Hydroxyl Research Articles

Structural forming of soil composites using as a pavement subgrade strengthening

The article substantiates the possibility of obtaining composite materials with improved functional properties to strengthen the subgrade, containing technogenic soil stabilized by an additive based on a gelling polymer. The introduction of technogenic soils into composites will not only reduce the consumption of expensive materials, but also solve a complex of acute environmental problems. Composite materials can be used in the construction of structural layers of road pavements, foundations of buildings and structures, sites for various purposes, for the prevention and elimination of defects in the foundations of engineering structures during their construction, reconstruction and repair, including in permafrost areas. Stabilized technogenic soils are more durable, frost-resistant and waterproof, which makes them applicable for creating impervious curtains in hydraulic structures and sealing storage facilities for hazardous substances. The cryogenic effect on a composite material allows one to vary its properties within a wide range and modify its macroporous structure. Studying the process of structure formation of the resulting organic-inorganic materials, consisting of macromolecules of high-molecular substances and inorganic inclusions that have undergone cryogenic treatment, will make it possible to specifically regulate their performance characteristics. The best values of strength characteristics were obtained for samples with a stabilizing additive concentration of 100g/l. The resulting composite materials are hydrophobic, frost-resistant, characterized by a compressive strength of 2.3-6.5MPa and a thermal conductivity of 0.19-0.20W/(m·K). Data from differential scanning calorimetry and thermogravimetry and IR spectroscopy revealed that the binding of mineral particles by a stabilizing additive occurs due to the formation of organomineral complexes with the participation of clay minerals and the restructuring of hydration shells. SEM data indicate that crystallinity zones formed due to hydrogen bonds of hydroxyl groups of neighboring polymer chains can participate in the formation of the composite structure. An increase in the number of cryogenic treatment cycles promotes additional structuring and strengthening of the polymer phase due to the formation of additional nodes of the supramolecular network, ordering of crystallinity zones and the appearance of compacted areas in the structure. Computed X-ray tomography revealed an increase in the density of the composite upon drying, which helps to increase its strength characteristics. The structure of the sample is characterized by heterogeneity of the pore space, which is characterized by the presence of both fine-porous and large-porous regions, which determines its thermophysical properties.

Preparation And Evaluation Of Polyherbal Scented Candle Using Volatile Oils Extracted By Enfleurage Method

Preparation And Evaluation Of Polyherbal Scented Candle Using Volatile Oils Extracted By Enfleurage Method

In Ukrainian

The paper discusses the results of saponite research from the Tashkiv deposit of Ukraine. X-ray structural analysis proved the necessity of preliminary cleaning of saponites from mineral impurities. The study of the morphology, nanoprofile and topography of the surface of saponite by the methods of SEM-microscopy and Atomic Force Microscopy revealed that the mineral is represented by aggregates of nano- and microparticles of a pyramidal shape. Its characteristic feature is the heterogeneity of isomorphic substitutions of ions in the tetrahedral and octahedral sheets of the structural elementary package. According to X-ray fluorescence analysis, saponite contains a significant amount of Fe3+, which isomorphically replaces magnesium Mg2+ and, accordingly, is located mastly in the octahedral sheet of the structural package with a charge from +0.37 to +0.35. The number and mechanism of isomorphic substitutions determine the presence of a total negative charge of the crystal lattice (from –0.38 to –0.3), the value of which ensures intensive interaction with water molecules of the interpacket space with the formation of surface OH groups. Accordingly, both acidic and alkaline Lewis and Brønsted centers are present on the surface with a predominance of acidic ones, so the acidity function is 5.82, and the point of zero proton charge is pH = 5.5. During dispersion in water, a part of the alkaline centers of the side surface are transformed into Brønsted acid centers as a result of their protonation, which causes an increase in the pH of the dispersion medium to pH = 8–8.6. Accordingly, the isoionic state is reached at pH = 7.5. The difference in pH values characterizing the isoionic state of the surface and the point of zero net proton charge (PZNPC) indicates the presence of weak acid-alkaline centers on the surface. The study of the adsorption of acid-alkaline dyes showed the adsorption of alkaline (pK = 1¸3) and acid (pK = 7¸14) dyes on saponites. The latter is significantly reduced due to the preliminary hydration of the solid surface - mainly the lateral edges of the particles. Acidic dyes are not adsorbed from a dispersion medium with pH < 5.5 (PZNPC), and basic dyes are adsorbed at pH > 5,5( PZNPC).

