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The study investigated the enhancement of soil quality of an oil-polluted ultisol using livestock wastes. Top soil (0 - 10 cm) was obtained as a pooled sample and polluted with spent lubricating oil at 10% w/w. The soil was subsequently amended with sun-dried goat (GT), rabbit (RB), and poultry (PG) dung at 10% w/w on dry weight basis both in singles, double-mixed, and triple-mixed combinations. Twelve weeks after treatment application, results showed that there was a 93.9% decrease (p<0.05) in bacterial colony count in the oil-polluted soil compared to the control. Penicillium notatum and Aspergillus niger as well as Bacillus sp. and Proteus sp. were the prominent fungal and bacterial species identified respectively. The most abundant plant in the soil seed bank was Panicum maximum with 10.4% abundance and this showed possible involvement of the plant in remediation of oil-pollution. The total hydrocarbon content of the oil-polluted soil was 9984.0 mg/kg, compared to 3170.6 mg/kg when amended with RB+GT, implying 76.77% remediation efficiency. Among several trials employed in this study, the combination of rabbit and goat wastes proved to be more effective in reducing the total hydrocarbon content of oil-polluted soil and therefore, is recommended as a potential candidate for application in the bioremediation of such soil.

This paper addresses recycling of waste engine oils treated using acetic acid. A recycling process was developed which eventually led to comparable results with some of the conventional methods. This gives the recycled oil the potential to be reused in cars’ engines after adding the required additives. The advantage of using the acetic acid is that it does not react or only reacts slightly with base oils. The recycling process takes place at room temperature. It has been shown that base oils and oils’ additives are slightly affected by the acetic acid. Upon adding 0.8 vol% of acetic acid to the used oil, two layers were separated, a transparent dark red colored oil and a black dark sludge at the bottom of the container. The base oils resulting from other recycling methods were compared to the results of this paper. The comparison showed that the recycled oil produced by acetic acid treatment is comparable to those recycled by the other conventional methods.

Waste engine oils are hazardous waste oils originating from the transportation sector and industrial heavy-duty machinery operations. Improper handling, disposal, and miscellaneous misuses cause significant air, soil, sediments, surface water, and groundwater pollution. Occupational exposure by prolonged and repeated contact poses direct or indirect health risks, resulting in short-term (acute) or long-term (chronic) toxicities. Soil pollution causes geotoxicity by disrupting the biocenosis and physicochemical properties of the soil, and phytotoxicity by impairing plant growth, physiology and metabolism. Surface water pollution impacts aquatic ecosystems and biodiversity. Air pollution from incineration causes the release of greenhouse gases creating global warming, noxious gases and particulate matter eliciting pulmonary disorders. The toxicity of waste engine oil is due to the total petroleum hydrocarbons (TPH) composition, including polycyclic aromatic hydrocarbons (PAHs), benzene, toluene, ethylbenzene, xylene (BTEX), polychlorinated biphenyls (PCBs) congeners, organometallic compounds, and toxic chemical additives. The paper aims to provide a comprehensive overview of the ecotoxicological effects, human and animal health toxicology and exposure to waste engine oils. It highlights the properties and functions of engine oil and describes waste engine oil generation, disposal and recycling. It provides intensive evaluations and descriptions of the toxicokinetics, metabolism, routes of exposure and toxicosis in human and animal studies based on toxicological, epidemiological and experimental studies. It emphasises the preventive measures in occupational exposure and recommends risk-based remediation techniques to mitigate environmental pollution. The review will assist in understanding the potential risks of waste engine oil with significant consideration of the public health benefits and importance.

Waste engine oil (WEO) and waste polyethylene (WPE) are two common wastes, which are easy to pollute the environment. As the primary material in road construction, natural asphalt is a non-renewable energy source and asphalt is vulnerable to ultraviolet (UV) radiation during the service life. It results in degradation of asphalt pavement performance. In this paper, 2 wt % to 8 wt % of WEO and WPE were used to modify asphalts and the UV aging simulation experiment was carried out. The physical parameters of asphalts before the UV aging experiment show that the asphalt containing 4 wt % WPE and 6 wt % WEO mixture (4 wt % WPE + 6 wt % WEO) has similar physical properties with that of the matrix asphalt. Besides, gel permeation chromatography (GPC) verifies that the molecular weight distribution of the asphalt containing 4 wt % WPE + 6 wt % WEO is close to that of the matrix asphalt. The storage stability test shows that 4 wt % WPE + 6 wt % WEO has good compatibility with the matrix asphalt. The functional groups and micro-morphology of asphalts before and after the UV aging experiment were investigated by Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). FTIR results display that 4 wt % WPE + 6 wt % WEO can effectively reduce the formation of carbonyl and sulfoxide functional groups. AFM shows that 4 wt % WPE + 6 wt % WEO can also retard the formation of a “bee-like” structure in asphalt after the UV aging experiment. Based on the above results, it can be concluded that WEO and WPE mixture can replace part of asphalt and improve the UV aging resistance of asphalt.

