Sustain. Chem., Volume 2, Issue 2 (June 2021) – 10 articles

An effective process to remove nitrogen-based compounds from fossil fuels without harming the process of sulfur removal is an actual gap in refineries. A success combination of desulfurization and denitrogenation processes capable of completely removing the most environmental contaminates in diesel under sustainable conditions was achieved in this work, applying polyoxometalates as catalysts, hydrogen peroxide as oxidant, and an immiscible ionic liquid as an extraction solvent. The developed process based in simultaneous oxidative desulfurization (ODS) and oxidative denitrogenation (ODN) involved initial extraction of sulfur and nitrogen compounds followed by catalytic oxidation. Keggin-type polyoxomolybdates revealed much higher reusing capacity than the related polyoxotungstate. Effectively, the first catalysts practically allowed complete sulfur and nitrogen removal only in 1 h of reaction and for ten consecutive cycles, maintaining the original catalyst and ionic liquid samples. Full article

Endocrine-disrupting compounds (EDCs) are exogenous compounds that interfere with the normal hormone functions and ultimately lead to health disorders. Parabens, phenols, and phthalates are well-known EDCs, produced globally in large quantities and widely used in a variety of applications. Several studies have monitored these compounds in a variety of environmental matrices, including air, water, sediment, fish, human tissues, soil, indoor dust, and biosolids, etc. In recent years, environmental contamination and human exposure to these chemicals have become a great concern, due to their residue levels exceeding the permissible/acceptable limits. In this review, we focus on the origin of these EDCs, aquatic contamination pathways, distribution, human exposure, health implications, and healthcare costs. Further, this review identifies critical challenges and future research needs in removing or minimizing environmental contamination and exposure to these chemicals to protect living resources. Full article

This article describes the synthesis of a new bio-based organocatalytic surfactant. The nine steps of the synthesis were optimized, fully respecting the principles of green chemistry. The surfactant aspect was then evaluated with the use of tensiometric studies. The molecular organization of the surfactant in vesicles in an aqueous medium was characterized by Dynamic Light Scattering (DLS) and confirmed using Density Functional Theory (DFT) modelling. Full article

The stability (longevity of activity) of three crude urease extracts was evaluated in a laboratory study as part of an effort to reduce the cost of urease for applications that do not require high purity enzyme. A low-cost, stable source of urease will greatly facilitate engineering applications of urease such as biocementation of soil. Inexpensive crude extracts of urease have been shown to be effective at hydrolyzing urea for carbonate precipitation. However, some studies have suggested that the activity of a crude extract may decrease with time, limiting the potential for its mass production for commercial applications. The stability of crude urease extracts shown to be effective for biocementation was studied. The crude extracts were obtained from jack beans via a simple extraction process, stored at room temperature and at 4 ℃, and periodically tested to evaluate their stability. To facilitate storage and transportation of the extracted enzyme, the longevity of the enzyme following freeze drying (lyophilization) to reduce the crude extract to a powder and subsequent re-hydration into an aqueous solution was evaluated. In an attempt to improve the shelf life of the lyophilized extract, dextran and sucrose were added during lyophilization. The stability of purified commercial urease following rehydration was also investigated. Results of the laboratory tests showed that the lyophilized crude extract maintained its activity during storage more effectively than either the crude extract solution or the rehydrated commercial urease. While incorporating 2% dextran (w/v) prior to lyophilization of the crude extract increased the overall enzymatic activity, it did not enhance the stability of the urease during storage. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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 (V_OC), short circuit current density (J_SC), 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 V_OC (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%). Full article