Mesoporous architectural magnetic halloysite-polymer beads for removing toxic streptomycin from water: A sustainable remediation approach

Streptomycin (STR) is a widely used antibiotic to treat various infectious diseases in humans and animals. Increased STR production and distribution result in harmful residue in soil and water. Consequently, STR exists in biotic- and abiotic-counterpart of the environment and poses potential toxicity and risk due to its bioaccumulation and biomagnification properties. Sustainable remediation of STR from wastewater requires selective, minimal, low-cost, regenerable, and reusable materials as adsorbents. In this study, magnetic-halloysite incorporated polymer composite beads (SPHM) were synthesized and used for the efficient clean-up of toxic STR from wastewater. SPHM has a mesoporous structure with an abundance of oxygen-containing functional groups and exhibits a synergistic STR clean up performance (qm = 235.71 ± 13.98 mg/g). Sorption and interfacial studies revealed that diffusion, hydrophobic and ionic interactions, including electrostatic interaction, are involved in STR remediation. Electrostatic interaction plays a vital role alongside the physical sorption mechanism due to the presence of hydroxyl and carboxyl groups induced from poly (vinyl alcohol) and sodium alginate. Moreover, X-ray photoelectron spectroscopy (XPS) and Time-of-flight secondary ion mass spectrometry (ToF-SIMS) analyses confirm the involvement of opposing charged groups of SPHM and STR in adsorption. SPHM can be magnetically separated in just 20 s and is regenerable and reusable up to 10 times, with outstanding performance and stability. The sorption process requires only a minimal amount of SPHM, i.e., 0.5 g/L for STR clean-up. Even the natural surface water composition did not affect its performance. Hence, natural nanoclay-based, biocompatible and low-cost SPHM has a great potential for the sustainable remediation of streptomycin and other similar antibiotics from wastewater.

Preparation of Hydrophobic Modified Silica with Si69 and Its Reinforcing Mechanical Properties in Natural Rubber

The inherent large number of hydroxyl groups of silica poses strong hydrophilicity, resulting in poor dispersibility in the natural rubber matrix. Here, the silica’s surface was hydrophobically modified with [3-(triethoxysiliconyl) propyl] tetrasulfide (Si69) to improve the dispersibility and reinforce the mechanical properties of silica/natural rubber composites. The structure and morphology of modified silica were characterized by Fourier infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray electron spectroscopy (XPS), nuclear magnetic resonance spectroscopy and the contact angle. Further, the mechanical properties, dynamic mechanical properties and morphology of silica/natural rubber composites were studied with a universal electronic tension machine, dynamic thermal mechanical properties analyzer (DMA) and scanning electron microscope (SEM). The experimental results show that the Si69 was successfully grafted onto the surface of silica, thereby significantly improving the water contact angle (a 158.6% increase) and enhancing the mechanical properties of modified silica/natural rubber composites.

Near-Complete Suppression of NIR-II Luminescence Quenching in Halide Double Perovskites for Surface Functionalization Through Facet Engineering.

Lanthanide-based NIR-II-emitting materials (1000-1700nm) show promise for optoelectronic devices, phototherapy, and bioimaging. However, one major bottleneck to prevent their widespread use lies in low quantum efficiencies, which are significantly constrained by various quenching effects. Here, a highly oriented (222) facet is achieved via facet engineering for Cs2NaErCl6 double perovskites, enabling near-complete suppression of NIR-II luminescence quenching. The optimally (222)-oriented Cs2Ag0.10Na0.90ErCl6 microcrystals emit Er3+ 1540nm light with unprecedented high quantum efficiencies of 90±6% under 379nm UV excitation (ultralarge Stokes shift >1000nm), and a record near-unity quantum yield of 98.6% is also obtained for (222)-based Cs2NaYb0.40Er0.60Cl6 microcrystallites under 980nm excitation. With combined experimental and theoretical studies, the underlying mechanism of facet-dependent Er3+ 1540nm emissions is revealed, which can contribute to surface asymmetry-induced breakdown of parity-forbidden transition and suppression of undesired non-radiative processes. Further, the role of surface quenching is reexamined by molecular dynamics based on two facets, highlighting the drastic two-phonon coupling effect of a hydroxyl group to 4I13/2 level of Er3+. Surface-functionalized facets will provide new insights for tunable luminescence in double perovskites, and open up a new avenue for developing highly efficient NIR-II emitters toward broad applications.

