Hydrophilic Functional Groups Research Articles

Chitosan/Graphene oxide/SiO2 Nanoadsorbents for the Removal of Cr(VI) from Wastewaters

The swift industrialization and urbanisation have led to the discharge of significant amounts of hazardous heavy metals into water environments. Heavy metal pollution is currently one of the most significant environmental challenges being addressed, attracting researchers due to its biotoxicity, and non-biodegradability even at minimal concentrations [1]. Chromium (Cr) is among the most prevalent heavy metal contaminants. Its oxidation state, Cr(VI), harms the environment yet has catastrophic consequences for human health [2]. It is removed by physical and chemical procedures such as ion exchange, chemical precipitation and electrochemical treatment. Yet, most of these procedures have downsides, such as the formation of hazardous sludge, causing disposal issues and the need for costly tools and monitoring systems [3]. Adsorption is regarded an appealing and favourable technology because to its ease of design, simplicity, and high efficiency. Carbon-based nanomaterials have been investigated as superior adsorbents in aqueous solutions for the separation of organic and inorganic contaminants. The current study recommends the usage of adsorbents based on graphene oxide (GO). GO is an oxygen-rich material that is produced during the oxidation of graphite. It features hydrophobic areas due to aromatic groups in the nanosheets' centres, along with a large number of hydrophilic functional groups such as hydroxy, aldehyde, epoxy, and carboxyl groups [4]. The latter allow GO to swell and perform electrostatic functions. Chitosan (Cs) is a great adsorbent since it is inexpensive, is biocompatible, and causes no secondary pollution. Its molecular chains include -NH2 and -OH groups, which can interact with heavy metal ions and give significant adsorption capacity [5]. Silicon dioxide (SiO2) nanoparticles with graphene oxide have better physical and chemical characteristics than graphene oxide-like surface area. Similar research has revealed that the presence of SiO2 increases the adsorbent's adsorption capacity for Cr(VI) [6]. The effect of the pH value, contact time and initial chromium concentration was examined in order to determine the feasibility of Cs/GO@SiO2. Its structure and the morphology were studied in detail by the application of BET, XRD, FTIR and SEM techniques. According to the results, the modification of Cs with GO@SiO2 enhanced the percentage removal of chromium ions, especially, in acidic conditions by using 0.5 g/L of the adsorbent. Experimental data of equilibrium were used to calculate adsorption isotherms. According to thermodynamics the spontaneous nature of their adsorption was confirmed. Overall, the results indicate that Cs/GO@SiO2 can be effectively employed for removal of chromium from aqueous solutions.

Effects of micro- and nano-bubbles on the flotation separation of unburned carbon from coal fly ash

ABSTRACT Nanobubble technology has found extensive use in enhancing the flotation efficiency of various minerals. The utilization of nanobubbles in flotation encompasses bulk nanobubbles, surface nanobubbles, and microbubbles; however, a comprehensive comparison of their respective roles is lacking. Furthermore, there is a dearth of studies on employing nanobubble systems in the flotation of coal fly ash. The coal fly ash characters were initially studied to reveal its ultrafine size (d50: 24.80 μm) and porous structure that includes a multitude of hydrophilic functional groups. These attributes contribute to the inadequate hydrophobicity of unburned carbon within the ash. Subsequently, the effects of different collector types, frother types, and air flow rates on the efficiency of carbon removal using conventional flotation methods were examined. Comparative analysis showed that conventional flotation using diesel oil outperformed that which employed kerosene as the collector. Additionally, higher carbon removal efficiency was achieved using MIBC, with a longer carbon chain length, as the frother, as opposed to sec-Octyl alcohol. Furthermore, a direct relationship between air flow rate and coal fly ash flotation performance was observed – higher air flow rates corresponded to improved flotation outcomes. Finally, a comparison between conventional flotation and nanobubble-assisted flotation (utilizing bulk nanobubbles, surface nanobubbles, and micro-nanobubbles) was conducted. Remarkably, micro-nanobubble flotation yielded the most promising results, with the lowest loss-on-ignition in flotation tailings (3.15%) and the highest removal efficiency of unburned carbon (85.01%). These findings satisfied the loss-on-ignition requirements of Grade I fly ash standards.

