Composite Ionic Liquid Research Articles

Harnessing the power of iron-alumina-based ionic liquid composites for simultaneous removal of Congo red dye and microplastics

Increased water shortage due to industrialization and population increase requires immediate action to address water contamination. Using dimethyl sulfate as a common anion, we synthesized imidazolium-based cations with varying chain lengths (Imidazole, 2-methyl imidazole, 2-ethyl imidazole, and 2-isopropyl imidazole). This allowed us to create novel room-temperature ionic liquids (RTILs) that can be stored and transported at room temperature. These RTILs were further modified to magnetic ionic liquid composites (MILCs) by adding iron-alumina composites. The synthesized RTILs and MILCs were further characterized using H-NMR, FTIR, TGA, SEM, and EDX techniques. The process of adsorption at varying parameters was studied for the removal of Congo red (CR) and microplastics using these materials. MILC-4 in results, demonstrated excellent adsorption effectiveness by reaching a high removal rate of 90% at a concentration of 10 ppm for CR. Furthermore, 10-μm polystyrene beads were successfully destroyed by the MILCs in about 30 min. Following the completion of 40 experimental data, an Artificial Neural Network (ANN) model with three layers was used to accurately predict the removal of CR dye from an aqueous solution by MILCs. For the prediction and modeling of CR dye removal, the minimal mean squared error (MSE) of 0.051 and coefficient of determination (R2) of 0.97 were discovered. These numerical findings demonstrate the amazing effectiveness of the synthesized MILCs in combating water pollution issues. Overall, the study emphasizes the necessity of cleaner production methods and sustainable solutions provided by MILCs for CR dye and microplastics removal from water bodies.

Ionic liquid-modified UiO-66-NH2 as sorbent of dispersive solid-phase extraction for rapid adsorption and enrichment of benzoylurea insecticides.

Ionic liquid (IL)-modified UiO-66-NH2 composite was prepared and used as sorbent of dispersed solid-phase extraction (dSPE) for extracting trace benzoylurea insecticides (BUs) from complex environmental matrices. The IL in framework endowed the prepared material had electropositive characteristics, which can produce interaction with electron rich guest molecules, such as BUs. The high thermal and chemical stability of UiO-66-NH2/IL enabled it to be reused for 16 times without significant reduction in adsorption performance. Due to the multiple forces including π-π, hydrogen bonding, and fluorine-fluorine interaction, UiO-66-NH2/IL showed good adsorption performance, short adsorption time (20 s) and rapid desorption ability (60 s) for BUs. Under the optimal conditions, the method exhibited wide linear range (0.02-500 ng mL-1) with correlation coefficient (R2) not worsethan 0.9928, high enrichment factor (252-300), and low detection limit (0.005-0.4 ng mL-1). The dispersed solid phase extraction coupling with high-performance liquid chromatography-diode array detector (dSPE-HPLC-DAD) was successfully used to detection of BUs in real environmental samples and satisfactory recoveries were obtained (80.5%±2.4-118%±3.2). The results indicated that UiO-66-NH2/IL composite can be a potential sorbent for the preconcentration of trace insecticidesin environmental samples.

Facile in-situ synthesis of carbon black@poly(ionic liquid) composites with a smooth U-link chain macrostructure within surfactant-free ionic liquid microemulsions

Poly(ionic liquid)s show tremendous potential in the application of strain sensing. However, their development is limited by tedious fabrication techniques and the instability factor of existing poly(ionic liquid)s-based strain sensing materials. In this work, we in situ synthesized a novel carbon black and poly(ionic liquid) composites (CB@PILs) by performing thiol-ene click reaction within a surfactant-free ionic liquid microemulsion. The successful construction and reaction of the composites were confirmed by FTIR, XRD, XPS, SEM, TG/DSC, strain test, and conductivity analyses. Results demonstrated that a composite that has a smooth U-link chain macrostructure could be prepared by altering the carbon black content at 3 wt%, and the resultant polymer presented good thermal stability and strain sensing performance. The mass ratio between polyethylene glycol diacrylate and hydroxyethyl methacrylate could further improve the conductivity and mechanical properties of CB@PIL composites. This work provides a potential avenue for designing CB@PIL composites, thus making them viable for strain sensing.

