Sustainable Chemistry

Single-network hydrogels can have an internal porous structure and biocompatibility, but have lower mechanical properties. Combining these properties with another biocompatible and mechanically strong network can help in mimicking the extracellular matrix of native tissues to make them suitable for tissue scaffolds with desired performance. In the current objective, we combine the properties of poly (ethylene glycol) dimethacrylate (PEGDMA) macromer and polysaccharides as the two components in double networks (DN) for synergistic effects of both components resulting in the interpenetrating polymeric network for making it functional for replacement of injured tissues. The hydrogels were characterized by physical properties like swelling ratio, mechanical properties like tensile and compressive modulus, and rheological behavior. The chemical composition was studied using Fourier transform infrared spectroscopy (FTIR), and the thermal behavior using differential scanning calorimetry (DSC) experiments. Biodegradability and mechanical strength both are gained using double networks (DN), thus making it resemble more like living tissues. DN hydrogels were tested for cell compatibility for possible application in tissue engineering. Furthermore, these properties may allow their application as tissue-engineered scaffolds. Full article

This study investigated and compared the acid-free electropolishing of copper with the state-of-the-art acidic electropolishing process. The acid-free medium used in this study is based on a deep eutectic solvent comprised of 2:1 ethylene glycol and choline chloride. The electrochemical study included voltammetry and chronoamperometry tests during the electropolishing process. The characterization techniques used were atomic force microscopy (AFM) and digital microscopy, and surface morphology comparisons summarized the electropolishing efficiency of phosphoric acid and acid-free deep eutectic solvent treatments for high-purity copper. Electropolishing copper with a deep eutectic solvent resulted in a mirror finish and a post-treatment surface that was 8× smoother than the original metal surface prior to electropolishing treatments with a smoothing efficiency of 91.1 ± 1.5%. This eco-friendly solution produced polished surfaces superior to those surfaces treated with industry standard acid electrochemistry treatments of 1 M H₃PO₄. Full article

Sustainable chemicals and materials management deals with both the risks and the opportunities of chemicals and products. It is not only focused on hazards and risks of chemicals for human health and the environment but also includes the management of material flows from extraction of raw materials up to waste. It becomes apparent meanwhile that the ever-growing material streams endanger the Earth system. According to a recent publication of Persson et al., the planetary boundaries for chemicals and plastics have already been exceeded. Therefore, sustainable chemicals and materials management must become a third pillar of international sustainability policy. For climate change and biodiversity, binding international agreements already exist. Accordingly, a global chemicals and materials framework convention integrating the current fragmented and non-binding approaches is needed. The impacts of chemicals and materials are closely related to climate change. About one third of greenhouse gas (GHG) emissions are linked to the production of chemicals, materials and products and the growing global transport of goods. Most of it is assigned to the energy demand of production and transport. GHG emissions must be reduced by an expansion of the circular economy, i.e., the use of secondary instead of primary raw materials. The chemical industry is obliged to change its feedstock since chemicals based on mineral oil and natural gas are not sustainable. Climate change in turn has consequences for the fate and effects of substances in the environment. Rising temperature implies higher vapor pressure and may enhance the release of toxicants into the atmosphere. Organisms that are already stressed may react more sensitively when exposed to toxic chemicals. The increasing frequency of extreme weather events may re-mobilize contaminants in river sediments. Increasing chemical and material load also threatens biodiversity, e.g., by the release of toxic chemicals into air, water and soil up to high amounts of waste. Fertilizers and pesticides are damaging the biocoenoses in agrarian landscapes. In order to overcome these fatal developments, sustainable management of chemicals and materials is urgently needed. This includes safe and sustainable chemicals, sustainable chemical production and sustainable materials flow management. All these three sustainability strategies are crucial and complement each other: efficiency, consistency and sufficiency. This obligates drastic changes not only of the quantities of material streams but also of the qualities of chemicals and materials in use. A significant reduction in production volumes is necessary, aiming not only to return to a safe operating space with respect to the planetary boundary for chemicals, plastics and waste but also in order to achieve goals regarding climate and biodiversity. Full article

