Adsorption performance of CMK-3 and C-FDU-15 in NO removal at low temperature

The efficient enrichment of marine peptides from the protein hydrolysate of the marine worm Urechis unicinctus by using mesoporous materials MCM-41, SBA-15 and CMK-3

Peptides found in marine life have various specific activities due to their special growth environment, and there is increasing interest in the isolation and concentration of these biofunctional compounds. In this study, the protein hydrolysate of the marine worm Urechis unicinctus was prepared by enzymolysis and enriched by using mesoporous materials of silica MCM-41 and SBA-15 and carbon CMK-3. The differences in pore structures and elemental composition of these materials lead to differences in surface area and hydrophobicity. The adsorption capacities of peptides were 459.5 mg g^-1, 431.3 mg g^-1, and 626.3 mg g^-1 for MCM-41, SBA-15 and CMK-3, respectively. Adsorption kinetics studies showed that the pseudo-second-order model fit the adsorption process better, where both external mass transfer and intraparticle diffusion affected the adsorption, while the Langmuir model better fit the adsorption of peptides on MCM-41 and SBA-15 and the Freundlich model was more suitable for CMK-3. Aqueous acetonitrile (ACN, 50/50, v/v) yielded the most extracted peptides. MALDI-TOF mass spectrometry of the extracted peptides showed that the three mesoporous materials, especially the CMK-3, gave good enrichment results. This study demonstrates the great potential of mesoporous materials in the enrichment of marine biofunctional peptides.

Low-temperature (NO + O2) adsorption performance of alkaline earth metal-doped C-FDU-15

To improve the removal capacity of NO + O₂ effectively, the alkaline earth metal-doped order mesoporous carbon (A-C-FDU-15(0.001) (A = Mg, Ca, Sr and Ba)) and Mg-C-FDU-15(x) (x = 0.001-0.003) samples were prepared, and their physicochemical and NO + O₂ adsorption properties were determined by means of various techniques. The results show that the sequence in (NO + O₂) adsorption performance was as follows: Mg-C-FDU-15(0.001) (93.2 mg/g) > Ca-C-FDU-15(0.001) (82.2 mg/g) > Sr-C-FDU-15(0.001) (76.1 mg/g) > Ba-C-FDU-15(0.001) (72.9 mg/g) > C-FDU-15 (67.1 mg/g). Among all of the A-C-FDU-15(0.001) samples, Mg-C-FDU-15(0.001) possessed the highest (NO + O₂) adsorption capacity (106.2 mg/g). The species of alkaline earth metals and basic sites were important factors determining the adsorption of NO + O₂ on the A-C-FDU-15(x) samples, and (NO + O₂) adsorption on the samples was mainly chemical adsorption. Combined with the results of (NO + O₂)-temperature-programmed desorption ((NO + O₂)-TPD) and in situ diffused reflectance infrared Fourier transform spectroscopy (DRIFTS) characterization, we deduced that there were two main pathways of (NO + O₂) adsorption: one was first the conversion of NO and O₂ to NO₂ and then part of NO₂ was converted to NO₂^- and NO₃^-; and the other was the direct oxidation of NO to NO₂^- and NO₃^-.

Efficient abatement of NOx emitted from automotive engines via adsorption on the Ba-CMK-3 adsorbents

The Ba-CMK-3(x) (x was the Ba(NO₃)₂:CMK-3 mass ratio and equals to 5, 10, and 15 wt%) samples were prepared by the incipient impregnation method, which were used for the adsorption of NO + O₂ at room temperature. The samples were characterized by the XRD, BET, TEM, TPD, TG, and DRIFTS techniques. The results showed that the CMK-3 and Ba-CMK-3(x) samples possessed an ordered two-dimensional hexagonal mesoporous structure, and Ba was uniformly dispersed on the surface of CMK-3. After Ba doping, the surface areas and pore size distributions of the Ba-CMK-3(x) samples were altered due to the synergistic effect of partial blocking of the channels by Ba and partial etching of the carbon materials by O₂ produced from Ba(NO₂)₃ decomposition at high temperatures. The sequence in NO adsorption capacity was Ba-CMK-3(10) (108.1 ± 0.55 mg/g) > Ba-CMK-3(15) (106.2 ± 0.72 mg/g) > Ba-CMK-3(5) (102.3 ± 1.33 mg/g) > CMK-3(88.8 ± 1.15 mg/g), with the Ba-CMK-3(10) sample showing the best (NO + O₂) adsorption performance. We proposed the two main adsorption pathways in the process of NO adsorption: (i) NO reacted with O₂ to form NO₂, part of NO₂ were weakly adsorbed on the surface hydroxyl groups, part of NO₂ were adsorbed to form the nitrite and nitrate species, and the left NO₂ was disproportionated to the NO, NO₂^-, and NO₃^- species; and (ii) NO was directly oxidized to the NO₂^- species by the oxygen-containing functional groups in carbon, and then some of the NO₂^- species were transformed to the NO₃^- species directly or via disproportionation. The regeneration efficiencies of the Ba-CMK-3(x) samples were slightly inferior to that of the CMK-3 sample.

