1. Introduction

2. Insights on contaminants of emerging concern (CECs)

3. Treatment technologies

4. Process intensification

5. Conclusions

Acknowledgments

References

Abstract

Urban wastewater treatment plants (WWTPs) are among the major sources of contaminants of emerging concern (CECs) release to surface water. This is mainly associated with the low performance of conventional technologies (e.g. activated sludge, sand filtration and UV disinfection processes) for the removal of residual amounts (ng L-1 – μg L-1) of CECs. In this review, a list of CECs commonly detected in the aquatic environments is presented. Light-driven chemical/catalytic processes for CECs removal, namely UV/oxidant and photocatalysis, are presented with discussion of their process, advantages, drawbacks, and the main attainments. In this context, process intensification has been gaining high relevance for wastewater treatment purposes due to its potential to overcome the main treatment limitations. Accordingly, an overview of advances to overcome the limitations in light-driven chemical/catalytic processes for CECs mitigation was carried out, focusing mainly on the design of novel reactors and devices. Some aspects related to reactor configuration, removal mechanism, devices applied, illumination system, comparison criteria, and catalyst immobilization through implementation of novel reactors designs are also discussed. Regarding the reactor design, several devices exhibit a satisfactory mass transfer due to a large surface-tovolume ratio or enhanced mixing conditions. However, improvements in photon transfer are still the biggest challenge to be overcome. The irradiation of the entire reaction solution and/or catalyst surface has shown to be challenging in many reactor configurations. Nevertheless, the reactor design and treatment process to be applied for CECs removal must be selected according to the site-specific conditions, in order to accomplish CECs mitigation and attain the best reactor performance.

Introduction

About 71 percent of the Earth’s surface is water-covered, however less than 3 percent of this amount can be considered as freshwater [1]. In addition, this limited resource is under threat from the  pollution, mainly caused by human factors. Power generation, industrial, agriculture and mining activities among others are some of the contributors to the aquatic compartments contamination, 6 which affects directly life on Earth [2]. Approximately two-thirds of the world’s population experiences water shortage for at least one month in a year [3]. Additionally, the World Health 8 Organization (WHO) reported that, in the year of 2017, 2 billion people living in various regions all over the world used drinking-water source contaminated with faeces [4]. In fact, it is estimated that almost 1.8 billion people worldwide might face moderate or severe water scarcity by 2025 [5].  Commonly, materials and chemicals used in daily human activities are continuously introduced into the environment. These so-called Contaminants of Emerging Concern (CECs) are one of the main causes of water pollution and, hence, being often related to the risks to human and biota health [6]. Therefore, as water safety and quality are fundamental to human development and well-being, the scientific community has been applying great efforts to the development of efficient technologies for water purification.

1. Introduction

2. Experimental

3. Results and discussion

4. Conclusions

Acknowldgement

Appendix A. Supplementary data

References

Abstract

Handling of petrochemical waste oil (PWO) is costly, tedious, and risky to human health and environment. Hence, upcycling of PWO for biomass conversion to platform chemicals would be very advantageous. Herein, a highly porous sheet-like structure of sulfonated graphene oxide (sGO) catalyst was synthesized from PWO. The synthesized sGO possessed high surface area (246.2 m2 g1) due to its mesoporosity and high content of sulfonic groups (2.4 mmol g−1) grafted onto its surface. As its application, the synthesized sGO was employed to convert fructose to levulinic acid (LA) within deionized water. The high yield (61.2 mol %) of LA was obtained under a condition of 160 °C, 1 h, and 6 g g−1 fructose to sGO weight ratio. It can be reused several times (5 runs) with no severe degradation of catalytic activity. Therefore, the sGO derived from petrochemical waste oil would be considered as an environmentally benign catalyst for producing platform chemicals, i.e. LA from fructose and other biomass derivatives.

