene sheets are prepared by marrying electrolyte-assisted self-assembly and shear-force-induced alignment of graphene oxide sheets, and the super elasticity and anisotropic mechanical, electrical, and thermal properties induced by this unique structure are systematically investigated. Its application in pressure sensing exhibits ultrahigh sensitivity of 313.23 kPa-1 for detecting ultralow pressure variation below 0.5 kPa, and it shows high retention rate for continuously intercepting dye molecules with a high flux of ≈18.7 L m-2 h-1 bar-1 and a dynamic removal rate of 510 mg m-2 h-1 .

14.
Small ; 13(14)2017 04.
Article in English | MEDLINE | ID: mdl-28145634

ABSTRACT

A nitrogen-doped 3D graphene foam assembled with nanoscroll structure is constructed via a facile mild-heating methodology using a polar molecule of formamide as the driving regent. The as-prepared graphene nanoscroll foam exhibits promising performance in organic pollutant removal with improved adsorption rate and high binding affinity, and is thought to be a novel adsorption material.

15.
Sci Rep ; 6: 33185, 2016 09 12.
Article in English | MEDLINE | ID: mdl-27615451

ABSTRACT

Graphene oxide (GO) based membranes have been widely applied in molecular separation based on the size exclusion effect of the nanochannels formed by stacked GO sheets. However, it's still a challenge to prepare a freestanding GO-based membrane with high mechanical strength and structural stability which is prerequisite for separation application in aqueous solution. Here, a freestanding composite membrane based on bacterial cellulose (BC) and GO is designed and prepared. BC network provides a porous skeleton to spread GO sheets and uniformly incorporates into the GO layers, which endows the BC + GO composite membrane with well water-stability, excellent tensile strength, as well as improved toughness, guaranteeing its separation applicability in water environment. The resulting BC + GO membrane exhibits obviously discrepant permeation properties for different inorganic/organic ions with different size, and in particular, it can quickly separate ions in nano-scale from angstrom-scale. Therefore, this novel composite membrane is considered to be a promising candidate in the applications of water purification, food industry, biomedicine, and pharmaceutical and fuel separation.


Subject(s)
Cellulose/chemistry , Graphite/chemistry , Membranes, Artificial , Polysaccharides, Bacterial/chemistry , Filtration , Oxides/chemistry , Permeability , Porosity , Solutions , Tensile Strength
16.
Nanoscale ; 8(1): 197-203, 2016 Jan 07.
Article in English | MEDLINE | ID: mdl-26646951

ABSTRACT

A novel layered graphene-based architecture is achieved via an ordered self-assembly process. Amphipathic graphene nanosheets are joined horizontally into large sheets via edge splicing, and a cross-linking agent of poly(vinyl alcohol) bridges them into integrated three-dimensional monoliths with tunable interlayer spacing. This layered architecture possesses highly ordered and favorable microchannels for molecular transfer.

17.
Environ Sci Technol ; 49(1): 67-84, 2015 Jan 06.
Article in English | MEDLINE | ID: mdl-25510293

ABSTRACT

Just as graphene triggered a new gold rush, three-dimensional graphene-based macrostructures (3D GBM) have been recognized as one of the most promising strategies for bottom-up nanotechnology and become one of the most active research fields during the last four years. In general, the basic structural features of 3D GBM, including its large surface area, which enhances the opportunity to contact pollutants, and its well-defined porous structure, which facilitates the diffusion of pollutant molecules into the 3D structure, enable 3D GBM to be an ideal material for pollutant management due to its excellent capabilities and easy recyclability. This review aims to describe the environmental applications and mechanisms of 3D GBM and provide perspective. Thus, the excellent performance of 3D GBM in environmental pollutant adsorption, transformation and detection are reviewed. Based on the structures and properties of 3D GBM, the removal mechanisms for dyes, oils, organic solvents, heavy metals, and gas pollutants are highlighted. We attempt to establish "structure-property-application" relationships for environmental pollution management using 3D GBM. Approaches involving tunable synthesis and decoration to regulate the micro-, meso-, and macro-structure and the active sites are also reviewed. The high selectivity, fast rate, convenient management, device applications and recycling utilization of 3D GBM are also emphasized.


Subject(s)
Environmental Pollutants/isolation & purification , Graphite/chemistry , Nanotechnology/methods , Adsorption , Coloring Agents/chemistry , Coloring Agents/isolation & purification , Diffusion , Environmental Monitoring/instrumentation , Environmental Monitoring/methods , Environmental Pollutants/chemistry , Metals, Heavy/chemistry , Metals, Heavy/isolation & purification , Organic Chemicals/chemistry , Porosity , Recycling
18.
J Environ Sci (China) ; 26(3): 493-501, 2014 Mar 01.
Article in English | MEDLINE | ID: mdl-25079260

