Sustainable Chemistry

Green chemistry and engineering encourage the usage of renewable sources, in replacement fossil fuels. The sector of bio-based products is one of the most predominant examples of such replacements in different fields. However, the impact of biomasses usage is far from being negligible or net zero. A life cycle perspective is required in order to assess all the different environmental impacts related to biomass exploitation and usage, in particular when dedicated sources are used. This study points out the importance of including the results of a Life Cycle Assessment (LCA) early in the design of new bio-based products, to identify the stage of the value chain with the greatest hotspots and set proper eco-design strategies. At the same time, the use of the LCA results may support purchasing activities through comparing products with different burdens. In this manuscript, a focus on land compartment is carried out, given its relevance to the cultivation phase. Five analysis methods are selected for further description. Three are classified as multi-impact approach methodologies (ReCiPe 2016, IMPACT World + and EF 3.0) since they are able to translate mass and energy balances into several impact categories at the same time, not only those on land comparts which are also included. In addition, the LANCA^® model and the True pricing method for agri-food products are discussed, underlining the importance of their usage when a detailed review of the impact on soil is necessary (e.g., during an environmental impact assessment). They are compared in this paper, underlining the main differences and potential fields of application. Full article

The microfluidic production of simple (microspheres) and core–shell (microcapsules) polymer microparticles, often called microencapsulation, has been the scope of several research works since the 1980s. It is a fast, thrifty, and efficient process because of its controlled properties, tuneability, and yield, which can reach 100%. However, the question of its greenness, sustainability, and scalability remains unclear, and more awareness/education is required in this field. The sustainability of production processes using microfluidic techniques can be realized/discussed based on three pillars: (i) waste generation, (ii) the solvents employed, and (iii) raw materials. On the other hand, although the scaling-up of these processes was reported on in several papers as procedures in which hundreds or thousands of microfluidic chips are set in parallel, the sustainability of this scale-up has not been addressed to our knowledge. This opinion paper highlights the advantages of microfluidic encapsulation processes, their greenness according to the above-mentioned pillars, (i–iii) and the necessary considerations to scale them up while preserving their sustainability. Full article

Graffiti can create detrimental aesthetic and environmental damage to city infrastructure and cultural heritage and requires improved removal methods. Incumbent laser, mechanical and chemical removal techniques are often not effective, are expensive or damage the substrate. Solvents are generally hazardous and not always effective because of the insolubility of the graffiti paint. This study proposes a simple strategy for safe and effective graffiti removal, using the bio-based, non-toxic and biodegradable solvent dihydrolevoglucosenone (Cyrene™). The results showed that the type of substrate influenced the cleaning performance; in benchmark studies a non-porous substrate was easy to clean, while porous ceramic showed the presence of residual paint and yellowing when the conventional polar aprotic solvents were used. Cyrene, however, showed good removability of graffiti paint from both glazed and porous substrates, with little paint remaining in the pores of ceramic tiles. The paint suffered a reversible change in colour and a selective solubility of its components when using N-methyl-2-pyrrolidone; no changes occurred when Cyrene was used. While N-methyl-2-pyrrolidone and N,N′-dimethylformamide were only effective when neat, a Cyrene–water mixture showed some cleaning results. The performance of Cyrene was validated with Hansen solubility parameters and represents a greener and more sustainable solvent for paint removal. Full article

The objective of this work was evaluation of the supercritical antisolvent extraction (SAE) process to generate microparticles with antioxidant activity from Moringa leaves. A biodegradable polymer was used as an inductor of particle precipitation. An ethanolic extract of 25 mg/mL was used in the SAE process, during which the influences of pressure (100–200 bar), temperature (35–55 °C) and extract–polymer ratio (0.11–0.33) on particle size and antioxidant activity were evaluated. An extract flow rate of 3 mL/min, a supercritical CO₂ (scCO₂) flow rate of 30 g CO₂/min and a nozzle diameter of 100 µm were kept constant. The identification of several compounds of Moringa leaves, namely, coumaric acid and quercetin 3D glucoside, were determined with ultra-performance liquid chromatography coupled with mass spectrometry. The antioxidant activity of the extract and the precipitates was measured with 2,2-Diphenyl-1-picrylhydrazyl. Spherical microparticles with diameters in the range of 2–5 µm were obtained, with moderate antioxidant activity. Full article

