Hydroxyl Functional Groups Research Articles

Selective SERS Detection of TATB Explosives Based on Hydroxy-Terminal Nanodiamond-Multilayer Graphene Substrate.

Selective surface-enhanced Raman scattering (SERS) detection of target explosives with good reproducibility is very important for monitoring soldiers' health and ecological environment. Here, the specific charge transfer pathway was constructed between a stable nanodiamond-multilayer graphene (MGD) film substrate and the target explosives. Two-step wet chemical oxidation methods of H2O2 (30%) and HNO3 (65%) solutions were used to regulate the terminal structure of MGD films. The experimental results showed that the hydroxyl (-OH) functional groups are successfully modified on the surface of MGD thin films, and the MGD-OH substrates having good selectivity for 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) explosive in mixed solutions of the TATB, 2,2-dinitroethene-1,1-diamine, 2,4,6-trinitrotoluene, and 1,3,5-trinitroperhydro-1,3,5-triazine explosives compared with MGD substrates were demonstrated. Finally, first-principles density functional theory simulations revealed that the SERS enhancement of the MGD-OH substrate is mainly attributed to the transferred electrons between the -NO2 groups of TATB and the -OH groups of the MGD-OH substrate.

Insights into Plastic Degradation Processes in Marine Environment by X-ray Photoelectron Spectroscopy Study.

The present study employs X-ray photoelectron spectroscopy (XPS) to analyze plastic samples subjected to degradation processes with the aim to gain insight on the relevant chemical processes and disclose fragmentation mechanisms. Two model plastics, namely polystyrene (PS) and polyethylene (PE), are selected and analyzed before and after artificial UV radiation-triggered weathering, under simulated environmental hydrodynamic conditions, in fresh and marine water for different time intervals. The object of the study is to identify and quantify chemical groups possibly evidencing the occurrence of hydrolysis and oxidation reactions, which are the basis of degradation processes in the environment, determining macroplastic fragmentation. Artificially weathered plastic samples are analyzed also by Raman and FT-IR spectroscopy. Changes in surface chemistry with weathering are revealed by XPS, involving the increase in chemical moieties (hydroxyl, carbonyl, and carboxyl functionalities) which can be correlated with the degradation processes responsible for macroplastic fragmentation. On the other hand, the absence of significant modifications upon plastics weathering evidenced by Raman and FT-IR spectroscopy confirms the importance of investigating plastics surface, which represents the very first part of the materials exposed to degradation agents, thus revealing the power of XPS studies for this purpose. The XPS data on experimentally weathered particles are compared with ones obtained on microplastics collected from real marine environment for investigating the occurring degradation processes.

Graphene oxide nanoparticles synthesized from waste tires: A multi-faceted analysis of structure, morphology and antibacterial behavior

In recent years, the sustainable utilization of waste materials has become a significant research area due to environmental concerns and resource scarcity. Graphene oxide nanoparticles (GONPs) are regarded as one of the most important materials due to their capacity to serve as a potentially scalable precursor to graphene and, more recently, as the most promising substance in biomedical research. This study successfully explores the synthesis of GONPs using recovered carbon black (rCB) derived from waste tires. The structural, morphological and antibacterial properties of the synthesised GONPs in this study were highlighted. The intensity ratio (ID/IG) from Raman spectroscopy analysis, obtained at 0.82, with FTIR spectral results shows the functional groups of hydroxyl, carboxyl and epoxy, similar to GO synthesised from pure graphite. TEM analysis showed that the surface morphology of the GONPs contains nanoparticles with a size of 44.95 nm. Despite using waste material, GONPs exhibited potential antibacterial activity towards the gram-positive and gram-negative bacteria tested in this study. The data presented here are novel and show the possibility of GONP synthesis from waste tires as a future cost-effective antibacterial agent.

Fully bio-sourced catalyst-free covalent adaptable networks from epoxidized soybean oil and L-tartaric acid

Epoxidized vegetable oil (EVO)-based epoxy systems offer a promising avenue for replacing non-recyclable petroleum-based thermoset elastomers. Looking towards future prospects, they also hold potential to evolve into sustainable covalent adaptable networks (CANs). Typically, transesterification-based CANs require catalysts to achieve crosslinked structures that are reprocessable at relatively high temperatures (T ≥ 150 °C). In this study, epoxidized soybean oil (ESBO) was cross-linked with a eutectic hardener composed of L-tartaric acid (TAR) and ethyl lactate (in an aqueous solution), resulting in the development of a fully bio-based 3D covalent network capable of reprocessing without the need for an exogenous catalyst. In addition, it was demonstrated that the peculiar structure of L-tartaric acid, with –OH groups linked to its backbone, plays a prominent role in the reactivity of the system. These free hydroxyl functions facilitate both the ring-opening of epoxides and transesterification reactions, thus enhancing both curing and covalent exchange kinetics.

