Chemical Adsorption Research Articles

Heavy metals remediation through alkali assisted ball-milling activation of copper smelting slag for resource utilization

This study describes the preparation of Silico-Calcium-adhesive (CS-SS) by alkali-assisted ball milling to activate copper smelting slag (CS) for the remediation of heavy metals contamination and consequent resource utilization. The adsorption behavior and mechanisms of Cd(II), Cu(II) and Pb(II) in mono-metallic and polymetallic coexisting systems were investigated. The adsorption capacities of CS-SS were 21.906mg/g, 30.893mg/g and 93.593mg/g for Cd(II), Cu(II) and Pb(II) at a pH of 6, respectively. Based on the experimental results of monometallic system indicated that CS-SS exhibited the highest adsorption capacity for Pb(II), followed by Cu(II) and Cd(II). In the polymetallic system, the inhibitory impact of Pb(II) was more potent compared to Cd(II) and Cu(II). The adsorption mechanisms included electrostatic attraction, chemical adsorption, physical adsorption, ion exchange, functional group complexation and surface precipitation. Simple economic estimates show that it costs about $4.72 to treat 1 m3 of Cd(II)-20 mg/L, Cu(II)-30 mg/L and Pb(II)-90 mg/L containing wastewater. Therefore, the CS treatment method proposed in this study has certain feasibility and economic applicability.

Recycling crayfish shell and waste activated sludge as biochar to in-situ enhance antibiotics removal from wastewater: Linking structure properties and reaction kinetics

Aquaculture water represents a substantial source of antibiotics in the environment, thereby implicating potential hazards to human health and ecological stability. Additionally, the cultivation of crayfish in such water exacerbates concerns regarding the management of shell waste. In this investigation, crayfish shells and waste activated sludge were repurposed as biochar for the in-situ mitigation of antibiotics elimination from aquaculture wastewater. Compared to crayfish biochar (C-BC) solely from crayfish shell, crayfish sludge biochar (CS-BC) significantly enhances the adsorption of typical antibiotics like tetracycline and ciprofloxacin by 50.3–77.1 %. Findings from kinetic and isotherm experiments suggest that antibiotics adsorption mainly involves physical pore filling, but sludge introduction shifts CS-BC towards chemical adsorption. Further analysis reveals that sludge introduction reduces biochar pore size, boosts specific surface area, and offers more active adsorption sites. Additionally, hydrogen bonding on hydroxyl groups and increased oxygen-containing functional groups enhanced antibiotic adsorption onto CS-BC surfaces. This research presents a promising strategy for addressing antibiotic pollution in aquatic environments while also improving the utilization of organic solid waste resources.

Flotation activation mechanism of trithiocyanuric acid to malachite

Malachite is a typical refractory copper oxide mineral. In this paper, trithiocyanuric acid (TMT) was used as a novel activator for the activated flotation of malachite for the first time. The effect of TMT on the flotation behavior of malachite was studied and the activation mechanism was discussed. The flotation test results showed that TMT exhibited superior activation performance over sodium sulfide, achieving a high flotation recovery rate of 97.50 % at TMT 90 mg/L and pH 7. The contact angle confirmed malachite improved from 53.3° to 90.1° after TMT treatment, indicating enhanced hydrophobicity of the mineral surface. FTIR and EDS analyses provided clear evidence of chemical adsorption of TMT tautomers onto the malachite surface. SEM images further illustrated the presence of dense particles formed after TMT treatment. XPS revealed that TMT exhibited a strong adsorption effect on malachite, leading to an increase in copper sites and the formation of highly reactive Cu+. The activation mechanism was elucidated as the reaction between Cu sites on malachite and S and N atoms in TMT, forming Cu-S and Cu–N fractions crucial for activation. The high efficiency and low dosage of TMT make it a promising activator for malachite, offering a novel avenue for the effective recovery of malachite-type copper oxide ore resources.