Formaldehyde-free bio-composites based on Pleurotus ostreatus substrate and corn straw waste

Corn straw-based board has great potential for the protection of forest resources, waste recycling, and sustainable economic development. However, corn stalk-based board has poor mechanical properties due to its short fiber length and poor water resistance because of the presence of numerous hydrophilic hydroxyl functional groups in its structure. Natural mycelium originating from waste Pleurotus ostreatus substrate is a hydrophobic bio-adhesive. In the present study, formaldehyde-free corn stalk/P. ostreatus substrate bio-composites were prepared using the hot-pressing technique without the addition of any chemical adhesive. The mechanical properties and water resistance of the prepared bio-composites were excellent. The highest internal bonding strength (IBS) of 2.16 MPa and the minimum thickness swelling (TS) of 18.3% were observed, which are beyond the national standards for particleboard in China. These bio-composites were prepared using a simple, green, and convenient manufacturing method to promote their popularization and application. The method may, therefore, be used as a novel technical measure to resolve the problem of overuse of forestry resources and waste disposal.

Investigation of Surface Modification of Bagasse Fibers: Performance of Asphalt Binders/Mixtures with Bagasse Fibers

The influence of surface modification on the properties of bagasse fibers and asphalt binders/mixtures was investigated. Bagasse fibers were modified by single, binary, and ternary methods with hydrochloric acid, sodium hydroxide, and sodium chlorite, respectively. The physical and chemical properties of bagasse fibers were analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy, and an adsorption test, respectively. The rheological properties of asphalt binders with bagasse fibers or lignin fibers were analyzed by the dynamic shear rheometer test and bending beam rheometer test. In addition, the performance of asphalt mixtures with bagasse fibers or lignin fibers were evaluated by a wheel rutting test, bending test at a low temperature, and water stability test, respectively. In conclusion, the hydrophilic functional groups on the fiber surface were partially eliminated by modification, facilitating the degradation of different fiber components. Furthermore, the degree of fibrillation was improved, and more interfaces with asphalt components were formed, thus enhancing the high-temperature deformation resistance of asphalt binders, but slightly impairing its low-temperature performance. Among all modification methods, the ternary composite modification exerted important influences on fiber structure, oil absorption, and rheological properties of asphalt binders, significantly enhancing the performance of asphalt mixtures. Combined with surface modification methods, bagasse fibers would be promising reinforced pavement materials.

Covalent Organic Framework Interlayer Spacings as Perfectly Selective Artificial Proton Channels

AbstractBiological proton channels have perfect selectivity in aqueous environment against almost all ions and molecules, a property that differs itself from other biological channels and a feature that remains challenging to realize for bulk artificial materials. The biological perfect selectivity originates from the fact that the channel has almost no free space for ion or water transport but generates a hydrogen bonded wire in the presence of protons to allow the proton hopping. Inspired by this, we used the interlayer spacings of covalent organic framework materials consisting of hydrophilic functional groups as perfectly selective artificial proton channels. The interlayer spacings are so narrow that no atoms or molecules can diffuse through. However, protons exhibit a diffusivity in the same order of magnitude as that in bulk water. Density functional theory calculations show that water molecules and the COF material form hydrogen bonded wires, allowing the proton hopping. We further demonstrate that the proton transport rate can be tuned by adjusting the acidity of the functional groups.

Mitigating autogenous shrinkage of cement with carbon nanotube sponge

Autogenous shrinkage can be mitigated by the addition of superabsorbent polymer (SAP), however, typically at the cost of a significant strength loss. To overcome such dilemma, hydrophilic carbon nanotube sponge (H-CNTSP) was proposed in this study as a novel internal curing agent. Due to the high porosity and enriched hydrophilic functional groups, H-CNTSP can absorb pore solution at 72 g/g driven by the capillary force, which is 176%–620 % higher than the commercial SAPs. The autogenous shrinkage of cement can be reduced or mitigated with the addition of 0.05–0.2 wt% H-CNTSP due to the continuous water release after final setting. Interestingly, the compressive strength loss resulting from the addition of H-CNTSP can be greatly diminished and even be overcompensated by the formation of CNT/hydrate nanocomposite shell with a higher modulus. This study illustrates the great potential to optimize concrete performance through proper design of assembly structures with chemically functionalized nanomaterials.