Research on the Interaction Mechanisms between ScCO2 and Low-Rank/High-Rank Coal with the ReaxFF-MD Force Field

CO2 geological sequestration in coal seams can be carried out to achieve the dual objectives of CO2 emission reduction and enhanced coalbed methane production, making it a highly promising carbon capture and storage technology. However, the injection of CO2 into coal reservoirs in the form of supercritical fluid (ScCO2) leads to complex physicochemical reactions with the coal seam, altering the properties of the coal reservoir and impacting the effectiveness of CO2 sequestration and methane production enhancement. In this paper, theoretical calculations based on ReaxFF-MD were conducted to study the interaction mechanism between ScCO2 and the macromolecular structures of both low-rank and high-rank coal, to address the limitations of experimental methods. The reaction of ScCO2 with low-rank coal and high-rank coal exhibited significant differences. At the swelling stage, the low-rank coal experienced a decrease in aromatic structure and aliphatic structure, and high-rank coal showed an increase in aromatic structure and a decrease in aliphatic structure, while the swelling phenomenon was more pronounced in high-rank coal. At the dissolution stage, low-rank coal was initially decomposed into two secondary molecular fragments, and then these recombined to form a new molecular structure; the aromatic structure increased and the aliphatic structure decreased. In contrast, high-rank coal showed the occurrence of stretches–breakage–movement–reconnection, a reduction in aromatic structure, and an increase in aliphatic structure. The primary reasons for these variations lie in the distinct molecular structure compositions and the properties of ScCO2, leading to different reaction pathways of the functional group and aromatic structure. The reaction pathways of functional groups and aromatic structures in coal can be summarized as follows: the breakage of the O–H bond in hydroxyl groups, the breakage of the C–OH bond in carboxyl groups, the transformation of aliphatic structures into smaller hydrocarbon compounds or the formation of long-chain alkenes, and various pathways involving the breakage, rearrangement, and recombination of aromatic structures. In low-rank coal, there is a higher abundance of oxygen-containing functional groups and aliphatic structures. The breakage of O–H and C–OH chemical bonds results in the formation of free radical ions, while some aliphatic structures detach to produce hydrocarbons. Additionally, some of these aliphatic structures combine with carbonyl groups and free radical ions to generate new aromatic structures. Conversely, in high-rank coal, a lower content of oxygen-containing functional groups and aliphatic structures, along with stronger intramolecular forces, results in fewer chemical bond breakages and makes it less conducive to the formation of new aromatic structures. These results elucidate the specific deformations of different chemical groups, offering a molecular-level understanding of the interaction between CO2 and coal.

Effect of lubricant functional groups on tribological properties of epoxy/graphene composites

AbstractThe functional group in the molecular chain of lubricants is a key factor for a boundary lubricating film, which can further enhance the friction performance by interfacial tribochemistry. In this paper, the tribological behavior of epoxy/graphene (EP/Gra) composites was investigated through varying lubrication conditions, including dry friction, or different lubricants (such as water, hexadecane, oleylamine, and oleic acid). The porosity and Shore hardness (SHD) of the EP composites were significantly improved by the addition of graphene. Results showed that the porosity of the EP/0.75 wt.% Gra composites was reduced by 75.6% and their SHD increased by 5.4 compared with the EP/0.05 wt.% Gra composites. The average coefficient of friction (COF) of the composites was reduced by at least 27.3% under dry friction conditions. For water as lubricant, the EP/0.5 wt.% Gra composite exhibited the lowest COF (0.0455). The EP/0.75 wt.% Gra composite displayed the lowest COF (0.0466) when hexadecane acted as lubricant. By contrast, EP/0.05 wt.% Gra showed the lowest COF (0.0389) with oleylamine as lubricant, and the EP/0.25 wt.% Gra composites gave the lowest COF (0.0433) under oleic acid. The amine group of oleylamine reacted with the EP group to form a hydroxyl group, resulting in a polymer with low friction adhered to the friction interface. Simultaneously, the EP group reacted with the carboxyl group, forming a network of hydrogen bonds with graphene, which reduced the shear stress on the friction interface. Therefore, the functional groups of lubricants have a vital influence on the tribological properties of frictional composites, which may provide a new approach to solving the problem of wear.

