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•Adsorption of CO2 molecule computationally investigated on modified χ3 borophene.•Charge injection, application of an electric field or strain can improve CO2 adsorption.•RSM was ...used to evaluate the simultaneous application of modification approaches.•The generated quadratic model predicts CO2 adsorption energy with high accuracy.
The study of χ3 borophene modification was considered finding an applicable technique to achieve more efficient approaches in CO2 capturing. In the framework of density functional theory (DFT), two surface modification methods were described, external electric field or strain application on χ3 borophene, and the effect of them was investigated on CO2 adsorption. All these methods affected the deformation charge density of the surface, which led to an increase in the CO2 binding energy, in the studied range. The turning point in CO2 capturing and structural changes appeared by applying an electric field of −0.030 a.u. strength with −0.48 eV adsorption energy. The uniaxial and biaxial compressive strain resulted in proper adsorption energy of −0.73 to −0.85 eV, although it caused a significant change in the planar structure of the surface. The structural and electronic properties, in addition to the charge density difference analysis, confirmed the chemisorption of CO2 on modified surfaces. Lastly, for the first time, the response surface methodology in the DFT framework was used to evaluate the simultaneous effect of applying an external electric field and strain as well as charge injection on CO2 adsorption. The generated quadratic equation predicts the CO2 adsorption energy with high accuracy as a function of the modification parameters. This result would be very helpful in adjusting the modification parameters to achieve the desired CO2 adsorption energy with lower experimental costs, where the χ3 surface is used for a special application such as CO2 removal or sensing.
Cotton-based adsorbents (CBAs) are promising materials for combating the problem of heavy metal pollution of environmental waters. This is ascribed to the low cost, abundance, biodegradability and ...efficiency of CBAs. Herein we review the adsorption of heavy metals (HMs) onto CBAs. We found that several surface modifications were employed to improve the efficiency of the CBAs. These modifications were effected via thermal, physical and chemical means to obtain activated carbons, biochars, ionic liquids, aerogels, hydrogels, chitosans and nanoparticle-derived CBAs. The CBAs exhibited maximum HMs uptake as low as 0.002 mg/g to as high as 505.6 mg/g. Although, the cotton-derived activated carbons and biochars exhibited enhanced HM uptake from that of the unmodified CBAs, they were less efficient than CBAs modified by other methods. Recent chemical, ionic liquid, chitosan and nano-derived CBAs were the most efficient, with high uptake and fast kinetic removal. However, the nanoparticle-based adsorbents are preferred to the chemically modified forms, due to the possibility of secondary pollution and the noxious effect of the latter to the environment. Findings showed that chemical treatment produced CBAs most efficient for As(V), Pb(II) and Fe(III), while ionic liquid CBA was more efficient for Cu(II) and Ni(II). Nano-based treatment was suitable for the uptake of Co(II), Zn(II), Pb(II) and Cd(II), while the chitosan based adsorbent was viable for Hg(II). Isotherm and kinetic evaluation of CBAs mostly conformed to the Langmuir and pseudo-second order models, respectively. Spontaneous adsorption of HMs onto CBAs was deduced from thermodynamic analysis, with endothermic and exothermic characteristics. Over 88% desorption of HMs was obtained from the CBAs studied with good average reusability from 3 to 20 cycles. We also discussed the directions for future research.
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•Cotton-based adsorbents were found to be viable for the treatment of heavy metals polluted water via biosorption.•The uptake of heavy metals onto cotton adsorbents was enhanced by various surface modifications.•The chemical, ionic liquid, chitosan and nanoparticle cotton based adsorbents were the most efficient.•Efficient regeneration and reuse of cotton-derived adsorbents was reported.
Zein colloidal nanoparticles can adsorb at the oil–water interface to form Pickering emulsion. However, zein Pickering emulsion is usually not stable due to the poor wettability of zein colloidal ...nanoparticles. The objective of this study was to modify the surface of zein nanoparticles using sodium caseinate (NaCas) and assess the properties of zein/NaCas nanocomplexes and the resultant oil-in-water Pickering emulsions. One percent (w/w) of zein/NaCas colloidal nanocomplexes were formed, with the zein:NaCas ratios (w/w) ranging from 10:1 to 10:4 at pH = 3 by an ultrasound treatment. The zeta-potential of the zein/NaCas nanocomplexes showed altered surface charges, indicating that NaCas adsorbed on the surface of the zein colloidal nanoparticles. Three-phase contact angle measurements suggested that the original zein colloidal nanoparticles were preferentially wetted in water. The incorporation of 0.1%–0.2% (w/w) NaCas significantly enhanced its wettability in the oil, and intermediate wettability was achieved at a zein:NaCas ratio of 10:3. Confocal laser scanning microscope (CLSM) images showed that the incorporation of NaCas improved the interfacial coverage of the Pickering emulsions. When the zein:NaCas ratio ranged from 10:1 to 10:3, the interface was composed of zein/NaCas nanocomplexes. At a zein:NaCas ratio of 10:4, NaCas can competitively adsorbed to the interface and formed a hybrid interfacial structure. The Zein/NaCas nanocomplexes stabilized the Pickering emulsions and exhibited greater centrifugal stability than plain zein emulsions at most pHs and ionic strengths. The underlying mechanisms of the improved emulsion stability are discussed in this paper. This study explored a novel approach to stabilizing Pickering emulsions via the surface modification method using a food-grade protein.