Investigation into the role of carboxylic acid and phenolic hydroxyl groups in the plant biostimulant activity of a humic acid purified from an oxidized sub-bituminous coal.

Humic substances (HS) are increasingly being applied as crop plant biostimulants because they have been shown to increase plant productivity, especially under environmentally stressful conditions. There has been intense interest in elucidating the HS molecular structures responsible for eliciting the plant biostimulant response (PBR). The polar and weakly acidic carboxylic (COOH) and phenolic hydroxyl (ArOH) functional groups play major roles in the acid nature, pH dependent solubilities, conformation, and metal- and salt-binding capabilities of HS. Reports on the role played by these groups in the PBR of HS found growth parameters being both positively and negatively correlated with COOH and ArOH functionalities. To investigate the role of COOH and ArOH in HS biostimulant activity we used a humic acid (HA), purified from an oxidized sub bituminous coal to prepare HAs with COOH groups methylated (AHA), ArOH groups acetylated (OHA), and with both COOH and ArOH groups methylated (FHA). The original HA was designated (NHA). The four HAs were subjected to elemental, 13C-NMR, FTIR, and EPR analyses and their antioxidant properties were assessed using the trolox equivalents antioxidant capacity assay (TEAC). 13C-NMR and FTIR analysis revealed significant alkylation/acetylation. To determine the effects of alkylating/acetylating these functional groups on the HA elicited PBR, the HAs were evaluated in a plant bioassay on corn (Zea mays L.) seedling under nutrient and non-nutrient stressed conditions. Treatments consisted of the four HAs applied to the soil surface at a concentration of 80 mg C L-1, in 50 ml DI H2O with the control plants receiving 50ml DI H2O. The HA-treated plants, at both fertilization rates, were almost always significantly larger than their respective control plants. However, the differences produced under nutrient stress were always much greater than those produced under nutrient sufficiency, supporting previous reports that HA can reduce the effects of stress on plant growth. In addition, for the most part, the HAs with the alkylated/acetylated groups produced plants equal to or larger than plants treated with NHA. These results suggests that COOH and ArOH groups play a limited or no role in the HA elicited PBR. Alternatively, the HA pro-oxidant to antioxidant ratio may play a role in the magnitude of the biostimulant response.

Access to Enantioenriched Allylic Alcohols via Peptide‐Mimic Phosphonium Salt‐Catalyzed Asymmetric Aerobic Hydroxylation

Comprehensive SummaryThe development of catalytic asymmetric methods that enable access to value‐added functionalities or structures, exemplified by allylic alcohols, is a highly interesting yet challenging topic from both academic and industrial perspectives. However, before recent advances in chemical catalysis, there were scarce protocols toward constructing enantioenriched tertiary allylic alcohol scaffolds. In this context, peptide‐mimic phosphonium salts were found to be highly efficient in catalytic asymmetric α‐hydroxylation of α,β‐unsaturated and/or β,ϒ‐unsaturated compounds with satisfactory regio‐ and stereochemical outcomes (up to 97% yield and 95% ee). This methodology tolerates a broad array of substrates and thus provides an expeditious and unified platform for the assembly of enantioenriched tertiary allylic alcohols by avoiding the use of additional reductants and expensive metal catalysts. Furthermore, the power of this protocol is enlarged by simple conditions and the use of air as a source of hydroxyl functionality.

