Mineral Oil Lubricant Research Articles

Thrust ball bearing fault identification from visualized data using optimized deep network

Bearings are the most common components employed in machine parts. The bearings' movement facilitates the smooth motion. They also help with friction reduction. The faults in bearings are often caused by tribological parameters. Various methods have been developed to identify faults in bearings, but they often fail to predict these accurately. This work has concentrated on designing an effective fault-recognizing model. Therefore, a framework, the Zebra-based Radial Basis Prediction Mechanism (ZbRBPM), was proposed in this work. Initially, the bearing datasets are collected, and mineral oil (MO) lubrication is added to minimize wear and friction. The primary goal of the work is to detect and classify the fault in the thrust ball bearing. The bearing vibration data included a normal vibration signal, a ball fault, and inner and outer race faults. Hence, Zebra fitness is enhanced for the optimization of tribological parameters and fault identification. The proposed model is executed in the MATLAB system. Finally, performance criteria like accuracy, precision, recall, F-score, error rate, computation time, speed, specific wear rate, friction torque, and energy consumption are validated. The performance of the proposed ZbRBPM gains better accuracy rate as 99.5 %, 99 % of precision and f-score and 99.4 % of recall. Also it significantly reduced the prediction error rate into 0.5 % with lower computation time and very low wear and friction.

Multi-response optimization of process parameters for sustainable machining of AISI 1018 steel with palm kernel oil-assisted minimum quantity lubrication technique

AbstractIn this study, palm kernel oil, an eco-friendly oil, was extracted from its seeds and then examined for thermal and physiochemical characterization. Subsequently, the performance of palm kernel oil was evaluated in comparison with standard mineral oil during the milling of AISI 1018 steel with a double milling tool using the MQL technique. The influence of cutting conditions such as feed rate, spindle speed, and DOC on response variables (cutting temperature and surface roughness) was studied using a Taguchi L9 orthogonal array. Using the TOPSIS approach (a compensatory method that provides a more realistic form of modeling than non-compensatory methods, and allows trade-offs between criteria, where a poor result in one criterion can be voided by a good result in another criterion) an integrated structure for modeling and optimizing the process was developed. The findings showed that palm kernel oil had a 54% oil yield. In terms of machining, palm kernel oil performed much better than mineral oil lubricants. From the results obtained, palm kernel oil reduced the surface roughness by about 15.6% over mineral oil. Effective cooling in palm kernel oil led to reduced cutting zone temperatures, which in turn extended tool life and improved cutting stability. Additionally, ANOVA was used to show the parameters' significant influence on the output responses. The findings showed that feed rate and depth of cut had the greatest impact on the responses for palm kernel oil and mineral oil, respectively.

Influence of Mango Seed Oil on Surface Roughness and Cutting Temperature During Sustainable Turning of AISI 1525 Steel Under Minimum Quantity Lubrication Environment

Mineral oil-based cutting fluids have several mechanical advantages. The use of mineral oil has been questioned due to its adverse effect on machinists and the environment. There is need for a sustainable and biodegradable cutting fluid that can perform the task of problematic mineral oil. This study considered a non-edible vegetable oil, mango oil, as a lubricant in the turning operation of AISI 1525 steel using an MQL mode of fluid application. The performance of mango oil was compared with commercial mineral oil using SR and CT as performance metrics. Experiments were conducted under three levels of SS (355, 500, and 710 rev/min), FR (0.10, 0.15, and 0.20 mm/rev), and DOC (0.75, 1.00, and 1.25 mm). Taguchi L9 orthogonal array was adopted for the experimental settings. Afterward, TOPSIS, a multi-optimization tool was employed to determine the best cutting parameters for machining the workpiece with the tungsten carbide tool. The finding showed that mineral oil outperformed mango oil lubricant in terms of both SR and CT. The optimum CT and SR can be achieved using an SS of 355 rev/min, FR of 0.15 mm/rev, and DOC of 1.00 mm for both mango and mineral oil lubricants.