Waste materials such as waste tire rubber (WTR), waste cooking oil (WCO), bio-oils, waste engine oil (WEO), and other waste oils have been the subject of various scientific studies in the sustainable and waste research field. The current environmental concerns have been identified to protect natural resources and reuse waste materials. Accordingly, this work reviews the use of recycled waste tire rubber mixed with waste oils (waste cooking oil, waste engine oil) and bio-oils that can be extracted from waste oils to rejuvenate asphalt in reclaimed pavements. This new solution may reduce the massive amounts of WTR and waste oils and produce a more environmentally sustainable material. Reclaimed, aged asphalt has been rejuvenated to achieve various penetration capabilities and properties by blending asphalt with one or more waste materials to evaluate the binder using standard tests. Many solutions with promising results in improving the properties of asphalt mixtures have been selected for further characterization. This review highlights that the addition of WTR and waste materials to rejuvenated asphalt binders improves stability, enhances the viscoelastic properties, provides better fatigue and crack resistance performance, and enhances the compatibility of the rejuvenated rubber oil asphalt. Moreover, the flashing point, softening point, ductility, and penetration of aged asphalt and Poly(styrene-butadiene-styrene)-rubber-rejuvenated and waste-rubber-oil-rejuvenated asphalt were enhanced after applying the rejuvenator compound. On the other hand, adding waste oil to WTR and asphalt reduces the viscosity and enhances the storage stability compared to the asphalt rubber binder.

In order to explore the applicability of waste engine oil and waste cooking oil used in aged asphalt, the effect of waste engine oil and waste cooking oil on aged asphalt recycling was studied through the analysis of the improvement of its physical, chemical, and rheological properties. Six aged asphalt binders with different aging times were obtained by indoor test simulation using the Thin Film Oven Test at 163 °C. Then, waste engine oil and waste cooking oil with five different dosages were added to investigate improvement performances. The results clearly demonstrated that waste engine oil and waste cooking oil could soften and recover the work ability of aged asphalt effectively. Furthermore, the physical, chemical, and rheological performances of six aged asphalts could be improved to normal level of virgin asphalt if the content of waste engine oil or waste cooking oil was suitable. The rheological properties of aged asphalt with waste cooking oil had better improvement than that with waste engine oil. Overall, the good applicability would provide waste oil a much wider service range in asphalt pavement recycling field. It also provided a method of developing new rejuvenating agent with the two waste oils to achieve complex synergism effect. Moreover, it realized the waste cyclic utilization and environmental protection.

This study aims to valorize waste engine oil (WEO) for synthesizing economically viable biosurfactants (rhamnolipids) to strengthen the circular bioeconomy concept. It specifically focuses on investigating the influence of key bioprocess parameters, viz. agitation and aeration rates, on enhancing rhamnolipid yield in a fed-batch fermentation mode. The methodology involves conducting experiments in a stirred tank bioreactor (3 L) using Pseudomonas aeruginosa gi |KP 163922| as the test organism. Central composite design and response surface methodology (CCD-RSM) are employed to design the experiments and analyze the effects of agitation and aeration rates on various parameters, including dry cell biomass (DCBM), surface tension, tensoactivity, and rhamnolipid yield. It is also essential to determine the mechanistic pathway of biosurfactant production followed by the strain using complex hydrophobic substrates such as WEO. The study reveals that optimal agitation and aeration rates of 200 rpm and 1 Lpm result in the highest biosurfactant yield of 29.76 g/L with minimal surface tension (28 mN/m). Biosurfactant characterization using FTIR, 1H NMR, and UPLC-MS/MS confirm the presence of dominant molecular ion peaks m/z 543.9 and 675.1. This suggests that the biosurfactant is a mixture of mono- and di-rhamnolipids (RhaC10C10, RhaRhaC10C12:1, RhaRhaC12:1C10). The findings present a sustainable approach for biosurfactant production in a fed-batch bioreactor. This research opens the possibility of exploring the use of pilot or large-scale bioreactors for biosurfactant production in future investigations.

