Solvent Waste Research Articles

Towards a Greener Approach for Biomass Valorization: Integration of Supercritical Fluid and Deep Eutectic Solvents.

A green and sustainable procedure for obtaining Lavandula stoechas extracts with antioxidant and antimicrobial properties was investigated. Green solvents, supercritical CO2, and natural deep eutectic solvents (NADES) together with ultrasound-assisted extraction were used for the sequential extraction of terpene and polyphenols fractions. After the CO2 extraction of the terpene fraction, the residue material was used in an extraction with different NADES (betaine-ethylene glycol (Bet:EG), betaine-glycerol (Bet:Gly), and glycerol-glucose (Gly:Glu)), intensified with an ultrasound-assisted method (at 30 and 60 °C). In the CO2 extract, the major group of components belonged to oxygenated monoterpenes, while the highest polyphenol content with the dominant rutin (438.93 ± 4.60 µg/mL) was determined in Bet:EG extracts (60 °C). Bet:EG extracts also exhibited the most potent antioxidant activity according to DPPH, ABTS, and FRAP assays. Moreover, Bet:EG extracts showed significant inhibitory activity against Gram-positive and Gram-negative bacteria, with minimum inhibitory activity of 0.781-3.125 and 1.563-6.250 mg·mL-1, respectively. By comparing the polyphenolic content and antioxidant and antimicrobial activities of Bet:EG extracts with extracts obtained with conventional solvents (water and ethanol), the superiority of NADES was determined. The established environmentally friendly procedure unifies the requirements of green and sustainable development and modern pharmacognosy because it combines the use of safe alternative solvents, the absence of solvent waste generation, more rational use of resources, and the attainment of safe and quality extracts.

Sample preparation of free sterols from vegetable oils by countercurrent chromatography in co-current mode

Countercurrent chromatography (CCC) is a preparative instrumental method where both the mobile and stationary phases are liquids and which are predominantly used for the isolation of natural products. In this study, we widened the scope of CCC by using it as an instrumental method for the direct enrichment of the free sterol fraction from plant oils to which they contribute with ~ 1%. For the enrichment of sterols in a narrow band, we employed the so-called co-current CCC (ccCCC) mode in which both liquid phases of the solvent system (here: n-hexane/ethanol/methanol/water (34:11:12:2, v/v/v/v)) are moved at different flow rates in the same direction. Different from previous applications of ccCCC, the lower and predominant “stationary” phase (LPs) was pumped twice as fast as the mobile upper phase (UPm). This novel reversed ccCCC mode improved the performance but also required a higher demand of LPs compared to UPm. Therefore, the exact phase composition of UPm and LPs was determined by gas chromatography and Karl Fischer titration. This step enabled the direct preparation of LPs which considerably reduced the waste of solvents. Internal standards (phenyl-substituted fatty acid alkyl esters) were synthesised and utilised to frame the free sterol fraction. This approach allowed a fractionation of free sterols based on the UV signal and compensated run-to-run variations. The reversed ccCCC method was then applied to the sample preparation of five vegetable oils. In addition to free sterols, free tocochromanols (tocopherols, vitamin E) were also eluted in the same fraction as free sterols.Graphical

Applying Automation and High-Throughput MALDI Mass Spectrometry for Peptide Metabolic Stability Screening

The discovery of peptide therapeutics represents a fast-growing segment of pharmaceutical research. During the early discovery process, a large number of peptide candidates needs to be rapidly screened for metabolic stability in relevant biological matrices. In most cases, peptide stability assays are quantified using LC-MS/MS, which may take hours to analyze 384 samples and generates liters of solvent waste. Herein, we introduce a high-throughput screening (HTS) platform for peptide stability assessment founded on Matrix Assisted Laser Desorption/Ionization (MALDI) mass spectrometry (MS). Full automation has been implemented for sample preparation with minimal manual intervention. The limit of detection, linearity, and reproducibility of the platform were evaluated, and metabolic stabilities have been determined for a number of peptide candidates. The MALDI-MS-based HTS workflow is able to analyze 384 samples in less than 1 h while only using 115 μL of total solvent. Although this process allows for very rapid assessment of peptide stability, given the nature of the MALDI process, it is noteworthy that spot-to-spot variations and ionization bias are observed. Therefore, LC-MS/MS may still be needed for confident, quantitative measurements and/or when the ionization efficiency of certain peptides is inadequate using MALDI.