Bioinspired porous microstructures of iron-tannate (Fe(III)-TA) coordination polymer framework were synthesized by catenating natural tannic acid with iron(II), using a scalable aqueous synthesis method in ambient conditions. The chemical composition, morphology, physiochemical properties, and colloidal stability of microstructures were elucidated. The surface area (S_BET) and the desorption pore volume were measured to be 70.47 m²/g and 0. 44 cm³/g, respectively, and the porous structure was confirmed with an average pore dimension of ~27 nm. Microstructures were thermally stable up to 180 °C, with an initial weight loss of 13.7% at 180 °C. They exhibited high chemical stability with pH-responsive amphoteric properties in aqueous media at pH levels ranging from 2 to 12. Supporting their amphoteric sorption, microstructures exhibited rapid removal of Pb⁺² from water, with 99% removal efficiency, yielding a maximum sorption capacity of 166.66 mg/g. Amphoteric microstructures of bioinspired metal–phenolate coordination polymers remain largely unexplored. Additionally, natural polyphenols have seldomly been used as polytopic linkers to construct both porous and pH-responsive amphoteric coordination polymer frameworks with a robust structure in both acidic and basic media. Thus, this de novo porous microstructure of Fe(III)-TA and its physiochemical surface properties have opened new avenues to design thermally and chemically stable, eco-friendly, low-cost amphoteric sorbents with multifunctionality for adsorption, ion exchange, separation, storage, and sensing of both anions and cations present in heterogeneous media. Full article

In this work, the photocatalytic activity of Hydrated Niobium Pentoxide (synthesized by a simple and inexpensive method) was explored in two unknown reactions reported for this catalyst: the photodegradation of phenol in seawater and the photoreforming of methanol. The Hydrated Niobium Pentoxide (Nb1) was synthesized from the reaction of niobium ammoniacal oxalate NH₄[NbO(C₂O₄)₂·H₂O]•XH₂O with a strong base (NaOH). Further treatment of this catalyst with H₂O₂ led to a light-sensitive Hydrated Niobium Pentoxide (Nb2). The photocatalysts were characterized by XRD, DRS, SEM Microscopy, FTIR-ATR, EDX, and specific surface area (SBET). The characterization results demonstrate that the treatment of Hydrated Niobium Pentoxide sensitized the material, increased the surface area of the material, diminished the average particle size, and modified its surface charge, and formed peroxo groups on the catalytic surface. Although both photocatalysts (Nb1 and Nb2) were active for both proposed reactions, the sensitization of the photocatalyst was beneficial in distinct situations. In the photocatalytic degradation of phenol in seawater, the sensitization of the photocatalyst did not enhance the photocatalytic activity. In both photoreactions studied, the addition of the Pt° promoter readily increased the photocatalytic performance of both photocatalysts; in this case, the sensitized photocatalyst recorded the best results. The presence of OH• radicals was confirmed, and the great contribution of the Pt° promoter was in the increase in OH• radical generation; this increase was more effective in the sensitized photocatalyst. Our work demonstrated a simple and inexpensive way to synthesize niobium photocatalysts that can effectively be used in the photodegradation of phenol in seawater and in the photoreforming of methanol to produce hydrogen. Full article

Synthetic ammonia, manufactured by the Haber–Bosch process and its variants, is the key to securing global food security. Hydrogen is the most important feedstock for all synthetic ammonia processes. Renewable ammonia production relies on hydrogen generated by water electrolysis using electricity generated from hydropower. This was used commercially as early as 1921. In the present work, we discuss how renewable ammonia production subsequently emerged in those countries endowed with abundant hydropower, and in particular in regions with limited or no oil, gas, and coal deposits. Thus, renewable ammonia played an important role in national food security for countries without fossil fuel resources until after the mid-20th century. For economic reasons, renewable ammonia production declined from the 1960s onward in favor of fossil-based ammonia production. However, renewable ammonia has recently gained traction again as an energy vector. It is an important component of the rapidly emerging hydrogen economy. Renewable ammonia will probably play a significant role in maintaining national and global energy and food security during the 21st century. Full article

This study aims to investigate the effect of Na doping on the structure, electrical, and electrochemical properties of lithium-rich cathode material. Pristine Li_1.2Ni_0.13Mn_0.54Co_0.13O₂ (LNMC) and Na-doped Li_1.17Na_0.03Ni_0.13Mn_0.54Co_0.13O₂ (Na-LNMC) layered lithium-rich/manganese-rich compounds are prepared by the sol-gel method. The structural and morphological characterization reveals that the Na doping leads to an ordered structure with regular cubic morphology and enlarged Li layer spacing. This enlargement facilitates the diffusion of lithium ion inside the bulk lattice. Electrochemical impedance spectroscopy (EIS) shows that doping by a small amount of Na (3 mol%) decreases the impedance by more than three orders of magnitude and enhances the diffusion of lithium ions in the same proportion. This remarkable improvement in the conductivity and diffusion coefficient of lithium ions of Na-LNMC improves its capacity retention. In addition, this structure and mode of preparation results in “U-shaped” capacity vs. cycle curves, similar to the curves observed for transition metal oxide electrodes, resulting in an exceptional cycle life, tested for up to 400 cycles at 2C. Full article