A Stable and Self‐Healing Thermochromic Polymer Coating for All Weather Thermal Regulation

AbstractEnergy‐free thermal regulation is in great demand nowadays. Thermochromic materials are widely explored and used in smart windows. However, most thermochromic materials have fixed transition temperature and still suffer from poor stability. To overcome this challenge, a thermochromic polymer coating based on ion–dipole interaction with switchable transition temperature, high stability toward several harsh environments, self‐healing, and radiative cooling property is developed. It can continuously tune from transparent to opaque according to the temperature change. The lower critical transition temperature can be tuned from 33 to 43 °C by simply adjusting the composition of ionic liquids. Owing to the fluorine polymer backbone and dynamic ion–dipole interactions, it can also keep stable in aquatic, −20 °C, and 70 °C environments and self‐heal upon damage thus prolonging its working life for real applications.

Phase Separation and Ion Diffusion in Ionic Liquid, Organic Solvent, and Lithium Salt Electrolyte Mixtures.

The highly desirable characteristics of ternary mixtures of ionic liquids, organic solvents, and metal salts make them a promising candidate for use in various electrothermal energy storage and conversion systems. In this study, using large-scale classical molecular dynamics simulations, we looked into 10 different ternary electrolyte mixtures using combinations of [EMIM]+, [BMIM]+, and [OMIM]+ cations with [NO3]-, [BF4]-, [PF6]-, [ClO4]-, [TFO]-, and [NTf2]- anions, tetraglyme, and Li salt to study the effect of ionic liquid composition on the phase behavior of ternary electrolyte mixtures. We uncovered that in these electrolytes, phase separation is mainly a function of pairwise binding energy of the constituents of the mixture. To corroborate this theory, several simulations are performed at various temperatures ranging from 260 to 500 K for each mixture, followed by calculating the binding energy of ionic liquid pairs using density functional theory. Our results verify that the transition temperature for the phase separation of each system is indeed a function of the pairwise binding energy of its ionic liquid pairs. It is also found that in some cases, the diffusion coefficient of the Li+ ions decreased even with the increase in the temperature, an effect that is attributed to the presence of condensed ionic domains in the electrolyte. This study provides a new insight for the design of multicomponent electrolyte mixtures for a wide range of energy applications.

Novel Fluid Ionic Liquid Composites with Self-Assembled Porosity and Chemical Sites for Facilitating CO2 Separation

Novel Fluid Ionic Liquid Composites with Self-Assembled Porosity and Chemical Sites for Facilitating CO₂ Separation

Lamellar Ionic Liquid Composite Electrolyte for Wide‐Temperature Solid‐State Lithium‐Metal Battery (Adv. Energy Mater. 23/2023)

Lithium Metal Batteries In article number 2300156, Jingtao Wang, Zhongyi Jiang, and co-workers propose a thin lamellar ionic liquid composite electrolyte with long-range ordered, defect-free, and robust nanocrystalline channels by manipulating the molecular configuration of ionic liquid electrolytes in 2D laminar channels, achieving rapid lithium-ion transport and excellent pouch cell performance in −40 – 100 °C.

Tuning the potential drop at graphene/protic ionic liquid interface by molecular structure engineering

Ionic liquids (ILs) have been extensively employed in many applications involving interfaces with carbon-based electrodes, such as energy storage devices (batteries or supercapacitors) or electrocatalytic devices, where the way each ion of the IL interacts with the electrode has a strong impact on the overall performance of the device. For instance, the amount of potential difference between the electrode and the bulk of the IL is highly sensitive to the IL composition and it is directly related to the device capacitance. The selection of the most suited pair of ions often proceeds by time-consuming and costly trial-and-error approaches. It is necessary to understand the atomistic features of the interface to determine the effect of each ion on the potential drop. By classical molecular dynamics simulations, we show that it is possible to quickly infer the interface potential arising at the carbon electrode by carefully inspecting the molecular structure of the IL. The ion orientation at the interface is, in fact, determined by the distribution of charges within the molecules. Depending on where charges are located, ions can either lie flat or perpendicular to the interface to minimize the surface energy. The interface potential is found to be mainly determined by ion–ion interactions dictating the interface energy minimization process, whereas ion–electrode interactions are found to enforce higher ordering and charge layers stacking but not to induce selective adsorption of an ion over the other.