Design and preparation of reticular superabsorbent hydrogel material with nutrient slow-release and high shear strength for ecological remediation of abandoned mines with steep slopes

In order to solve ecological remediation issues for abandoned mines with steep slopes, a kind of hydrogels with high cohesion and water-retaining were designed by inorganic mineral skeleton combining with polymeric organic network cavities. This eco-friendly hydrogel (MFA/HA-g-p(AA-co-AM)) was prepared with acrylic acid (AA)-acrylamide (AM) as network, which was grafted with humic acids (HA) as network binding point reinforcement skeleton and polar functional group donors, KOH-modified fly ash (MFA) as internal supporter. The maximum water absorption capacities were 1960 g/g for distilled water, which followed the pseudo-second-order model. This super water absorption was attributed to the first stage of 62 % fast absorption due to the high specific surface area, pore volume and low osmotic pressure, moreover, the multiple hydrophilic functional groups and network structure swell contributed to 36 % of the second stage slow adsorption. In addition, the pore filling of water in mesoporous channels contributed the additional 2 % water retention on the third stage. The high saline-alkali resistance correlated with the electrostatic attraction with MFA and multiple interactions with oxygen-containing functional groups in organic components. MFA and HA also enhanced the shear strength and fertility retention properties. After 5 cycles of natural dehydration and reabsorption process, these excellent characteristics of reusability and water absorption capacity kept above 97 %. The application of 0.6 wt% MFA/HA-g-p(AA-co-AM) at 15° slope could improve the growth of ryegrass by approximately 45 %. This study provides an efficient and economic superabsorbent material for ecological restoration of abandoned mines with steep slopes.

Rates of air flow in and out of closed atmospheric-pressure plasma jet system affected surface properties of treated polysulfone membrane

The cold plasma jet works in an atmospheric-pressure condition, and is used to modify polymer membranes by creating hydrophilic functional groups on the membrane surface. Since it can be used without a pressure-reducing system, treatment time and cost are reduced. However, the plasma jet has a narrow beam which limits the area of the membrane surface that can be activated. In this study, a plasma jet was generated in a closed system with controllable rates of air flow in and out of the system. The plasma discharge was recorded with a camera and analyzed by optical emission spectroscopy (OES). Polysulfone membrane surfaces were treated with various conditions of plasma discharge, and the induced membrane hydrophilicity was assessed from water contact angle (WCA) and surface energy (SE) measurements. Atomic force microscopy (AFM), Fourier Transform Infrared Spectroscopy (FTIR) and WCA contour mapping were respectively employed to study surface roughness, functional groups, and WCA distribution on the treated membrane surfaces. The airflow had distinctly different effects on the plasma characteristics. The inflow rate condition affected the width of the plasma beam, and the outflow rate condition affected the diffusion of the plasma beam. Water flux was changed according to the plasma characteristic, and an air outflow rate of 6L/min was the optimum condition for this experiment.

Novel in-situ zwitterionization of carbon quantum dots on membrane surface for oil/water separation

Industrial growth led to an increase in the release of hazardous oily wastewater that seriously threatens human health and the ecosystem. Developing polymeric membranes for treating such wastewater has garnered significant attention, yet their fouling resistance remains a challenge. In this study, an anti-fouling zwitterionic cellulose acetate (CA) membrane, called ZQDs-g-CA, was fabricated by grafting carbon quantum dots (CQDs) on the surface of the CA membrane, followed by zwitterionization of CQDs (Zwitterionic carbon quantum dots, ZQDs). The grafting of ZQDs increased the hydrophilicity and oleophobicity of the membrane due to the hydrophilic functional groups present in the nanomaterial. The surface roughness was increased, allowing a greater surface area for contact between water molecules and the membrane. The modified CA membrane demonstrated excellent water flux (602.2 ± 30.2 L m−1 h−1 bar−1 (LMHB)) and oil/water emulsion separation performance, with a permeation flux of 426.1 ± 9.6 LMHB and oil rejection of 99.4 %. Additionally, the anti-fouling tests demonstrated remarkable performance with more than 96 % flux recovery ratio (FRR), 30.35 % reversible fouling ratio (Rr), and 3.05 % irreversible fouling ratio (Rir). The results showed that the in-situ ZQDs on the CA membrane exceeded the 96 % rejection rate for different oil/water emulsions. ZQDs were successfully applied on the CA membrane, which would provide a reference for the application of ZQDs-g-CA in oil/water separation.