Introduction

Heavy reliance on depleting fossil resources to produce platform chemicals and fuels contributes to the economic dilemma and rising emission of greenhouse gases [1-3]. Hence, alternative ways including utilization of biomass in integrated biorefineries have been explored to compete with fossil-based refineries [4]. Biomass is a renewable resource that can be exploited to produce many high value-added products, i.e. alcohol, 5- hydroxymethylfurfural (5-HMF), furfural, formic acid (FA) and levulinic acid (LA) [5, 6]. LA is considered as top ten platform chemicals, which could be further utilized to produce succinic acid, resins, polymers, herbicides, pharmaceuticals, flavoring agents, solvents, plasticizers, anti-freeze agents and biofuels/oxygenated fuel additives [3, 7]. Generally, conversion of biomass into LA involves multiple steps, which are (1) hydrolysis of cellulose to glucose, (2) isomerization of glucose to fructose, (3) dehydration of fructose to HMF, and (4) further hydrolysis to form equimolar LA and FA [2, 8]. These processes are often realized through chemical or enzymatic routes. Nevertheless, the chemical route has been recognized as high potential for commercially viable LA production [9, 10].

In the past, homogeneous acid catalysts (e.g. H2SO4, HCl, H3PO4) were used to ensure a high conversion of reactants because of lower mass transfer resistance [11]. However, those acidic catalysts are corrosive, detrimental to the environment, and non-recyclable [8, 10, 12]. Hence, heterogeneous solid acid catalysts, such as ion-exchange resins, sulfated metal oxides, modified mesoporous silica, zeolites, and natural clays have been developed to overcome the disadvantages of those homogeneous acid catalysts [13, 14]. Recently, several of these types of catalysts have been used for conversion of fructose to LA from actual biomass [15-17].

Introduction

Energy band engineering

Z-scheme overall water splitting

Strategies for photocatalytic hydrogen generation activity improvement

Conclusions

References

Abstract

Bismuth-based composite oxides are always considered the best visible-light photocatalysts for oxygen production. However, they are failed to photocatalytic reduce the hydrogen from water, due to their lower conduction band made up by Bi 6p and O 2p. Thus, it is significant to modulate their levels of the conduction and valence bands satisfying the redox potential for both H+/H2 and O2/H2O, which will directly lead to discovering new visible-light materials for photocatalytic hydrogen generation. Recent years, some modified bismuth-based composite oxides have been reported to achieve photocatalytic hydrogen production. In this paper, a review of photocatalytic hydrogen generation by bismuth-based composite oxides is presented, mainly including energy band engineering, Z-scheme overall water splitting, and strategies for photocatalytic activity improvement.

Introduction

Photocatalytic hydrogen generation from pure water, known as the “holy grail” in chemistry, can convert solar energy directly into green storable chemical energy [1,2]. After decades of development, solar-to-hydrogen energy conversion efficiency has exceeded 1% [3]. However, it is still far from the practical application requirement of at least 10% solar energy conversion efficiency. Thus, photocatalytic hydrogen generation is still in the experimental research stage. Discovering new materials (especially visible-light photocatalysts) and improving solar energy conversion efficiency are still two major themes in research.

Material and methods

Results and discussion

Conclusion

References

Introduction

The diversity of distilled spirits consumed around the world is large. In Europe, the definition, description, labelling and protection of geographical indications of spirit drinks are specified in regulation 110/2008 (1). The standard unit for ethanol concentration is the alcoholic strength by volume (annex I point 11), or ABV (alcohol by volume) in % v/v. The distillation process concentrates the ethanol and volatile aroma compounds from the fermented must, as well as those formed in situ through chemical reactions (2). The quality and specific characteristics of a spirit beverage are highly dependent on the nature and concentration of the volatile compounds and, to a lesser extent, its ethanol concentration. The volatile compounds responsible for the overall aroma perception of spirit beverages belong to many chemical families, such as alcohols, carboxylic acids, esters and aldehydes (2). The precise relationship between volatile compounds and aroma perception is still difficult to assess, owing to the variable nature of volatile compounds, concentration relative to sensory threshold and possible synergies. The diversity of volatile compounds and differences in concentration is mainly due to the raw materials, fermentation method and the distillation process, which includes both the apparatus and the method (3,4). Three main methods are commonly used with a typical distillation apparatus: (a) continuous distillation in a multistage distillation column (e.g. rum, vodka, Armagnac, Calvados, neutral alcohol), (b) batch (simple discontinuous) distillation involving recycling (e.g. Cognac, Armagnac, Auge, Calvados, rum) and (c) batch distillation in a column involving recycling (fruit brandies). The preferred method depends on the organoleptic qualities desired. For instance, full-bodied, single malt whiskies are produced with a batch method in traditional pot stills, while lighter grain whiskies are produced in multistage distillation columns (5). According to Ferrari et al. (6), the behaviour of volatile compounds is different during distillation in pot stills and rectification columns. Indeed, in contrast to esters, it was observed that larger quantities of higher alcohols were recovered in the distillate in continuous distillation than in the simple batch process. This study focused on the behaviour of volatile compounds during simple batch distillation. This method is generally conducted in a traditional copper still, known as an ‘alambic charentais’ (Fig. 1) (3,7–9). Distillation is carried out in two successive cycles. During the first cycle, known as ‘wine distillation’, the wine is introduced into the boiler. An initial small fraction of distillate (‘heads’) is collected and separated. Distillation then continues until the ABV of the distillate reaches ~2% v/v. This second fraction constitutes the low wine, with ethanol concentration between 27 and 30% v/v. The second cycle is the low wine distillation. In analogy with wine distillation, the first fraction of distillate (‘heads’) with the highest ethanol concentration is removed.