Lamellar Ionic Liquid Composite Electrolyte for Wide‐Temperature Solid‐State Lithium‐Metal Battery

AbstractElectrolytes that can work over a wide temperature range are crucial forsustainable advanced energy systems. Here, a kind of lamellar ionic liquid composite electrolyte (L‐ILCE) is explored through confining ionic liquids (ILs) in ordered interlayer nanochannels of 2D vermiculite framework. It is demonstrated that, within nanochannels, the finely tuned microstructure can induce the rearrangement and crystallinity of ILs, affording L‐ILCE the combined superiorities of liquid electrolyte and solid‐state electrolyte. L‐ILCE exhibits high ionic conductivities (0.09–1.35 × 10−3 S cm−1 at −40 to 100 °C), whereas polymer and inorganic electrolytes usually lose ionic conduction ability below 0 °C. Additionally, L‐ILCE exhibits high transference number (0.89, comparable with single‐ion conductors) and wide electrochemical window (0–5.3 V). LiFePO4||Li and high‐voltage LiNi0.8Mn0.1Co0.1O2||Li cells assembled from L‐ILCEs exhibit highly stable electrochemical performance in −20 to 60 °C. Furthermore, pouch cells (0.1 Ah) exhibit high capacity of 93.8 and 45.0 mAh after 50 cycles along with capacity retention of 97% and 98% at 60 and −20 °C, respectively, as well as excellent flexibility and safety. This study offers promise in the rational design of advanced ion conductors for lithium‐based batteries with wider operating temperatures.

Copper Recovery from Industrial Bimetallic Composite Ionic Liquids by Direct Electrodeposition and the Effect of Temperature and Ultrasound.

Critical processing protocols of industrial bimetallic composite ionic liquid (IL) are necessary to assure good mass transfer rates for process optimization and efficient metal recovery. Here, the effects of different conditions on the electrochemical behavior and copper recovery from the industrial bimetallic composite IL are crucial for effective resource utilization. Cyclic voltammetry (CV) shows that the reduction of Cu(I) to Cu(0) during the cathodic reduction region is the irreversible diffusion-controlled process, and the diffusion coefficient increased with temperature which indicated that increasing temperature could promote the diffusion and mass transfer. During electrodeposition, metallic copper is obtained exclusively on the cathode, while CuCl2 accumulates exclusively on the anode. Scanning electron microscopy shows that the micron-size electrodeposits become larger and significantly rougher with increasing temperature and ultrasonic frequency, illustrating that these factors hasten the nucleation and crystallization rates at high overpotentials. The efficiency of copper recovery is greatly improved by employing high temperature and ultrasonic cavitation, and the highest values correspond to r = 76.9% at 80 °C and r = 63.6% at 40 kHz. The study lays the foundation for efficient and rapid recovery of copper from spent ILs.

Porous multi-site ionic liquid composites for superior selective and reversible adsorption of ammonia

Ionic liquids (ILs) with low vapor pressure, tunable structures and good NH3 affinity provide an inspiring way to efficiently capture NH3. However, the high viscosity of most ILs limited mass transfer, which incumbers their industrial applications. Besides, how to simultaneously achieve high selectivity, capacity and reversibility of NH3 still face great challenge. Herein, four novel hydroxyl ammonium protic ILs (HAPILs), including methyldiethanolammonium trifluoromethanesulfonate ([MDEAH][CF3SO3]), triethanolammonium trifluoromethanesulfonate ([TEAH][CF3SO3]), dimethylethanolammonium trifluoromethanesulfonate ([DMEAH][CF3SO3]) and diethylethanolammonium trifluoromethanesulfonate ([DEEAH][CF3SO3]), with multiple hydrogen bonding donors that can interact with more over two NH3 molecules were designed and synthesized, and were further supported onto porous molecular sieves to overcome the above problem. Among the prepared porous HAPIL composites, 50 wt% [TEAH][CF3SO3]@MCM-41 showed the highest NH3/CO2 selectivity of 62 under 313 K and 0.1 MPa compared with the state-of-the-art values, along with high capacity of 114.3 mgNH3/g-adsorbent. The excellent NH3 adsorption performance was attributed to the synergistic interaction of mesoporous effect and multiple hydrogen bonding between NH3 and HAPILs. Furthermore, the porous HAPIL composites exhibited great recyclability after six cycles, revealing great potentials in industrial application of efficient and reversible NH3 separation.

A non-enzymatic electrochemical sensor based on nitrogen-doped mesoporous carbon@hydroxyl-functionalized ionic liquid composites modified electrode for the detection of fenitrothion.