Scalable, flexible, ultra-strong, free-standing papery all carbon nanotube membrane with excellent separation and antifouling properties

Carbon nanotube (CNT) based membranes have shown tremendous promise for water purification. However, fabricating free-standing all CNT membranes with excellent separation and antifouling properties remains challenging. Here, a densified flexible, ultra-strong, free-standing papery all CNT membrane with excellent separation and antifouling properties is reported. The chemically densified free-standing CNT membrane has an extremely high tensile strength up to 330 MPa, four times higher than the original CNT membrane and one order of magnitude higher than most polymeric membranes. The negatively charged surface of the densified CNT membrane enables efficient separation of two dyes even with similar molecular sizes. Meanwhile, the densified CNT membrane exhibits superior antifouling performance during the filtration of dyes, humic acid and bovine serum albumin solutions, and oil-in-water emulsions due to its reinforced hydration layer induced by the hydrophilic functional groups resulting from chemical densification. The chemically densified CNT membrane shows not only excellent separation and antifouling performance, but also superior long-term stability and regeneration performance in the filtration of foulant-containing solutions. This study may pave the way for large-scale application of densified free-standing all CNT membranes in the realm of water treatment.

Staggered structural dynamic-mediated selective adsorption of H2O/D2O on flexible graphene oxide nanosheets

Graphene oxide (GO) is the one of the most promising family of materials as atomically thin membranes for water-related molecular separation technologies due to its amphipathic nature and layered structure. Here, we show important aspects of GO on water adsorption from molecular dynamics (MD) simulations, in-situ X-ray diffraction (XRD) measurements, and ex-situ nuclear magnetic resonance (NMR) measurements. Although the MD simulations for GO and the reduced GO models revealed that the flexibility of the interlayer spacing could be attributed to the oxygen-functional groups of GO, the ultra-large GO model cannot well explain the observed swelling of GO from XRD experiments. Our MD simulations propose a realistic GO interlayer structure constructed by staggered stacking of flexible GO sheets, which can explain very well the swelling nature upon water adsorption. The transmission electron microscopic (TEM) observation also supports the non-regular staggered stacking structure of GO. Furthermore, we demonstrate the existence of the two distinct types of adsorbed water molecules in the staggered stacking: water bonded with hydrophilic functional groups and “free” mobile water. Finally, we show that the staggered stacking of GO plays a crucial role in H/D isotopic recognition in water adsorption, as well as the high mobility of water molecules.

Leaf carbon chemistry effectively manipulated soil microbial profiles and induced metabolic adjustments under different revegetation types in the loess Plateau, China

Microorganisms are essential components of underground life systems and drive elemental cycling between plants and soil. Yet, in the ecologically fragile Loess Plateau, scant attention has been paid to the response of microbial communities to organic carbon (C) chemistry of both leaves and soils under different revegetation conditions, as well as subsequent alternation in their C metabolic functions. Here, Fourier transform infrared (FTIR) spectrum, amplicon sequencing of 16S rRNA and ITS, and temporal incubation with Biolog-Eco 96 plates were combined to explore the vegetative heterogeneity of microbial community properties and metabolic functions, as well as their regulatory mechanisms in three typical revegetation types including Robinia pseudoacacia L. (RF), Caragana korshinskii KOM. (SL), and abandoned grassland (AG). We observed higher bacterial-to-fungal ratios (B: F = 270.18) and richer copiotrophic bacteria (Proteobacteria = 33.08%) in RF soil than those in AG soil, suggesting that microbes were dominated by r-strategists in soil under RF treatment, which is mainly related to long-term priming of highly bioavailable leaf C (higher proportion of aromatic and hydrophilic functional groups and lower hydrophobicity). Conversely, microbial taxa in AG soil, which was characterized by higher leaf organic C hydrophobicity (1.39), were dominated by relatively more abundant fungi (lower B: F ratio = 149.49) and oligotrophic bacteria (Actinobacteria = 29.30%). The co-occurrence network analysis showed that microbial interactive associations in RF and AG soil were more complex and connective than in SL soil. Furthermore, Biolog-Eco plate experiments revealed that microorganisms tended to utilize labile C compounds (carbohydrates and amino acids) in RF soil and resistant C compounds (polymers) in AG soil, which were consistent with the substrate adaptation strategies of predominant microbial trophic groups in different revegetation environments. Meanwhile, we observed greater microbial metabolic activity and diversity advantages in RF vegetation. Collectively, we suggest that besides the nutrient variables in the leaf-soil system, the long-term regulation of the microbial community by the C chemistry of the leaf sequentially alters the microbial metabolic profiles in a domino-like manner. RF afforestation is more conducive to restoring soil microbial fertility (including microbial abundance, diversity, interactive association, and metabolic capacity). Our study potentially paves the way for achieving well-managed soil health and accurate prediction of C pool dynamics in areas undergoing ecological restoration of the Loess Plateau.