Preparation of Symmetrical Capacitors from Lignin-Derived Phenol and PANI Composites with Good Electrical Conductivity.

As a natural polymer, lignin is only less abundant in nature than cellulose. It has the form of an aromatic macromolecule, with benzene propane monomers connected by molecular bonds such as C-C and C-O-C. One method to accomplish high-value lignin conversion is degradation. The use of deep eutectic solvents (DESs) to degrade lignin is a simple, efficient and environmentally friendly degradation method. After degradation, the lignin is broken due to β-O-4 to produce phenolic aromatic monomers. In this work, lignin degradation products were evaluated as additives for the preparation of polyaniline conductive polymers, which not only avoids solvent waste but also achieves a high-value use of lignin. The morphological and structural characteristics of the LDP/PANI composites were investigated using 1H NMR, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis and elemental analysis. The LDP/PANI nanocomposite provides a specific capacitance of 416.6 F/g at 1 A/g and can be used as a lignin-based supercapacitor with good conductivity. Assembled as a symmetrical supercapacitor device, it provides an energy density of 57.86 Wh/kg, an excellent power density of 952.43 W/kg and, better still, a sustained cycling stability. Thus, the combination of polyaniline and lignin degradate, which is environmentally friendly, amplifies the capacitive function on the basis of polyaniline.

Solubility of tris(2-methylbutyl) phosphate in supercritical carbon dioxide and its application for the recovery of uranium from U-Zr and U-Th aqueous solutions

The employment of supercritical fluid extraction (SFE) within the nuclear industry may reduce the environmental burden by reduction in solvent waste generation. In this perspective, a SFE based method was developed for selective extraction of uranium from U-Zr and U-Th solutions using tris-(2-methylbutyl) phosphate (T2MBP) as a ligand in supercritical carbon dioxide (SCCO2). Prior to SFE studies, the utilisation of T2MBP in SCCO2 was examined by carrying out solubility measurements using dynamic flow technique at (313−333) K and (10−20) MPa. T2MBP has sufficient solubility in SCCO2 and ranges from 2.55 × 10-2 mol·mol-1 to 8.95 × 10-2 mol·mol-1. The solubility increases with pressure and decreases with temperature, resulting in retrograde solubility behaviour. The experimental solubility data was successfully correlated using different density based semi-empirical equations. Based on the solubility data, selective recovery of uranium from U-Zr and U-Th solutions was demonstrated using SCCO2+T2MBP.

Phosphodiester Stationary Phases as Universal Chromatographic Materials for Separation in RP LC, HILIC, and Pure Aqueous Mobile Phase.

Modern analytical chemistry techniques meet the need for greater attention to ecological and economic aspects. It is becoming necessary to seek solutions to reduce harmful waste production, especially in large quantities. High-performance liquid chromatography is a technique widely used in many industries, including mainly pharmaceuticals, and requires an approach to reduce the significant amount of organic solvent waste. One of the green chemistry solutions is using environmentally benign substitutes, such as pure water, supercritical dioxide, and ethanol. Our work focuses on the preparation and application of new stationary phases with embedded hydrophilic groups for separations using pure water in liquid chromatography. Polar-embedded stationary phases are obtained by attaching a phosphodiester group and 4 different hydrophobic molecules. The studies consisted of hydrophobicity measurements, concentration dependence of retention of the organic additive to the mobile phase, and chromatographic separations of polar and non-polar substance mixtures in RP-LC and HILIC systems. Three mixtures were studied: purine alkaloids, benzene, and polycyclic aromatic hydrocarbons and nucleosides. The stationary phases interact differently with the analytes depending on the attached hydrophobic group. It is possible to use pure water to separate each mixture under study. It is also significant that it has been possible to separate a mixture of completely non-polar compounds using pure water for the first time. The research being carried out is crucial in synthesizing new polar-embedded stationary phases, providing work versatility and high environmental performance.