Efficiency and mechanism of enhanced norfloxacin removal using amorphous TiO2-modified biochar

Inadequate treatment of antibiotic-contaminated wastewater, including compounds such as norfloxacin (NOR), poses a substantial treat to both ecological safety and human well-being. An innovative approach was devised to address NOR pollution using amorphous TiO2 modified biochar (A-TiO2/BC) prepared via sol-gel impregnation. The resultant had a commendably specific surface area of 131.8 m2/g−1, which was 1.91 times more than the original surface area of unmodified BC. A-TiO2/BC also exhibited abundant hydroxyl and oxygen-containing functional groups, thereby provided adequately active sites for NOR adsorption. R2 values obtained from NOR isotherm adsorption models descended in order of Freundlich < Temkin < Sips < Langmuir, which indicated that the NOR removal by A-TiO2/BC mainly complied with monolayer adsorption accompanied by heterogeneous surface adsorption. Under weakly acidic conditions, NOR adsorption benefits from the synergistic physicochemical interactions of A-TiO2 and BC. Notably, A-TiO2/BC demonstrated an impressive NOR adsorption capacity of up to 78.14 mg g−1, with a dosage of 20 mg L−1 at 25 °C under pH 6. Such A-TiO2 modified biochar thus presents a promising alternative for NOR removal.

The Resource Utilization of Poplar Leaves for CO2 Adsorption.

Every late autumn, fluttering poplar leaves scatter throughout the campus and city streets. In this work, poplar leaves were used as the raw material, while H3PO4 and KOH were used as activators and urea was used as the nitrogen source to prepare biomass based-activated carbons (ACs) to capture CO2. The pore structures, functional groups and morphology, and desorption performance of the prepared ACs were characterized; the CO2 adsorption, regeneration, and kinetics were also evaluated. The results showed that H3PO4 and urea obviously promoted the development of pore structures and pyrrole nitrogen (N-5), while KOH and urea were more conductive to the formation of hydroxyl (-OH) and ether (C-O) functional groups. At optimal operating conditions, the CO2 adsorption capacity of H3PO4- and KOH-activated poplar leaves after urea treatment reached 4.07 and 3.85 mmol/g, respectively, at room temperature; both showed stable regenerative behaviour after ten adsorption-desorption cycles.

Combination Mechanism of Soil Dissolved Organic Matter and Cu2+ in Vegetable Fields, Forests and Dry Farmland in Lujiang County

Dissolved organic matter (DOM) serves as a critical link in the migration and transformation of heavy metals at the soil–solid interface, influencing the migration behaviour and transformation processes of Cu2+ in soil. There have been studies on the combination mechanisms between DOM and Cu2+ in paddy soils. However, the adsorption/complexation and redox processes between DOM and Cu2+ in other agricultural soil types (such as dry farmland and vegetable fields) are unclear. In order to reveal the combination process of DOM with Cu in different agricultural soil types and the dynamic changes in chemical behaviour that occur, this study analysed the variability of DOM components and structure in three soils using three-dimensional fluorescence spectroscopy and X-ray photoelectron spectroscopy. In addition, the priority order of different DOM compounds in combination with Cu and the change process in relation to the Cu valence state in the soil of Lujiang County, Anhui Province, was revealed based on laboratory experiments. The results showed that the composition of soil DOM was mainly composed of humic-like and fulvic-like substances with a clear terrestrial origin and that the organic matter showed a high degree of decomposition characteristics. The results indicated that the composition of soil DOM is mainly composed of humic and fulvic acid-like substances, and they have obvious characteristics of terrestrial origin. In addition, the soil organic matter showed high decomposition characteristics. The complex stability constants (lgKM) of humic acid-like substances with Cu2+ follow the order of forest land (lgKM = 5.21), vegetable land (lgKM = 4.90), and dry farmland (lgKM = 4.88). The lgKM of fulvic acid-like substances with Cu2+ is in the order of dry farmland (lgKM = 4.51) and vegetable land (lgKM = 4.39). Humic acid-like substances in soil DOM combine preferentially with Cu2+, showing a stronger chelating affinity than fulvic acid-like substances. Cu2+ complexes mainly include hydroxyl, phenolic hydroxyl and amino functional groups are included in soil DOM, accompanied by redox reactions. In comparison to dry farmland, the soil DOM in forest and vegetable fields undergoes more intense redox reactions simultaneously with the chelation of Cu2+. Therefore, the application of organic fertilisers to vegetable and forest soils may lead to uncertainties concerning the fate of heavy metals with variable chemical valence. These results contribute to a deeper understanding of the interaction mechanisms between DOM and Cu2+ in agricultural soils.