An analysis of ramie fiber (Boehmeria nivea L. Gaud) treated with low temperature plasma using a mathematical model

This research aims to characterize low-temperature plasma-treated ramie fibers (Boehmeria nivea L. Gaud), create a mathematical model, and analyze them using image processing. The effects of low-temperature plasma treatment on ramie fibers were investigated using 30 kV output powers, 4-min treatment times, and a 4 cm electrode distance. SEM and FT-IR spectroscopy were used to investigate various aspects of the ramie fiber’s chemical properties and surface topography. This study used a statistical approach to analyze the SEM images. The statistical analysis was used to investigate the surface roughness using the SEM images. FT-IR analysis discovered that fibers that were exposed for four minutes differed from untreated fibers. According to the findings, plasma treatment caused: (1) ramie fiber became more hydrophilic, as indicated by the presence of hydrophilic functional groups such as hydroxyl (O–H), carboxyl (O–C), and carbonyl (C=O) in FT-IR with a deeper T%, (2) ramie fiber mass reduction was accompanied by an increase in surface roughness via SEM testing and image processing, and (3) plasma-treated fiber had a coefficient of mass variation (CV) of 0.7211 higher than untreated fiber. The novelty of this study is the use of image processing in SEM to observe surface roughness and its relationship to the chemical structure of ramie fibers observed with FT-IR. Another novelty of this research is the mathematical model of the interaction of plasma species with the ramie fibers on the plane electrode for the first time.

Ultra-highly efficient adsorbent for CO2 capture from air by directional deprotonation regulation of MOFs-based amine grafting

In recent years, the solid amine of Metal-Organic Frameworks (MOFs) has shown promise as a direct air capture (DAC) adsorbent. However, the efficiency of amine groups under ultra-low CO2 concentrations requires improvement. In this study, we propose a novel method to regulate proton migration through solvent effects during amine grafting, to enhance the synthesis of MOFs as solid amine adsorbents and improve amine group utilization. This approach yielded outstanding results with a MIL-100(Cr)-based DAC adsorbent, demonstrating a CO2 adsorption capacity of 2.15 mmol/g and an ultra-high amine group utilization of 89.6 % at ambient conditions. By directional deprotonation regulation, the CO2 adsorption performance of the UiO-66(Zr)-based adsorbent significantly increased from 0.06 mmol/g of using H2O as solvent to 1.71 mmol/g of using NMP, with a 27.5-fold increase. Specifically, organic polar aprotic solvents enhanced the binding energy and reduced the energy barrier for deprotonation during the grafting process, thereby improving CO2 adsorption performance and amine group utilization, which shed a new light on the development of MOFs based CO2 adsorbent. Furthermore, due to the coordination of secondary amine groups with metal sites leads to the decrease of hydrophilic functional groups in the CO2 adsorption products, the hydrophobicity of products was reduced significantly resulting in an increase in the ΔS of the hydrated ion pairs after the adsorption, which reduced the heat of CO2 adsorption about 15 % than that reported in the literature. Based on changes in humidity conditions, the regeneration energy consumption of the MF-Cr-AEEA is less than 2.5 GJ/t CO2 under a relatively lower humidity, demonstrating outstanding industrial applications potential of the adsorbent.

Synergetic conditioning via oxalic acid enhanced Fe2+/CaO2 and skeleton construct to achieve deep dewatering of sewage sludge