Self‐Supporting Solid Electrolyte Based on Supramolecular Interaction for Stable Li Metal Batteries

AbstractLi metal batteries based on solid polymer electrolytes offer the benefits of high energy density and safety, as well as extended cycling life, making them an excellent candidate for the next‐generation battery system. However, current solid polymer electrolytes still suffer from low ion conductivity and Li+ transfer number, which seriously restricts its practical application. Herein, a self‐supporting composite solid polymer electrolyte was prepared, where phenolic resin rich in hydroxyl groups (BR) and polyethylene oxide (PEO) are mixed evenly and poured onto a cellulose membrane in one step. In such an electrolyte, PEO and BR combine to form intermolecular hydrogen bonds, lowering the crystallinity of PEO and increasing the Li+ transfer number. Lastly, the obtained solid electrolytes exhibited a high ion conductivity (1.1×10−4 S cm−1) and Li+ transfer number (0.53), as well as improved electrochemical window. Consequently, Li || Li symmetrical cells can run stably for more than 700 h at 0.1 mA cm−2/0.25 mAh cm−2. And full cells with LiFePO4 cathode can also demonstrate high discharge capacity of 152.12 mAh g−1 and rate performance. We believe that such a design based on supramolecular interaction offer a new avenue to advanced solid polymer electrolytes.

In situ growth of HKUST-1 on electrospun polyacrylonitrile nanofibers/regenerated cellulose aerogel for efficient methylene blue adsorption

Dyes, as organic pollutants, are causing increasingly severe environmental problems. Metal-organic frameworks (MOFs) are considered promising dye adsorbents; however, their application is limited due to their powder or solid particle forms and limited reusability. Therefore, this study proposes an innovative approach to develop a novel MOF-based composite aerogel, specifically a HKUST-1/polyacrylonitrile nanofibers/regenerated cellulose (HKUST-1/PANNs/RC) composite aerogel adsorbent, for the adsorption of pollutants in water. This adsorbent was successfully prepared using a simple method combining covalent crosslinking, quick freezing, freeze-drying, in-situ growth synthesis, and solvothermal techniques. The HKUST-1/PANNs/RC composite aerogel exhibits a significantly large specific surface area, which is approximately 64 times greater than that of PANNs/RC (10.45 m2·g−1), with a specific surface area of 669.9 m2·g−1. The PANNs serve as a support framework, imparting excellent mechanical properties to the composite aerogel, enhancing its overall stability and recoverability. Additionally, the composite aerogel contains numerous -COOH and -OH groups on its surface, providing strong acid resistance and facilitating interactions with pollutant molecules through electrostatic interactions, π-π conjugation, n-π* interactions, and hydrogen bonding, thereby promoting the adsorption process. Using methylene blue (MB) as a probe molecule, the study results demonstrate that the HKUST-1/PANNs/RC composite aerogel has an adsorption capacity of 522.01 mg·g−1 for MB (25 h), exhibiting excellent adsorption performance. This composite aerogel shows great potential for application in water pollution control.

Starch exploration in Nelumbo nucifera and Trapa natans: Understanding physicochemical and functional variations for future perspectives

The current research emphasis on identifying unconventional starch sources with varied properties to broaden industrial applications. The focus of this research is on the search for alternative sources of starch with different properties in order to expand their potential use in the industrial sector. Starch was extracted from Trapa natans and Nelumbo nucifera and analyzed for their physicochemical and functional properties. They had similar protein (0.35 %) and ash contents, but the nitrogen-free extract was slightly higher in Nelumbo starch (87.58 %) than in Trapa starch (85.09 %). The amylose and amylopectin contents were 23.89 % and 76.11 % in Trapa starch and 15.70 % and 84.30 % in Nelumbo starch, respectively. Fourier-transform infrared spectroscopy identified both as polysaccharides. The characteristic absorption bands assigned to the stretching of OH groups (3324 cm−1; 3280 cm−1), the asymmetric and symmetric stretching of aliphatic chain groups (2925 cm−1; 2854 cm−1), the bending vibration of CHO groups (1149 cm−1; 1144 cm−1) were present in both the starch samples, with the exception of CH3 which could not be detected in Trapa natans starch. X-ray diffraction confirmed hexagonal and orthorhombic crystal structures in Nelumbo nucifera and Trapa natans starch. Scanning electron microscopy revealed a smooth oval and a rough cuboidal shape for lotus and chestnut starch, respectively. Rheological analysis showed that both starch solutions exhibited gel behavior, with Trapa showing stronger gel behavior after the crossover point. These results suggest potential applications in various industries, including the food industry and beyond.

