ALBERT

Description: Neodymium (Nd) is one of the most essential rare-earth metals due to its outstanding properties and crucial role in green energy technologies such as wind turbines and electric vehicles. Some of the key uses includes permanent magnets present in technological applications such as mobile phones and hard disk drives, and in nickel metal hydride batteries. Nd demand is continually growing, but reserves are severely limited, which has put its continued availability at risk. Nd recovery from end-of-life products is one of the most interesting ways to tackle the availability challenge. This perspective concentrates on the different methods to recover Nd from permanent magnets and rechargeable batteries, covering the most developed processes, hydrometallurgy and pyrometallurgy, and with a special focus on electrodeposition using highly electrochemical stable media (e.g., ionic liquids). Among all the ionic liquid chemistries, only phosphonium ionic liquids have been studied in-depth, exploring the impact of temperature, electrodeposition potential, salt concentration, additives (e.g., water) and solvation on the electrodeposition quality and quantity. Finally, the importance of investigating new ionic liquid chemistries, as well as the effect of other metal impurities in the ionic liquid on the deposit composition or the stability of the ionic liquids are discussed. This points to important directions for future work in the field to achieve the important goal of efficient and selective Nd recovery to overcome the increasingly critical supply problems.

Description: The concomitant hydrolysis and dehydration of biomass-derived cellulose and hemicellulose to furfural (FUR) and 5-(hydroxymethyl)furfural (HMF) under acid catalysis allows a dramatic reduction in the oxygen content of the parent sugar molecules with a 100% carbon economy. However, most applications of FUR or HMF necessitate synthetic modifications. Catalytic hydrogenation and hydrogenolysis have been recognized as efficient strategies for the selective deoxygenation and energy densification of biomass-derived furfurals generating water as the sole byproduct. Efficient and eco-friendly catalysts have been developed for the selective hydrogenation of furfurals affording renewable furanic compounds such as 2-methylfuran, 2,5-dimethylfuran and 2-methyltetrahydrofuran with potential applications as biofuel, solvent and chemical feedstock. Hydrogen gas or hydrogen donor molecules, required for the above processes, can also be renewably obtained from biomass using catalytic processes, enabling a circular economy. In this review, the recent developments in the energy densification of furfurals to furanic compounds of commercial significance are elaborated, emphasizing the role of catalyst and the reaction parameters employed. Critical discussion on sourcing hydrogen gas required for the processes, using hydrogen donor solvents, catalyst design and the potential markets of furanic intermediates have been made. Critical evaluations of the accomplishments and challenges in this field are also provided.

Description: Herein, an inexpensive commercially available sensor is presented for the detection of 4-nitrophenol (4NP) pollutant. Sodium fluorescein (NaFl) is used as a sensor to detect trace amounts of 4NP in acetonitrile (MeCN). The photophysical properties of NaFl were studied in two different solvents, MeCN (aprotic) and water (protic), with varying concentrations of different nitroaromatics using UV-visible absorption and fluorescence spectrophotometry. In an aqueous medium, photophysical properties of NaFl did not change in the presence of nitroaromatics. However, examination of the photodynamics in MeCN demonstrated that NaFl is extremely sensitive to 4NP (limit of detection: 0.29 µg/mL). This extreme specificity of NaFl towards 4NP when dissolved in MeCN, as compared to other nitroaromatics, is attributed to hydrogen bonding of 4NP with NaFl in the absence of water, resulting in both static and dynamic quenching processes. Thus, NaFl is demonstrated as a simple, inexpensive, sensitive, and robust optical turn off sensor for 4NP.

Description: Commercially available Purolite CT151 demonstrated to be an efficient acid catalyst for the synthesis of alkyl levulinates via alcoholysis of furfuryl alcohol (FA) at mild temperatures (80–120 °C) and short reaction time (5 h). Reaction conditions were first optimized for the synthesis of ethyl levulinate and then tested for the preparation of methyl-, propyl-, isopropyl-, butyl, sec-butyl- and allyl levulinate. Preliminary scale-up tests were carried out for most of the alkyl levulinates (starting from 5.0 g of FA) and the resulting products were isolated as pure by distillation in good yields (up to 63%). Furthermore, recycling experiments, conducted for the preparation of ethyl levulinate, showed that both the Purolite CT151 and the exceeding ethanol can be recovered and reused for four consecutive runs without any noticeable loss in the catalyst activity.

Description: With the global biodiesel production growing as never seen before, encouraged by government policies, fiscal incentives, and emissions laws to control air pollution, there has been the collateral effect of generating massive amounts of crude glycerol, a by-product from the biodiesel industry. The positive effect of minimizing CO2 emissions using biofuels is jeopardized by the fact that the waste generated by this industry represents an enormous environmental disadvantage. The strategy of viewing “waste as a resource” led the scientific community to propose numerous processes that use glycerol as raw material. Solketal, the product of the reaction of glycerol and acetone, stands out as a promising fuel additive capable of enhancing fuel octane number and oxidation stability, diminishing particle emissions and gum formation, and enhancing properties at low temperatures. The production of this chemical can rely on several of the Green Chemistry principles, besides fitting the Circular Economy Model, once it can be reinserted in the biofuel production chain. This paper reviews the recent advances in solketal production, focusing on continuous production processes and on Process Intensification strategies. The performance of different catalysts under various operational conditions is summarized and the proposed industrial solketal production processes are compared.