Development of a Manufacturing Process toward the Convergent Synthesis of the COVID-19 Antiviral Ensitrelvir.

We describe the development of the practical manufacturing of Ensitrelvir, which was discovered as a SARS-CoV-2 antiviral candidate. Scalable synthetic methods of indazole, 1,2,4-triazole and 1,3,5-triazinone structures were established, and convergent couplings of these fragments enabled the development of a concise and efficient scale-up process to Ensitrelvir. In this process, introducing a meta-cresolyl moiety successfully enhanced the stability of intermediates. Compared to the initial route at the early research and development stage, the overall yield of the longest linear sequence (6 steps) was improved by approximately 7-fold. Furthermore, 9 out of the 12 isolated intermediates were crystallized directly from each reaction mixture without any extractive workup (direct isolation). This led to an efficient and environmentally friendly manufacturing process that minimizes waste of organic solvents, reagents, and processing time. This practical process for manufacturing Ensitrelvir should contribute to protection against COVID-19.

Mechanochemistry-Directed Ligand Design: Development of a High-Performance Phosphine Ligand for Palladium-Catalyzed Mechanochemical Organoboron Cross-Coupling

Mechanochemical synthesis that uses transition-metal catalysts has attracted significant attention due to its numerous advantages, including low solvent waste, short reaction times, and the avoidance of problems associated with the low solubility of starting materials. However, even though the mechanochemical reaction environment is largely different from that of homogeneous solution systems, transition-metal catalysts, which were originally developed for use in solution, have been used directly in mechanochemical reactions without any molecular-level modifications to ensure their suitability for mechanochemistry. Alas, this has limited the development of more efficient mechanochemical cross-coupling processes. Here, we report a conceptually distinct approach, whereby a mechanochemistry-directed design is used to develop ligands for mechanochemical Suzuki-Miyaura cross-coupling reactions. The ligand development was guided by the experimental observation of catalyst deactivation via the aggregation of palladium species, a problem that is particularly prominent in solid-state reactions. By embedding the ligand into a poly(ethylene glycol) (PEG) polymer, we found that phosphine-ligated palladium(0) species could be immobilized in the fluid phase created by the PEG chains, preventing the physical mixing of the catalyst into the crystalline solid phase and thus undesired catalyst deactivation. This catalytic system showed high catalytic activity in reactions of polyaromatic substrates close to room temperature. These substrates usually require elevated temperatures to be reactive in the presence of catalyst systems with conventional ligands such as SPhos. The present study hence provides important insights for the design of high-performance catalysts for solid-state reactions and has the potential to inspire the development of industrially attractive, almost solvent-free mechanochemical cross-coupling technologies.

Surrogate model-based optimisation of a batch distillation process

A surrogate model-based method is proposed for optimising batch distillation processes and applied to the recovery of methanol from a five-component azeotropic waste solvent mixture, where pollutants are removed in two fore-cuts and an after-cut. The objective function is the profit of a single batch, while constraints are for the purity of the main cut and composition of the second fore-cut to be recycled. Simulations are performed by a flow-sheet simulator in a set of points in the space of optimisation variables (reflux ratios of steps, stopping criteria of fore-cuts). Algebraic surrogate models are fitted by ALAMO to simulation results to describe the objective function and the constraints. The resulting optimisation problem is solved numerically. The profit obtained is by 5% higher than the one previously obtained by genetic algorithm (commonly used for optimisation of batch distillation), while the number of simulations is reduced to its third. The highest profit, previously obtained by the Nelder-Mead simplex method, is approached within 1%. Although the simplex method required fewer simulations, the new method proposed here is a global one. The process is re-optimised for different prices to investigate their influence on the profit and optimal values of operational parameters.