The overuse of organophosphorus pesticides (OPs) results in severe environmental pollution and food safety issues. Fenitrothion (FNT) is a typical derivative of OPs, so rapid and sensitive detection of FNT plays an important role in environmental protection and public health. An FNT non-enzymatic electrochemical sensor based on nitrogen-doped mesoporous carbon@functionalized ionic liquid composites (N-CMK-3@IL) was constructed in this work. The surface topography and electrochemical properties of the sensor were investigated by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), respectively. Because N-CMK-3@IL composites could improve the conductivity and increase the active surface area of the modified electrode, the sensor exhibited good electrocatalytic activity to FNT. Under the optimal experimental conditions, a good linear relationship for FNT was obtained in the range of 0.5-100 ng mL-1, and the detection limit was 0.1 ng mL-1 (S/N = 3). The sensor was successfully applied for the detection of FNT in vegetable samples.

An electrochemical sensor based on metal–organic framework–chiral ionic liquid composites for the enantiorecognition of tryptophan enantiomers

Metal organic framework–chiral ionic liquid composites Fe-CIL was first used to construct the chiral sensor, which could be used to chiral recognize tryptophan (Trp) enantiomers based on the DPV peak potential difference (ΔEp) of l/d-Trp.

Metal Ions Removal from Contaminated Water Using Membranes Functionalized with Ionic Liquids

The present work studies the efficiency of new innovative quaternized polysulfone (PSFQ)/ionic liquid (IL) membranes in the treatment process of water containing cadmium ions (Cd(II)). The design and development of the polysulfone membranes with morphology tailored by the use of ILs (Cyphos 101 IL and Aliquat 336) was based on the rheological study of the casting solutions that dictated the optimal compositions of ILs and facilitated the preparation of the membranes for performance tests. Thus, according to the variation of the rheological functions obtained (G′, G″), it was demonstrated that Aliquat 336 has better compatibility with PSFQ, facilitating the workability of the solution and improving the final properties of the membranes relative to Cyphos 101 IL. However, the casting solutions consisting of 5 wt.% Ph-IL and 15 wt.% Am-IL content produce membranes with superior physico-chemical properties. Also, the surface chemistry and morphology analysis of the membranes obtained were investigated in order to understand the relationship between the PSFQ and ILs, as well as their surface properties, as indicators for their future applications. Additionally, the results obtained from the kinetic studies regarding Cd(II) removal from aqueous solutions and the amount of Cd(II) accumulated onto the membranes showed that the ILs enhance the filtration efficiency of the membranes studied and underlined the positive effect of IL in the structure of the quaternized polysulfone membranes. A content of 15 wt.% Aliquat 336 in PSFQ membranes shows the best properties for Cd(II) removal from aqueous solutions; the maximum amount of Cd(II) accumulated on the membrane studied was 3300 mg/m2. This behaviour was maintained for two cycles of washing/filtration, and then the efficiency decreased by 20%. The results obtained showed that the membranes functionalized with ionic liquid could be used efficiently in the treatment of water containing trace concentration of cadmium.

Anion Equilibria and Stability of Quaternary Phosphonium Chloroaluminate Ionic Liquids

While imidazolium based chloroaluminate ionic liquids have been studied for decades, with interest increasing over the last several years, phosphonium analogues have received less attention. Recent work has shown phosphonium-based chloroaluminate ionic liquids have significant potential as battery electrolytes due to their high thermal stability and wide electrochemical windows. In order to realize their full potential, fundamental studies on the ion dynamics and transport properties of these systems are required. This work focuses on studying the anion speciation and ion dynamics of a series of acidic chloroaluminates containing phosphonium cations with incrementally varied structures. Their properties are probed through broadband dielectric spectroscopy and oscillatory shear rheology to reveal the frequency and temperature dependence of properties such as conductivity, permittivity, and modulus. We will present preliminary work on the impact of changes in cation structure and ionic liquid composition on anion speciation, transport properties, and dynamics. The results expand our understanding of these important electrolyte systems that hold significant promise for applications such as energy storage, electrodeposition, and chemical synthesis.