Tribological behaviors of an attapulgite-graphene nanocomposite as an additive for mineral lubricating oil.

In this work, an attapulgite-graphene nanocomposite was prepared. The tribological properties of the prepared attapulgite-graphene nanocomposite as an additive for 200SN mineral lubricating oil were investigated using an SRV-IV tribometer through ball-on-disk contact mode for the first time. The characterization of the prepared nanocomposite indicated that attapulgite nanofibers are enveloped by the graphene nanosheets and present fine combination. The tribological test results show that the friction-reducing and antiwear properties of 200SN were obviously improved by adding the attapulgite-graphene nanocomposite. Through the characterization and analysis of the worn surface and cross-section, it was found that a tribofilm composed of Fe, Fe3O4, FeO, Fe2O3, FeOOH, graphite, graphene, SiO2 and organic compounds was formed on the worn surface. Furthermore, the bonding between the tribofilm and steel matrix is tight. The tribofilm and lubricating oil achieve a solid-liquid coupling lubrication effect, which is responsible for the improvement of the friction-reducing and antiwear properties.

Mechanistic approach on comparative biosorption of dyes by extracellular polymer of Ochrobactrum pseudintermedium C1 utilizing waste mineral lubricating oil

Dyes are widely used in manufacturing of various consumer products for their ability to impart characteristic color. However, dyes are also one of the most important hazardous pollutants in this present day. Presence of hydroxyl, phosphate, ether, carbonyl and alkyl groups also enable bacterial extracellular polymers to function as biosorbent. In this study, negatively charged biosorbent EP-C1 produced by Gram-negative bacterium Ochrobactrum pseudintermedium C1 utilizing waste mineral lubricating oil has given different decolorization percentages for triphenylmethane cationic Malachite Green and azoic anionic Congo Red at neutral pH. Time wise absorbances from Ultraviolet-Visible Spectrophotometry has estimated maximum biosorption of Malachite Green after 300 min. Biosorption capacities have differed with initial dye concentrations, biosorbent dosages and contact time. Time taken by each dye to reach saturation has depended upon their charged bearing groups of each dye and biosorbent. Kinetic (pseudo first and pseudo second order) and diffusion (intra particle and liquid film) parameters in presence of different dye concentrations and biosorbent dosages were studied for understanding the biosorption mechanism. Morphological differences in chemical structure, chemical functional groups of EP-C1 and EP-C1 loaded dye was studied by Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy and Zeta potential measurements. A compiled overview on comparative mechanistic biosorption of Malachite Green and Congo Red dyes by a bacterial extracellular polymer in miniature laboratory shake flask experiments was done in this study. Newer advents on biological remediation of dyes with mineral lubricating oil as sole carbon source can add a new feather to the already available bioremediation techniques in mitigation of hazardous wastes.

Experimental investigation of the effects of boron oil additive in internal combustion engine

Using additives to engine oils increases engine performance, extending engine maintenance life, boosting the competitiveness of mineral-based oils technically and economically. In this study, the effects of liquid boron oil additive added to mineral-based 10 W-40 engine lubricating oil used in a single-cylinder diesel engine were investigated. 15 % of the engine oil volume was added to the engine as an additive. Experimental studies were carried out at three different engine speeds (i.e., 1500, 1750, and 2000 rpm). The engine, on which no changes were made, was first run with mineral lubricating oil, and then the experiments were repeated with mineral lubricating oil with 15 % boron additive. In the studies, engine torques, specific fuel consumption, and exhaust emissions (HC, CO, CO2, and NOx) were evaluated. In addition, the effects of operating the engine for 100 h without adding any additives and with oil additives containing 15 % boron were also investigated. It was found that engine torque and EGT increased while BSFC, CO2, HC, and NOx decreased in boron-added mineral lubricating oil for all revolutions. In addition, there was a general decrease in CO emissions. In-cylinder SEM images and oil analyses, which were operated with a 15 % boron additive to the engine oil, showed that the boron additive positively affected the engine.