This review was devoted to outlining the use and potential increasing application of the Design of Experiment (DoE) approach to the rational and planned synthesis of inorganic nanomaterials, with a particular focus on polycrystalline nanostructures (metal and alloys, oxides, chalcogenides, halogenides, etc.) produced by sustainable wet chemistry routes based on a multi-parameter experimental landscape. After having contextualised the stringent need for a rational approach to inorganic materials’ synthesis, a concise theoretical background on DoE is provided, focusing on its statistical basis, shortly describing the different sub-methodologies, and outlining the pros and cons of each. In the second part of the review, a wider section is dedicated to the application of DoE to the rational synthesis of different kinds of chemical systems, with a specific focus on inorganic materials. Full article

The management of municipal and industrial organic solid wastes has become one of the most critical environmental problems in modern societies. Nowadays, commonly used management techniques are incineration, composting, and landfilling, with the former one being the most common for hazardous organic wastes. An alternative eco-friendly method that offers a sustainable and economically viable solution for hazardous wastes management is fast pyrolysis, being one of the most important thermochemical processes in the petrochemical and biomass valorization industry. The objective of this work was to study the application of fast pyrolysis for the valorization of three types of wastes, i.e., petroleum-based sludges and sediments, residual paints left on used/scrap metal packaging, and creosote-treated wood waste, towards high-added-value fuels, chemicals, and (bio)char. Fast pyrolysis experiments were performed on a lab-scale fixed-bed reactor for the determination of product yields, i.e., pyrolysis (bio)oil, gases, and solids (char). In addition, the composition of (bio)oil was also determined by Py/GC-MS tests. The thermal pyrolysis oil from the petroleum sludge was only 15.8 wt.% due to the remarkably high content of ash (74 wt.%) of this type of waste, in contrast to the treated wood and the residual paints (also containing 30 wt.% inorganics), which provided 46.9 wt.% and 35 wt.% pyrolysis oil, respectively. The gaseous products ranged from ~7.9 wt.% (sludge) to 14.7 (wood) and 19.2 wt.% (paints), while the respective solids (ash, char, reaction coke) values were 75.1, 35, and 36.9 wt.%. The thermal (non-catalytic) pyrolysis of residual paint contained relatively high concentrations of short acrylic aliphatic ester (i.e., n-butyl methacrylate), being valuable monomers in the polymer industry. The use of an acidic zeolitic catalyst (ZSM-5) for the in situ upgrading of the pyrolysis vapors induced changes on the product yields (decreased oil due to cracking reactions and increased gases and char/coke), but mostly on the pyrolysis oil composition. The main effect of the ZSM-5 zeolite catalyst was that, for all three organic wastes, the catalytic pyrolysis oils were enriched in the value-added mono-aromatics (BTX), especially in the case of the treated wood waste and residual paints. The non-condensable gases were mostly consisting of CO, CO₂, and different amounts of C₁–C₄ hydrocarbons, depending on initial feed and use or not of the catalyst that increased the production of ethylene and propylene. Full article

Coal Fly Ash (CFA) is a hazardous waste from coal-fired power plants, but has increasingly become a popular supplementary cementitious material for cement in the construction industry. As a secondary resource of REE, its main advantage lies in its fine particle size that eliminates the need for costly and energy-intensive comminution. In this study, the potential of CFA from the Philippines as a secondary REE resource was investigated by direct leaching of REEs with hydrochloric acid (HCl). The CFA sample came from a coal-fired power plant with a circulating fluidized bed combustion (CFBC) technology. For the leaching tests, the effects of HCl concentration, leaching time and leaching temperature on REE extractions were elucidate optimized via Response Surface Methodology (RSM). The RSM results showed that the optimum leaching occurred at 3M HCl, 65 °C and 270 min with extractions of Nd, Er, Eu, Tb and Dy at 70.8%, 76.34%, 88.02%, 90.01% and 73.38%, respectively. According to these results, the CFA from the Philippines is a promising secondary resource of REE and the extraction method employed was effective in achieving a relatively high REE dissolution. Moreover, the empirical model that was established accurately predicted the dissolution of REE with an accuracy of 98.20%, 96.66%, 97.09%, 98.17% and 97.78% for Nd, Er, Eu, Tb and Dy, respectively. Full article