Hierarchical Co-doped hollow Ti3C2Tx tubes with built-in electron/ion transport network for high-performance lithium sulfur batteries

A crucial approach to enhancing the electrochemical performance of lithium-sulfur batteries (LSBs) is to develop a dependable sulfur host material possessing reasonable structure, high electrical conductivity, and exceptional adsorption/catalytic capabilities towards lithium polysulfides (LiPSs). Herein, Co-doped hollow Ti3C2Tx tubes with in-situ grown CNTs as a built-in electron/ion transport network (HTCTs/Co/CNTs) are prepared via electrospinning technique combined with the self-catalyzed growth strategy. The unique hierarchical porous structure of HTCTs/Co/CNTs not only increases the sulfur loading and alleviates the volume expansion, but also effectively suppresses the shuttling effect of LiPSs through the synergism between physical confinement and chemical adsorption. It is revealed that the combination of Ti3C2Tx MXene and metallic Co enhances the LiPSs absorbability and accelerates the catalytic conversion of sulfur species, thereby improving sulfur utilization and electrochemical reversibility. The corresponding cells with HTCTs/Co/CNTs/S cathode retain high capacities of 901.9 mAh g−1 after 100 cycles at 0.2 C and 725.9 mAh g−1 after 500 cycles at 1.0 C. More importantly, a high areal capacity of 4.83 mAh cm−2 is achieved under a high sulfur loading of 5.8 mg cm−2 and a low E/S ratio of 4.3 µL mg−1 after 50 cycles at 0.1 C.

Pretreatment of wastepaper with an aqueous solution of amino acid-derived ionic liquid for biochar production as adsorbent.

The carbonization of lignocellulosic biomass with ionic liquids (ILs) are considered as an advantageous approach for the preparation of carbonaceous materials. The commonly used imidazolium and pyridinium based ILs have drawbacks such as toxicity, resistance to biodegradation, high cost and viscosity. These issues can be mitigated by diluting ILs with water, although excessive water content above 1wt% can reduce the solubility of biomass. This research aims to investigate the potential of pretreating wastepaper with a "fully green" ILs, amino acid-based IL with high water content, followed by pyrolysis without IL, in enhancing the properties of biochar. For this purpose, the paper was treated with an aqueous solution of IL cysteine nitrate ([Cys][NO3]), and the IL was not involved in the pyrolysis process to prevent the formation of secondary gaseous pollutants. The findings revealed that the hemicellulose and mineral filler in the paper were eliminated during pretreatment, leading to higher carbon content but lower oxygen content. As a result, the biochar exhibited micropores of 0.42 cm3g-1 and a specific surface area of 1011.21m2g-1. The biochar demonstrated high adsorption capacities for Cd2+, enrofloxacin, bisphenol A, ciprofloxacin, and tetracycline, with values of 45.20mgg-1, 49.82mgg-1, 49.90mgg-1, 49.88mgg-1, and 49.65mgg-1, respectively. The proposed mechanism for the adsorption of enrofloxacin by the biochar primarily involves physical adsorption such as pore filling and electrostatic interactions, along with chemical adsorption facilitated by graphitic nitrogen.

Artificial neural network-based modeling of Malachite green adsorption onto baru fruit endocarp: insights into equilibrium, kinetic, and thermodynamic behavior

In this study, artificial neural network (ANN) tools were employed to forecast the adsorption capacity of Malachite green (MG) by baru fruit endocarp waste (B@FE) under diverse conditions, including pH, adsorbent dosage, initial dye concentration, contact time, and temperature. Enhanced adsorption efficiency was notably observed under alkaline pH conditions (pH 10). Kinetic analysis indicated that the adsorption process closely followed a pseudo-second-order model, while equilibrium studies revealed the Langmuir isotherm as the most suitable model, estimating a maximum adsorption capacity of 57.85 mg g−1. Furthermore, the chemical adsorption of MG by B@FE was confirmed using the Dubinin–Radushkevich isotherm. Thermodynamic analysis suggested that the adsorption is spontaneous and endothermic. Various ANN architectures were explored, employing different activation functions such as identity, logistic, tanh, and exponential. Based on evaluation metrics like the coefficient of determination (R 2) and root mean square error (RMSE), the optimal network configuration was identified as a 5–11-1 architecture, consisting of five input neurons, eleven hidden neurons, and one output neuron. Notably, the logistic activation function was applied in both the hidden and output layers for this configuration. This study highlights the efficacy of B@FE as an efficient adsorbent for MG removal from aqueous solutions and demonstrates the potential of ANN models in predicting adsorption behavior across varying environmental conditions, emphasizing their utility in this field.