Exposure to benzene and other hydrocarbons and risk of bladder cancer among male offshore petroleum workers

BackgroundOccupational exposures constitute the second leading cause of urinary bladder cancer after tobacco smoking. Increased risks have been found in the petroleum industry, but high-quality exposure data are needed to explain these observations.MethodsUsing a prospective case-cohort design, we analysed 189 bladder cancer cases (1999–2017) and 2065 randomly drawn non-cases from the Norwegian Offshore Petroleum Workers cohort. Cases were identified in the Cancer Registry of Norway, while work histories (1965–1998) and lifestyle factors were recorded by questionnaire at baseline (1998). Occupational petroleum-related hydrocarbon exposures were assessed by expert-developed job-exposure matrices. Hazard ratios were estimated by weighted Cox-regressions, adjusted for age, tobacco smoking, education, and year of first employment, and with lagged exposures.ResultsIncreased risks were found in benzene-exposed workers, either long-term exposure (≥18.8 years, HR = 1.89, 95% CI: 1.14–3.13; p-trend = 0.044) or high-level cumulative benzene exposure (HR = 1.60, 95% CI: 0.97–2.63; p-trend = 0.065), compared with the unexposed. Associations persisted with 20-year exposure lag. No associations were found with skin or inhalation exposure to crude oil, mineral oil (lubrication, hydraulics, turbines, drilling), or diesel exhaust.ConclusionsThe results suggest that exposures in the benzene fraction of the petroleum stream may be associated with increased bladder cancer risk.

Tribological Performance Evaluation of Blended Lubricants Incorporated with Organic Polymer

Eco-friendly lubricants have drawn a lot of interest in the lubrication industry as a way of promoting global sustainability in response to the growing environmental pollution danger posed by the use of petroleum-based lubricants. As a result of these, developing lubricants with organic additives stands as a promising technique in solving the environmental challenges caused by non-degradable materials. This research investigates the effect of bio-based water hyacinth (Eichhornia crassipes) (EC) carboxylmethyl cellulose (CMC) polymer in different base lubricants as well as under different volumetric blend to determine their compatibility effect on lowering friction and wear using base rapeseed oil (BRO) and mineral oil (MO) as a base lubricant sample. High frequency reciprocating rig tribo-tester machine was used in the experiment, followed by substrate surface analysis via energy dispersive x-ray spectroscopy. The additives were evaluated for their potential to improve tribology in terms of friction, surface roughness and wear reduction, load-carrying capacity, and mechanism of repair. Testing the additive concentrations, produced recommendable result at 0.8 mass% EC-CMC. The best performance was obtained when BRO70/MO30 was blended with 0.8 mass% EC-CMC. When compared to base BRO and MO lubricants under 80 N, 0.8 mass% BRO70/MO30 reduced the coefficient of friction and wear scar diameter by 44%, 32%, and 33%, 21% respectively. However, it was shown that nanoparticles had greater tribological performance at higher working capacities owing to the rapid and active tribo-film formation.

Mass spectrometry molecular fingerprinting of mineral and synthetic lubricant oils.

The molecular composition of lubricating oils has a strong impact on how automotive engines function, but the techniques used to monitor the quality parameters of these oils only inspect their gross physical-chemical properties such as viscosity, color, and bulk spectroscopy profiles; hence, bad-quality, adulterated, or counterfeit oils are hard to detect. Herein, we investigated the ability of direct infusion electrospray ionization mass spectrometry (ESI-MS) to provide simple, rapid but characteristic fingerprint profiles for such oils of the mineral and synthetic types. After a simple aqueous extraction, ESI-MS analyses, particularly in the positive ion mode, did indeed show characteristic molecular markers with unique profiles, which were confirmed and more clearly visualized by partial least squares-discriminant analysis (PLS-DA). Nuclear magnetic resonance and Fourier transform infrared-attenuated total reflection spectroscopy were also tested for the bulk samples but showed nearly identical spectra, thus failing to reveal their distinct molecular composition and to differentiate the oil samples. To simulate adulteration, mixtures of mineral and synthetic oils were also analyzed by ESI(+)-MS, and additions as low as 1% of mineral oil to synthetic oil could be detected. The technique therefore offers a simple and fast but powerful tool to monitor the molecular composition of lubricant oils, particularly vias their more polar constituents.

