Novel graphene oxide-ordered mesoporous silica materials with two-dimensional mesoporous structure and large surface area were successfully fabricated through sol–gel and self-assembly methods. The ...synthesized materials were characterized by small-angle X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption–desorption. By taking advantage of the excellent properties, the hybrid materials were employed as the adsorbent for removal of heavy metals in environmental waters by adsorption separation—inductively coupled plasma mass spectrometry. The results showed that the materials exhibited superior adsorption capacity, the removal efficiencies for As, Cd, Cr, Hg, and Pb reached 97.7, 96.9, 96.0, 98.5, and 78.7 %, respectively. The facile, low-cost, and environmental friendly synthesis method as well as highly efficient adsorption ability made it become a promising adsorbents for the removal of toxic heavy metals at low or trace concentrations from wastewater.
The development of an effective method for detecting heavy-metal ions remains a serious task because of their high toxicity to public health and environments. Herein, a new electrochemical method ...based on a graphene aerogel (GA) and metal–organic framework (MOF) composites was developed for simultaneous detection of multiple heavy-metal ions in aqueous solutions. The GA-MOF composites were synthesized via the in situ growth of the MOF UiO-66-NH2 crystal on the GA matrix. GA not only serves as the backbone for UiO-66-NH2 but also enhances the conductivity of the composites by accelerating the electron transfer in the matrix. UiO-66-NH2 worked as a binding site for heavy-metal ions because of the interaction between hydrophilic groups and metal cations. The detection performance of the GA-UiO-66-NH2 composite-modified electrodes was determined. The developed electrochemical method can be successfully applied for individual and simultaneous detection of heavy-metal ions, namely, Cd2+, Pb2+, Cu2+,and Hg2+, in aqueous solutions with high sensitivity and selectivity. The method can also be used for simultaneous detection of Cd2+, Pb2+, Cu2+, and Hg2+ in river water and the leaching solutions of soil and vegetable with high accuracy and reliability. This work provides a new approach for simultaneous detection of multiple heavy-metal ions in practical applications.
The slow kinetics of the Co3+/Co2+ catalytic redox cycle on the surface of Co-based solid catalysts greatly limits their application in sulfate radical-based advanced oxidation processes. To overcome ...this challenge, nanoparticle-assembled rod-like S-doped Co3O4 (S-Co3O4) with abundant oxygen vacancies (OVs) and a mesoporous structure was prepared to activate peroxymonosulfate to degrade various organic dye contaminants. The abundant OVs and good charge transfer capability of S-Co3O4 accelerated the Co3+/Co2+ redox cycle due to the incorporation of S atoms, which improved the Co2+ recovery. The S-Co3O4 catalysts exhibited excellent catalytic activities, and the methylene blue (MB) degradation rate reached 100% within 6 min. The degradation rate constant of the catalytic reaction for the S-Co3O4 + PMS system (0.78 min−1) was 30 times higher than that of the Co3O4 + PMS system (0.026 min−1), which may be due to the synergy between the high Co2+ content, abundant OVs, and large surface area. After six consecutive cycles, the MB degradation efficiency still reached 94.5%, and the cobalt leaching of S-Co3O4 was only 0.42 mg L−1. In the S-Co3O4-activated PMS system, SO4·− and 1O2 were the main active species, but 1O2 played the main role in contaminant degradation. This study provides a novel method for accelerating Co3+/Co2+ circulation and reducing Co ion leaching from the surface of heterogeneous Co-based catalysts to substantially enhance their performance.
The slow kinetics of the Co 3+ /Co 2+ catalytic redox cycle on the surface of Co-based solid catalysts greatly limits their application in sulfate radical-based advanced oxidation processes. To ...overcome this challenge, nanoparticle-assembled rod-like S-doped Co 3 O 4 (S-Co 3 O 4 ) with abundant oxygen vacancies (OVs) and a mesoporous structure was prepared to activate peroxymonosulfate to degrade various organic dye contaminants. The abundant OVs and good charge transfer capability of S-Co 3 O 4 accelerated the Co 3+ /Co 2+ redox cycle due to the incorporation of S atoms, which improved the Co 2+ recovery. The S-Co 3 O 4 catalysts exhibited excellent catalytic activities, and the methylene blue (MB) degradation rate reached 100% within 6 min. The degradation rate constant of the catalytic reaction for the S-Co 3 O 4 + PMS system (0.78 min −1 ) was 30 times higher than that of the Co 3 O 4 + PMS system (0.026 min −1 ), which may be due to the synergy between the high Co 2+ content, abundant OVs, and large surface area. After six consecutive cycles, the MB degradation efficiency still reached 94.5%, and the cobalt leaching of S-Co 3 O 4 was only 0.42 mg L −1 . In the S-Co 3 O 4 -activated PMS system, SO 4 ˙ − and 1 O 2 were the main active species, but 1 O 2 played the main role in contaminant degradation. This study provides a novel method for accelerating Co 3+ /Co 2+ circulation and reducing Co ion leaching from the surface of heterogeneous Co-based catalysts to substantially enhance their performance.