Simultaneous determination of 114 pesticides in complex Chinese herbal medicine Fritillaria using ordered mesoporous carbon CMK-3 as a reversed-dispersive solid phase extraction sorbent

Fritillaria, a traditional Chinese herbal medicine, is classified into many medicinal species and contains numerous complex components. It is thus difficult to simultaneously detect multiple pesticide residues in different Fritillaria species. An easy, reliable, and widely applicable analytical method based on a modified Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) method coupled with LC-MS/MS was developed to solve these problems encountered during pesticide residue analysis in complex Fritillaria matrices. Ordered mesoporous carbon CMK-3 and a primary secondary amine (PSA) were used as efficient purification sorbents by optimization of the QuEChERS process. Systematic method validation was performed for four species of Fritillaria. The matrix effect of pesticides varied among different Fritillaria species, and matrix-matched standard solutions were thus employed for quantitative analysis. The mean recoveries of all pesticides ranged from 88.6% to 95.5%, with mean relative standard deviations (RSD) lower than 6% at spiked concentrations of 30, 120, and 240 μg kg⁻¹. The limits of quantification (LOQ) for the developed method were in the range of 30–120 μg kg⁻¹. This method was further used to analyze 47 Fritillaria samples from Zhejiang province, China, and seven pesticides were detected in 22 Fritillaria samples. These results demonstrate that the developed method is suitable for an accurate analysis of multiple pesticide residues in various Fritillaria.

Fritillaria, a traditional Chinese herbal medicine, is classified into many medicinal species and contains numerous complex components.

Utilization of rice husk wastes in synthesis of graphene oxide-based carbonaceous nanocomposites

Rice husk is an agricultural waste-based biomass that can provide an alternative renewable source of bioenergy. Rice husk carbon and rice husk ash are major solid residues obtained after converting rice husk to bioenergy. This paper reports the synthesis of two graphene oxide-based activated carbons using rice husk carbon through H₃PO₄ and ZnCl₂ activation, respectively. By contrast, mesoporous silica was produced using recycled rice husk ash. Graphene oxide/ordered mesoporous carbon was prepared using mesoporous silica as a template source. These composites were inspected using a Raman spectrometer, Fourier transform infrared spectrometer, transmission electron microscope, field-emission scanning electron microscope, X-ray diffractometer, and surface area analyzer. Experimental results indicated that graphene oxide-based H₃PO₄ activated carbon, ZnCl₂ activated carbon, and ordered mesoporous carbon had a surface area of 361, 732, and 936 m²/g, respectively; a pore volume of 0.299, 0.581, and 1.077 cm³/g, respectively; and an average pore size of 2.31, 3.17, and 4.35 nm, respectively. The carbonaceous composites with graphene oxide exhibited a higher adsorption ability than did pure carbon materials without graphene oxide. The maximum adsorption capacities using methylene blue as adsorbate followed the order of ordered mesoporous carbon (1591 mg/g) > ZnCl₂ activated carbon (899 mg/g) > H₃PO₄ activated carbon (747 mg/g). The isothermal adsorption and kinetics study for graphene oxide/ordered mesoporous carbon indicated that adsorption followed the Langmuir isotherm model and pseudo-second order kinetic model. Rice husk waste has excellent prospective potential for producing highly valuable nanoproducts and for reducing environmental pollution.