Extracellular polymeric substance (EPS) with highly hydrophilic groups and sludge with high compressibility are determined sludge dewaterability. Herein, Fe2+ catalyzed calcium peroxide (CaO2) assisted by oxalic acid (OA) Fenton-like process combined with coal slime was applied to improve sludge dewaterability. Results demonstrated that the sludge treated by 0.45/1/1.1-OA/Fe2+/CaO2 mM/g DS, the water content (WC), specific resistance to filtration and capillary suction time dropped to 53.01%, 24.3 s and 1.2 × 1012 m/kg, respectively. Under coal slime ratio as 0.6, WC and compressibility were further reduced to 42.72% and 0.66, respectively. The hydroxyl radicals generated by OA/Fe2+/CaO2 under near-neutral pH layer by layer collapsed EPS, resulting in the degradation and migration of inner releasing components and the exposure of inner sludge flocs skeleton. The hydrophilic tryptophan-like protein of TB-EPS were degraded into aromatic protein of S-EPS and exposed inner hydrophobic sites. The protein secondary structures were transformed by destroying hydrophilic functional groups, which were attributed to the reducing α-helix ratio and reconstructing β-sheet. Moreover, coal slime as the skeleton builder lowered compressibility and formed more macropores to increase the filterability of pre-oxidized sludge for the higher intensity of rigid substances. This study deepened the understanding of OA enhanced Fenton-like system effects on sludge dewaterability and proposed a cost-effective and synergistic waste treatment strategy in sludge dewatering.

Influence of surfactant adsorption on coal oxidation and wettability: Experimental discussion and model development

To further investigate the physicochemical properties and wettability changes of surfactant-modified coal after oxidation, the contact angle, industrial composition, and functional groups of the surfactant-modified coal were measured. The experimental data were analyzed using a ridge regression prediction model to explore the relationship between the physicochemical properties and the wettability. The results indicate that the oxidated-modified coal has a worse wettability at room temperature. The adsorption of SL and CDEA surfactants effectively impedes the increase in the contact angle of the oxidized coal. The hydrophilic functional group (2#CO, C–O–C, RHCCH2) in coal demonstrates higher sensitivity to surfactants, while the hydrophobic functional group (2# Free OH, 1#CC) exhibits greater reactivity. There is a strong correlation between the industrial composition, structural parameters, and the contact angle. The quantitative influence of the parameters on the contact angle is as follows: FCad > Vad > P1 ≥ P4 ≥ Mad ≥ P3 ≥ P2. A coal wetting model is established that considers the combined action of surfactants and coal quality. These findings suggest that wettability is determined by multiple parameters, providing a basis for discovering new reagents that significantly enhance coal wettability and reduce coal oxidation activity.

Enhancing Efficiency and Stability in Carbon-Based Perovskite Solar Cells by Double Passivation with Ultralow-Cost Coal-Derived Graphene and Its Derivatives.

Coal-derived carbon nanomaterials possess numerous superior features compared to other classic carbon, such as readily accessible surfaces, tunable pore structure, and facile and precise surface functionalization. Therefore, the controllable preparation of coal-derived carbon nanomaterials is anticipated to be of great significance for the performance improvement and commercialization process of carbon-based perovskite solar cells (C-PSCs). In this study, we successfully synthesized highly stable and commercially valuable graphene oxide (GO) and reduced graphene oxide (rGO) utilizing coal. Compared to traditional methods and commercial graphene, the chemical oxidation and pyrolysis process used in this study is mild and simple, offering the advantages of controlled composition and the absence of other impurities. GO or rGO was incorporated into the top of the SnO2 electron transport layer (ETL) of C-PSCs. Under optimized conditions and ultraviolet-ozone (UVO) irradiation, the ultimate power conversion efficiency (PCE) increased from the unmodified 12.4 to 14.04% (based on rGO) and 15.18% (based on GO), representing improvements of 22 and 31%, respectively. The improved photovoltaic performance is mainly owing to enhanced charge transport capabilities, denser interfacial contacts, improved carrier separation properties, increased conductivity, and abundance of hydrophilic functional groups in GO, which can form more stable hydrogen bonds with SnO2. After being stored at room temperature and ambient humidity for 30 days, the modified, unpacked devices retained 87% of the highest power conversion efficiency (PCE). This study introduces a practical and manageable method to enhance the performance of C-PSCs by using functional carbon nanomaterials derived from coal.