Owing to the low cost, abundance and high working voltage, graphite cathodes have attracted tremendous attention in rechargeable batteries, especially in aluminum ion batteries (AIBs) and dual-ion batteries (DIBs). In this review, firstly, a general introduction is given to distinguish the working mechanism of graphite from the conventional metal oxide used as cathode in batteries. Secondly, the characterization methods of anion intercalated compounds, theoretical simulation of anion intercalation behavior into the graphitic cathode and the kinetic study of anion diffusion in graphite are discussed. Then, progresses and challenges of AIBs with different types of graphite cathode materials are presented. Next, typical DIBs systems with graphite cathode, a variety of anodes and electrolytes are introduced in detail. Finally, a conclusion for battery systems with anion intercalation graphite cathodes is draw, and a perspective is outlined to address the existing technical barriers that need to be overcome in future research direction.

Introduction

Background

A rechargeable battery is an electrochemical device that can store electrical energy as chemical energy in its anode and cathode during the charging process, and releases the energy as electrical output during the discharging process [1-3]. An ideal rechargeable battery is expected to have high energy density, high power density, long cycle life, excellent environmental compatibility and low cost [4-15]. Metal ion batteries (MIBs), including lithium ion batteries (LIBs), sodium ion batteries (SIBs) and potassium ion batteries (PIBs) et al. are typical rechargeable batteries, which rely on the metal ions shuttling between the anode and cathode to realize charging and discharging. Among them, LIBs, which possess the merits of long cycle life, high energy and power density and no memory effect, have dominated the battery market of portable electronics and electric vehicles for around two decades and are as well widely used in grid-scale energy storage [5, 16-20]. Despite currently enormous successes in portable electronics and electric vehicles (EVs), LIBs are limited in meeting the growing demand for higher energy and power densities [21-40]. In another aspect, LIBs are plagued by the shortage and high cost of resource metals (Li, Co, Ni etc.) needed in the battery manufacture, and the corresponding environmental pollution of abandoned batteries [17, 41, 42]. Therefore, searching for novel electrode materials, especially cathode materials that of resource-abundant and easily recyclable properties, is in great demand [1]. Graphite is a unique layered structure composed of graphene layers stacked together by the van der Waals force. Since its interlayer space are highly tunable, graphite can accommodate a variety of ions and molecules to form graphite intercalation compounds (GICs), which display applications in electrical, electrochemical and chemical industries because of their unique physicochemical properties. For instance, the reversible intercalation/de-intercalation of metal ions (Li+ , Na+ and K+ et al.) into/from the graphite makes it widely used as anodes for MIBs. Although comparatively less developed, graphite, which have also exhibited the reversible intercalation and de-intercalation of anions such as hexafluorophosphate anion (PF6 – ), bis(trifluoromethanesulfonyl)imide anion (TFSI- ) [43-48], is becoming a promising cathode materials in dual-ion batteries (DIBs), hybrid electrochemical capacitors (ECs) [49, 50] and aluminum ion batteries (AIBs). Among these, DIBs and AIBs are gaining more attention since they have obvious advantages over conventional MIBs: 1) lower cost and resource abundance compared to conventional metal oxide cathode in MIBs; 2) higher voltage, which benefits for a higher energy density [51, 52].

