Due to the similarity in chemical structure, lignin has presented great potential in the synthesis of bio-based phenolic resin. Herein, a facile and scalable synthesis strategy for a novel cage-like ...lignin-based phenolic resin was proposed through direct spray drying of the mixture of phenolic resin and unmodified lignin. The as-prepared lignin-based phenolic resin was pre-carbonized and carbonized using KOH to produce mesoporous carbon materials (LPRAC) that were further employed as supercapacitor electrodes. The results revealed that the lignin addition led to the noticeable change of the resin shape from perfect sphere to cage-like structure owing to the surfactivity and hydrophilicity of lignin. The cage-like structure promoted the KOH-activated pore generation and expansion in the carbonization process, resulting in the significantly increased specific surface area of the phenolic carbon and the intensified mesoporous formation. The electrochemical performance determination indicated that the specific capacitance of LPRAC-20% (20% lignin addition) was 217.3 F/g at 0.5 A/g, which was considerably higher than that of the lignin-free phenolic carbon (122.6 F/g). Moreover, the LPRAC-20% also exhibited preferable capacitance retention and excellent cycling stability. Accordingly, the present work offers a simple and scalable approach to prepare cage-like mesoporous carbon with excellent electrochemical performance from lignin-based phenolic resin and thus provides a promising route for lignin valorization in energy storage materials.
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Metal-organic frameworks (MOFs) have received much attention in analytical science for their large langmuir surface and high thermostability. Herein MOF-177-coated solid-phase micro-extraction (SPME) ...fibers were fabricated on etched stainless steel by an adhensive method, and applied to the enrichment of polychlorinated biphenyls (PCB01, PCB05, PCB29, PCB47, PCB98, PCB154, PCB171, PCB201) and polycyclic aromatic hydrocarbons (ANY, ANA, FLU, PHE, ANT, FLT, PYR) from environmental water samples. Several parameters affecting the extraction efficiency were optimized prior to the gas chromatography-mass spectrometry analysis, including extraction temperature and time, desorption time, stirring rate and salt addition. The results indicated that the coated fiber gave low detection limits (0.69–4.42ngL−1) and good repeatability with the RSD ranging from 1.47% to 8.67% for PCBs and PAHs. The recoveries were between 81.8% and 113% with the spiked level of 10ngL−1 for the real water samples. Besides, the MOF-177 coated fiber was stable enough over 100 extraction cycles and the RSD for fiber-to- fiber reproducibility was less than 9.82% during the experiment.
A 5μL micro-syringe was used totally as the SPME appliance coated with MOF-177. The prepared fiber showed low LODs and excellent extraction efficiency towards PCBs and PAHs compared to the commercial fibers.
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•MOF-177 was prepared and first used as SPME coating.•A 5μL micro-syringe was used totally as the HS-SPME appliance.•MOF-177 was coated by a direct adhesive method with diluted silicone sealant.•The prepared fibers showed excellent extraction efficiency for PCBs and PAHs.
This paper presents a 31.5-GHz bandwidth (BW) 56-GS/s time-interleaved (TI) analog-to-digital converter (ADC) with 5.7-b effective number of bits (ENOB) and 5.2-b ENOB up to 17.5 and 27.1 GHz, ...respectively. To achieve the ENOB requirement over the entire Nyquist BW in 100-/200-Gb/s digital coherent receivers, several ENOB and BW enhancement techniques are presented. First, a low-noise parametric T/H amplifier is proposed to amplify the sampled signal and improve the SNR of the subsequent sub-channel ADCs. Second, a switched sub-channel buffer is proposed to avoid the distortion caused by the limited BW of the sub-channel buffer during tracking. Finally, multiple BW enhancing techniques are employed. The entire chip is fabricated in the 28-nm CMOS process, occupies an active area of 0.878 mm 2 , and consumes 702 mW.
•Solid acid catalytic phenolation (SACP) is applied to treat enzymatic hydrolysis lignin (EHL).•EHL is depolymerized significantly during SACP treatment without condensation.•Phenol is incorporated ...into EHL by a nucleophilic reaction that stops lignin condensation.•Treated EHL shows increased phenolic hydroxyl content and reactivity with formaldehyde.•50% phenol is substituted by treated EHL to prepare phenolic foam with satisfactory properties.