Development of Graphene Oxide-Based Anticancer Drug Combination Functionalized with Folic Acid as Nanocarrier for Targeted Delivery of Methotrexate.

Graphene has become a prominent material in cancer research in recent years. Graphene and its derivatives also attract attention as carriers in drug delivery systems. In this study, we designed a graphene oxide (GO)-based methotrexate (MTX)-loaded and folic acid (FA)-linked drug delivery system. MTX and FA were bound to GO synthesized from graphite. MTX/FA/GO drug delivery system and system components were characterized using Fourier transform infrared spectroscopy (FTIR), differential calorimetric analysis (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), zeta potential analysis, and dimension measurement (DLS) studies. SEM and TEM images confirmed the nanosheet structure of GO synthesized from graphite, and it was shown that MTX/FA binding to GO transformed the two-dimensional GO into a three-dimensional structure. FTIR and DSC graphs confirmed that oxygen atoms were bound to GO with the formation of carboxylic, hydroxyl, epoxide, and carbonyl groups as a result of the oxidation of graphite, and GO was successfully synthesized. Additionally, these analyses showed that MTX and FA bind physicochemically to the structure of GO. The in vitro Franz diffusion test was performed as a release kinetic test. The release kinetics mathematical model and correlation coefficient (R2) of MTX-loaded GO/FA nanomaterials were found to be the Higuchi model and 0.9785, respectively. Stiffness analyses showed that adding FA to this release system facilitated the entry of the drug into the cell by directing the system to target cells. As a result of the stiffness analyses, the stiffness values of the control cell group, free MTX, and MTX/FA/GO applied cells were measured as 2.34 kPa, 1.87 kPa, and 1.56 kPa, respectively. According to these results, it was seen that MTX/FA/GO weakened the cancer cells. Combined use of the MTX/FA/GO drug delivery system had a higher cytotoxic effect than free MTX on the MDA-MB-231 breast cancer cell line. The results showed that the synthesized MTX/FA/GO material has promising potential in cancer cell-specific targeted therapy for MTX as a drug delivery system.

Formation of Inclusion Complexes of 2-Hydroxypropyl β-Cyclodextrin with 2-Hydroxychalcone: Experimental and Theoretical Study

The formation of inclusion complexes of 2-hydroxypropyl-β-cyclodextrin (HP β-CD) with 2-hydroxychalcone (2HOCH) in solution and solid state was investigated using UV–Visible, fluorescence, Fourier transform-infrared (FT-IR) spectroscopy, powder X-ray diffraction (PXRD), scanning electron microscope (SEM) techniques. The results obtained confirmed that 2HOCH formed the stable inclusion complex with HP β-CD. Moreover, the spectral data and Benesi–Hildebrand plots results indicated that the stoichiometry of the inclusion complex was 1:1. Theoretically, the structure of the inclusion complexes and the physical parameters such as complexation energy, highest occupied molecular orbital–lowest unoccupied molecular orbital, and energy gap were obtained using the DFT/B3LYP/6-311G method. It was found that the complexation energy for orientation B was lower than that for orientation A as evidenced by the theoretical calculations. Moreover, the carbonyl group of molecules was located outside of the cyclodextrin cavity while the hydroxyl group was located inside the cavity. The antioxidant capacity and antibacterial responses of the inclusion complexes and, for comparison, the parent compounds were also carried out.

Probing the interaction mechanism of choline chloride-based deep eutectic solvents with flavonoid and polyphenol systems

Choline chloride-based deep eutectic solvents (DES) have been demonstrated as promising green solvents for the extraction of flavonoids and polyphenols. This study investigates the interaction between six different hydrogen bond donors (HBD) choline chloride-based DES and three types of polyphenolic flavonoid substrates. Density functional theory (DFT) and molecular dynamics (MD) simulations suggest that Cl− dominates the interaction primarily through electrostatic forces. The extraction effect of alcohol DES on rutin was optimized obviously, and the maximum interaction could reach 737.6 kJ/mol. Acid DES has a better extraction effect on anthocyanins, with a maximum interaction of 376.4 kJ/mol. With the increase of the carbon chain of HBA and the increase of the number of functional groups, the interaction between DES and the active substance decreases. As HBD, ethanolamine with both hydroxyl and amino groups showed the best effect in the extraction process of DES, forming the maximum interaction energy of 1575.8 kJ/mol. Additionally, multivariate analysis is employed to establish the relationship between different variables and interaction energy. This study provides micro-theoretical support for the extraction of flavonoids and polyphenols.