The detection of blood glucose level receives much attention, because diabetes has become one of the significant threats to human health worldwide. In this paper, we described a novel core-shell ...MOF@MOF composite-based electrochemical sensor for nonenzymatic glucose sensing in alkaline media. The core-shell UiO-67@Ni-MOF composites were synthesized by internal extended growth of shell Ni-MOF on the core UiO-67 under polyvinylpyrrolidone (PVP) regulation. In the sensor system, UiO-67 with large specific surface area and good conductivity was used to accelerate the rate of electron transfer of UiO-67@Ni-MOF. Ni-MOF served as an electrocatalytic material due to excellent electrochemical activity toward glucose oxidation. The morphology, structure, and electrochemical performance of UiO-67@Ni-MOF composites were characterized. To demonstrate the detection performance of the UiO-67@Ni-MOF composite-based sensor, it was successfully used for nonenzymatic glucose sensing. The results indicated that UiO-67@Ni-MOF composites exhibited high electrocatalytic activity toward glucose oxidation compared with individual UiO-67 and Ni-MOF. Moreover, the sensor possessed high sensitivity and selectivity for real-time amperometric detection of glucose. It performed glucose level detection in human serum samples with acceptable reliability and accuracy. The present work suggested that the as-fabricated sensor is promising for nonenzymatic glucose sensing in real samples and holds great potential as an alternative tool for the rapid diagnosis of diabetes and for monitoring blood glucose levels daily.
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•A novel core-shell MOF@MOF composite were synthesized by internal extended growth of shell Ni-MOF on the core UiO-67.•The UiO-67@Ni-MOF composites-based electrochemical sensor was presented for nonenzymatic glucose sensing.•The electrochemical sensor exhibited high selectivity and sensitivity for the detection of glucose in human serum.
Novel phenyl-modified magnetic graphene/mesoporous silica (MG-MS-Ph) composites with hierarchical bridge-pore structure were successfully synthesized. The magnetic graphene (MG) as bridge were ...obtained by one-step solvothermal approach and then phenyl-functionalized mesoporous silica (MS-Ph) as pore modified the MG surfaces through one-pot facile strategy. The resulting MG-MS-Ph exhibited large surface area (446.5 m2g−1), highly ordered mesopores with uniform pore size (2.8 nm) and pore volume (0.32 cm3g−1) and higher saturation magnetization (25 emu g−1). These wonderful features made MG-MS-Ph as a promising magnetic solid-phase extraction adsorbent for the removal of pesticides from wastewater. Batch adsorption studies indicated that the novel composites exhibited superior adsorption capacity of pesticides compared with other adsorbents including Activated carbon, Multi-walled carbon nanotube and Single-walled carbon nanotube. Therefore, MG-MS-Ph as a low cost and efficient adsorbents for the removal of toxic pesticides would be economically and technically feasible.
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•A magnetic graphene/mesoporous silica with hierarchical bridge-pore structure was synthesized.•The unique materials solve a problem of graphene retrieval or separation from solution.•The novel composites exhibited superior adsorption capacity for toxic pesticides.
The slow kinetics of the Co
3+
/Co
2+
catalytic redox cycle on the surface of Co-based solid catalysts greatly limits their application in sulfate radical-based advanced oxidation processes. To ...overcome this challenge, nanoparticle-assembled rod-like S-doped Co
3
O
4
(S-Co
3
O
4
) with abundant oxygen vacancies (OVs) and a mesoporous structure was prepared to activate peroxymonosulfate to degrade various organic dye contaminants. The abundant OVs and good charge transfer capability of S-Co
3
O
4
accelerated the Co
3+
/Co
2+
redox cycle due to the incorporation of S atoms, which improved the Co
2+
recovery. The S-Co
3
O
4
catalysts exhibited excellent catalytic activities, and the methylene blue (MB) degradation rate reached 100% within 6 min. The degradation rate constant of the catalytic reaction for the S-Co
3
O
4
+ PMS system (0.78 min
−1
) was 30 times higher than that of the Co
3
O
4
+ PMS system (0.026 min
−1
), which may be due to the synergy between the high Co
2+
content, abundant OVs, and large surface area. After six consecutive cycles, the MB degradation efficiency still reached 94.5%, and the cobalt leaching of S-Co
3
O
4
was only 0.42 mg L
−1
. In the S-Co
3
O
4
-activated PMS system, SO
4
&z.rad;
−
and
1
O
2
were the main active species, but
1
O
2
played the main role in contaminant degradation. This study provides a novel method for accelerating Co
3+
/Co
2+
circulation and reducing Co ion leaching from the surface of heterogeneous Co-based catalysts to substantially enhance their performance.