A facile, green synthesis of carbon quantum dots from folium cycas for rapid and sensitive determination of Fe3+ and cell imaging

In this study, biomass-derived carbon quantum dots (CQDs) were synthesized by an one-step hydrothermal method using folium cycas as a carbon source. By optimizing the reaction conditions, the fluorescence quantum yield of CQDs was obtained to be as high as 8.91%, and strong blue emission light was emitted. The characterization results showed that the CQDs were quasi-spherical with an average particle size of 2.69 ± 0.08 nm and contained a large number of hydrophilic functional groups with excellent water solubility and photostability. The CQDs showed high selectivity and sensitivity for the detection of Fe3+, with a low limit of detection of 0.72 μM and a wide linear range of 0–200 μM. The practical applicability of the CQDs was further established by carrying out Fe3+ detection in environmental sample analysis. Besides, CQDs have been successfully applied to in vitro cell imaging and bioimaging. The final by-product of the hydrothermal reaction, biochar, is used for dye adsorption. This work identifies the importance of using a relatively green process and an inexpensive biomass precursor to produce high-quality CQDs that hold a promising future for use in metal ion detection, bioimaging, and practical sensing applications.

Covalent Organic Framework Interlayer Spacings as Perfectly Selective Artificial Proton Channels.

Biological proton channels have perfect selectivity in aqueous environment against almost all ions and molecules, a property that differs itself from other biological channels and a feature that remains challenging to realize for bulk artificial materials. The biological perfect selectivity originates from the fact that the channel has almost no free space for ion or water transport but generates a hydrogen bonded wire in the presence of protons to allow the proton hopping. Inspired by this, we used the interlayer spacings of covalent organic framework materials consisting of hydrophilic functional groups as perfectly selective artificial proton channels. The interlayer spacings are so narrow that no atoms or molecules can diffuse through. However, protons exhibit a diffusivity in the same order of magnitude as that in bulk water. Density functional theory calculations show that water molecules and the COF material form hydrogen bonded wires, allowing the proton hopping. We further demonstrate that the proton transport rate can be tuned by adjusting the acidity of the functional groups.

Integration of metal organic framework nanoparticles into sodium alginate biopolymer-based three-dimensional membrane capsules for the efficient removal of toxic metal cations from water and real sewage

Sodium alginate (SA) biopolymer has been recognized as an efficient adsorbent material owing to their unique characteristics, including biodegradability, non-toxic nature, and presence of abundant hydrophilic functional groups. Accordingly, in the current research work, UiO-66-OH and UiO-66-(OH)2 metal organic framework (MOF) nanoparticles (NPs) have been integrated into SA biopolymer-based three-dimensional (3-D) membrane capsules (MCs) via a simple and facile approach to remove toxic metal cations (Cu2+ and Cd2+) from water and real sewage. The newly configured capsules were characterized by FTIR, SEM, XRD, EDX and XPS analyses techniques. Exceptional sorption properties of the as-developed capsules were ensured by evaluation of the pertinent operational parameters, i.e., contents of MOF-NPs (1–100 wt%), adsorbent dosage (0.001–0.05 g), content time (0–360 h), pH (1–8), initial concentration of metal cations (5–1000 mg/L) and reaction temperature (298.15–333.15 K) on the eradication of Cu2+ and Cd2+ metal cations. It was found that hydrophilic functional groups (-OH and -COOH) have performed an imperative role in the smooth loading of MOF-NPs into 3-D membrane capsules via intra/inter-molecular hydrogen bonding and van der waals potencies. The maximum monolayer uptake capacities (as calculated by the Langmuir isotherm model) of Cd2+ and Cu2+ by 3-D SGMMCs-OH were 940 and 1150 mg/g, respectively, and by 3-D SGMMCs-(OH)2 were 1375 and 1575 mg/g, respectively, under optimum conditions. The as-developed capsules have demonstrated superior selectivity against targeted metal cations under designated pH and maintained >80 % removal efficiency up to six consecutive treatment cycles. Removal mechanisms of metal cations by the 3-D SGMMCs-OH/(OH)2 was proposed, and electrostatic interaction, ion-exchange, inner-sphere coordination bonds/interactions, and aromatic ligands exchange were observed to be the key removal mechanisms. Notably, FTIR and XPS analysis indicated that hydroxyl groups of Zr-OH and BDC-OH/(OH)2 aromatic linkers played vital roles in Cu2+ and Cd2+ adsorption by participating in inner-sphere coordination interactions and aromatic ligands exchange mechanisms. The as-prepared capsules indicated >70 % removal efficiency of Cu2+ from real electroplating wastewater in the manifestation of other competitive metal ions and pollutants under selected experimental conditions. Thus, it was observed that newly configured 3-D SGMMCs-OH/(OH)2 have offered a valuable discernment into the development of MOFs-based water decontamination 3-D capsules for industrial applications.