Description: The combustion of fossil fuels is intensifying global warming and destructing the ecosystem with negative human health impacts as well. Even so, other anthropogenic activities have unfortunately constituted pollution also to our environment, say, in the form of waste waters. Beside these, the existing technologies for waste water treatment have problems such as high costs, sludge disposal challenges, etc. Thus, it is now important to find economically viable and safe alternatives to decontaminate waste waters. Hence, low cost, renewable, easily accessible, and readily prepared biosorbents have become favourable alternatives to traditional counterpart for the elimination of pollutants from aqueous systems. Fortunately, these biosorbents also have requisite and comparable properties necessary for adsorption of pollutants. Many studies have been reported on the application of biosorbents for pollutants removal. However, this paper provides an overview of biosorbents preparation, properties, their applications in pollutants removal and related use. Biosorbents are usually used in raw or processed forms such as activated carbon (AC), biobar (BC), and charcoal (CC) for removal of pharmaceuticals, pesticides, organics, inorganics, mycotoxins, etc. from aqueous systems. Besides classical sorption of the pollutants, biosorbents have prospect of applications as electrodes in the microbial fuel cells, green packaging materials, energy storage devices, catalysts, soil remediation agent, carbon sequestration, etc. Hence, further concerted investigations should be exercised to develop feasibly best conditions for the preparations and modifications of biosorbents. In addition, mean pore size, pore size distribution, porosity, surface functionality, and zeta potential studies are necessary to be had about biosorbents, especially novel types. There is need for development of biosorbents for specific tasks. Another essential thing is to determine desorption studies of these novel biosorbents. Focus should also be directed on more economically viable and sustainable biosorbents to enhance their use. Again, it is suggested that more suitable biomasses be identified to enable successful preparation of efficient biosorbents. More so, biosorbents can be recycled after use to avoid littering and possible pollution.

Description: Solvents are an inevitable part of industries. They are widely used in manufacturing and processing industries. Despite the numerous controlling measures taken, solvents contaminate our environment to a vast extent. Green and sustainable solvents have been a matter of growing interest within the research community over the past few years due to the increasing environmental concerns. Solvents are categorized as “green” based on their nonvolatility, nonflammability, availability, biodegradability and so on. The use of ionic liquids, super critical carbon dioxide and aqueous solvents for the fabrication of polymer composites is discussed in this review. The progress of utilizing solvent-free approaches for polymer composite preparation and efforts to produce new biobased solvents are also summarized.

Description: The present work evaluates the techno-economic feasibility of a rhamnolipids production process that utilizes digestate from anaerobic digestion (AD) of food waste. Technical feasibility, profitability and extent of investment risks between fermenter scale and its operating strategy for rhamnolipids production was investigated in the present study. Three scenarios were generated and compared: production using a single large fermenter (Scenario I), using two small fermenters operated alternately (Scenario II) or simultaneously (Scenario III). It was found that all the scenarios were economically feasible, and Scenario III was the most profitable since it allowed the most optimum fermenter operation with utilization of multiple small-scale equipment to reduce the downtime of each equipment and increase the production capacity and overall productivity. It had the highest net present value, internal rate of return and shortest payback time at a discount rate of 7%. Finally, a sensitivity analysis was conducted to indicate how the variation in factors such as feedstock (digestate) cost, rhamnolipids selling price, extractant recyclability and process capacity influenced the process economics. The work provides important insights on techno-economic performance of a food waste digestate valorization process which would be useful to guide its sustainable scale-up.

Description: Different alkali deep eutectic solvents (DES), such as LiI:nEG, NaI:nEG, and KI:nEG, have been tested as electrolytes for dye sensitized solar cells (DSSCs). These DSSCs were prepared using pure DES or, alternatively, DES combined with different amounts of iodine (I2). The most important parameters, such as open circuit voltage (VOC), short circuit current density (JSC), fill factor (FF), and the overall conversion efficiency (η), were evaluated. Some DES seem to be promising candidates for DSSC applications, since they present higher VOC (up to 140 mV), similar FF values but less current density values, when compared with a reference electrolyte in the same experimental conditions. Additionally, electrochemical impedance spectroscopy (EIS) has been performed to elucidate the charge transfer and transport processes that occur in DSSCs. The values of different resistance (Ω·cm2) phenomena and recombination/relaxation time (s) for each process have been calculated. The best-performance was obtained for DES-based electrolyte, KI:EG (containing 0.5 mol% I2) showing an efficiency of 2.3%. The efficiency of this DES-based electrolyte is comparable to other literature systems, but the device stability is higher (only after seven months the performance of the device drop to 60%).

Description: This study compared the yield of biodiesel produced from tall oil fatty acids (TOFA) via (i) homogeneous catalyst (sulfuric acid) and (ii) a heterogeneous catalyst (Amberlyst® BD20, together with Ambersep BD 19 (Midcontinental Chemical Co., Olathe, KS, USA)® using a batch reactor. The effect of operation conditions including temperature, catalyst concentration, methanol: oil ratio and reaction time on esterification yield were investigated. Gas chromatographic data showed that the major fatty acids present in the TOFA are oleic acid (C18:1n9) and linoleic acid (C18:2n6). Homogenous catalysis yielded 96.76% biodiesel compared to 90.24% for heterogeneous catalysis. Optimized conditions for homogenous catalysis were at a catalyst concentration of 0.5 w/w%, 15:1 methanol: oil mass ratio at 55 °C for 60 min. FTIR results also showed that the homogeneous catalyst yielded a more complete reaction toward biodiesel production in a shorter time (60 min) compared to the heterogeneous catalyst (4.7 h). For heterogeneous catalysis, the highest yield and the lowest acid value were achieved after a second recycling because the reactants were not fully in contact with the catalyst during the first recycling. The catalyst did not show a reduction in catalytic activity even after the fourth recycling. However, the acid value was higher than that for ASTM standards for biodiesel.