Preparation of MOR/P(S‐co‐VPh) nanofiber composite membrane and its adsorption properties for rubidium ions

AbstractRubidium (Rb), a rare and precious metal, is widely used in high‐tech fields. In this work the structural advantages of mordenite (MOR) and group affinity of phenolic hydroxyl polymers (poly (styrene‐4‐hydroxystyrene) (P(S‐co‐VPh)) are combined to prepare MOR/P(S‐co‐VPh) nanofiber composite membranes with high selectivity and adsorption specificity for Rb+ by electrospinning. The test results show that MOR is successfully anchored on the nanofiber substrate and maintained its complete crystal structure. Adsorption experiments show that the adsorption capacity of Rb+ increases with the increase of MOR content, and pH = 9.0, T = 25°C are the best adsorption conditions. K+ shows the most obvious interference with the adsorption capacity decreased from 60.03 to 39.33 mg/g. The adsorption process follows with the Langmuir isothermal model and pseudo‐second‐order kinetic equation. The chemical adsorption based on the coordination reaction is the control step, and the intraparticle diffusion also has an important effect on the adsorption rate. The recycling test indicates that the prepared nanofiber composite membrane not only has efficient adsorption of Rb+, but also exhibits excellent regeneration and stability, which helps to achieve its widespread application and long‐term operation in harsh environments.

Oil Spill: Their Impact, Recovery and future prevention

An oil spill is the release of a liquid petroleum hydrocarbon into the environment especially marine areas due to human activity. Oil is the most common pollutant in the oceans. Oil spill have a devastating and long-term impact on water ways and coastal areas around the world. Oil spill can be partially controlled by chemical dispersion, combustion, mechanical containment and adsorption. These days there are so many import and export business are going in the world. Because of expansion of business and shipping by seas in the cheapest mode it’s used on large scale due to huge cargo shipping these are so many cases of oil spill in the sea. World has witnessed big oil spill accidents into the oceans and made huge impact on the industries as well as the ecosystem. Due to these oil spills there were so many deaths if sea mammals and bird species. After oil spills creates a slick (a thick layer of oil) that ensure the sunlight and oxygen pass through water. It affects the life below the water due to lack of oxygen and sunlight. As some of the oil are dangerous and poisonous they are quite harmful for human too when it comes to physical contact with them. This paper deals with the separation of oil and water to find out the better solution for oil recovery from the water surface mixture empress oil spill to produce oil free water. There are different methods to remove the oil form the water but disc type oil skimmer is mostly used and efficient. The oil skimmer is used to separate oil, from mixture of aqua and oil. It causes highly acidic alkaline and salty environment remains a great challenge to aquatic organisms and also pollute the coastal area. Every year 706 million gallons of waste oil enter the water resources and pollute the environment. Sea water has been polluted due to oil spillage, it also affects the water bodies. It the oil spill increase it result in serious damage to environment. About 90% of contaminated oil can be removed by continuous separation of oil by skimmer.

Simulation model of carbon capture with MEA and the effect of temperature and duty on efficiency

Humans continue to rely on fossil fuels to generate electricity. In other words, fossil fuels are the world's largest energy producers. Fossil fuels produce significant carbon dioxide, mostly in areas where humans live. Although the share of carbon dioxide produced in big cities is minimal compared to the carbon dioxide production of volcanoes, the production of carbon dioxide in big cities has destructive effects. Process Simulator is utilized to evaluate the effectiveness of their simulation model by subjecting it to various experimental conditions, including liquid loading, temperature, and CO2 absorption (PPS). Comparing empirical and simulated mass transfer coefficients distinguishes this study from others. This procedure consists of two steps: Carbon dioxide (CO2) absorption in a solvent produces highly concentrated CO2 gas following solvent regeneration. A chemical adsorption process's scalability depends on accurate simulation models, typically validated using data from a pilot plant. With the aid of this study, a simulation model of a desorption column is constructed with ASPEN PLUS and 42% MEA validated. In addition, the effect of the weight percentage of 20-42 MEA in the inlet stream on the efficiency is investigated, and the influence of the MEA inlet temperature on system efficiency is examined. Then, the recommended temperature is confirmed based on the MEA's heat tolerance capacity of 303 Kelvin.