Sustainable chromatographic purification of milbemectin: Application of high-speed countercurrent chromatography coupled with off-line atmospheric pressure solid analysis probe-high resolution mass spectrometry

Isolation of valuable chemicals is an important process in reagent manufacturing for the pharmaceutical and food science industries. This process is traditionally time-consuming, expensive, and consumes vast amounts of organic solvents. Considering green chemistry and sustainability concerns, we sought to develop a sustainable chromatographic purification methodology for obtaining antibiotics by focusing on the reduction of organic solvent waste generation. Milbemectin (mixture of milbemycin A3 and milbemycin A4) was successfully purified using high-speed countercurrent chromatography (HSCCC) and pure fractions (>98% purity, HPLC) could be identified using the organic solvent fee atmospheric pressure solid analysis probe mass spectrometry (ASAP-MS). The organic solvents required for HSCCC could be redistilled and recycled for continued HSCCC purification, thus reducing the consumption of organic solvent (n-hexane/ethyl acetate) by 80+%. Optimization of the two-phase solvent system (n-hexane/ethyl acetate/methanol/water, 9/1/7/3, v/v/v/v) for HSCCC was assisted computationally, thereby reducing solvent waste from an experimental determination. Our proposal application of HSCCC and offline ASAP-MS provides proof of concept for a sustainable, preparative scale, chromatographic purification methodology for obtaining antibiotics in high purity.

Elimination of VOC Emissions from Surface Coating Operations with Solvent Management and Waste Disposal In GM Egypt

Elimination of VOC Emissions from Surface Coating Operations with Solvent Management and Waste Disposal In GM Egypt

Development of an Interactive Software Tool for Designing Solvent Recovery Processes.

Solvents are used in chemical and pharmaceutical industries as a reaction medium, selective dissolution and extraction media, and dilution agents. Thus, a sizable amount of solvent waste is generated due to process inefficiencies. Most common ways of handling solvent waste are on-site, off-site disposal, and incineration, which have a considerable negative environmental impact. Solvent recovery is typically not used because of potential difficulties in achieving required purity guidelines, as well as additional infrastructure and investments that are needed. To this end, this problem must be studied carefully by involving aspects from capital needs, environmental benefits, and comparison with traditional disposal methods, while achieving the required purity. Thus, we have developed a user-friendly software tool that allows engineers to easily access solvent recovery options and predict an economical and environmentally favorable strategy, given a solvent-containing waste stream. This consists of a maximal process flow diagram that encompasses multiple stages of separations and technologies within those stages. This process flow diagram develops the superstructure that provides multiple technology pathway options for any solvent waste stream. Separation technologies are placed in different stages; depending on the component, they can separate in terms of their physical and chemical properties. A comprehensive chemical database is created to store all relevant chemical and physical properties. The pathway prediction is modeled as an economic optimization problem in General Algebraic Modeling Systems (GAMS). With GAMS code as the backend, a Graphical User Interface (GUI) is created in Matlab App Designer to provide a user-friendly tool to the chemical industry. This tool can act as a guidance system to assist professional engineers and provide an easy comparative estimate in the early stages of process design.

Updating the Benzoin Condensation of Benzaldehyde Using Microwave-Assisted Organic Synthesis and N-Heterocyclic Carbene Catalysis

The benzoin condensation of benzaldehyde is a staple of the undergraduate organic chemistry laboratory, introducing the current topic of nucleophilic carbene organocatalysis. Our procedure makes notable improvements to current practice, including the elimination of solvent waste and an 18-fold reduction of reaction time. We have demonstrated that microwave heating provides yields comparable to current practice in 5 min, using significantly less power (70 W) than traditional heating methods. The highest yields were obtained with N,N′-(2,4,6-trimethylphenyl)imidazolium chloride (IMes·HCl) as the catalyst and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as the base. Our procedure has been successfully executed by multiple cohorts of organic chemistry undergraduates, both with and without pandemic social distancing constraints.