ABSTRACT

A series of calcined carbonate layered double hydroxides (CLDHs) with various metal compositions and different M(2+)/M(3+) ratios were prepared as adsorbents for perchlorate. Adsorption isotherms fit Langmuir model well, and the adsorption amount followed the order of MgAl-CLDHs ≥ MgFe-CLDHs >> ZnAl-CLDHs. The isotherms of MgAl-CLDHs and MgFe-CLDHs displayed a two-step shape at low and high concentration ranges and increased with an increase in the M(2+)/M(3+) ratio from 2 to 4. The two-step isotherm was not observed for ZnAl-CLDHs, and the adsorption was minimally affected by the M(2+)/M(3+) ratio. The LDHs, CLDHs and the reconstructed samples were characterized by X-ray diffraction, SEM, FT-IR and Raman spectra to delineate the analysis of perchlorate adsorption mechanisms. The perchlorate adsorption of MgAl-CLDHs and MgFe-CLDHs was dominated by the structural memory effect and the hydrogen bonds between the free hydroxyl groups on the reconstructed-LDHs and the oxygen atoms of the perchlorates. For ZnAl-CLDHs, the perchlorate adsorption was controlled by the structural memory effect only, as the hydroxyl groups on the hydroxide layers preferred to form strong hydrogen bonds with carbonate over perchlorate, which locked the intercalated perchlorate into a more confined nano-interlayer. Several distinct binding mechanisms of perchlorate by CLDHs with unique M(2+) ions were proposed.


Subject(s)
Carbonates/chemistry , Hydroxides/chemistry , Metals/chemistry , Perchlorates/isolation & purification , Water Pollutants, Chemical/isolation & purification , Adsorption , Hydrogen Bonding
19.
Environ Sci Technol ; 48(1): 279-88, 2014.
Article in English | MEDLINE | ID: mdl-24289306

ABSTRACT

The pH-dependent adsorption of perchlorate (ClO4(-)) by wood-derived biochars produced at 200-700 °C (referred as FB200-FB700) was investigated to probe the anion retention mechanisms of biochars and to identify the interactions of water and biochar. ClO4(-) adsorption was controlled by the surface polarities and structural compositions of the organic components of biochars, rather than their inorganic mineral components. FB500-FB700 biochars with low polarity and high aromaticity displayed a superior ClO4(-) adsorption capacity, but which was affected by solution pH. Besides electrostatic interaction, hydrogen bonding to oxygen-containing groups on biochars was proposed the dominant force for perchlorate adsorption, which led to the maximum adsorption occurring near pHIEP, where surface charge equals zero. The dissociation of these surface oxygen-containing groups was monitored by zeta potential curves, which indicated that the H-bonds donors on biochar surface for ClO4(-) binding were changed from -COOH (ClO4(-)···HOOC-) and -OH (ClO4(-)···HO-) to -OH alone with an increase in pH. The H-bond force was strengthened by the condensed aromatic surfaces, since high temperature biochars provided a hydrophobic microenvironment to accommodate weakly hydrated perchlorate and facilitated the H-bonds for ClO4(-) binding to functional groups by the large π subunit of their aromatic substrate. Lastly, the batch and column tests of ClO4(-) adsorption showed that biochars like FB700 are effective adsorbents for anion pollutant removal via H-bonding interaction.


Subject(s)
Charcoal/chemistry , Perchlorates/chemistry , Wood/chemistry , Adsorption , Hot Temperature , Hydrogen Bonding , Hydrogen-Ion Concentration , Hydrophobic and Hydrophilic Interactions , Oxygen/chemistry , Water/chemistry
20.
Environ Sci Technol ; 47(19): 11013-22, 2013 Oct 01.
Article in English | MEDLINE | ID: mdl-24020648

ABSTRACT

In this study, molecular interactions of perchlorate (ClO4(-)), an emerging pollutant, with cetyltrimethylammonium(CTMA(+)) complexed in the nanointerlayer of negatively charged montmorillonite were characterized using the zeta potentials, FTIR, Raman, and XRD spectroscopy and quantified using quantum mechanical calculations and sorption experiments. We found that blue-shifting hydrogen bonds assisted in the uptake of ClO4(-) from water into the nanointerlayer spacing of CTMA(+)-montmorillonite and were tunable according to CTMA(+) loading. FTIR spectra presented an obvious 47 cm(-1) blue shift in the C-H vibration coming from the N-terminal methyl group of CTMA(+) when ClO4(-) was absorbed. Quantum mechanical calculations based on density functional theory demonstrated that triplex blue-shifting hydrogen bonds of C-H···O were formed between the three terminal methyl groups of CTMA(+) and three oxygen atoms of ClO4(-). The contribution of blue-shifting hydrogen bonds to perchlorate uptake switched from a ClO4(-)/CTMA(+) ratio of 0.0453 at low CTMA(+) loadings to a ClO4(-)/CTMA(+) ratio of 0.2563 (5.6-fold) at high CTMA(+) loadings, which can be ascribed to the evolution of the nanointerlayer microenvironments from hydrophilic properties to hydrophobic properties. The blue-shifting hydrogen bond of C-H···O that is tunable with the hydrophobic nature of the organic phase should be recognized to elucidate the biochemical behavior of perchlorate in organisms.


Subject(s)
Bentonite/chemistry , Cetrimonium Compounds/chemistry , Perchlorates/chemistry , Cetrimonium , Hydrogen Bonding , Hydrophobic and Hydrophilic Interactions
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