Isomeric Porous Cu(I) Triazolate Frameworks Showing Periodic and Aperiodic Flexibility for Efficient CO Separation.

Guest-induced (crystal-to-crystal) transformation, i.e., periodic flexibility, is a typical feature of molecule-based crystalline porous materials, but its role for adsorptive separation is controversial. On the other hand, aperiodic flexibility is rarely studied. This work reports a pair of isomeric Cu(I) triazolate frameworks, namely, α-[Cu(fetz)] (MAF-2Fa) and β-[Cu(fetz)] (MAF-2Fb), which show typical periodic and aperiodic flexibility for CO chemical adsorption, respectively. Quantitative mixture breakthrough experiments show that, while MAF-2Fa exhibits high adsorption capacity at high pressures but negligible adsorption below the threshold pressure and with leakage concentrations of 3-8%, MAF-2Fb exhibits relatively low adsorption capacity at high pressures but no leakage (residual CO concentration <1 ppb). Tandem connection of MAF-2Fa and MAF-2Fb can combine their advantages of high CO adsorption capacities at high and low pressures, respectively. MAF-2Fa and MAF-2Fb can both keep the separation performances unchanged at high relative humidities, but only MAF-2Fb shows a unique coadsorption behavior at a relative humidity of 82%, which can be used to improve purification performances.

Unlocking the potential of biochar: an iron-phosphorus-based composite modified adsorbent for adsorption of Pb(II) and Cd(II) in aqueous environments and response surface optimization of adsorption conditions.

In this work, iron-phosphorus based composite biochar (FPBC) was prepared by modification with potassium phosphate and iron oxides for the removal of heavy metal ions from single and mixed heavy metal (Pb and Cd) solutions. FTIR and XPS characterization experiments showed that the novel modified biochar had a greater number of surface functional groups compared to the pristine biochar. The maximum adsorption capacities of FPBC for Pb(II) and Cd(II) were 211.66mg·g-1 and 94.08mg·g-1 at 293K. The adsorption of Pb(II) and Cd(II) by FPBC followed the proposed two-step adsorption kinetic model and the Freundlich isothermal adsorption model, suggesting that the mechanism of adsorption of Pb(II) and Cd(II) by FPBC involved chemical adsorption of multiple layers. Mechanistic studies showed that the introduction of -PO4 and -PO3 chemisorbed with Pb(II) and Cd(II), and the introduction of -Fe-O increased the ion exchange with Pb(II) and Cd(II) during the adsorption process and produced precipitates such as Pb3Fe(PO4)3 and Cd5Fe2(P2O7)4. Additionally, the abundant -OH and -COOH groups also participated in the removal of Pb(II) and Cd(II). In addition, FPBC demonstrated strong selective adsorption of Pb(II) in mixed heavy metal solutions. The Response Surface Methodology(RSM) analysis determined the optimal adsorption conditions for FPBC as pH 5.31, temperature 26.01°C, and Pb(II) concentration 306.30mg·L-1 for Pb(II). Similarly, the optimal adsorption conditions for Cd(II) were found to be pH 5.66, temperature 39.34°C, and Cd(II) concentration 267.68mg·L-1. Therefore, FPBC has the potential for application as a composite-modified adsorbent for the adsorption of multiple heavy metal ions.

Simultaneous Removal of Seven Pharmaceutical Compounds from a Water Mixture Using Modified Chitosan Adsorbent Materials

Pharmaceuticals are used to improve the lives of people across the globe. The high demand for their fabrication and use causes a very serious environmental threat since their presence is ubiquitous in aqueous matrices. For this reason, the synthesis, characterisation, and efficiency of three chitosan-based materials to eliminate pharmaceutical mixtures from aqueous solutions were examined in the present study. The target mixture comprised seven widely used drugs: carbamazepine, cyclophosphamide, adefovir, levofloxacin, metronidazole, glibenclamide, and trimethoprim. The grafting of poly(ethylene imine) and poly(acrylamide) on the chitosan structure allowed its physical characteristics to be controlled. An adsorption assessment was performed at different pH values, and it was concluded that pH = 4 was the optimum value. The adsorption kinetics revealed that the adsorption of a drug mixture involves a combination of physical and chemical adsorption. The adsorption process appeared to be finished after 1 h for all compounds of the studied mixture, with CS-AMI exhibiting the fastest kinetics. Mass adsorption experiments were also carried out to determine its effects. Overall, the grafting process significantly increased the adsorption capacity over the pristine material. Specifically, the highest capacity increase for CS-PEI was ~220% for carbamazepine, and for CS-AMI, it was 158% for trimethoprim. FT-IR, SEM, and XRD were used for the characterisation of the polymers. Based on the findings, the three materials are suggested as very effective adsorbents for the elimination of medicine residues from aqueous matrices.