Bioinspiration synthesis of hydroxyapatite nanoparticles using eggshells as a calcium source: Evaluation of Congo red dye adsorption potential

Hydroxyapatite nanoparticles (HAp NPs) were synthesized with Muntingia calabura leaf extract as solvent and eggshell waste as a calcium source. The synthesized nanoparticles were irregular rod-like, as visualized by FESEM, while EDX and XPS studies confirmed the formation of hydroxyapatite. The synthesized HAp NPs were polycrystalline and highly thermostable as per XRD and TGA studies respectively. FTIR confirmed the stable coating of plant phytochemicals onto the HAp NPs. Congo red adsorption using HAp NPs nanoadsorbent was optimized by central composite design, wherein 89.96% of 33.18 mg/L dye was adsorbed in 137 min at 180 RPM. The adsorption process was in line with pseudo-second-order model and the Freundlich isotherm indicated chemical adsorption. The adsorption process was feasible, exothermic, and spontaneous as indicated by the thermodynamic studies. The adsorption capacity of HAp NPs stood at a maximum of 217 mg/g, indicating its superiority among other adsorbents reported earlier. It is evident from the convincing results that the HAp NPs synthesized in the present investigation may have a major role in developing novel adsorbents for dye removal out of wastewater streams.

Construction of a spatial–temporal metabolic path for hazardous waste management based on the fusion of reported data and web text data

This study employs mining and fusion of the waste reported data and web text data to construct a spatial–temporal metabolic path for hazardous waste management. According to the reported data, the generation and inventory of organic solvent waste account for a large proportion of hazardous waste; thus, they were selected as the representative waste in the construction of metabolic paths from the generation to the final disposal during 2016 to 2019. Web text data were obtained by a web crawler to identify where waste was produced, stored, and disposed. Based on the matching logic, the reported data and web text data were fused to realize the spatio-temporal expression for the logical metabolic path. The results showed that the generation of organic solvent waste displayed rapid growth, increasing from 17,922 to 22,005 tons between 2016 and 2019. The number of waste production enterprises also showed growth, with most of them disconnected downstream, accounting for an average of 43.84% of the total metabolic paths. The number of metabolic paths representing the complete waste disposal decreased significantly by 23.02% during this period. Most of the waste was transferred outside the Chengdu metropolitan area for final disposal, accounting for an average of 14.90% of the total waste generation. In addition, the contributions to organic solvent waste were identified; the automobile and electronic device manufacturing industries were the major sources. These results provided insight into hazardous waste management, making a call for improvement in the existing management system. • A spatial–temporally metabolic path regarding hazardous waste is constructed. • The path is constructed through the fusion and mining of waste reported data and web text data. • The managerial issues related to the existing waste management system are identified. • Policy implications for hazardous waste management system optimization are proposed.

Exploiting phase inversion for penta-amine impregnation of ultrafiltration support matrix for rapid fabrication of a hyper-cross-linked polyamide membrane for organic solvent nanofiltration

For the sake of recovery of precious organic solvents from industrial organic solvent waste stream or alternatively for recovery of active principle ingredient (API) synthesized in pharmaceutical companies, organic solvent nanofiltration (OSN) membranes have recently been emerged. A thin film composite (TFC) membrane was fabricated by using rapid membrane fabrication technique. The PA(TEPA-TCL)@PSU/PETP membrane was fabricated by penta-amine (TEPA) impregnation of polysulfone (PSU) matrix during phase inversion which in turn was reacted with terephthaloyl chloride (TCL) through interfacial polymerization (IP). The PA(TEPA-TCL)@PSU/PETP membrane was characterized by scanning electron microscopy (SEM), water contact angle (WCA), energy dispersive X-ray (EDX) analysis, ATR-FTIR and elemental mapping. The PA(TEPA-TCL)@PSU/PETP membrane was applied for OSN by using water, methanol, ethanol and isopropanol as solvents. When methanol was used as feed, it showed a permeate flux of 28 L m−2 h−1 (LMH) at 20 bar. An inverse relationship was found between viscosity and flux of the solvents. A feed composed of methanol and dyes (dyes were used as model pollutants) was used to evaluate the OSN performance of the membrane. Apparently, size exclusion mechanism was found to be responsible for rejection of dyes as EBT was rejected up to > 92 % and Congo red (CR; M.W. = 696.6 g mol−1) rejection reached > 96% while it stayed at ≈ 88 % for Methylene blue (MB; M.W. = 319.8 g mol−1). The UV-Visible analysis of feed and permeate was conducted which confirmed the rejection of CR and MB. Hence, the PA(TEPA-TCL)@PSU/PETP membrane was found to be efficient for the purification of organic solvents contaminated with organic dyes.