Palm oil mill effluent (POME) is considered the most environmentally harmful when discharged without proper treatment. In addition to conventional biological treatment methods, physicochemical treatment techniques are considered alternative methods to treat POME as polishing or post-treatment techniques to meet the discharge water quality standards set by authorities. Recently, electroflotation (EF) has gained popularity in wastewater treatment owing to its high efficiency, no harmful by-products, and ease of operation. However, EF has limitations on energy consumption because high current density and long electrolysis time are often used to increase the density of gas bubbles and metallic ions produced in the EF system used in pollutant removal. Polyaluminum chloride (PAC) and cationic polyacrylamide (CPAM) are used as alternative options for the production of coagulants instead of using a sacrificial anode in EF. In this study, we hypothesized that PAC and CPAM could enhance the efficiency and reduce the specific energy consumption of EF by minimizing the electrolysis time used in POME treatment. The effects of electrolysis time, current density, and coagulant dosage on POME treatment were investigated. EF treatment at a current density of 2.5 mA/cm² has achieved 82% of turbidity and 47% of chemical oxygen demand (COD) removal after 45 min electrolysis time, consuming 0.014 kWh of specific energy for the treatment of one gram of COD. There was no improvement in terms of turbidity removal when the current density was increased from 2.5 to 5 mA/cm²; however, the COD removal efficiency was increased up to 52% at 5 mA/cm². When EF was performed at 1 A combined with PAC at a dosage of 40 mg/L and CPAM at a dosage of 20 mg/L, it was noticed that turbidity and COD removal increased up to 96% and 54%, respectively, within 15 min electrolysis. Subsequently, the specific energy consumption was reduced to 0.004 kWh (by 71%) per one gram of COD treatment. Results confirmed that the chemical coagulants could increase the POME treatment efficiency and reduce the specific energy consumption of EF. However, this method can be improved aiming at further reduction of COD by mineralizing the dissolved organic compounds to fulfill the POME discharge quality standards. Full article

The current study examines the feasibility of recycling artificially polluted wastewater that contains crystal violet (CV) organic dye by using Azadirachta indica sawdust (AISD) waste as a highly cost-effective adsorbent. Different analytical techniques, viz., SEM/EDX, TEM/SAED, BET, XRD, TGA-DTG, point of zero charge (pH_pzc), and FTIR, were used to characterize the adsorbent. Studies of batch adsorption were performed with varying contact times, starting concentrations of CV, pH levels, doses and particle sizes of AISD, and temperatures. After assessing the results using the Langmuir, Freundlich, and Temkin isotherm models, it was observed that the Langmuir model best fits the data. Various models were employed to analyze the kinetic findings, and it was confirmed that the pseudo-second-order model appears to be the most accurate. The values of ΔH° (50.01 kJ mol⁻¹), ΔG° (−10.254 to −5.043 kJ mol⁻¹), and ΔS° (182.47 J K⁻¹mol⁻¹), obtained in a temperature range of 303–333 K, revealed that the process was spontaneous, endothermic, and accompanied by an increase in entropy. Based on experimental findings and their analyses, it was concluded that the adsorbent made from AISD is one of the most effective among those obtained from domestic, agricultural, and industrial wastes. Thus, the present adsorbent can be effectively exploited to make dye-contaminated water reusable. Full article