In recent years, the upgrading of lignocellulose bio-oils from fast-pyrolysis by means of ketonization has emerged as a frontier research domain to produce a new generation of biofuels. Propionic acid (PA) ketonization is extensively investigated as a model reaction over metal oxides, but the activity of other materials, such as metal phosphates, is mostly unknown. Therefore, PA ketonization was preliminarily investigated in the gas phase over both phosphates and oxides of Al, Zr, and La. Their catalytic activity was correlated to the physicochemical properties of the materials characterized by means of XRD, XRF, BET N₂ porosimetry, and CO₂- and NH₃-TPD. Noteworthy, monoclinic ZrO₂ proved to be the most promising candidate for the target reaction, leading to a 3-pentanone productivity as high as 5.6 h⁻¹ in the optimized conditions. This value is higher than most of those reported for the same reaction in both the academic and patent literature. Full article

Biomass valorization plays a significant role in the production of biofuels and various value-added biochemicals, in addition to lowering greenhouse gas emissions. In terms of biorefining methods, hydrothermal (HT) and biological techniques have demonstrated the capability of valorizing biomass raw materials to yield value added end-products. An inter-disciplinary bio-economical approach is capable of optimizing biomass’s total potential in terms of environmental perspective and circular bioeconomy standpoint. The aim of this review is to provide an in-depth overview of combinatorial HT and biological techniques to maximize biomass value, which includes biological valorization following HT pretreatment and HT valorization of lignocellulosic substrates emanating from biocatalytic hydrolysis/anaerobic digestion and/or pretreated food waste for the ultimate yield of biogas/biochar and biocrude. In this study, we discuss recent advances regarding HT and biological treatment conditions, synergies between the two technologies, and optimal performance. Additionally, energy balances and economic feasibility assessments of alternative integrated solutions reported in previous studies are compared. Furthermore, we conclude by discussing the challenges and opportunities involved in integrating HT and biologicals methods toward complete biomass utilization. Full article

The reuse of waste materials for water treatment purposes is an important approach for promoting the circular economy and achieving effective environmental remediation. This study examined the use of bone char/titanium dioxide nanoparticles (BC/nTiO₂) composite and UV for As(III) and As(V) removal from water. The composite was produced via two ways: addition of nTiO₂ to bone char during and after pyrolysis. In comparison to the uncoated bone char pyrolyzed at 900 °C (BC900), nTiO₂ deposition onto bone char led to a decrease in the specific surface area and pore volume from 69 to 38 m²/g and 0.23 to 0.16 cm³/g, respectively. However, the pore size slightly increased from 14 to 17 nm upon the addition of nTiO₂. The composite prepared during pyrolysis (BC/nTiO₂)_P had better As removal than that prepared after pyrolysis with the aid of ultrasound (BC/nTiO₂)_US (57.3% vs. 24.8%). The composite (BC/nTiO₂)_P had higher arsenate oxidation than (BC/nTiO₂)_US by about 3.5 times. Arsenite oxidation and consequent adsorption with UV power of 4, 8 and 12 W was examined and benchmarked against the composite with visible light and BC alone. The highest UV power was found to be the most effective treatment with adsorption capacity of 281 µg/g followed by BC alone (196 µg/g). This suggests that the effect of surface area and pore volume loss due to nTiO₂ deposition can only be compensated by applying a high level of UV power. Full article

Ribulose-1,5-biphosphate carboxylase/oxygenase (RuBisCO) is the most abundant protein on the planet, being present in plants, algae and various species of bacteria, with application in the pharmaceutical, chemical, cosmetic and food industries. However, current extraction methods of RuBisCO do not allow high yields of extraction. Therefore, the development of an efficient and selective RuBisCOs’ extraction method is required. In this work, aqueous solutions of biocompatible ionic liquids (ILs), i.e., ILs derived from choline and analogues of glycine-betaine, were applied in the RuBisCO’s extraction from spinach leaves. Three commercial imidazolium-based ILs were also investigated for comparison purposes. To optimize RuBisCO’s extraction conditions, response surface methodology was applied. Under optimum extraction conditions, extraction yields of 10.92 and 10.57 mg of RuBisCO/g of biomass were obtained with the ILs cholinium acetate ([Ch][Ac]) and cholinium chloride ([Ch]Cl), respectively. Circular dichroism (CD) spectroscopy results show that the secondary structure of RuBisCO is better preserved in the IL solutions when compared to the commonly used extraction solvent. The obtained results indicate that cholinium-based ILs are a promising and viable alternative for the extraction of RuBisCO from vegetable biomass. Full article