Sulfur vacancy-rich bismuth sulfide nanowire derived from CAU-17 for radioactive iodine capture in complex environments: Performance and intrinsic mechanisms

Effective capture and immobilization of volatile radioiodine from the off-gas of post-treatment plants is crucial for nuclear safety and public health, considering its long half-life, high toxicity, and environmental mobility. Herein, sulfur vacancy-rich Vs-Bi2S3@C nanocomposites were systematically synthesized via a one-step solvothermal vulcanization of CAU-17 precursor. Batch adsorption experiments demonstrated that the as-synthesized materials exhibited superior iodine adsorption capacity (1505.8 mg g−1 at 200 °C), fast equilibrium time (60 min), and high chemisorption ratio (91.7%), which might benefit from the nanowire structure and abundant sulfur vacancies of Bi2S3. Furthermore, Vs-Bi2S3@C composites exhibited excellent iodine capture performance in complex environments (high temperatures, high humidity and radiation exposure). Mechanistic investigations revealed that the I2 capture by fabricated materials primarily involved the chemical adsorption between Bi2S3 and I2 to form BiI3, and the interaction of I2 with electrons provided by sulfur vacancies to form polyiodide anions (I3-). The post-adsorbed iodine samples were successfully immobilized into commercial glass fractions in a stable form (BixOyI), exhibiting a normalized iodine leaching rate of 3.81 × 10−5 g m−2 d−1. Overall, our work offers a novel strategy for the design of adsorbent materials tailed for efficient capture and immobilization of volatile radioiodine.

One-pot synthesis of novel polyvinylphosphonic acid hydrogels for efficient separation of low-enriched uranium in water

Uranium extraction from seawater and the treatment of radioactive wastewater has traditionally been a hot topic. Herein, p(VPA-AM)n solid hydrogels with high uranium extraction properties based on vinylphosphonic acid (VPA) were successfully prepared by one-step copolymerization for the first time. The batch adsorption experiments demonstrated that p(VPA-AM)n has strong uranium chelating ability, fast uranium adsorption kinetics (within 200 min) and high uranium adsorption capacity (644.67 mg/g), and its adsorption behavior conforms to the pseudo-second-order kinetic model and the Langmuir adsorption isotherm model, which is a spontaneous heat-absorbing chemical monolayer adsorption process. After 15 adsorption–desorption tests, the adsorption capacity was kept above 96 % of the original capacity, and the uranium extracted from the salt lake water achieved at 3.56 mg/g, which showed superb behavior in treating complex uranium systems. Mechanism studies revealed that the strong interaction between UO22 + and −PO43- dominated the adsorption and the robust complexation might have led to the electron transfer in the structure. The maximum uranium removal rate of p(VPA-AM)n in simulated seawater reached 90 %, and the simple in situ zinc oxide-modified p(VPA-AM)n hydrogel showed good anti-biosludge properties against three common bacteria (E. coli, B. subtilis and S. aureus), which has a great potential for application in seawater uranium extraction and uranium wastewater treatment.

Mesoporous Electrocatalysts with p-n Heterojunctions for Efficient Electroreduction of CO2 and N2 to Urea.