A mesoporous S-doped Co
3
O
4
with abundant oxygen vacancies was developed and applied as a new Fenton-like catalyst.
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•A 3D graphene aerogels–mesoporous silica materials were successfully fabricated.•The novel materials exhibited superior absorption capacity for four phenols even though at low or ...trace concentrations.•The low-cost and environmental friendly adsorbent with highly removal efficiency could be applied to the real wastewater.
Three-dimensional (3D) graphene aerogels–mesoporous silica (GAs–MS) frameworks were successfully fabricated. The interconnected macropores were obtained from hydrothermally assembled 3D GAs, while the mesopores were generated by the silica uniformly grown on the surface of graphene. The resulting GAs–MS exhibited narrow mesopore size distribution (1.87nm), high surface area (1000.80m2g−1), and hierarchical macro- and mesoporous structures. These wonderful features made GAs–MS as a promising adsorbent for the removal of hazardous phenols from wastewater. The adsorption study implied that the novel materials exhibited superior adsorption capacity of phenols to such as phenol, catechol, resorcinol and hydroquinone, with removal efficiencies of 68.6%, 86.6%, 91.1% and 94.7%, respectively.
Electrochemical determination of luteolin and baicalein always needs acidic supporting electrolyte to guarantee good sensitivity. Therefore, most of the reported electrochemical sensors of luteolin ...and baicalein are unsuitable for detection of neutral actual samples. It is necessary to design a highly sensitive sensor for direct determination of them in neutral conditions. In this study, poly(N-isopropylacrylamide-acrylic acid) hydrogel particles (NIPA/AA) and multiwall carbon nanotubes (MWCNTs) composite modified glassy carbon electrode (GCE) was fabricated by a simple casting method. The voltammetric results showed that the NIPA/AA particle film provided acidic environment for proton-electron coupled reaction in neutral mediums. The near-surface pH of the electrode was related on the loaded amount of the NIPA/AA particles in pH range from 4.2 to 5.9. The voltammetric behaviors of luteolin and baicalein at the NIPA/AA-MWCNTs-GCE were studied by cyclic voltammetry. The peak separations between cathodic and anodic peaks were decreased and peak currents were increased because of decrease in pH and increase in ion conductivity at the local electrode surface. The sensitivity of the electrode was investigated by differential pulse voltammetry. Even under neutral conditions, the plots of the oxidation currents of luteolin and baicalein were dependent linearly on their concentration with detection limit of 14.5 pM and 44.4 pM, respectively. Moreover, the proposed NIPA/AA-MWCNTs-GCE was also successfully applied for determination of luteolin and baicalein in peanut shell, Huang-qin and tomato samples.
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•NIPA/AA particle provided acidic condition for proton-electron coupled reactions.•The particle film at electrode surface was worked as a local pH buffer.•Voltammetric response of luteolin and baicalein were remarkably improved.•The electrode was successfully applied for detection of neutral actual samples.
Graphene aerogel–mesoporous carbon (GA–MC) composites with three-dimensional (3D) hierarchical nanostructures were synthesized using a nanocasting technique. The honeycomb-like GA–MC composites ...exhibited very high surface areas (728.3 m 2 g −1 ), and ultra large pore sizes (48 nm) and pore volumes (0.96 cm 3 g −1 ) due to the synergistic combination of the advantages of both macro-porous graphene aerogels and the meso-pores of mesoporous carbon. These wonderful features made GA–MC a promising enrichment material for SPME fiber coating. Under the optimum conditions, the home-made fiber (GA–MC) was successfully applied to extract BFRs in real wastewater samples and ideal results were obtained with recoveries of 74.6–96.2%. The new fibers demonstrated excellent enrichment capabilities compared to commercial polydimethylsiloxane (PDMS) and polyacrylate (PA) fibers for six brominated flame retardants (BFRs). The ideal extraction performance of the novel graphene aerogel–mesoporous composites creates new opportunities for SPME applied in environmental analysis.