Potential of palm oil with tert-Butylhydroquinone in place of mineral oil lubricant for reducing environmental degradation

Lubrication has remained an important aspect of machines maintenance and designs since time immemorial, yet the quest for improved lubricant for sustainable life of both equipment and environment continues to intensify. Many lubricants that is, research for a lubricant that is capable of providing maintenance of sustainable equipment without compromise to the environment is on the rise have been formulated and a lot of discoveries have been found in approaches toward enhanced and sustainable lubricants performance. Addition of foreign materials in nano quantity to fortify base oil properties for special purposes has also received greater attention in recent years. While this approach has yielded amazing results, concerns bordering on non-biodegradability of the mineral oils and safety of their additives to the environment equally continue to grow. This has escalated research interest in vegetable oils and their derivatives such as palm oil and other seed oils as a substitute toward limiting the consequences of improper disposal and eventual natural habitat degradation. A new approach to this quest is the adoption of palm oil (in Super Olein IV64 grade) with 150–450particles per million of tert-Butylhydroquinone for comparison with tribological behavior of mineral oil (Shell Helix SAE40W10) within the temperatures of 40°C to 100°C using linear reciprocating tribometer Winducom ASTM G133 test rig. The results showed tremendous similarity in coefficient of friction values between 0.1 and 0.12 of Super Olein with 150 particles per million and 300 particles per million of tert-Butylhydroquinone correlating closely with that of Shell Helix SAE40W10 at 80°C and 100°C, respectively. Wear track on the 20mm square plate was observed on the low-resolution microscope while wear scar diameter of the 6 mm SKD11 ball was observed on the high-resolution microscope. The results obtained at a temperature of 100°C in Super Olein IV64 + 150 particles per million tert-Butylhydroquinone and Super Olein IV64 + 300 particles per million tert-Butylhydroquinone is very similar to that of SAE40W10 except for Super Olein IV64 + 450 particles per million TBHQ whose coefficient of friction maintained a higher value of 0.3 at those temperatures.

Research On Biodegradable Lubricant in Combustion Engine

Lubricants predominantly used to reduce friction and gain smooth functioning of a vehicle. Biodegradable lubricants are perceived to be alternative to mineral oil lubricants because of their properties and biodegradability. This review paper discusses the effect of biodegradable lubrication in term of emission performance, wear, friction and viscosity effect to the internal combustion engine using multiple types of biodegradable lubrications. Bench wear test was conducted using Yamaha, ET 950 to carry out the effect of the biolubricant in spark ignition (SI) engine. The bench test was conducted under several conditions: pressure, 3.0 MPa; sliding speed, 0.20 m/s; sliding stroke, 80 mm; room temperature, >25°C. The second experiment were conducted with 100 percentage SAE 40, palm oil and palm oil (14%) + castor oil (86%) blend as its crankcase lubricant using four stroke compression ignition (CI) engine.A thermocouple was used to measure the parameters temperature every 5 minutes’interval with the engine operating for an hour under no load, 2.5 kg, 5 kg, and 7 kg load condition. The emission performance was run using neem oil blends as samples. The brief discussion is made on emission performance, fuel efficiency, viscosity index and coefficient of friction. Also, deduction was made for the temperature of crank case oil, coolant and the exhaust gas.