The electrocatalytic synthesis of high-value-added urea by activating N2 and CO2 is a green synthesis technology that has achieved carbon neutrality. However, the chemical adsorption and C-N coupling ability of N2 and CO2 on the surface of the catalyst are generally poor, greatly limiting the improvement of electrocatalytic activity and selectivity in electrocatalytic urea synthesis. Herein, novel hierarchical mesoporous CeO2/Co3O4 heterostructures are fabricated, and at an ultralow applied voltage of -0.2 V, the urea yield rate reaches 5.81 mmol g-1 h-1, with a corresponding Faraday efficiency of 30.05%. The hierarchical mesoporous material effectively reduces the mass transfer resistance of reactants and intermediates, making it easier for them to access active centers. The emerging space-charge regions at the heterointerface generate local electrophilic and nucleophilic regions, facilitating CO2 targeted adsorption in the electrophilic region and activation to produce *CO intermediates and N2 targeted adsorption in the nucleophilic region and activation to generate *N ═ N* intermediates. Then, the electrons in the σ orbitals of *N ═ N* intermediates can be easily accepted by the empty eg orbitals of Co3+ in CeO2/Co3O4, which presents a low-spin state (LS: t2g6eg0). Subsequently, *CO couples with *N ═ N* to produce the key intermediate *NCON*. Interestingly, it was discovered through in situ Raman spectroscopy that the CeO2/Co3O4 catalyst has a reversible spinel structure before and after the electrocatalytic reaction, which is due to the surface reconstruction of the catalyst during the electrocatalytic reaction process, producing amorphous active cobalt oxides, which is beneficial for improving electrocatalytic activity.

Evaluating nickel removal efficacy of Filtralite under laboratory conditions: Implications for sustainable urban drainage systems

Our study deals with the critical issue of heavy metal pollution in urban runoff; we focused particularly on the threat posed by heavy metals such as nickel to living organisms and water resources owing to their toxicity at low concentrations and non-biodegradability. In this study, we evaluated the efficacy of Filtralite, a filtration medium with excellent hydraulic properties, in removing nickel from water through laboratory experiments and advanced simulation tools. We analysed the geochemical processes involved in nickel removal, including precipitation and adsorption. Importantly, we implemented an innovative approach for numerical modelling using HP1, by combining HYDRUS-1D and PHREEQC for modelling solute transport in porous media and geochemical reactions, respectively. The experimental results revealed that the Filtralite-laden column achieved a removal efficiency of 93.5 % for injected nickel. We observed a significant increase in the effluent pH from 7.0 to 11.5 during the interaction with Filtralite, affecting the solubility of the nickel phases. The model showed the highest nickel concentration in the initial column layers because of rapid chemical precipitation and adsorption upon contact with Filtralite. High-resolution scanning electron microscopy images confirmed the presence of amorphous precipitates around the soil particles, aligning with the changes in pH. This study contributes significantly to environmental engineering and urban water management by introducing an innovative numerical model in HP1 to accurately simulate the removal of nickel using Filtralite. These findings validate the efficiency of Filtralite in extracting nickel from aqueous solutions. Thus, Filtralite is a strong candidate for inclusion in sustainable urban drainage systems.

Hierarchical porous carbon with abundant N/O doping as an anode for zinc ion hybrid supercapacitors

Aqueous zinc-ion hybrid supercapacitors (ZISCs) known for their affordability, stability, and high energy density represent innovative energy storage devices. Porous carbon is usually used as the cathode material of ZISCs, and its structure significantly affects the dual performance of high power density and energy density of ZISCs. Herein, a one-pot carbonization strategy is proposed, eliminating the need for templates, additional heteroatom compounds, and activation processes. By precisely controlling the temperature to optimize the structure and electrochemical performance of carbon materials, we successfully synthesized hierarchical porous carbon materials (NOPC-800) with a high specific surface area of 1545.7 mg, featuring dual doping of 12.3 at% nitrogen and 13.35 at% oxygen. The self-doping of abundant nitrogen and oxygen atoms facilitates the chemical adsorption of ions and accelerates pseudocapacitive reaction kinetics. Leveraging these advantages, ZISCs were assembled using NOPC-800 as the positive electrode and zinc as the negative electrode, showcasing remarkable performance: a specific capacity of up to 121.9 mAh g, an energy density of 97.5 Wh kg, and a power density of up to 16000 W kg. Remarkably, NOPC-800 maintained an excellent capacity retention of 94.9% after 10,000 cycles at a current density of 10 A g. This research paves an innovative and feasible path for the design and advancement of novel heteroatom-rich carbon cathodes.