Regulation of Ethanol on Ferrous Oxalate Particle Size and Properties: Theoretical and Experimental Study

AbstractSurfactants containing hydroxyl functional groups have a significant influence on the morphology of ferrous oxalate dihydrate. However, few studies have provided a theoretical explanation for this effect. In this investigation, the size of ferrous oxalate dihydrate was reduced from micron to nanometer scale using anhydrous ethanol, and its mechanism was elucidated through density functional theory calculations. The calculational results reveal that anhydrous ethanol molecules bound to the ferrous oxalate dihydrate crystal via hydrogen bonding and van der Waals forces, thereby controlling crystal growth. It means that anhydrous ethanol molecules preferentially affected the interlayer interaction in the structure of ferrous oxalate dihydrate, leading to a significant impact on its overall crystal growth way. Furthermore, the electrochemical properties of ferrous oxalate dihydrate synthesized in aqueous and anhydrous ethanol systems were compared and tested. The specific capacitance (242 F ⋅ g−1 at 0.5 A ⋅ g−1 current density) of ferrous oxalate dihydrate synthesized in anhydrous ethanol system is obvious higher than that of ferrous oxalate dihydrate synthesized in water system (186 F ⋅ g−1), due to its smaller particle size (75 nm). Furthermore, the specific capacitance of this material can be improved to 469 F ⋅ g−1 during composite process of ferrous oxalate dihydrate with graphene oxide.

Investigation of pyruvic acid photolysis at the air-liquid interface as a source of aqueous secondary organic aerosols

Pyruvic acid (PA) is a ubiquitous 2-oxocarboxylic acid in the atmosphere. Its photochemical process at the air-liquid (a-l) interface has been suggested as an important source of aqueous secondary organic aerosols. We investigated the photochemical reaction pathways of PA at the a-l interface using synchrotron-based vacuum ultraviolet single-photon ionization mass spectrometry (VUV SPI-MS) coupled with the System for Analysis at the Liquid Vacuum Interface (SALVI) microreactor. Results from mass spectral analysis and the determination of appearance energies (AEs) indicate that photolysis of PA can generate radicals, then they recombine with carboxylic acids and simple molecular oligomers. Furthermore, the preliminary products could form larger oligomers via radical reaction or esterification in the presence of hydroxyl and carboxyl functional groups. Mass spectral comparison shows that most photochemical reactions would complete within 4 h. The expanded photochemistry-driven reaction flowchart of PA is proposed based on the newly discovered products. Our results reveal that the interfacial PA photochemical reactions have different mechanisms from the bulk liquid due to the interfacial properties, such as molecular density, composition, and ion concentration. Our findings show that in situ mass spectral analysis with bright photon ionization is useful to elucidate the contribution of a-l interfacial reactions leading to aqSOA formation.

Unraveling Ammonia and Trimethylamine Uptake on Conductive Doped Polyaniline.

Polyaniline (PAni)-based sensors are a promising solution for ammonia (NH3) detection at the ppb level. However, the nature of the NH3-PAni interaction and underlying drivers remain unclear. This paper proposes to characterize the interaction between doped PAni (dPAni) sensing material and NH3 by using a Knudsen cell. First, to characterize the dPAni interface, the probe-gas method, i.e., titration of surface sites with a gas of specific properties, is deployed. The dPAni interface is found to be homogeneous with more than 96% of surface sites of acid nature or with hydroxyl functional groups. This result highlights that basic gases such as amines might act as interfering gases for NH3 detection by polyaniline-based sensors. Second, the adsorption isotherms of NH3 and trimethylamine (TMA) on dPAni are reported at ambient temperature conditions, 293 K. The uptake of NH3 and TMA on dPAni follows a Langmuir-type behavior. This approach allows for the first time to quantify the uptake of NH3 and TMA on gas-sensor materials and determine typical Langmuir adsorption parameters, i.e., the partitioning coefficient, KLang, and the maximum surface coverage, Nmax. The corresponding values obtained for NH3 and TMA are Klang (NH3) = 19.7 × 10-15 cm3 molecules-1 Nmax (NH3) = 11.6 × 1014 molecules cm-2, KLang (TMA) = 7.0 × 10-15 cm3 molecules-1 Nmax (TMA) = 5.0 × 1014 molecules cm-2. KLang and Nmax values of NH3 are higher than those of TMA, suggesting that NH3 is more efficiently taken up than TMA on dPAni. The results of this work suggest that strong hydrogen bonding drives the performance of a polyaniline-based gas sensor for NH3 and amines. In conclusion, the Knudsen cell approach allows reconsidering the fundamentals of NH3 interactions with dPAni and provides new insights on drivers to enhance sensing properties.

