查看更多>>摘要：To optimize the highly stacked, lamellar covalent organic frameworks (COF) with more easily accessible micropores for molecular separations, a facile and economical strategy, using the naturally available diatomite (Dt) as a substrate, is proposed to fabricate hierarchical Dt@COF hybrids through an in-situ solvothermal method to grow a uniform COF shell on Dt. This strategy not only enormously enhances the adsorption capacity of diatomite through introducing abundant micropores, but also endows the grown COFs with highly accessible adsorption sites for molecular adsorption owing to the ultrathin COFs shell and the intrinsic porosity of the diatomite matrix. The maximum adsorption capacity of COFs from Dt@COF-0.04 is 686 mg g~(-1) toward bisphenol A (BPA), outperforming the bulk COFs adsorbent (～381 mg g~(-1)). Significantly, in a more convenient column separation mode, the equilibrium adsorption amount of Dt@COF-0.04 is ～3 times greater than that of the COF/Dt mixture. It is found that the thin COFs shell and the intrinsic microchannels of diatomite nanoplates svnergisticallv facilitate the diffusion of water molecules and pollutants, leading to the outstanding performance of Dt@COF adsorbents. The results indicate that the hierarchical Dt@COF hybrids have great application potential in the separation of organic pollutants from water for environmental remediation.
查看更多>>摘要：Biofuels from biomass have attracted increasing attention in response to the excessive consumption of petroleum-based fuels. To face the high demands for biofuels, the fermentation-separation coupled system is developed to reduce the use of toxic solvents. Pervaporation (PV) has been integrated with a fermentation unit due to its high selectivity for organics, low energy consumption and because it does not have an impact on the microorganisms in the fermentation broth. As the core of the separation unit, polydimethylsiloxane (PDMS) based membranes are the most widely used organophilic membranes, and can be considered the benchmark of alcohols-selective membranes. Furthermore, PDMS based mixed matrix membranes (MMMs) are suggested to boost the bioalcohols to be produced and further enhance its application in biofuels. The literature indicates a dimension of PDMS based membranes for biofuels PV that reaches a new stage, however, few-reviews have summarized the latest progress. In this work, a comprehensive overview is given, including the interrelationship of structure design, functionalization and fabrication methods of PDMS based membranes as well as fermentation-PV coupled system. Furthermore, the key preparation and application issues of membranes are summarized, and the opportunities and challenges of enhanced PDMS based membranes for biofuels PV are also given.
M. Alejandra QuintanaRafael R. SolisM.Angeles Martin-Lara
10页
查看更多>>摘要：Graphitic carbon nitride is a non-metal photocatalyst easily prepared from nitrogen organic compounds through green synthesis processes that do not require the use of solvents. This work proposes the use of boron to modify the layered g-C3N4 structure by incorporating B to induce defects aimed at the enhancement of the photocatalytic activity. Boron-modified graphitic carbon has been obtained using elemental B and NaBH4 as precursors. The XRD and FTIR characterization results suggest that the C and N positions of g-C3N4 can be replaced by B, resulting in a layered modified structure in which the tri-s-triazine units are altered. The exchange of B atoms differed from the boron precursor according to the analysis of the chemical properties of the surface. Thus, the elemental B had a preference to exchange positions with N atoms, whereas the use of NaBH4 led to the substitution of B into the C positions. This difference considerably affected the photocatalytic activity during the selective oxidation of benzyl alcohol The sample modified with NaBH4 led to the highest oxidation rate and selectivity linked to a lesser recombination effect than the other samples according to photoluminescence tests. This work provides evidence about the convenience of the selection of precursors during the modification of g-C3N4. The photon absorbance rate was determined for the estimation of the quantum yield. Although the photon absorbance rate was quite similar in all the cases, the different registered kinetics led to a maximum quantum efficiency of 0.15% for NaBCN.