1- Introduction

2- Materials & methods

3- Results & discussion

4- Process analysis

5- Conclusions

References

Abstract

The present paper describes the experimental tests for the recycling of fluid catalytic cracking catalysts (FCCCs). The process aims at the recovery of cerium (Ce) and lanthanum (La) as well as the reuse of the leaching solid residue that represents the actual problem in terms of global amount landfilled every year. Landfilling is still the main choice for the handling of such catalysts. This novel process proposes an alternative recycling approach that leads to the production of synthetic zeolites, that have several industrial applications. FCCC was leached by 1.5 mol/L of HNO3, HCl and H2SO4 solutions at 80 °C, for 2 h with a solid to liquid ratio of 20 %wt, and the two rare earth elements were recovered by precipitation with an overall yield in the range 70–80%. The solid residues from the leaching stage were used as the base material for the synthesis of the zeolites by means of a combined thermal-hydrothermal treatment. The characterization of the zeolites demonstrated that the Na-A phase was predominant over the Na-X phase. The zeolites were tested as sorbent material for CO2 separation from CH4, in order to simulate the upgrading of biogas to biomethane. The maximum adsorption rate of CO2 was 0.778 mol CO2/kg of zeolite at 3 bar, with a resulting CH4 recovery of 62% and 97 %vol as purity. Since the results in adsorption of CO2 were not satisfying, the same zeolites were used to remove heavy metals from a synthetic wastewater solution containing three metals. Equilibrium and kinetic models were also developed in order to describe the adsorption process. The maximum adsorption load was calculated by the Langmuir isotherm and resulted to be 24–32 mg/g for Ni, 52–60 mg/g for Zn and 122–181 mg/g for Cu. The results also showed that the kinetics of the adsorption process is almost fast, as after 1 h at least 95% of zinc and copper were removed, whereas the kinetics of nickel was slower for all the three zeolites. As a conclusion, the zeolites are more efficient in metal adsorption than CO2 capture, but other applications will be tested in the future.

Introduction

In the last fifty years, the significant expansion of the industrial, commercial and agricultural sectors was accompanied by a huge increase in production of petrochemical products and intermediates, as well as refined fuels like gasoline, diesel fuel, kerosene, jet fuel, naphtha, and gas oil. Hence, this led to massive use of catalysts for typical refinery processes like hydrotreating (HT), fluid catalytic cracking (FCC), catalytic reforming (CR), hydrodesulphurization (HDS), alkylation, isomerization. Many of them, once exhaust, can be regenerated by thermal treatments in presence of nitrogen, air or oxygen at a controlled temperature, but after a certain number of regenerations, the catalytic activity is irretrievably compromised. Other kinds of catalysts, like those for FCC, are poisoned by heavy metals such as nickel and vanadium, so that they cannot be regenerated and have to be replaced from time to time with fresh catalyst. The use of rare earths in FCC catalysts was driven by the need for more active and hydrothermally stable products with better yield performance. Rare earth oxides (REO) achieved these goals by enhancing catalytic activity and preventing the loss of acid sites during operation. REO concentration gradually increased over the years, and the average is currently in the range 3e5 %wt. China produces 95% of the world’s rare earths elements (REEs) supply, thus the recovery of such elements from industrial waste will play a crucial role in the future economy of the European countries (BASF, 2018).

With the development of urban infrastructure, subway and other underground projects are gradually being constructed in various cities. The influence of water absorption on surface of cement-based materials has therefore become more and more important. A mathematical model and the relative experiment of water absorption in cement mortar were investigated. The results showed that the change of radius of pore was decreased and absorption mass fraction was increased with the increased of absorption time. The possibility and direction of reaction during this process were studied, and the result showed that hydrolysis was not merely occurred in this process.