Multiscale modeling of CO2 capture in dicationic ionic liquids: Evaluating the influence of hydroxyl groups using DFT-IR, COSMO-RS, and MD simulation methods.

This work employs a combination of density functional theory-infrared (IR), conductor-like screening model for real solvents (COSMO-RS), and molecular dynamic (MD) methods to investigate the impact of hydroxyl functional groups on CO2 capture within dicationic ionic liquids (DILs). The COSMO-RS reveals that hydroxyl groups in DILs reduce the macroscopic solubility of CO2 but improve the selectivity of CO2 over CO, H2, and CH4 gases. Quantum methods in the gas phase and MD simulations in the liquid phase were conducted to delve deeper into the underlying mechanisms. The IR spectrum analysis confirms red shifts in CO2's asymmetric stretching mode and blue shifts in the CR-HR bond of the dication, indicating CO2-DIL interactions and the weakening of the anion-cation interactions caused by the presence of CO2. The results show that the positioning of anions around hydroxyl groups and HR atoms in rings inhibits the proximity of CO2 molecules, causing the hydrogen atoms within methylene groups to accumulate CO2. van der Waals forces were found to dominate the interaction between ions and CO2. The addition of hydroxyl groups strengthens the electrostatic interactions and hydrogen bonds between dications and anions. The stronger interaction energy between ions in [C5(mim)2-(C2)2(OH)2][NTf2]2 limits the displacement of CO2 molecules within this DIL compared to [C5(mim)2-(C4)2][NTf2]2. Compared to [C5(mim)2-(C4)2][NTf2]2, [C5(mim)2-(C2)2(OH)2][NTf2]2 exhibits stronger ion-ion interactions, higher density, and reduced free volume, resulting in a reduction in CO2 capture. These results provide significant insights into the intermolecular interactions and vibrational properties of CO2 in DIL complexes, emphasizing their significance in developing efficient and sustainable strategies for CO2 capture.

Arsenate Adsorption from Aqueous Solutions Using Chitosan/Fe‐Nanoparticles Composite Microspheres

AbstractThe adsorption behavior and synthesis of a chitosan microsphere composite with iron nanoparticles (Ch‐Fe) for the removal of arsenates [As(V)] from aqueous solutions were investigated. First, the chitosan microspheres (Ch‐SD) were obtained using the Spray Dryer volatilization technique (SD), optimizing their particle size. Then, the iron nanoparticles (Fe‐NPs) were prepared using the microwave precipitation technique. The composite was characterized, and the arsenate adsorption parameters were determined through batch‐type experiments. Significantly fast adsorption rates were observed for both adsorbents. Besides, Ch‐Fe and Ch‐SD effectively removed arsenates over a wide pH range. The hydroxyl and amino functional groups are involved in removing arsenates. The Pseudo‐second order and the Elovich models described arsenate kinetic sorption data for Ch‐Fe and Ch‐SD, respectively. The As(V) maximum adsorption capacities were 27.46 mg/g and 29.94 mg/g for Ch‐SD and Ch‐Fe, respectively, increasing significantly at elevated temperatures. The Langmuir‐Freundlich model adequately described the isothermal data for both materials, suggesting adsorption heterogeneity. The composite's surface impregnation with Fe‐NPs enhanced the Ch‐SD adsorption properties. The SD method was suitable for obtaining the chitosan/Fe‐NPs microspheres and effectively removed As(V) from aqueous solutions.

Multimode sensing and imaging platform for versatile detection of GSH based on surface modification strategy of Ru(bpy)32+ doped SiO2 nanoparticles

A multimode sensing and imaging platform based on surface modification strategy of Ru(bpy)32+ doped SiO2 nanoparticles (RuSiO2 NPs) was constructed for versatile detection of glutathione (GSH). RuSiO2 NPs as the luminophore models had outstanding fluorescence (FL) and electrochemiluminescence (ECL) signals. Furthermore, its FL signal could be captured by electrophoresis analyzer, and the ECL signal could be imaged with mobile phone to achieve visualization. So, a unique and convenient multi-mode sensing and imaging platform could be developed based on RuSiO2 NPs. SiO2 NPs could realize enrichment of Ru(bpy)32+ based on the nanoconfined effect to achieve signal amplification, and its surface was rich with abundant hydroxyl functional groups, which offered a channel for surface modification. Sulfhydryl modification on the RuSiO2 NPs was realized by using silane coupling agent, and KMnO4 was used to in situ generate MnO2 shell on the surface of RuSiO2 NPs for quenching its ECL, FL, and colorimetric (CL) signals based on resonance energy transfer (RET). Target GSH could reduce MnO2 shell to realize recovery of all signals, thus achieving the label-free multimode detection of GSH. Therefore, this work developed a multimode sensing and imaging platform without signal labels or layer-by-layer assembly of electrodes, which had the advantages of simple steps, low cost, and high detection accuracy, showing important application potential in the field of bioanalysis.