This work deals with the development of non-isocyanate polyurethane (NIPU) composites with an aniline oligomer, viz., tetraniline (TANI) for corrosion-resistant coatings. Firstly, epoxidizedsoyabean oil was converted to carbonated oil by inserting CO₂ under high temperature and pressure into the epoxy ring. Then, varying weights of oligoaniline—0.5, 1, 2 and 4 wt % (based on the weight of CSBO)—were added to CSBO and cured with tetraethylenepentamine (TEPA, 25 wt % based on CSBO) at 80 °C for 12–15 h. The effects of oligomer loading on the thermal, mechanical and surface wetting properties of the free standing films were studied. The ATR-FTIR spectra of the films exhibited peaks corresponding to the bis-carbamate linkages, confirming the formation of urethane linkages. TGA analysis showed that the addition of oligoaniline did not alter the initial degradation temperature much; however, the residue increased with increasing loading of tetraniline. Both tensile strength and elongation (at break) increased with increasing oligoaniline content. While the glass transition temperature of the films was observed at approximately room temperature, i.e., 20–30 °C, for all the compositions, the contact angles of the composites were found to be less than that of the bare NIPU films. However, all the compositions were hydrophobic, exhibiting contact angles in the 98–110° range. SEM analysis of the cross-sections of the films confirmed the uniform distribution of tetraniline particles and surface morphology showed that the roughness increased with the loading of tetraniline from 0.5 to 4%. MS panels coated with NIPU exhibited good barrier properties and as loading of TANI increased, the rate of corrosion decreased. Salt spray tests indicated that oligoaniline improved the adhesion of the coating to MS and corrosion resistance compared to the neat NIPU coating. Full article

Owing to the unique property of large surface area/volume of nanoparticles, scientific developments have revolutionized the fields of nanotechnology. Nanoparticles can be synthesized through physical, chemical, and biological routes, where biologically synthesized nanoparticles are also referred to as biogenic-synthesized nanoparticles or bionanoparticles. Bionanoparticles exploit the inherent reducing property of biological entities to develop cost-effective, non-toxic, time-efficient, sustainable, and stable nanosized particles. There is a wide array of biomedical focus on metallic nanoparticles, especially silver nanoparticles, due to their distinctive physiochemical properties making them a suitable therapeutic molecule carrier. This article aims to provide a broad insight into the various classes of living organisms that can be exploited for the development of silver nanoparticles, and elaboratively review the interdisciplinary biomedical applications of biogenically synthesized silver nanoparticles in health and life sciences domains. Full article

Solvent-free mechanochemical reactions represent an important path towards sustainable chemistry. The preparation of Prussian blue from solid iron and hexacyanoferrate compounds by the simple use of a mortar and pestle is an easy, inexpensive, and fast method to teach mechanochemical reactions. The course of the reaction can be followed very well visually via the color change of the solid mixture towards blue. With this communication, earlier publications on Prussian blue and mechanochemistry in the field of chemical education are updated and extended. Full article

Bioactive compounds like piperine (alkaloids) offer a variety of health benefits due to their biological and pharmacological potential. Piperine has been revealed to have anti-inflammatory, anti-aging, anti-diabetes, anti-bacterial, anti-ulcer, and anti-carcinogenic characteristics. Recent research has been conducted to extract piperine using effective and environmentally friendly techniques. In this study, we sought to assess the potential and efficacy of natural deep eutectic solvents to extract piperine from black pepper seeds using an ultrasound-assisted extraction technique. A Box–Behnken design combined with response surface methodology was used to evaluate the optimum extraction conditions of piperine. Extraction efficiency was evaluated based on the extraction yields of piperine, antioxidant activity, total polyphenols, and total flavonoids. The results showed that the choline chloride-citric acid-1,2-propylene glycol combination (1:2:2 molar ratio) with 25% (v/v) of water was the most effective at extracting piperine from black pepper. It was found that the extraction yield of piperine was significantly influenced by the liquid–solid ratio and extraction time. The optimal extraction conditions were determined and it was found that antioxidant activities and total polyphenol content in the piperine-rich extracts were remarkably related to the piperine content. The piperine extract purity was found to be 90%. Our results indicate that black pepper could be used as a functional food application. Full article