Introduction

Cement-based material is one of the most useful materials in civil engineering. Based on the characteristic of porous of cement-based material, its service performance change accordingly. When they are built in the underground environment, water tends to penetrate cement-based materials as capillary force. Because of existence of other ions in groundwater, it penetrated into the materials and lead to be affected of durability of materials. Therefore, the research of absorption of underground water on surface of cement-based materials is important. The recent research of absorption behavior was mainly focused on the fitting equation. the fitting method was adopted in the research of Martys et al.

1- Introduction

2- Experimental methods

3- Results and discussion

4- Conclusions

References

Abstract

Cu2O-CuO layers were prepared in situ on copper foam substrates by thermal oxidation at 400 °C in air using different pretreatments with acetone, HCl and NaOH. The effect of the pretreatment in the shape and physicochemical properties of the Cu2O-CuO layers, as well as in the growth or inhibition of the copper oxide nanostructures was studied, and a growth mechanism is proposed. It was found that the pretreatment modulates the nucleation and growth of the copper oxide nanostructures, being the process with NaOH the most suitable to promote the formation of well-defined nanoneedles, while in the case of the samples pretreated with acetone and HCl, copper oxide layers with irregular shape microstructures were obtained. The composition, structural, morphological and optical properties of the copper oxide structures were determined by X-ray diffraction, scanning electron microscopy, UV-vis diffuse reflectance and photoluminescence spectroscopy. The results showed that in all cases, the presence of both copper oxides, Cu2O and CuO was observed, with an optical band gap of 1.0 and 1.3 eV. The copper oxide structures exhibited photoluminescence emission centered at 551 nm, related to the recombination of the electron-hole pairs in the samples. The materials prepared with a NaOH pretreatment showed the lower emission and recombination rate.
Moreover, the 3D Cu-Cu2O-CuO based materials were evaluated as photocathodes in a 0.5 M Na2SO4 solution and under Xe lamp illumination. The photoelectrode where 1D nanostructures were grown, exhibited the lower resistance to the charge transference in the Nyquist plots, the highest current density in the linear voltammetry and the highest photoresponse in the on-off light experiments. The improved electrical and physicochemical properties of the samples pretreated with NaOH was related to the particular 1D nanoneedle morphology, which promoted higher conductivity and photoresponse, lower resistance to the charge transference and lower recombination of free charge carriers, demonstrating the potential use of these electrodes for photoelectrochemical applications. Finally, this work proved that it is possible to grow well-defined and highly crystalline CuO nanoneedles on copper foam porous substrates through a simple, fast and clean method.

Introduction

1D nanostructured copper oxides have attracted attention recently due to their potential use in several applications such as cathodes for lithium-ion batteries [1,2], gas sensors [3] and biosensors [4,5], catalysts [6] and photocatalysts [7], as well as photocathodes for hydrogen generation from water [8,9], since cuprous and cupric oxides are usually p-type semiconductors, with a direct band gap of approximately 2.0–2.5 eV and 1.3–1.7 eV, respectively [10]. Moreover, these nanostructures are obtained from copper, an earth-abundant metal, and can be synthesized through facile and scalable methods such as simple thermal oxidation of the copper substrate [3,7,11]. Typically, copper oxide structures in the form of nanowires or nanoneedles are grown on copper substrates by thermal annealing at temperatures between 400 °C and 600 °C in air or oxygen atmospheres [12]. CuO wires, sheets and flower nanostructures have been grown on copper foam substrates and studied as supercapacitors [13], while in other work, highly porous CuO structures for batteries and fuel cells were sculptured tunning the pore sizes through the variation of the deposition conditions [14]. The scalable and facile anodization-calcination process was used also for the preparation of copper oxide anodes for ion-lithium batteries [15]. Moreover, the copper-based nanostructures prepared by this method have exhibited high selectivity, sensitivity and stability for gas sensing applications [16]. The shape of the nanostructures has been also modified through the use of surfactants, such as Triton X-100, for obtaining cabbage rose CuO structures on copper foam substrates [17], and core-shell CuO-NiO hybrid structures with enhanced supercapacitance performance have been prepared [18].