Tribological Analysis of Molybdenum Disulfide (MOS2) Additivated in the Castor and Mineral Oil Used in Diesel Engine

The lubrication phenomenon is used to reduce friction and wear between two rubbed surfaces, such as in engine and cutting processes. Different oils such as mineral oil and synthetic lubricant are being used for this purpose. With the passage of time, the demand of energy will get higher and natural resources and mineral lubricants will be diminished. Furthermore, biodegradation of mineral oil is too slow, and it remains on the surface of earth for a long period of time, creating atmospheric pollution. To overcome this problem, bio lubricants are being used to reduce wear and friction due to their high biodegradability. In order to increase the lubrication capacity of castor oil, a 1 wt. % concentration of MoS2 nanoparticles was added to the base oil. Moreover, to stabilize the additives, 2 wt. % gum arabic and 1 wt. % Oleic acid (OA) were also added. Then, multiple tests, such as of physicochemical properties, Fourier transform infrared (FTIR), and atomic absorption spectroscopy (AAS) of synthetic lubricant and conventional lubricant, were carried out before and after the operational running of 100 h on the diesel engine for each lubricant at 75% throttle, 2200 rpm, and 50% of total load. The results show that the behavior of newly prepared MoS2-based synthetic lubricant possessed higher characteristics in some physicochemical properties and was marginally lacking in other properties compared to shell lubricant. The flash point and specific gravity of synthetic lubricant were decreased compared to shell oil, with relative decreases of 0.27% and 1.15%, respectively. Ash and kinematic viscosity of 40 °C had a relative increase of 4.17% and 1.61%, respectively, and at a kinematic viscosity of 100 °C, the pour points and total base number (TBN) were relatively increased at 1.09%, 6.02%, and 1.38%, respectively, with respect to the properties of the shell lubricant. Moreover, this analysis evaluated that the reduction of wear and tear in synthetic lubricant regarding chromium (Cr), copper (Cu), and iron (Fe) was decreased by 21.12%, 3.39%, and 0.96%, respectively, but in the case of aluminum (Al) the wear and tear was marginally increased, at 1.17%, compared to shell lubricant. In the case of calcium (Ca) and zinc (Zn), the concentration was decreased by 3.59% and 17.41%, respectively. The FTIR analysis shows that all the peaks of the synthetic lubricant and shell lubricant were overlapping each other in the first three regions of the mid-IR spectra from 4000 to 1500 cm−1 and had the same functional groups—hydroxyl stretch (O-H), alkanes (C-H), carbonyls (C=O), aromatic amines (C-N), and alkyl halides (C-Br)—which were attached but fluctuating in the fingerprint region. The results show that shell lubricant can be replaced with MoS2-based synthetic lubricant because the latter has superior friction reduction and load-bearing capability and can compete favorably with commercial shell oil in wear protection when additivated with MoS2-based nanoparticles, and hence can be a good alternative for diesel engine oil.

Analysis of the Biodegradable Lubricant in Internal Combustion Engine

Lubricants predominantly used to reduce friction and gain smooth functioning of a vehicle. Biodegradable lubricants are perceived to be alternative to mineral oil lubricants because of their properties and biodegradability. This review paper discusses the effect of biodegradable lubrication in term of emission performance, wear, friction and viscosity effect to the internal combustion engine using multiple types of biodegradable lubrications. Bench wear test was conducted using Yamaha, ET 950 to carry out the effect of the biolubricant in spark ignition (SI) engine. The bench test was conducted under several conditions: pressure, 3.0 MPa; sliding speed, 0.20 m/s; sliding stroke, 80 mm; room temperature, >25°C. The second experiment were conducted with 100 percentage SAE 40, palm oil and palm oil (14%) + castor oil (86%) blend as its crankcase lubricant using four stroke compression ignition (CI) engine. A thermocouple was used to measure the parameters temperature every 5 minutes interval with the engine operating for an hour under no load, 2.5 kg, 5 kg, and 7 kg load condition. The emission performance was run using neem oil blends as samples. The brief discussion is made on emission performance, fuel efficiency, viscosity index and coefficient of friction. Also, deduction was made for the temperature of crank case oil, coolant and the exhaust gas.