Hymenaea courbaril resin-mediated gold nanoparticles as catalysts in organic dyes degradation and sensors in pharmaceutical pollutants

In this study, green synthesis of gold nanoparticles (AuNPs) using aqueous extract from Hymenaea courbaril resin (HCR) is reported. The successful formation, functional group involvement, size, and morphology of the subject H. courbaril resin mediated gold nanoparticles (HCRAuNPs) were confirmed by Ultra Violet-Visible (UV–vis) spectroscopy, Fourier-Transform Infrared spectroscopy (FTIR), and Transmission Electron Microscopy (TEM) techniques. Stable and high yield of HCRAuNPs was formed in 1:15 (aqueous solution: salt solution) reacted in sunlight as indicated by the visual colour change and appearance of surface Plasmon resonance (SPR) at 560 nm. From the FT-IR results, the phenolic hydroxyl (–OH) functional group was found to be involved in synthesis and stabilization of nanoparticles. The TEM analysis showed that the particles are highly dispersed and spherical in shape with average size of 17.5 nm. The synthesized HCRAuNPs showed significant degradation potential against organic dyes, including methylene blue (MB, 85 %), methyl orange (MO, 90 %), congo red (CR, 83 %), and para nitrophenol (PNP, 76 %) up to 180 min. The nanoparticles also demonstrated the effective detection of pharmaceutical pollutants, including amoxicillin, levofloxacin, and azithromycin in aqueous environment as observable changes in color and UV–Vis spectral graph.

Construction of coal pitch-based HA-K grafted poly condensates and their excellent anti-temperature and viscosity-reducing properties

Humic acids (HAs) are widely used as filtrate and viscosity reducers in drilling fluids. However, their practical utility is limited due to poor stability in salt resistance and high-temperature resistance. High-temperature coal pitch (CP) is a by-product from coal pyrolysis above 650 °C. The substance's molecular structure is characterized by a dense arrangement of aromatic hydrocarbon and alkyl substituents. This unique structure gives it unique chemical properties and excellent drilling performance, surpassing traditional humic acids in drilling operations. Potassium humate is prepared from CP (CP-HA-K) by thermal catalysis. A new type of high-quality humic acid temperature-resistant viscosity-reducer (Graft CP-HA-K polymer) is synthesized with CP-HA-K, hydrolyzed polyacrylonitrile sodium salt (Na-HPAN), urea, formaldehyde, phenol and acrylamide (AAM) as raw materials. The experimental results demonstrate that the most favorable conditions for the catalytic preparation of CP-HA-K are 1 wt% catalyst dosage, 30 wt% KOH dosage, a reaction temperature of 250 °C, and a reaction time of 2 h, resulting in a maximum yield of CP-HA-K of 39.58%. The temperature resistance of the Graft CP-HA-K polymer is measured to be 177.39 °C, which is 55.39 °C higher than that of commercial HA-K. This is due to the abundant presence of amide, hydroxyl, and amine functional groups in the Graft CP-HA-K polymer, which increase the length of the carbon chains, enhance the electrostatic repulsion on the surface of solid particles. After being aged to 120 °C for a specified duration, the Graft CP-HA-K polymer demonstrates significantly higher viscosity reduction (42.12%) compared to commercial HA-K (C-HA-K). Furthermore, the Graft CP-HA-K polymer can tolerate a high salt concentration of 8000 mg·L−1, measured after the addition of optimum amount of 3 wt% Graft CP-HA-K polymer. The action mechanism of Graft CP-HA-K polymer on high-temperature drilling fluid is that the Graft CP-HA-K polymer can increase the repulsive force between solid particles and disrupt bentonite's reticulation structure. Overall, this research provides novelty insights into the synthesis of artificial humic acid materials and the development of temperature-resistant viscosity reducers, offering a new avenue for the utilization of CP resources.