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•Zein colloidal nanoparticle wettability can be tuned by sodium caseinate.•Surface modification of zein improves Pickering emulsion centrifugal stability.•Surface loading of Pickering emulsions is higher than conventional emulsions.•Above a critical zein:NaCas ratio, NaCas competitively adsorbs to the interface.
•This review work provides an up-to date information regarding the nanocellulose production from biomass by mechanical process.•A special focus is devoted to the pretreatment of lignocellulosic ...biomass for less energy consumption.•Application of nanocellulose-based materials for high performance nanobiocomposites and nanopaper technology are presented and discussed.•Chronology, challenges and obstacles of nanocellulose are discussed.
Nanofibrillated cellulose from biomass has recently gained attention owing to their biodegradable nature, low density, high mechanical properties, economic value and renewability. Although they still suffer from two major drawbacks. The first challenge is the exploration of raw materials and its application in nanocomposites production. Second one is high energy consumption regarding the mechanical fibrillation. However, pretreatments before mechanical isolation can overcome this problem. Hydrophilic nature of nano-size cellulose fibers restricts good dispersion of these materials in hydrophobic polymers and therefore, leads to lower mechanical properties. Surface modification before or after mechanical defibrillation could be a solution for this problem. Additionally, drying affects the size of nanofibers and its properties which needs to study further. This review focuses on recent developments in pretreatments, nanofibrillated cellulose production and its application in nanopaper applications, coating additives, security papers, food packaging, and surface modifications and also for first time its drying.
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•Pure CNCs show a very good microwave absorption performance under a filling ratio of 6%.•The coating of N-doped carbon layers on CNCs further enhance the microwave absorption ...intensity.•The uniform anchoring of Co nanoparticles improves the low frequency absorption performance.
Surface modification and composition control for nanomaterials are effective strategies for designing high-performance microwave absorbing materials (MWAMs). Herein, we have successfully fabricated Co-anchored and N-doped carbon layers on the surfaces of helical carbon nanocoils (CNCs) by wet chemical and pyrolysis methods, denoted as Co@N-Carbon/CNCs. It is found that pure CNCs show a very good microwave absorption performance under a filling ratio of only 6%, which is attributed to the uniformly dispersed conductive network and the cross polarization induced by the unique chiral and spiral morphology. The coating of N-doped carbon layers on CNCs further enriches polarization losses and the uniform anchoring of Co nanoparticles in these layers generates magnetic losses, which enhance the absorption ability and improve the low frequency performance. As compared with the pure CNCs-filling samples, the optimized Co@N-Carbon/CNCs-2.4 enhances the absorption capacity in the lower frequency range under the same thickness, and realizes the decreased thickness from 3.2 to 2.8 mm in the same X band, as well as the decreased thickness from 2.2 to 1.9 mm in the Ku band. Resultantly, a specific effective absorption wave value of 22 GHz g−1 mm−1 has been achieved, which enlightens the synthesis of ultrathin and light high-performance MWAMs.
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A novel terephthalate acid (TPA) and TiO2 system was developed by chemically bonding between the −COOH groups on TPA and −OH groups on the surface of TiO2 under hydrothermal ...conditions. The crystallization, morphology and photochemical properties of TiO2-TPA were studied by XRD, FTIR, XPS, TEM, UV–vis absorption spectroscopy measurements, respectively. The prepared TiO2-TPA nanoparticles exhibited excellent photoactivity under visible light by a ligand-metal charge transfer (LMCT) mechanism. Even though TPA is often used as a ligand for titanium–organic frameworks, there has been no report about the fact that TiO2-TPA is capable of forming an LMCT complex. The optimized TiO2-TPA (molar ratio of 0.5) composite showed a superior photodegradation than TiO2. The removal rate of Rhodamine B (RhB) was 94.10 % in 60 min, which were 31.3 times than that of pure TiO2 (3.34 %). The result indicated that TiO2 and TPA had tight synergistic effect. In detail, TPA-modified composite showed a smaller band gap and stronger light respond under visible range. Meanwhile, the charge transfer from TPA to TiO2 reduced the recombination rate of electron holes.