Lignin valorization offers a significant opportunity for the commercial operation of a cellulosic ethanol-derived biorefinery. In this work, a novel solid acid catalytic phenolation (SACP) process was employed to treat enzymatic hydrolysis lignin (EHL) and the obtained product was further applied to prepare lightweight phenolic foams (ρ = 30–40 kg/m3). The changes of the molecular weight and structure of lignin under the SACP treatment were investigated by GPC, Py-GCMS, and 2D-NMR analyses. The results indicated that under the optimized SACP conditions (140 °C, 4% HZSM-5, and 2 h), the molecular weight (M¯w) of EHL sharply decreased from 6695 to 2418 g/mol without condensation. The Py-GCMS and 2D-NMR analyses suggested that phenol was incorporated at the Cα position through a nucleophilic reaction and this reaction inhibited the lignin condensation during the acidic treatment. Due to the simultaneous depolymerization and phenolation, the treated lignin showed noticeable increase in phenolic hydroxyl content and reactivity with formaldehyde. The further characterization of lignin-based phenolic foams showed that the treated lignin could replace 50% phenol to prepare phenolic foams with satisfactory thermal insulation and compression strength properties. Consequently, this work demonstrates that SACP is effective to depolymerize and activate lignin for high lignin content phenolic foam preparation and offers a value-added way of lignin application as heat-insulating foam materials.
Sourcing polymers from biobased materials is desirable for a transition to a more sustainable world. However, finding new monomers sourced from biobased molecules requires extensive experimental ...effort, due to the fact that most biomolecules lack the functional groups or properties needed to serve as a monomer in a particular polymeric system without chemical modification. Here, we demonstrate a computational screening method to obtain monomers of a nonisocyanate polyurethane (NIPU), polyhydroxyurethane (PHU), from biomolecules. Our method generates candidate monomers from a list of 15 selected biobased starting molecules by performing chemical transformations that are standard to chemical catalysis and organic synthesis on these starting molecules and then screening the results for molecules with moieties that can be used as monomers for a PHU. Product molecules from two generations of reaction, a total number of 22,571, were analyzed automatically to identify molecules that have two or more epoxy or cyclic carbonate functional groups as candidates for further derivatization. These 21 candidate molecules were then subjected to another two generations of reaction, producing a set of 17,913 additional molecules. Further scrutiny of this set for desired functional groups characterizing PHUs and querying against the PubChem database were carried out, and 15 known molecules that are commercially available were identified, with the desirable features that they are predicted to be derived from biobased starting molecules in four or fewer steps. Moreover, molecule space generated from this process was primarily comprised of molecules that were not known to PubChem, indicating the framework also has the ability to generate novel candidate monomers that originate from biobased starting points.
Optimizing three-dimensional (3D) k-space sampling trajectories is important for efficient MRI yet presents a challenging computational problem. This work proposes a generalized framework for ...optimizing 3D non-Cartesian sampling patterns via data-driven optimization.
We built a differentiable simulation model to enable gradient-based methods for sampling trajectory optimization. The algorithm can simultaneously optimize multiple properties of sampling patterns, including image quality, hardware constraints (maximum slew rate and gradient strength), reduced peripheral nerve stimulation (PNS), and parameter-weighted contrast. The proposed method can either optimize the gradient waveform (spline-based freeform optimization) or optimize properties of given sampling trajectories (such as the rotation angle of radial trajectories). Notably, the method can optimize sampling trajectories synergistically with either model-based or learning-based reconstruction methods. We proposed several strategies to alleviate the severe nonconvexity and huge computation demand posed by the large scale. The corresponding code is available as an open-source toolbox.
We applied the optimized trajectory to multiple applications including structural and functional imaging. In the simulation studies, the image quality of a 3D kooshball trajectory was improved from 0.29 to 0.22 (NRMSE) with Stochastic optimization framework for 3D NOn-Cartesian samPling trajectorY (SNOPY) optimization. In the prospective studies, by optimizing the rotation angles of a stack-of-stars (SOS) trajectory, SNOPY reduced the NRMSE of reconstructed images from 1.19 to 0.97 compared to the best empirical method (RSOS-GR). Optimizing the gradient waveform of a rotational EPI trajectory improved participants' rating of the PNS from "strong" to "mild."