Physicochemical Analysis of Biofilms from Cocos nucifera Linn. (Coconut) Flour and Manihot esculenta Crantz (Cassava) Starch with Polyvinyl Alcohol (PVA)

The province of Northern Samar, its municipalities including Pambujan, is a place abundant of Manihot esculenta Crantz (cassava), and Cocos nucifera Linn. (coconut). However, its industry is mainly limited to food production. This study developed biofilms from cassava starch (CasS), and coconut flour (CoF) with polyvinyl alcohol (PVA). The physicochemical properties were analyzed to determine their pH, solubility, moisture content, and tensile strength. Functional groups were investigated using FTIR, and the antibacterial properties were evaluated. The results showed that both biofilms with PVA were weakly acidic and insoluble in all solvents. Meanwhile, CoF biofilm contained higher moisture content than the CasS biofilm. CoF biofilms also carried more weight and higher force than CasS biofilm. Hydroxyl, alkyl, and alkene functional groups were identified for both biofilms. Meanwhile, both biofilms showed no inhibitory effect against E. coli, and S. aureus. Therefore, the developed biofilms with PVA showed good physicochemical properties and can be used for packaging applications. The slight acidity can prolong their shelf-life. Moreover, both will not easily dissolve. CoF biofilm comprised more water than CasS but both are still suitable for packaging due to their tensile strength attributed to the presence of the functional groups. However, CasS, CoF, and PVA do not have antibacterial properties. More physicochemical tests, further characterization, and incorporation of antibacterial agents were recommended.

Evolution of oxygen-containing functional groups on coal char surface during gasification in H2O/CO2

Gasification converts coal into syngas (CO and H2) for downstream utilization. The most important reaction in an autothermal gasifier is the char−H2O/CO2 reaction. The evolution of C(O) complexes on the coal char surface directly determines the pathways and rates of CO and H2 generation. This study mainly used a fixed bed reactor to prepare Zhundong coal char with different reaction levels in H2O and CO2, and its surface carboxyl, lactone, phenolic hydroxyl, and hydroxyl functional groups were systematically analyzed by using Boehm titration, FT-IR, and XPS. The results show that the contents of the four oxygen-containing groups in raw coal are in the order of carboxyl＞lactone＞phenol hydroxyl＞hydroxyl. In H2O gasification, the lactone groups were more susceptible to H2O resulting in a significant increase in carboxyl content at the early stage of the reaction. The hydroxyl, as a very active group in the reaction, and the amount of its generation and consumption was very obvious. The phenolic hydroxyl−the least thermally stable group among these four types of groups, was unable to participate in the inter-transformation between oxygen-containing functional groups during the gasification. During CO2 gasification, the hydroxyl was rapidly consumed at the initial stage of the reaction and then shown a slow growth trend, and the newly generated hydroxyl would continue to undergo dehydrogenation to form new functional groups. At the end of the reaction, the transformation of other oxygen-containing functional groups into more stable carbonyl groups leads to a sudden increase in the content of carboxyl and lactone. In this work, Boehm titration was introduced into the determination of oxygen-containing functional groups on the surface of char during gasification in H2O/CO2.

The in-situ excitation on internal electrode of DBD-OES system for cadmium sensitive detection

The utilization of microplasma excitation sources in miniature systems offers reliable tools for the portable detection of heavy metal contamination. Dielectric barrier discharge (DBD)-based optical emission spectrometry has emerged as a significant technique for the detection of metal ions recently. Here, a sensitive miniature DBD-OES system for cadmium enrichment and detection is developed. A piece of ceramic tube with abundant hydroxyl (-OH) and alumina (AlO) functional groups is used for cadmium pre-concentration and serve as a part of the internal electrode of the DBD. When microplasma generates, the cadmium on the surface of the internal electrodes is desorbed and in-situ excited, and the characteristic emission line of cadmium appears. The mechanism of cadmium excitation on ceramic tube, the characteristics of the microplasma excitation and the enrichment on the internal electrode are discussed. Under the working conditions, the emission intensity of cadmium shows linear relationship within the range of 0.5–8 μg L−1, and the limit of detection (LOD) is 0.3 μg L−1. Finally, a series of water samples are determined to validate the applicability of the present system.