Improving the Electrochemical Properties of Cathode Materials for Sodium Ion Batteries

Energy storage systems made from abundant materials are essential for the transition to a more sustainable economy. Although today lithium-ion batteries (LIBs) are the most popular battery technology, the growing demand and low availability of lithium, as well as the use of cobalt and other rare metals raise questions about the sustainability and long-term viability of LIB as the only energy storage solution. The high abundance of sodium content and relative similarity to LIBs, allows the sodium ion batteries (SIBs) to be considered as alternative for stationary energy storage [1]. However, the widespread adoption of SIB technology is hampered by many challenges, including the relatively low energy density compared to LIB. Lower energy density electrodes, such as Na2FeP2O7, are generally stable during cycling [2], while many higher energy density electrodes, such as NaxMnO2, have had a shorter cycle life [3]. In this work we show several possible solutions how to improve the electrochemical properties of the SIBs made of these cathode materials.The promising cathode material Na2FeP2O7 was studied to improve its electrical conductivity, which is often low in the case of sodium pyrophosphates. Solution synthesis was used to prepare pristine Na2FeP2O7 and Na2FeP2O7/C composite cathode materials for sodium-ion batteries, using glucose as a carbon source. While the pristine Na2FeP2O7 displays capacity of only 45 mAh/g due to the relatively large grain size, the addition of carbon increases the capacity to up to 92 mAh/g (95% of the theoretical 97 mAh/g capacity) with excellent rate capability, as 44 mAh/g capacity is still retained even at 20 C (1.94 A/g) current. The optimal content of carbon was found to be 4.8%. The initial capacity of 81 mAh/g is fully retained after 500 cycles at 1 C, indicating excellent cycle life of Na2FeP2O7/C. Electrochemical measurements were carried out in 1 M NaClO4 salt in propylene carbonate as electrolyte and show that the addition of 5 wt.% fluoroethylene carbonate solid electrolyte interphase stabilizing additive greatly benefits the rate and cycling performance of Na2FeP2O7/C as measured in half-cells [4].Na0,67MnO2 is another compound that is widely studied as cathode materials in sodium ion batteries. Currently polyvinylidene fluoride (PVDF) is the most popular binder choice. In our study, a novel tetrabutylammonium (TBA) alginate binder is used to prepare a Na0,67MnO2 electrode for sodium-ion batteries with improved electrochemical performance. The ageing of the electrodes has been characterized. TBA alginate-based electrodes are compared to PVDF and Na alginate-based electrodes and show favorable electrochemical performance, with gravimetric capacity values of up to 164 mAh/g, which is 6% higher than measured for the electrode prepared with PVDF binder. TBA alginate-based Na0,67MnO2 electrodes also display good rate capability and improved cyclability and their solid–electrolyte interface is similar to that of PVDF-based electrodes. As the only salt of alginic acid soluble in non-aqueous solvents, TBA alginate emerges as a good alternative to PVDF binder in battery applications where the water-based processing of electrode slurries is not feasible, such as the demonstrated case with Na0,67MnO2 [5].Overall, we have shown that binder and electrolyte selection can significantly improve the electrochemical properties of electrode materials for SIBs.The financial support of projects No. 1.1.1.2/VIAA/1/16/166 “Advanced materials for sodium Ion batteries” and No. lzp-2020/1-0391 “Advanced polymer – ionic liquid composites for sodium-ion polymer batteries” is greatly acknowledged. Institute of Solid-State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Program H2020-WIDESPREAD-01–2016-2017-Teaming Phase 2 under grant agreement No. 739508, project CAMART2. Vaalma, C.; Buchholz, D.; Weil, M.; Passerini, S. A cost and resource analysis of sodium-ion batteries. Nat. Rev. Mater. 2018, 3, 18013.Jin, T.; Li, H.; Zhu, K.; Wang, P.-F.; Liu, P.; Jiao, L. Polyanion-type cathode materials for sodium-ion batteries. Chem. Soc. Rev. 2020, 49, 2342.Lyu, Y.; Liu, Y.; Yu, Z.-E.; Su, N.; Liu, Y.; Li, W.; Li, Q.; Guo, B.; Liu, B. Recent advances in high energy-density cathode materials for sodium-ion batteries. Sustain. Mater. Technol. 2019, 21, e00098.Kucinskis, G.; Nesterova, I.; Sarakovskis, A.; Bikse, L.; Hodakovska, J.; Bajars, G. Electrochemical performance of Na2FeP2O7/C cathode for sodium-ion batteries in electrolyte with fluoroethylene carbonate additive. J. Alloys Compd. 2022, 895, 162656.Kucinskis, G.; Kruze, B.; Korde, P.; Sarakovskis, A.; Viksna, A.; Hodakovska, J.; Bajars, G. Enhanced Electrochemical Properties of Na67MnO2 Cathode for Na-Ion Batteries Prepared with Novel Tetrabutylammonium Alginate Binder. Batteries 2022, 8, 6. Figure 1

Superior selective adsorption of trace CO2 induced by chemical interaction and created ultra-micropores of ionic liquid composites