The fabrication of metal oxide nanofibers using (titanium (IV) isopropoxide) and (tin (IV) tert-butoxide) of weight ratio 1:1 precursor in presence of poly (vinyl pyrrolidone) as a binder using a well-known electrospinning technique is reported. The average diameter of TiO₂, SnO₂, and composite TiO₂-SnO₂ nanofibers were found to be in the range 75–110 nm. The nanofibers were characterized using thermogravimetric analysis (TGA) to understand the polymer evaporation temperature and further analyzed using scanning electron microscopy (SEM) to study the morphology of the nanofibers. The oxidation states of titanium (Ti) and tin (Sn) ions were analyzed using X-ray photoelectron spectroscopy (XPS), indicating that the TiO₂ undergoes a change even after loading SnO₂. The photocatalytic efficiency of the composite TiO₂-SnO₂ fibers was investigated to study the degradation capabilities under ultraviolet (UV) light towards industrial polluting dyes such as Alcian Blue, Alizarin Red S, Bilirubin, Brilliant Blue, Bromophenol Blue, and Rhodamine B ITC. Rhodamine B showed a significant degradation rate of about 0.0064 min⁻¹ in comparison to the other dyes. Full article

In this work, a greener approach for the extraction of Greek propolis using ultrasound-assisted extraction method in combination with Natural Deep Eutectic Solvents (NADES) is presented. Propolis is a natural material of outmost interest as it possesses various biological and pharmacological activities and is therefore used for the manufacturing of extracts useful to various fields, such as pharmaceutics, cosmetics etc. Herein, five NADES were task-specifically selected as appropriate extraction solvents since they provide important assets to the final NADES-extracts, comparing to the conventionally used organic solvents. The screening study of the prepared solvents indicated the NADES L-proline/D,L-Lactic acid as the most effective medium for the raw propolis extraction due to the extract’s high total phenolic content as well as its’ significantly higher antioxidant activity. Then, the extraction using the selected NADES, was optimized by performing Experimental Design to study the effect of extraction time, propolis-to-solvent ratio and the %NADES content in the NADES-water system. All the extracts were characterized regarding their antioxidant activity and total phenolic content. The optimum NADES-extract as well as an extract derived by extraction using a conventional hydroethanolic solution were further characterized by performing LC/MS/MS analysis. The results showed that the NADES-extracts composition was similar or superior to the hydroethanolic extracts regarding the presence of valuable phytochemicals such as apigenin, naringenin etc. A disadvantage that is usually mentioned in the literature regarding the extractions using NADES is that the extracted bioactive compounds cannot be easily separated from the NADES in order to obtain dry extracts. However, this drawback can be converted to an asset as the task-specifically designed NADES that are used in this study add value to the end product and the optimum as-obtained NADES-extract has been successfully incorporated in a cosmetic cream formulation. In this work, The antioxidant activity and organoleptic characteristics of the cream formulation were also determined. Full article

Shellac and aleuritic acid manufacturing industries generate a lot of alkaline aqueous effluent during the process of manufacture of shellac and aleuritic acid from the seedlac/sticklac. The generated effluent contains lac resin, lac wax, lac dye and other water-soluble organic acids. Shellac industries in India face problems with the disposal of aqueous effluent due to the presence of considerable amounts of natural organic molecules and the dark colour solution. To address these problems, we have developed a novel method for the selective recovery of the lac resin from the alkaline aqueous effluent of shellac manufacturing industry. The recovered lac resin has been characterized by ¹³C-NMR, FT-IR and melting point and the data were compared with standard industrial-grade resin. The recovered lac resin was evaluated by the lac manufacturing industry for commercial applications. Full article

The facile and green synthesis of 1,1′-binaphthalene-2,2′-diamine (BINAM) derivatives was established via the anodic dehydrogenative homo-coupling of 2-naphthylamines. The sustainable protocol provided a series of BINAMs in excellent yields of up to 98% with good current efficiency (66%) and H₂ as the sole coproduct without utilizing transition-metal reagents or stoichiometric oxidants. Full article