Impact of end groups of small molecules grafted to reverse osmosis membranes on their separation and antifouling performance

In this study, surface hydroxylation and methoxylation were employed to fabricate polyamide (PA) reverse osmosis (RO) membranes with enhanced permeability and antifouling performance. Diethanolamine (DEA) and bis(2-methoxyethyl) amine (BMEA) were grafted onto PA of RO membranes, and the impact of their end groups of hydroxyls and methoxyls on PAs were investigated. Benefiting from the increased surface hydrophilicity (particularly for the DEA-grafted RO) and the tailored cross-linking structure of PA layers, both DEA- and BMEA-grafted membranes showed high water permeance (1.58-fold than the pristine RO membrane) with highly competitive NaCl rejection of 99 %. The DEA-grafted membrane exhibited the enhanced antifouling performance against both positively and negatively charged foulants, while the BMEA-grafted membrane exhibited exceptional performance against small cationic foulants. Quantum chemistry simulations reveal that hydroxyl groups grafted on PA possess a relatively low binding energy with both positively and negatively charged small foulants, whereas methoxyl groups grafted on PA exhibited an exceptionally low binding energy with positively charged small foulants, which rendered them less likely to be adsorbed onto the corresponding grafted PA and to form a loose cake layer. Our study provides new insights into design of small molecules with different end groups used for the simple and effective modification of antifouling RO membranes.

High-Entropy Lanthanide-Organic Framework as an Efficient Heterogeneous Catalyst for Cycloaddition of CO2 with Epoxides and Knoevenagel Condensation.

Multimetallic synergistic effects have the potential to improve CO2 cycloesterification and Knoevenagel reaction processes, outperforming monometallic MOFs. The results demonstrate superior performance in these processes. To investigate this, we created and characterized a selection of single-component Ln(III)-MOFs (Ln=Eu, Tb, Gd, Dy, Ho) and high-entropy lanthanide-organic framework (HE-LnMOF) using solvent-thermal conditions. The experiments revealed that HE-LnMOF exhibited heightened catalytic efficiency in CO2 cycloesterification and Knoevenagel reactions compared to single-component Ln(III) MOFs. Moreover, the HE-LnMOF displayed significant stability, maintaining their structural integrity after five cycles while sustaining elevated conversion and selectivity rates. The feasible mechanisms of catalytic reactions were also discussed. HE-LnMOF possess multiple unsaturated metal centers, acting as Lewis acid sites, with oxygen atoms connecting the metal, and hydroxyl groups on the ligand serving as base sites. This study introduces a novel method for synthesizing HE-LnMOF and presents a fresh application of HE-LnMOF for converting CO2.

Unveiling the Nature of lignin's Interaction with Molecules: A Mechanistic Understanding of Adsorption of Methylene Blue Dye.

The valorization of lignin into advanced materials for water and soil remediation is experiencing a surge in demand. However, it is imperative that material research and manufacturing be sustainable to prevent exacerbating environmental issues. Meeting these requirements necessitates a deeper understanding of the role of lignin's functional groups in attracting targeted species. This research delves into the interaction mechanisms between lignin and organic molecules, using the adsorption of the cationic dye Methylene Blue (MB+) as a case study. Herein, we aim to quantitatively estimate the contribution of different interaction types to the overall adsorption process. While carbonyl groups were found to have no significant role in attraction, carboxylic groups (-COOH) exhibited significantly lower adsorption compared with hydroxyl groups (-OH). Through alternately blocking aliphatic and phenolic -OH groups, we determined that 61% of the adsorption occurred through hydrogen bonding and 38% via electrostatic interactions. Performance studies of modified lignin along with spectroscopic methods (XPS, FTIR) confirmed the negligible role of π-π interactions in adsorption. This study offers fundamental insights into the mechanistic aspects of MB adsorption on lignin, laying the groundwork for potential modifications to enhance the performance of lignin-based adsorbents. The findings underscore the importance of hydroxyl groups and provide a roadmap for future studies examining the influence of steric factors and interactions with other organic molecules.