Effective capture of trace CO2 in atmosphere or confined spaces to ensure human beings safety draw a lot of attention, however, how to simultaneously improve CO2 capacity and selectivity still faces great challenge. Herein, combining porous molecular sieves (SBA-15 and MCM-41) and the anion-functionalized ionic liquid (IL) tetraethylammonium glycinate ([N2222][Gly]), a series of hierarchically porous IL composites with different IL loadings were designed and prepared. Compared with pristine supports, the incorporation of [N2222][Gly] simultaneously improves CO2 capacity and CO2/N2 selectivity by ordersofmagnitude, especially for confined spaces (<5000 ppm) and air (415 ppm). When the IL loading was 60 wt%, novel micropores were created, especially ultra-micropores (<0.65 nm), which are not present in bare supports and other [N2222][Gly]@SBA-15 (15, 30 and 45 wt%). Among them, 60 wt%[N2222][Gly]@SBA-15 showed the highest CO2 uptake of 1.45 and 1.88 mmolCO2/g-adsorbent at 0.0005 and 0.005 bar under 313 K along with recyclability, which are much superior to the state-of-the-art reported values. Moreover, superb ideal CO2/N2 selectivity of 11,545 at 0.005 bar and 288 K was achieved, which was 288 times that of SBA-15. Meanwhile, mixed gas breakthrough experiments demonstrated that 60 wt% [N2222][Gly]@SBA-15 shows outstanding CO2 separation performance under simulative confined spaces and ambient air. The ultra-high CO2 separation performance was attributed to the synergy of chemical interaction between the IL anion and CO2 as well as newly created micro- and ultra-micropores effect. This work provides guidelines for the design of IL composites with ultra-micropores for efficient trace CO2 removal.

Carbon electrode sensitivity enhancement for lead detection using polypyrrole, ionic liquid, and nafion composite

This paper concerns enhancing a lead detection sensor using a combination of polypyrrole (PPy), Nafion (N), and ionic liquid (IL) with thick-film or screen-printing technology on sensitive material-based carbon electrodes. Electrode characterization using a scanning electron microscope (SEM) was conducted to see the morphology of sensitive materials, showing that the spherical particles were distributed evenly on the electrode surface. Analysis using energy dispersive spectroscopy (EDS) shows that the element's atomic composition is 84.92 %, 8.81 %, 6.26 %, and 0.01 % for carbon, nitrogen, oxygen, and bismuth, respectively. Potentiostat measurement with the ambient temperature of 25 °C on a standard lead solution with concentration ranging from 0.05 to 0.5 mg/l yields an average output voltage ranging from 2.16 to 2.27 V. It can be concluded that the sensor is able to detect lead with a sensitivity of 0.21 V in each addition of solution concentration (mg/l) and give an 84 % concentration contribution to the voltage.

Lignin composite ionic liquid lubricants with excellent anti-corrosion, anti-oxidation, and tribological properties

A new type of lubricating material (BTA-P4444-Lig) was synthesized by combining lignin with tetrabutylphosphorus and benzotriazole. The tribological properties, corrosion resistance, and anti-oxidation properties of BTA-P4444-Lig as a lubricant were investigated. The lubricating material exhibits excellent friction reduction and wear resistance, as well as good thermal stability and excellent oxidation resistance. Mechanistic analysis reveals that the active elements N and P in the lubricating material react with the metal substrate, and the reaction film effectively blocks direct contact between the friction pairs, affording excellent friction reduction and wear resistance. At the same time, the phenolic hydroxyl group in lignin reacts with oxygen free radicals to form a resonance-stable semi-quinone free radical, which interrupts the chain reaction and affords good anti-oxidant activity.

Lignin composite ionic liquid lubricating material as a water-based lubricating fluid additive with excellent lubricating, anti-wear and anti-corrosion properties

A new type of ionic liquid was synthesized from lignin, tetrabutylphosphorus hydroxide, and benzotriazole, and its potential utility as a water-based lubricating additive was studied by comparing the performance of water containing the lubricating additive with that of water. The additive not only decreases the friction and wear of water on steel but also decreases the corrosive effect of water on steel, and improves the utilization rate of lignin, which is difficult to use. The mechanistic analysis of the lubrication in the presence of the ionic liquid revealed that a protective film containing nitrogen is formed on the surface of the steel/steel friction pair, which blocks direct contact of the friction pair and thus induces excellent tribological properties.