Among the various existing metals, zinc and copper are predominant metals in several effluents from industries such as electroplating, plastics production and mining. Technical methods have been applied in the treatment of effluents containing metals, including chemical removal, adsorption, ion exchange, membrane technologies and electrochemistry. However, it is necessary to develop technologies that minimize costs and increase treatment quality while reducing residual sludge generation. Adsorption using biological materials stands out for removing metals, a low-cost technique and high efficiency. Thus, this study evaluated metal adsorption using an adsorbent from granular and powdered anaerobic sludge, followed by a kinetic analysis, aiming at a new alternative for wastewater treatment. Evaluation of the copper and zinc adsorption process using granular and powdered biomass resulted in maximum removals of 72.9% and 62.7% for zinc, respectively, and 92.8% and 85.0% for copper, respectively. Analyzing the kinetic models, the pseudo-second-order model fitted the data better. Applying the kinetics of other studies in the literature for copper and zinc removal by other adsorbents, the pseudo-second-order model was the most representative model. In this context, kinetic modeling allowed the determination of the solute removal rate, estimating the adsorption mechanism. Full article

The following article introduces, in a thorough manner, how the chemical pozzolanic reaction takes place in cement composites containing the fly ash (FA) additive. In the research part, however, the development of phases in the structure of the cement paste in the initial period of its curing and after 28 days from its preparation was traced. For this purpose, a Scanning Electron Microscope (SEM) was used. In order to accurately highlight all the characteristic stages of the formation of the structure of the composite containing FA, an analysis of the cement matrix was carried out between 0.5 and 28 days of their curing. Microstructural studies were complemented by tests of pozzolanic activity of FAs used. In order to conduct a full analysis of this feature, experiments were carried out using two types of research methods, i.e., chemical and physical. On the basis on the conducted studies it was found that: in cement composites with the addition of FA, in the period until the third day of curing, the development of the material structure is mainly the result of the hydration reaction, and between the seventh and fourteenth day after sample preparation, the first signs of the pozzolanic reaction on FA grains are visible; however, in the period between 14 and 28 days, there is a clear homogenization of the structure of the cement composite with the addition of FA, resulting from the change of disordered phases into compact and homogeneous forms and filling in the composite of porous places with pozzolanic reaction products. The use of cement composites based on materials whose application makes it possible to reduce GHG emissions to the atmosphere, reduce energy consumption, and reduce industrial waste landfills leads towards the development of ecological and sustainable building engineering. Full article

Brown carbon is a type of strong light-absorbing carbonaceous aerosol associated with radiative forcing. Nevertheless, the difficulty in correlating the chemical composition of brown carbon with its light absorption properties impairs the proper elucidation of its role in radiative forcing. Here, we have used a time-dependent density functional theory (TD-DFT)-based procedure to revisit the “real-world” absorption spectra of polycyclic aromatic hydrocarbons (PAHs) over the city of Porto, in Portugal, while correcting the spectra for their quantity in PM₁₀ particulate matter. Our aim is to, by comparing these new results with those obtained previously regarding PM_2.5 data, evaluate the role of different groupings of particulate matter in the light absorption of brown carbon. The results indicate that irrespective of the absorption spectra corresponding to their PM₁₀ or PM_2.5 data, the studied PAHs should contribute to radiative forcing by light absorption at UVA and (sub)visible wavelengths. However, the identity of the individual PAH species that contribute the most for the considered wavelengths can be quite different. Thus, different groupings of particulate matter appear to provide distinct contributions to light absorption and radiative forcing over the same location, even when considering the same class of molecular compounds. Full article

The presence of abrasive particles in ceramic reinforced composite materials makes the machining complicated by generating friction at elevated temperatures. Lubricants can be used to prohibit the hazard of higher temperatures. This research work is focused on examining the effects of lubricants on the grinding performances of Al matrix composites reinforced with nano-SiC particles under minimum quantity lubrication (MQL). A cylindrical grinding machine is used to perform the grinding experiments by employing a Box–Behnken design. Multiple performances, such as surface roughness, grinding forces and temperature, are optimized by considering the depth of cut, speed of the workpiece, wheel speed and wt % of nano-SiC using response surface methodology (RSM)-based artificial bee colony (ABC) algorithm. Atomic force microscope (AFM) and scanning electron microscopy (SEM) are used to observe the morphologies of the machined surfaces and the wheel. Full article