查看更多>>摘要：This study examines the accumulation of yeast cells at the membrane surface and the morphology of the formed cake through microscale monitoring and analysis of the microfiltration process. An original dead-end microfiltration device with a model membrane was designed and coupled with an optical imaging system to provide direct observation from the side, allowing in-situ real time study of the filtration operation (Valencia et al. 2020 [1]). Here, the deposition of yeast cells, monodispersed and polydispersed particles, in the same size range that yeast cells, was analyzed. Image processing was used to perform a quantitative characterization of cake morphological properties in terms of height, porosity, permeability, Kozeny coefficient and specific resistance. The cakes formed by monodispersed spherical and non-spherical rigid particles exhibit a similar incompressible behavior with higher porosity than yeast cakes, with mean porosity values of 0.38 for the rigid particles and 0.15 for the yeast at the end of the filtration run, respectively. The cake obtained by the microfiltration of a model suspension of polydispersed particles close to yeast size and shape is more compact (porosity of 0.29) and less permeable. However, polydispersity does not fully explain yeast cake properties, in particular its compressibility. Indeed, the yeast cake has a high compressibility index n = 1.1, which is reflected in a significant volume expansion of the yeast cake after transmembrane pressure was removed.
查看更多>>摘要：In this study, a new magnetic dual-template imprinted polymer modified with functionalized SBA-15 and graphene oxide (Fe3O4@SBA-15-NH-GO/dtMIP) was synthesized using surface imprinting technique. The synthesized polymer was used for preconcentration of amitriptyline and nortriptyline in plasma of mice (male BALB / cJRj mice) using μ-solid phase extraction (μ-SPE) and simultaneous determination by HPLC technique. The mice plasma was studied at regular intervals after taking two drugs. The polymer was characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray energy diffraction spectroscopy (XRD), vibrating sample magnetometer (VSM), and Nitrogen adsorption/desorption analysis. By studying the response surface methodology (RSM) and desirability function (DF), the optimal experimental condition was determined as 16.72 min for ultrasonic time, 8.11 for pH and 40.51 mg for polymer dosage. The results of the analysis were reported for amitriptyline in mice plasma in the concentration range 6.0-950.0 and the detection limit was achieved as 1.5 ng mL~(-1) respectively. For nortriptyline the LDR and LOD was reported as 5.0-850.0 and 1.1 ng mL~(-1) respectively.
查看更多>>摘要：Concerns about water contamination caused by pesticide residues have driven attempts to exploit efficient adsorbents with high adsorption, easy recycling and reuse. Herein, inspired by the accumulation and toxic mechanism of herbicides in corals, a separation-free shapable adsorbent was developed by enveloping a MOF-on-COF hybrid into chitosan (CS) aerogel to remove 2,4-dichlorphenoxyacetic acid (2, 4-D) and glyphosate (GLP) herbicides. The hybrid which prepared via in situ loading of Zr based metal organic framework (UiO-67) onto a flower-like covalent-organic framework (COF) can function as anchoring tentacles to capture herbicides and improve adsorption. Additionally, the porous structure of CS aerogel can mimic the three-dimensional structure of corals, allowing for the rapid delivery of herbicides from aqueous solution to the aerogel interior. Benefiting from these appealing advantages, the adsorbent displayed excellent removal performance with rapid adsorption equilibrium (2, 4-D: 60 min; GLP: 120 min) and high adsorption capacities (2, 4-D: 615.12 mg/g; GLP: 675.48 mg/g). Moreover, the aerogel possessed satisfactory recyclability after five successive cycles. In addition to hydrogen-bonding and electrostatic interactions, π-π interaction and chemical adsorption between phosphate moieties of GLP and Zr-O clusters was also involved in 2, 4-D and GLP adsorption. Accordingly, the tactics presented a viable option for designing novel adsorbents with porous structures, abundant function groups and ease-of-reusability to remove pollutants.
查看更多>>摘要：The strategy of intensifying toluene absorption with π-electron donor-based deep eutectic solvents (DESs) is first proposed and systematically investigated from the molecular mechanism to absorption performance. A series of DESs with benzyl as a n-electron donor by combining hydrogen bond acceptors (HBAs, i.e., TEBAC, TEAC and TAAC) with hydrogen bond donors (HBDs, i.e., EG, LA and PhOH) are prepared. The absorption performance of toluene in DESs are measured experimentally, and the result demonstrates that TEBAC + PhOH (1:3) has the highest absorption capacity (304 mg/g at 298.15 K) among all the DESs studied in this work. The microscopic mechanism of toluene absorption is explored by ~1HMR and FT-IR spectra and quantum chemical (QC) calculations. The reason that intensifying toluene absorption is the π-electron donor can both enhance the original O-H ππ and C-H ππ interactions of HBD/HBA-toluene and add an extra n-n interaction with toluene. This work provides a theoretical guideline to develop and search task-specific DESs for efficient toluene absorption.