Macroscale Superlubricity with High Pressure Enabled by Partially Oxidized Violet Phosphorus for Engineering Steel

AbstractAs a novel cross‐structured 2D material, violet phosphorus (VP) promises to further develop the dynamic performance, energy efficiency, and service lifetime of mechanical components owing to its high strength and toughness, large carrier mobility, wide bandgap, and good friction‐reducing properties. In this work, the partially oxidized violet phosphorus nanosheets (oVP) are synthesized and employed as the lubricating additives in the poly alpha olefin (PAO) oil environment with less oleic acid (OA) improver, which can trigger the macroscale superlubricity on the diamond‐like carbon (DLC) film deposited steel surface at high loading pressures (&gt;800 MPa) and sliding speeds (&gt;0.1 m s−1). The friction coefficient (COF) of the steel‐DLC tribopair lubricated by the oVP‐PAO oil can reduce down to 0.0064 with little wear. At the high‐pressure sliding interface, the force‐thermal coupling action during the running‐in process promotes the cleavage and recombination of oVP nanosheets and OA molecules to form a reliable chemical adsorption tribofilm mainly composed of phosphorus oxides and amorphous carbon, which prevents the original asperities from direct contact and provides an ultralow shear strength. These findings suggest a new method to achieve macroscale oil‐based high‐pressure superlubricity for engineering steel through the lubrication and catalyzation effects of oVP.

Adsorption Properties of the Alkalized Accordion‐Like Ti3CN MXene for Pb(II) Ion

AbstractThe presence of poisonous Pb(II) ions in water resources has raised global health concerns. Herein, the adsorption performance of accordion‐like Ti3CN MXene for Pb(II) ions was investigated for the first time. Batch experiments were carried out by varying modifications, pH values, initial Pb(II) concentrations, adsorption time and temperatures. The results prove that the alkalized‐Ti3CN shows enhanced adsorption performance. Although the temperature effect is insignificant, the Pb(II) adsorption is strongly pH‐dependent. The maximum Pb(II) adsorption capacity of alkalized −Ti3CN is about 2.5 times higher than that of activated carbon. The adsorption ratio of Pb(II) is up to 96.6 %. The adsorption capacity increases with increasing the initial concentration of Pb(II). The alkalized‐Ti3CN adsorbs Pb(II) very quickly and the adsorption equilibrium is nearly achieved within 70 minutes. The adsorption follows the quasi‐second‐order kinetic model as well as the Langmuir model, and is mainly controlled by chemical adsorption. It is preliminarily concluded that Pb(II) replaces Na(I) of the −ONa functional groups on the alkalized‐Ti3CN surfaces. This study proves the alkalized‐Ti3CN MXene has potential application for the purification treatment of wastewater contaminated with Pb(II) ions.

Innovative carbon materials from lignocellulosic wastes for electrochemical hydrogen peroxide production: Bridging biomass conversion and material properties

This study aims to assess the electrochemical generation of hydrogen peroxide and hydroxyl radicals (*OH) using carbon cathodes synthesized from three different lignocellulosic residues, Phragmites australis (PA), Cladium mariscus (CM) and Typha domingensis (TD). These vegetal species are commonly used in natural wetlands and phytoremediation processes and can accumulate recalcitrant pollutants within these treatment processes, generating a waste that should be properly managed. To convert these residues into valuable carbon materials, they underwent hydrothermal carbonization (HTC) followed by either chemical activation with KOH or pyrolysis at 1000 ºC. The best results were obtained with chemically activated materials, yielding a maximum H2O2 concentration of 313 mg L−1 with the carbon cathode produced from PA. The specific surface area, oxygenated functional groups and presence of structural defects in carbonous structures, were key parameters related to a good performance as catalysts towards the 2e- Oxygen Reduction Reaction (ORR). It was also demonstrated, in comparison with previous studies, that the presence of heavy metals in the structure of the lignocellulosic residue enhanced the decomposition of H2O2 into *OH. However, in the study of the degradation of a model organic contaminant as methylene blue (MB), it was shown that these *OH were not the main contributors to degradation, as direct H2O2 chemical degradation and adsorption on the carbon materials played the most significant role. Therefore, the outstanding capacity of these lignocellulosic residues as catalysts for the electrogeneration of H2O2 was confirmed, suggesting their potential future application in advanced oxidation processes for water decontamination.