Magic angle intensity decay and dynamic fluorescence anisotropy measurements were made on the binary solvent system composed of ethylammonium nitrate ([N_2,0,0,0⁺][NO₃⁻], EAN) + methanol (MeOH) across the complete EAN mole fraction range (x_IL = 0–1) using the neutral dipolar solute coumarin 153 (C153) at 295 K. Stokes–Einstein–Debye (SED) hydrodynamic theory was used as a model framework to assess the C153 rotational reorientation dynamics. Departure from stick SED prediction was observed (in contrast to literature reports that used cationic or anionic dyes) and indicated a significant influence of domain nanoheterogeneity on probe dynamics. Steady-state spectroscopy indicated minimal changes in spectral peak and width with mole fraction, except at x_IL = 0.3 where absorption widths decreased by ~170 cm⁻¹, signaling that C153 sensed a change in solution heterogeneity. Magic angle intensity decays corroborated the steady-state observation and the excited-state lifetimes showed a marked change from x_IL = 0.2–0.4 where EAN-EAN interactions became notably more significant. C153 average rotation times ($⟨{\tau }_{rot}⟩$) showed significant solvent decoupling with increased EAN. The rotational data were fit to a power law dependence, $⟨{\tau }_{rot}⟩\propto {\left(\frac{\eta }{T}\right)}^p$, where p = 0.82, demonstrating the presence of dynamic heterogeneity in the EAN/MeOH solutions. With increased EAN, rotation times showed that the heterogeneity became increasingly more significant since the rotation times systematically decreased away from the hydrodynamic stick limit. Full article

Chlorophylls and their derivatives have been extensively studied due to their unique and valuable properties, including their anti-mutagenic and anti-carcinogenic features. Nevertheless, high-purity-level chlorophylls extracted from natural sources are quite expensive because the methods used for their extraction have low selectivity and result in low yields. This study aimed to develop a “greener” and cost-effective technology for the extraction of chlorophylls from biomass using aqueous solutions of ionic liquids (ILs). Several aqueous solutions of ILs, with hydrotropic and surface-active effects were evaluated, demonstrating that aqueous solutions of surface-active ILs are enhanced solvents for the extraction of chlorophylls from spinach leaves. Operating conditions, such as the IL concentration and solid–liquid ratio, were optimized by a response surface methodology. Outstanding extraction yields (0.104 and 0.022 wt.% for chlorophyll a and b, respectively, obtained simultaneously) and selectivity (chlorophyll a/b ratio of 4.79) were obtained with aqueous solutions of hexadecylpyridinium chloride ([C₁₆py]Cl) at moderate conditions of temperature and time. These extraction yields are similar to those obtained with pure ethanol. However, the chlorophyll a/b ratio achieved with the IL aqueous solution is higher than with pure ethanol (3.92), reinforcing the higher selectivity afforded by IL aqueous solutions as viable replacements to volatile organic compounds and allowing the obtainment of more pure compounds. Finally, the recovery and reuse of the solvent were evaluated by using a back-extraction step of chlorophylls using ethyl acetate. The results disclosed here bring new perspectives into the design of new approaches for the selective extraction of chlorophylls from biomass using aqueous solutions of surface-active ILs. Full article

With the fast depleting rate of fossil fuels, the whole world is looking for promising energy sources for the future, and fuel cells are perceived as futuristic energy sources. Out of the different varieties of fuel cells, solid oxide fuel cells (SOFCs) are promising due to their unique multi-fuel operating capability without the need for an external reformer. Nonetheless, the state-of-the-art anode material Ni–YSZ undergoes carburization in presence of hydrocarbons (HCs), resulting in performance degradation. Several strategies have been explored by researchers to overcome the issue of carburization of the anode. The important strategies include reducing SOFC operating temperature, adjustment of steam: carbon ratio, and use of alternate anode catalysts. Among these, the use of alternate anodes is a promising strategy. Apart from the carburization issue, the anode can also undergo sulfur poisoning. The present review discusses carburization and sulfur poisoning issues and the different strategies that can be adopted for tackling them. The quintessence of this review is to provide greater insight into the various developments in hydrocarbon compatible anode catalysts and into the synthesis routes employed for the synthesis of hydrocarbon compatible anodes. Full article