Removal of oxygen atoms from triglycerides is the most important step in their conversion into hydrocarbons. Basic catalysts have proven to be highly efficient in deoxygenation, whereby the oxygen atoms are removed in the form of CO and CO2, yielding pyrolytic oil with acid number below 10 mg KOH,g
1 . We have now investigated the deoxygenation abilities of composite basic catalysts during the thermochemical conversion process. The dynamics of the catalytic cracking reaction using metal oxides, such as calcium oxide, in the presence of sodium carbonate, has been tested. According to thermogravimetric analysis (TGA) data, the activation energy for catalytic cracking was influenced by cations. By using calcium oxide as a catalyst, the activation energy was reduced from 260 kJ/mol to 185 kJ/mol, leading to a reduction in the reaction temperature of approximately 20e40 C. The yield of the cracked liquid fraction was of the order of 66e70%, more than 90% of which could be recovered as liquid hydrocarbons. The results presented herein indicate an alternative reaction pathway, allowing thermochemical conversion to be conducted at a lower operational temperature, which would be beneficial for industrial production with lower energy consumption.

Introduction

Biomass is a renewable resource that can be transformed into a variety of chemicals (Dodds and Gross, 2007), biofuels (Dupont et al., 2009a,b), and solid carbon (Simona et al., 2016) through physical and chemical techniques (Liu et al., 2017). The global biomass potential amount is about 200 EJ (up to 600 EJ), accounting for about one-third of the world’s total energy consumption (Rong and Tao, 2016). Making full use of this resource is attractive for addressing resource shortages (Zhang et al., 2018) and environmental pollution problems (Taromi and Kaliaguine, 2018). However, there are economic obstacles to making full use of biomass energy; to obtain the full environmental benefit, green production routes need to be ensured by considering technical conditions, which means green supply chain management (Oliveira. and Rebula, 2018
). Compared with other research, many cases of biomass production are significantly favorable from an environmental point of view, but government subsidies are needed to fully realize the economic benefits (Haskov
a. et al., 2016). So, it is important for economic and environmental friendly production when utilization the biomass energy. Triglycerides are important biomass materials, occurring widely in plant oils and animal fats, and have been used as biofuels for transportation in place of petroleum-based fuels (Lin et al., 2018). Many such oils are used as edible oils in China. As such, considering the economic benefit and resource efficiency, they are not suitable raw materials for hydrocarbon fuels. Nevertheless, abundant waste oil is produced in the refining and consumption of edible oils (Xu et al., 2016). Therefore, non-edible (Marousek et al., 2013) and waste cooking oils (Di_zge N et al., 2009) are primarily used as raw materials.

Introduction

Experimental section

Results and discussion

Conclusions

References

Abstract

Intrinsic activity modifying of electrocatalysts is crucial to realizing the excellent catalytic performance towards hydrogen evolution reaction. Herein, we demonstrate a highly efficient electrocatalyst based on heterogeneous cobalt phosphides nanoparticles. The ultrafine size of the as-prepared catalyst (∼5 nm) ensures the efficient extension of active sites. Furthermore, the incorporation of orthorhombic CoP and Co2P contributes to the improvement of the inherent catalytic property. As a consequence, the as-prepared heterogeneous cobalt phosphides nanoparticles supported on carbon cloth exhibit impressive electrocatalytic activity, which only acquire a small overpotential of 90 mV at a current density of 10 mA cm−2, and present a low Tafel slope (67.9 mV dec−1), a large exchange current density (0.58 mA cm−2) as well as good durability. Therefore, this work provides a favorable guidance for exploring executable strategies to improve catalyst activity.

Introduction

The excessive depletion of fossil fuels has led to many terrible issues, such as the global warming and “energy crisis”. Therefore, the urgency of developing eco-friendly and renewable energy sources attracts a large number of researchers to explore in the energy-related fields [1e4]. Hydrogen, due to its high-energy density and pollution-free combustion products, has been considered as an ideal energy carrier to replace exhaustible traditional energy in the future [5e8]. Electrochemical water-splitting is acknowledged to be the simplest method to gathering high-purity hydrogen, while it always requires highly active catalysts to decrease the overpotential and increase the reactive rate towards hydrogen evolution reaction (HER) [9e11]. Considerable studies have manifested that Pt group metals show excellent HER performance in acidic medium, but their large-scale applications are restricted due to their high economic cost and low abundance [12,13].