Surface modification is an efficient post-treatment method to optimize the properties of nanofiltration (NF) membranes. Here, we report a facile surface modification strategy coupling with heat ...curing for grafting monoethanolamine (MEA), a monomer containing both a primary amine and a primary alcohol group, onto a nascent polyamide NF membrane. With grafting 0.5 wt% MEA at 50 °C, the pure water permeability of the polyamide NF membranes was improved from 7.9 to 19.5 L m−2 h−1 bar−1 due to their enhanced physicochemical property, such as superior hydrophilicity, rough surface morphology, and enlarged membrane pores. Meanwhile, the rejection of Na2SO4 remained above 97.5%. More importantly, the optimal membrane modified with 0.5 wt% MEA exhibited a high Na2SO4 rejection of 99.1% and a negative NaCl rejection of −20.1% when treating a mixed salt solution containing 2 g/L Na2SO4 and 2 g/L NaCl. Our study provides a novel insight for the fabrication of high permselectivity NF membranes via surface modification.
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•Surface grafting was creatively coupled with heat curing in water.•Monoethanolamine molecule was successfully grafted onto the nascent membrane, rendering a better hydrophilic nanofiltration membrane.•The modified membrane exhibited enhanced pure water permeability of 19.5 L m−2 h−1 bar−1.•The modified membrane owned superior Cl−/SO42− selectivity.
•Polyphenols surface functionalized CeO2 core-shell structure was constructed.•The polyphenols shell enhances the stability and compatibility of CeO2.•Accelerated regeneration of active sites by ...polyphenols improve antioxidation.•Optimized PEMFC maintains excellent performance after 404 h durability test.
The chemical degradation of proton exchange membranes (PEMs) suffering from radical attack is a crucial issue in the development of proton exchange membrane fuel cells (PEMFCs), while incorporating cerium oxide (CeO2) nanoparticles (NPs) with regenerative redox properties to eliminate radicals could effectively alleviate degradation. However, the low stability and restricted activity of CeO2 in the PEMFC operating condition and the poor compatibility with PEM due to CeO2 agglomeration stimulate the urgency for structural modulation of CeO2. Achieving a balance of membrane performance and oxidation resistance through a rational surface modification strategy of CeO2 is important for expanding PEMFC applications. Herein, polyphenols surface functionalized CeO2 core-shell structure (CeO2@TP) were constructed via assembling oxidation-induced coupling tea polyphenols (TP) on CeO2 NPs. The TP oligomeric shell as a protective layer enhances the stability of CeO2, mitigating radical scavenging activity degradation and improving compatibility with PEMs. Physicochemical characterisation shows that the overall performance of the nanocomposite membrane is improved due to the interaction of CeO2@TP nanoparticles with the polymer matrix. Gratifyingly, the phenolic hydroxyl-rich reductive TP oligomeric shell accelerates the regeneration of Ce(IV) to Ce(III), increasing the proportion of Ce(III) and oxygen vacancies on the CeO2 surface, thus boosting antioxidation efficiency. As a result, the CeO2@TP-based PEMs exhibited an OCV decay rate of 0.22 mV h−1, a maximum power density of 1.06 W cm−2, an H2 crossover value of 2.18 mA cm−2, thickness retention (91.1%), and negligible Ce migration after 404 h of accelerated degradation testing. It is proven that the desired consequences of doping antioxidants in PFSA matrix can be intensified by surface modulation of the physicochemical properties of CeO2.
Schematic illustration for the synthesis of the POS@HNTs and the superhydrophobic POS@HNTs surfaces fabricated by spray-coating (the blue-colored globule represents water droplet on the surfaces).
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•Halloysite nanotubes (HNTs) were treated by n-hexadecyltriethoxylsilane and tetraethoxysilane.•Superhydrophobic coating was fabricated by spray-coating polysiloxane modified HNTs.•Silane affects transparency, morphology, and superhydrophobicity of HNTs coating.•HNTs coatings exhibit super self-cleaning and oil/water separation functions.
Superhydrophobic coatings with high water contact angles, ultralow sliding angles, excellent stability, oil/water separation, and self-cleaning functions were fabricated by spray-coating the suspensions of polysiloxane modified halloysite nanotubes (POS@HNTs) onto various substrates. The hydrophobic treatment of HNTs was performed by hydrolytic co-condensation of n-hexadecyltriethoxylsilane and tetraethoxysilane on the surfaces of the HNTs. A thick POS layer is located on the surfaces of the HNTs, which makes HNTs hydrophobic. The POS@HNTs were characterized using scanning electron microscopy, transmission electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy and thermogravimetric analysis. The effects of the ratio of silane and HNTs on the transparency, morphology, and wettability of the coatings were investigated. The transparency of the coating decreases with the increase in the silane loading. The water contact angles of the POS@HNTs coating increase with the increase in the silane loading, but the water sliding angles of the coatings are nearly independent on their ratio. The stability, oil/water separation, and self-healing capability of the coatings were also studied. The coatings on different substrates show high contact angle towards different liquid, e.g. 1 M HCl, 1 M NaOH, tea, and milk. Also, the POS@HNTs coated meshes can efficiently separate oils from water with high separation efficiency. In addition, the POS@HNTs coated gloves show a self-cleaning effect. All these results suggest that the POS@HNTs exhibit great potential for their application in waterproof materials, self-cleaning coating, and oil/water separation devices.
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