SNOPY provides an efficient data-driven and optimization-based method to tailor non-Cartesian sampling trajectories.
In this work, steam explosion (SE) was exploited as a potential hydrothermal-humification process of vegetable wastes to deconstruct their structure and accelerate their decomposition to prepare ...humified substances. Results indicated that the SE process led to the removal of hemicellulose, re-condensation of lignin, degradation of the cellulosic amorphous region, and the enhancement of thermal stability of broccoli wastes, which provided transformable substrates and a thermal-acidic reaction environment for humification. After SE treatment, total humic substances (HS), humic acids (HAs), and fulvic acids (FAs) contents of broccoli samples accounted for up to 198.3 g/kg, 42.3 g/kg, and 166.6 g/kg, and their purification were also facilitated. With the increment of SE severity, structural characteristics of HAs presented the loss of aliphatic compounds, carbohydrates, and carboxylic acids and the enrichment of aromatic structures and N-containing groups. Lignin substructures were proved to be the predominant aromatic structures and gluconoxylans were the main carbohydrates associated with lignin in HAs, both of their signals were enhanced by SE. Above results suggested that SE could promote the decomposition of easily biodegradable matters and further polycondensation, aromatization, and nitrogen-fixation reactions during humification, which were conducive to the formation of HAs.
Chemically activated biochars prepared from sorghum distillers grain using two base activators (NaOH and KOH) were investigated for their adsorption properties with respect to ammonium nitrogen from ...aqueous solution. Detailed characterizations, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetry (TG), and specific surface area analyses, were carried out to offer a broad evaluation of the prepared biochars. The results showed that the NaOH- and KOH-activated biochars exhibited significantly enhanced adsorption capacity, by 2.93 and 4.74 times, respectively, in comparison with the pristine biochar. Although the NaOH-activated biochar possessed larger specific surface area (132.8 and 117.7 m2/g for the NaOH- and KOH-activated biochars, respectively), the KOH-activated biochar had higher adsorption capacity owing to its much higher content of functional groups. The adsorption kinetics and isotherms of the KOH-activated biochar at different temperatures were further studied. The biochar had a maximum adsorption capacity of 14.34 mg/g at 45 °C, which was satisfactory compared with other biochars prepared using different feedstocks. The adsorption process followed pseudo-second-order kinetics, and chemical adsorption was the rate-controlling step. The equilibrium data were consistent with the Freundlich isotherm, and the thermodynamic parameters suggested that the adsorption process was endothermic and spontaneous. Consequently, this work demonstrates that chemically activated biochar from sorghum distillers grain is effective for ammonium nitrogen removal.
The complex photocatalysts of Ag–BiOBrxI1−x represent high activity and composition-dependent property. The load of Ag improved the separation of photogenerated electron–hole pairs and enhanced the ...light absorption in the visible region.
•A series of Ag–BiOBrxI1−x were prepared by a simple solution route at room temperature.•Ag–BiOBrxI1−x complex photocatalysts show composition-dependent property and enhanced photocatalytic activity.•The enhanced activity results from the optimum band gap structure and the plasmon resonance absorption of Ag on the surface of photocatalysts.
A series of Ag-loaded photocatalysts of Ag–BiOBrxI1−x have been synthesized by a solution method and characterized by variety methods. The degradation of rhodamine B (RhB) showed that these samples exhibited excellent and composition-dependent performance in the visible light region. The Ag–BiOBr0.75I0.25 composite photocatalyst shows the highest photocatalytic activity in the degradation of RhB and 4-CP pollution. The load of metal Ag has remarkably improved the photocatalytic activity. The significant enhancement in the Ag–BiOXs photoactivity could be both the effect of Ag deposits as electron traps and the surface plasma resonance absorption effect of Ag. A possible mechanism of enhanced activity of Ag–BiOXs was proposed based on the analysis of the band gap structure.
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