Traditional asphalt rubber (AR) has a high viscosity and poor fluidity, which makes its construction very difficult. Reducing viscosity has been identified as one of the effective way of solving these problems. Meanwhile, the mass production and improper discharge of waste engine oil (WEO) have a serious impact on the ecological environment, and its rational reuse needs to be addressed. In this paper, molecular models of AR and WEO-modified asphalt rubber (WEOMAR) was established by molecular dynamics (MD) simulations. The influence of WEO on asphalt component’s behavior was studied by radial distribution function (RDF) and diffusion coefficient ( D ). Then, the microscopic mechanism of viscosity reduction was evaluated. Furthermore, the viscosity reduction behavior of WEO in AR was analyzed and verified by basic properties and low field nuclear magnetic resonance (LF-NMR) laboratory tests. The results showed that the RDF peak value of rubber molecules in WEOMAR is 14.07 higher than that of AR, at r  = 2.16 Å. The D of saturated and aromatic components in WEOMAR obviously increased by 140% and 67.9%, respectively. The light component molecules increased after adding WEO into AR. The rubber molecule reduces the contact with asphaltene and resin, and the viscosity of AR is significantly reduced, which is confirmed by the macro tests.

Determination of optimum rejuvenator dosage is critical to the performance of 100% hot recycled asphalt mixtures. Further, at the optimum dosage, the rejuvenated binder is expected to have chemical and mechanical properties similar to the targeted virgin/control binder. The present study used waste engine oil (WEO) and tall oil (TO) to rejuvenate recycled asphalt pavement (RAP) binders obtained from two different sources. The optimum dosages of the rejuvenators were evaluated using different test procedures. The chemical, morphological, and performance characteristics of the RAP binders rejuvenated at the optimum dosages were studied. True fail temperature was identified as the most suitable parameter for estimating the optimum rejuvenator dosage. The optimum rejuvenator dosages of WEO were found to be 19% and 18%, respectively, for the two RAP sources considered in this study. The corresponding dosages for TO were estimated as 17% and 14%, respectively. Saturates-aromatics-resins-asphaltenes (SARA) analysis indicated that the rejuvenators were able to restore the chemical properties of the RAP binders, the degree of restoration being a function of the rejuvenator type and stiffness of the RAP binder. Results from atomic force microscopy (AFM) analysis confirmed that the rejuvenated binders showed the formation of new structures that were unique for different combinations of RAP binder and rejuvenator. Rutting and fatigue characteristics, evaluated using multiple stress creep and recovery (MSCR) and linear amplitude sweep (LAS) tests, respectively, improved after rejuvenating the RAP binders. In terms of rejuvenation and performance characteristics, TO showed better results in comparison to WEO.

Due to the high viscosity, rubber asphalt displays poor construction workability, which ultimately compromises the comfort and safety of pavement. In this study, specified control variates were used to study the effect of the waste engine oil (WEO) addition sequence on the properties of rubber asphalt while ensuring the consistency of other preparation parameters. Initially, in order to evaluate their compatibility, the storage stability and aging properties of the three groups of samples were determined. The variation of asphalt viscosity was then analyzed using a low-field nuclear magnetic resonance (LF-NMR) test, by predicting the fluidity of each sample. Subsequently, the results showed that the rubber asphalt prepared by premixing WEO and crumb rubber (CR) had the best properties of low temperature, compatibility, and fluidity. On this basis, the effects of WEO content, shear rate, shear temperature, and shear time on the properties of low viscosity rubber asphalt were investigated separately through response surface methodology (RSM). Quantitative data from the basic performance experiment were used to fit the high precision regression equation, thereby correlating a more precise level of factors with experimental results. The response surface model prediction analysis showed that the optimal preparation parameters of the low viscosity rubber asphalt were 60 min shear time, 180 °C shear temperature, and 5000 r/min shear rate. Simultaneously, the addition of 3.5% of WEO showed great potential as an asphalt viscosity reducer. Ultimately, this study provides an accurate method for determining the optimum preparation parameters of asphalt.