Solid-State Red Carbon Dots Based on Biomass Furan Derivatives.

In the preparation of carbon dots (CDs), precursors are crucial, and abundant precursors endow CDs with various structures and fluorescence characteristics. Furan (FU) and its derivatives are considered excellent carbonization materials due to their π conjugated structures and active functional groups, such as hydroxyl and aldehyde groups. Herein, we prepare FU-derivative-based CDs by a solvothermal method and investigate the influences of the precursor structure on the fluorescence characteristics. Surprisingly, CDs prepared from 5-hydroxymethylfurfural (HMF) with both aldehyde and hydroxyl groups exhibit red-shifted fluorescence characteristics in the solid state. We postulate that this solid-state fluorescence characteristic is due to the enhancement of supramolecular cross-linking fluorescence between CDs. The unique precursor structure leads to carboxyl groups on the surface of HMF-CDs that are conducive to the hydrogen bond formation. As the concentration of CDs increases, the hydrogen bonding effect increases, leading to a red-shift in the fluorescence wavelength. Therefore, basically full-color CDs/poly(vinyl alcohol) (PVA) phosphor-based light-emitting diodes can be achieved by controlling the degree of supramolecular cross-linking of CDs in PVA. This research provides a new approach for the preparation of solid-state luminescent CDs.

Polyvinyl alcohol nanofibrous mat impregnated with ClCNTs/Fe2O3 nanocomposite for absorption of diesel oil in water

Abstract Oil contamination is one of the main sources of water pollution in the world. In this study, a sorption material that showed great promise as an absorbent for diesel oil in aqueous solution was developed. Chlorinated carbon nanotubes (CNTs) previously synthesized using a chemical vapor deposition (CVD) method were loaded with iron oxide nanoparticles via a co-precipitation method. The sorption materials were prepared by embedding ClCNTs/Fe2O3 nanocomposite into a polyvinyl alcohol (PVA) polymer matrix via electrospinning. The PVA mat containing only ClCNTs was also prepared for comparison and the maximum sorption capacity of 9.7 g/g was obtained. The optimum concentration of ClCNTs/Fe2O3 nanocomposite that gave uniform, and well-distributed nanofibers was 0.5 wt.%. Crosslinking the PVA/ClCNTs/Fe2O3 nanofiber mat with glutaraldehyde (GA) resulted in increased absorption capacity for oil of ~ 9.4 g/g in comparison with an absorption capacity of ~ 7.6 g/g attained with a pure nanofiber mat. The crosslinked nanofiber mat remained stable even after 60 min of oil absorption which proves that crosslinking assisted in increasing the affinity of PVA for oil by reducing the amount of OH groups through acetal formation making PVA less soluble to water. The oil sorption capacity of the prepared materials was not maintained even after two cycles indicating poor reusability. 

Highly acid-stable polyvinyl alcohol/chitosan/phytic acid aerogel for selective separation of uranium from actual wastewater

Conventional adsorption materials encounter difficulties in achieving optimal selectivity in uranium-containing wastewater (UCW) because of the low uranium concentration and the presence of diverse coexisting ions. Aerogel, renowned for its abundance of adsorption sites and remarkable structural flexibility, is widely regarded as an innovative material. Nonetheless, its stability in solution hinders its utility in the separation of uranium during wastewater treatment. To counter this limitation, a polyvinyl alcohol/chitosan/phytic acid aerogel (PCPA) was synthesized by employing several polymerization agents. An exceptional degree of selectivity, speed, and stability was achieved in the separation of low concentration uranium from UCW. The results indicated that polyvinyl alcohol (PVA) proved to be the most effective in generating stable aerogels, even when immersed in 0.1 M HCl or acidic UCW. PCPA displayed the highest efficacy in isolating U(VI) in UCW at a pH of 6.0. The novel aerogel exhibited remarkable resistance to ion interference during adsorption, leading to an impressive 96.3 % efficiency in the separation of U(VI) from actual low-concentration UCW. Even after five desorption, PCAC could still achieve U(VI) separation efficiencies of more than 80 %. The adsorption of U(VI) in this aerogel is characterized by chemisorption. PVA plays a crucial role in the condensation process of the aerogel, resulting in an increase in the presence of easily dissociable -OH groups. This, in turn, effectively improves the selectivity of the aerogel. PCPA has demonstrated successful capability in the efficient recovery of uranium from UCW.