A mini-review of the behaviour characteristic of machining processes of aluminium alloys

The study of aluminum alloys cannot be overemphasized due to their sustainable mechanical, corrosion, and lightweight characteristics. This mini-review paper reviews various aluminum alloys used for the machining process. This study looks at the importance of aluminum alloy's application in the industry, reviewing their behaviour in machining processes under vegetable oil, mineral oil, and Nano lubricant. In order to understand the performance analysis of some selected aluminium alloys (Al) such as Al6060, Al6061, Al6063, Al2024, Al7050, Al7075, and Al8112 Alloys. From the review, it can be seen that bio-degradable Nano-lubricant assists in improving response parameters like surface roughness, materials removal rate, and cutting force during the machining. Furthermore, the authors highlight the challenges of aluminum alloys during machining operations and give a sustainable recommendation of solutions to solve the said challenges.

An experimental investigation and comprehensive modelling of thermal and rheological behaviour of graphene oxide nano platelets suspended mineral oil nano lubricant

Suspension of nano additives in lubricants enhances its thermo-physical behaviour and prolongs the compressor durability in eco-friendly refrigeration systems. Therefore, this study investigates the influence of graphene oxide (GO) nano platelet concentration range of 0.05 – 0.75 vol%, temperature range of 30 – 90 °C and shear rate range of 5.48 s−1 to 190 s−1 on the thermal and rheological behaviour of mineral oil lubricant. Field Emission Scanning Electron Microscopy (FESEM) analysis confirms the platelet structure of GO with a maximum sheet thickness of 5 nm. FT-IR result confirms the pure physical interaction of GO with lubricant. Thermal conductivity and dynamic viscosity of nano lubricants ascended with increasing GO concentration and descended with increasing temperature. The maximum thermal conductivity enhancement of 70% was achieved for the nano lubricant with 0.75 vol% at 30 °C with respect to pure oil. Non - Newtonian shear thinning behaviour was possessed by both pure and nano lubricants at all temperatures. The Artificial Neural Networking (ANN) and mathematical correlation were developed to predict the thermo physical properties of nano lubricants. The maximum R-square value of 0.99998 and 0.9988 was achieved for ANN models of thermal conductivity ratio and relative viscosity of nano lubricants. The ANN model outperforms mathematical correlation by achieving maximum R-square and minimum mean square error (MSE).

Study of Friction and Wear Effects in Aluminum Parts Manufactured via Single Point Incremental Forming Process Using Petroleum and Vegetable Oil-Based Lubricants.

This paper focuses on studying how mineral oil, sunflower, soybean, and corn lubricants influence friction and wear effects during the manufacturing of aluminum parts via the single point incremental forming (SPIF) process. To identify how friction, surface roughness, and wear change during the SPIF of aluminum parts, Stribeck curves were plotted as a function of the SPIF process parameters such as vertical step size, wall angle, and tool tip semi-spherical diameter. Furthermore, lubricant effects on the surface of the formed parts are examined by energy dispersive spectroscopy (EDS) and scanning electron microscope (SEM) images, the Alicona optical 3D measurement system, and Fourier-transform infrared spectroscopy (FTIR). Results show that during the SPIF process of the metallic specimens, soybean and corn oils attained the highest friction, along forces, roughness, and wear values. Based on the surface roughness measurements, it can be observed that soybean oil produces the worst surface roughness finish in the direction perpendicular to the tool passes (Ra =1.45 μm) considering a vertical step size of 0.25 mm with a 5 mm tool tip diameter. These findings are confirmed through plotting SPIFed Stribeck curves for the soybean and corn oils that show small hydrodynamic span regime changes for an increasing sample step-size forming process. This article elucidates the effects caused by mineral and vegetable oils on the surface of aluminum parts produced as a function of Single Point Incremental Sheet Forming process parameters.