One-pot room-temperature direct synthesis of bovine serum albumin-based fluorescent carbon nanoparticles

Fluorescent carbon nanoparticles (FC-NPs) with a mean size of 5.5 nm were fabricated at room temperature by means of a novel one-pot direct synthesis method, using bovine serum albumin (BSA), as a biomass-based precursor, and glutaraldehyde in a mixture of water/ethanol (1:4 v/v) under alkali conditions. This novel method shortens the times of synthesis and purification of the nanoparticles, and does not require thermal energy, since no calcination is needed for the nanoparticles production, and the waste of reactants and solvents is minor. The FC-NPs displayed two emission peaks: one around 450 nm, and the second at 555 nm, being the later the most intense for wavelength excitations from 450 nm; fluorescence quantum yields values varied from 11.6 to 27 %, depending on their synthesis conditions, and in fact, the solutions emit a strong green-yellow fluorescence when excited with 532 nm. The FTIR spectra indicated that the main functional groups present were -NH2 and -COOH. XPS analysis confirmed the FTIR results and showed that carbon dots were composed mainly of C, N, O and Na. Finally, we tested the fluorescent carbon nanoparticles as cell biomarkers in human, plant cell lines and microbial cultures, achieving good results for this application.

Direct search methods for the fast optimisation of batch distillation processes

Batch distillation can be conveniently modelled by professional flow-sheet simulators. Optimisation can be performed by coupling an external optimiser to the simulator. The most frequently used method is the genetic algorithm (GA), which, however, requires a high number of simulations to evaluate the objective function. Two direct search methods, the Nelder-Mead simplex and the Box-complex algorithms are applied to reduce the computational intensity of optimisation. Calculations are performed for a case study from the literature where the profit of the regeneration of a multicomponent azeotropic waste solvent mixture was maximised by a GA. The influence of the parameters of the optimisation methods is investigated for each method. The highest profit is reached by the simplex algorithm. Both the simplex and complex algorithms generally outperform GA with a much lower number of simulations. Therefore, direct search methods can be used for fast and efficient optimisation of batch distillation processes.

Synthesis of Benzimidazole and Benzothiazole Derivatives using Reusable Waste Stem of Trigonella Foenum-graecum Assisted Zinc Sulphide Nanoparticles: A Green and Efficient Solid Acid Catalyst

In this study, the simple and rapid methods for the preparation of benzimidazole and benzothiazole by the condensation of o-phenylenediamine with the aromatic aldehyde in presence of the zinc sulphide nanoparticles derived from the waste stem of the Trigonella foenum-graecum. The catalyst was prepared by using the waste stem of the Trigonella foenum-graecum. Most of the reaction carried under the mild condition with very high excellent yield. The method is used for the aromatic, unsaturated and heteroaromatic aldehyde. The main advantage of this method is that it takes very short reaction time, solvent free reaction condition, reusable catalyst, milder reaction, easy workup and waste stem of the plant was used.

Automatable downstream purification of the benzohydroxamic acid D-DIBOA from a biocatalytic synthesis

Herbicides play a vital role in agriculture, contributing to increased crop productivity by minimizing weed growth, but their low degradability presents a threat to the environment and human health. Allelochemicals, such as DIBOA (2,4-dihydroxy-(2H)-1,4-benzoxazin-3(4 H)-one), are secondary metabolites released by certain plants that affect the survival or growth of other organisms. Although these metabolites have an attractive potential for use as herbicides, their low natural production is a critical hurdle. Previously, the synthesis of the biologically active analog D-DIBOA (4-hydroxy-(2H)-1,4-benzoxazin-3(4H)-one) was achieved, using an engineered E. coli strain as a whole-cell biocatalyst, capable of transforming a precursor compound into D‐DIBOA and exporting it into the culture medium, although it cannot be directly applied to crops. Here a chromatographic method to purify D-DIBOA from this cell culture medium without producing organic solvent wastes is described. The purification of D-DIBOA from a filtered culture medium to the pure compound could also be automated. Biological tests with the purified compound on weed models showed that it has virtually the same activity than the chemically synthesized D-DIBOA.