Sustain. Chem., Volume 4, Issue 2 (June 2023) – 8 articles

In this paper, we illustrate the synthesis, characterization, and application of a Bovine Serum Albumin-stabilized copper nanocluster (BSA@CuNCs)-based photoluminescence (PL) bifunctional sensor for the selective and rapid sensing of picric acid (PA) and hydrogen peroxide (H₂O₂). Blue-emitting copper nanoclusters were synthesized using one-pot synthesis at room temperature. The PL intensity of BSA@CuNCs was shown to be quenched (“Turn-off”) with an increase in the concentration of PA and intensified (“Turn-on”) with the addition of H₂O₂. The quenching of PL intensity of BSA@CuNCs was shown to be extremely selective and rapid towards PA. A linear decrease in the PL emission intensity of BSA@CuNCs was observed with a PA concentration in the range of 0–15 μM. An extremely low detection limit of 60 nM (3σ/k) was calculated. The as-prepared BSA@CuNCs also exhibited superior selectivity for PA detection in aqueous medium. The developed sensor was also utilized for the sensing of PA in natural water samples. The probe was found to be extremely sensitive towards the detection of H₂O₂. An increase in the PL intensity of BSA@CuNCs was seen with the addition of H₂O₂, with a detection limit of 0.11 μM. Full article

Water pollution caused by emerging contaminants such as pharmaceutical compounds is a growing problem worldwide. In this reported work, graphene oxide (GO) was directly used to remove an antihistamine drug, cetirizine. GO was prepared from graphite using a modified Hummer’s method and was characterized by UV–vis spectroscopy, Fourier-transformed infrared spectroscopy (FTIR), thermogravimetric analyzer (TGA), field scanning electron microscope (FE-SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), etc. GO was demonstrated to be a highly efficient adsorbent for removing cetirizine from an aqueous solution. The adsorption of cetirizine on GO at various pH levels showed that in acidic pH with the adsorption shows faster kinetics and complete removal of cetirizine within 10 min, followed by neutral pH, which showed relatively slower kinetics but complete removal of cetirizine. However, at basic pH, GO could not completely remove cetirizine after 24 h. At a neutral pH, GO showed maximum adsorption of 81.30 mg g⁻¹ of cetirizine. The adsorption isotherm results showed good agreement with the Langmuir isotherm. The BET surface area analysis showed the presence of mesoporosity in GO. In addition, the BET analysis further revealed a type IV isotherm curve being followed. A plausible mechanism is also discussed in the paper. The recyclability experiment demonstrates an adsorption efficiency of 85% after four cycles. The thermodynamic study reveals that adsorption is thermodynamically less favorable at higher temperatures. Hence, the current study successfully demonstrates the use of GO as an efficient adsorbent in removing cetirizine. It also studies the various factors and interactions affecting adsorption. Thus, this study sheds light on the adsorption characteristics of cetirizine on graphene oxide. Full article

Highly efficient silicone surfactants are typically based on polyether hydrophiles. As part of a program to increase the natural content of silicones, we describe the synthesis of silicone surfactants with amino acid hydrophiles (cysteine, arginine, and lysine). The compounds were prepared using a radial thiol–ene reaction with vinylsilicones for cysteine derivatives and a catalyst-free aza-Michael reaction with arginine and lysine. Short chain surfactants with silicone monomer:hydrophile ratios of 5:1 or less (e.g., telechelic silicones of lysine-linker-(Me₂OSi)_n-linker-lysine n = 10) were ineffective at stabilizing emulsions of silicone oil (D₄): water. However, excellent surfactants were realized as the chain length (n) increased to 25 or 50, stabilizing water-in-oil emulsions with high water content (80% or 90%). The surfactants, especially the longer chain compounds, were stable against pH except <4 or >9 and survived freeze/thaw cycles. These surfactants contain 12–25% natural materials, improving their sustainability compared to those containing synthetic hydrophiles. Full article

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