查看更多>>摘要：Biomass-based activated carbon fiber paper is a promising support for metal or metal oxide owing to its high specific surface area and three-dimensional network. In this work, CuO-loaded phosphorus-doped activated carbon fiber paper (CuO/ACFP) was fabricated by phosphoric acid activation and further copper nitrate calculation. The sisal fiber-based CuO/ACFP was employed as a heterogeneous Fenton-like catalyst for degradation of phenol. The influence of calculation temperature on catalyst properties were also investigated as well as the pH value effect on phenol catalytic reaction. The 100% phenol degradation efficiency was achieved by the CuO/ACFP for activating H2O2, in which CuO/ACFP possessed the specific surface area of 190 m~2g~(-1) and micropores accounted for 80.4% of the total pore volume. The catalytic performance could be well maintained after five times recycle. The high catalytic performance and the great stability were ascribed to its three-dimensional reticulated hollow structure and the synergistic effect between the well-dispersed CuO and the introduction of phosphorus. Moreover, the quenching experiments and electron paramagnetic resonance indicated that the hydroxyl radical generated from H2O2, which was activated via CuO/ACFP, played an important role in phenol degradation. This work proposed a promising heterogeneous catalyst for activating H2O2 to degrade phenolic wastewater.
查看更多>>摘要：The development of efficient ionic liquids (ILs) for disposable separation and recovery of various precious metals was of great importance, but still faced difficult challenges. A phase change temperature-controlled system composed of IL and HCl solution was developed for the extraction and separation of Au(III), Pd(II) and Pt(IV) from secondary resources. UCST (upper critical solution temperature)-type IL ([1,4,7-TMTA][Tf2N]) possessed outstanding selectivity of precious metals and the property of temperature-controlled phase transition. The ability of ILs to form solvated hydrogen bonds was confirmed by quantum-chemical calculation to be correlated with their corresponding UCST. Different experimental parameters were optimized to explore the extraction behavior of IL. It is noteworthy that homogeneous liquid-liquid extraction system (HLLE) constructed by UCST-type IL could significantly enhance the extraction kinetic of Au(III), Pd(II) and Pt(IV) by decreasing phase interface resistance. For Au(III), Pd(II) and Pt(IV), when the system temperatures were higher than 40 °C, 49 °C and 65 °C, the maximum values were 98.5%, 98.3% and 93.2% at the highest efficiency. In addition, the extraction mechanism of anion exchange was revealed by UV-vis, IR, NMR and LC-MS spectrometry. At last, Au(III), Pd(II) and Pt(IV) could be selectively separated from multi-metal solutions where impurity ions coexist by K2C2O4, NH3 · H2O and CS(NH2)2/HCl, respectively. After 5 cycles, the extraction performance of [1,4,7-TMTA][Tf2N] maintained. In summary, this paper overcame the obstacle of slow kinetics of solvent extraction technology, and pointed out a way for polymetallic co-extraction and separation in HLLE system.
查看更多>>摘要：Access to clean water has become a global concern in recent years, especially in rural communities due to the contamination of groundwater induced by intensive anthropogenic activities. The current study proposed a solution for this issue by the evaluation of the feasibility of forward osmosis (FO) coupled with membrane distillation (MD) to treat nitrate-contaminated groundwater using seawater as draw solution. The studied groundwater had high nitrate levels of 150 mg/L. The evaluation of different operating conditions indicated that working at lower FS concentration, higher DS concentration, higher DS temperature and under active layer draw solution (AL-DS) mode had positive effects on FO water flux. However, reverse solute flux and nitrate flux showed an increment with increasing FS concentration, DS concentration and DS temperature. Application of optimal operating conditions on real groundwater using seawater as DS, during 15 h of continuous operating time, led to obtain FO water flux of 6.25 LMH, MD permeate flux of 12.44 LMH, nitrate flux of 0.69 gMH, reverse solute flux of 20.24 gMH, FO rejection rate of 98.34% and MD salt rejection rate of 99.05%. Moreover, FO-MD process produced freshwater with almost free-nitrate content and very low conductivity of 78 μS/cm suitable for drinking and irrigation purposes. Thus, the integrated FO-MD process can be applied efficiently to remove nitrate from contaminated groundwater.
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