Study on hardness and wear resistance of shot peened AA7075-T6 aluminum alloy

AA7075-T6 aluminum alloy samples were shot peened at various shot peening pressures in the range of 10–70 psi to study their mechanical and tribological properties under dry and mineral oil lubrication conditions. The surface roughness of the shot peened AA7075-T6 samples apparently increased with increased shot peening pressure. The best bearing surface was obtained when the shot peening process was carried out at the highest shot peening pressure of 70 psi. It was found that the increased shot peening pressure increased the hardness and decreased the wear of the shot peened samples. The shot peened samples tested under the mineral oil lubrication condition also had lower wear for higher shot peening pressures due to the combined effects of their higher surface wear resistance and better bearing surfaces. The results clearly showed that using the mineral oil lubricant during sliding apparently decreased the wear of the shot peened samples as a result of the lubricating effect of the lubricant. It could be deduced that the tribological properties of the shot peened AA7075-T6 samples under the dry and lubrication conditions were affected by the shot peening pressure.

Oxidative Stability of Vegetal Oil-Based Lubricants.

Lipids are widely distributed in nature and are one of the most important components of natural foods, synthetic compounds, and emulsions. To date, there is a strong social demand in the industrial sector for the use of sustainable products with a minimal environmental impact. Depending on their origin and composition, lipids can be employed as a plausible alternative as biodegradable lubricants in order to reduce the use of conventional mineral oil lubricants and mitigate their environmental impact. This perspective provides an overview of the advantages and constrains of vegetal oils under different lubrication regimes and the tribochemical reactions that can take place. Also, the different factors and pathways that influence their oxidation, the key role of moisture, and the changes of physical properties under pressure and temperature are reviewed. Special emphasis is devoted to the oxidation instability of fatty acids and vegetal oils and the physical and chemical approaches to improve oxidative and thermal stability are described in detail.

Biolubricant Production from Several Oleaginous Feedstocks Using Lipases as Catalysts: Current Scenario and Future Perspectives

In recent years, biolubricants have been gaining further prominence than conventional petroleum-based lubricants. This trend is observed in almost all sectors relying on these products, regardless of their applications. Environmental problems caused by coventional lubricants and the depletion of oil reserves that have led to the need for renewable and biodegradable lubricants are among the factors that contribute to such growing trend. Biolubricants have several advantages over mineral oil lubricants such as high biodegradability, low toxicity, excellent lubricating performance, and minimal impact on the environment and human health. In addition, they can be produced using several types of oleaginous feedstocks and distinct chemical reactions that can be efficiently catalyzed by lipases, which make them quite attractive in the context of Green Chemistry. Thereby, this review describes different aspects of biolubricants by detailing their main applications, properties, uses, and potential feedstocks such as vegetable oils. In this review, chemical modification of their structures using different routes has been highlighted in order to overcome a few limitations for direct application of oleaginuous feedstocks as biolubricants. It also depicts the progress of enzymatic catalysis and immobilization protocols for preparing heterogenous biocatalysts (immobilized lipases), once it is a promising route to obtain a variety of biolubricants based on recent studies described in available literature. Furthermore, future prospects and challenges for enzymatic biolubricant production on an industrial scale are also reviewed.

Synthesis and Characterization of Green Carbon Dots for Scavenging Radical Oxygen Species in Aqueous and Oil Samples.

Carbon dots (CDs) due to their unique optical features, chemical stability and low environmental hazard are applied in different fields such as metal ion sensing, photo-catalysis, bio-imaging and tribology, among others. The aims of the present research were to obtain CDs from vegetable wastes (tea and grapes) as carbon sources and to explore their potential properties as radical scavengers. CDs from glutathione/citric acid (GCDs) were synthetized for comparison purposes. The CDs were investigated for their chemical structure, morphology, optical and electronical properties. The antioxidant activity has been explored by DPPH and Folin-Ciocelteau assays in aqueous media. Due to their solubility in oil, the CDs prepared from tea wastes and GCDs were assayed as antioxidants in a mineral oil lubricant by potentiometric determination of the peroxide value. CDs from tea wastes and GCDs exhibited good antioxidant properties both in aqueous and oil media. Possible mechanisms, such as C-addition to double bonds, H-abstraction and SOMO-CDs conduction band interaction, were proposed for the CDs radical scavenging activity. CDs from natural sources open new application pathways as antioxidant green additives.