1- Introduction

2- Materials and methods

3- Results and discussion

4- Conclusions

References

Abstract

In the present work, an optimization method called Particle Swarm Optimization (PSO) was applied to study the kinetics of alkali-catalyzed rapeseed oil transesterification, using methanol, in a batch process.
The validation of the PSO program was realized using numerical and experimental data from literature. The PSO method resulted in a 4 times lower error compared to classic methods used in the domain, which showed its efficiency and strength.
After validation, an experimental study was led on the transesterification of rapeseed oil and methanol in a batch process using KOH as catalyst (1wt/wt %) with a methanol:oil molar ratio of 6:1 at 45 °C, 55 °C and 65 °C respectively. Then, PSO was used in order to determine the reaction rate constants () of the reversible 3-steps of transesterification mechanism as well as the kinetic parameters (activation energy Ea and pre-exponential factor A).
Then, the kinetic model was used in order to investigate the effects of methanol: oil molar ratio variation (3:1, 4:1, 5:1, 6:1, 8:1, 12:1) on rate constants, yield and conversion rate at 65 °C.
The results of the simulation showed a perfect agreement with experimental results.

Introduction

The consumption and production of biodiesel continue to increase worldwide. Biodiesel being a source of green and renewable energy, it is considered as an alternative fuel to conventional diesel oil [1]. The synthesis of biodiesel from oil can be performed by several methods such as thermochemistry [2, 3] i.e. esterification and transesterification via catalytic or non-catalytic pathways [4, 5, 6, 7]. Alkali-catalyzed transesterification is the most commonly used and consists in reacting a triglyceride molecule with three molecules of alcohol to produce three molecules of methyl ester, known as biodiesel, and one molecule of glycerol [8, 9]. The catalytic transesterification reaction follows a three-stepped reaction scheme, as illustrated in Fig. 1. During the first, step the decomposition of triglycerides (TG) to diglycerides (DG) occurs with a formation of one methyl ester, the second one transforms diglycerides to monoglycerides (MG) and methyl ester, and the last step is the decomposition of monoglycerides into glycerol and methyl ester [10]. In order to determine the kinetic parameters of the reaction (activation energy and pre-exponential factor), a kinetic study is required. This study is essential to design and upscale facilities to industrial level. Several researches on the kinetics of homogeneous and heterogeneous catalysis of transesterification have been carried out using different raw materials and synthesis methods [11, 12, 13, 14, 15]. Ramezani et al. [16] studied parameters affecting the transesterification reaction of castor oil in order to optimize its yield and used their results to adjust a kinetic correlation using the pseudo-first order hypothesis.

Mechanical characteristics of the asphalt binders and mixtures were enhanced by utilising modifiers. The crumb rubber modifier has been introduced to the asphalt modification as an environmentally friendly procedure of scrap tires, to improve the mechanical characteristics of the asphalt. This study aims to modify the dry method for mixing crumb rubber modifier with asphalt and aggregate based on the binder mix design. To achieve this goal crumb rubber modified asphalt mixtures were prepared and tested by applying various tests such as Marshall Stability test, indirect tensile strength test, and wheel tracking test. Three mixing methods of CRM were studied regarding evaluating the stability, rutting, and moisture susceptibility. The crumb rubber modifier dry mixing method was modified and named the complex process. Better results were achieved for enhancing mechanical properties.

Introduction

To reduce the environmental effects of roads building and maintenance, necessary to find solutions capable of increasing the performance of the pavement while decreasing the negative impacts. In this context, the utilisation of recycled materials appropriate for other re-uses must be progressed and enhanced [1,2]. The fields of application of CRM in road constructions are miscellaneous. The previous researchers validate them are as numerous as the number of positive results achieved in recycling this material [1]. The usage of the recycled rubber from the End of Life Tires into the bitumen concretes was began in the 1960s. The technology that has spread more is the so-called Asphalt Rubber (AR) one. AR binders produced with the manufacturing process innovated by Charles McDonald, and that is at the foundation of the wet process. This method began with the mix of the end of life tire ground rubber with the asphalt binders utilising mechanical stirring systems, operating at temperatures ranging between 190 and 218 C, for a time interval of 45–60 min [3–6].