Solvent Waste Research Articles

Selective chiroptical sensing of D/L-cysteine.

A chromophoric bifunctional probe design that allows selective chiroptical sensing of cysteine in aqueous solution is introduced. The common need for chiral HPLC separation is eliminated which expedites and simplifies the sample analysis while reducing solvent waste. Screening of the reaction between six phenacyl bromides and the enantiomers of cysteine showed that cyclization to an unsaturated thiomorpholine scaffold coincides with characteristic UV and CD effects, in particular when the reagent carries a proximate auxochromic nitro group. The UV changes and CD inductions were successfully used for determination of the absolute configuration, enantiomeric composition and total concentration of 18 test samples. This assay is highly selective for free cysteine while other amino acids, cysteine derived small peptides and biothiols do not interfere with the chiroptical signal generation.

Exploitation of Distillation for Energy-Efficient and Cost-Effective Environmentally Benign Process of Waste Solvents Recovery from Industrial Waste

Exploitation of Distillation for Energy-Efficient and Cost-Effective Environmentally Benign Process of Waste Solvents Recovery from Industrial Waste

A green approach to the analysis of co-administered ampicillin/sulbactam and paracetamol in human urine.

The novelty of this work is the simultaneous analysis of sulbactam (SUL), ampicillin (AMP), and paracetamol (PARA) in human urine samples, using the environmentally benign RP-HPLC method. A C18 column was used in chromatographic separation using potassium dihydrogen phosphate (10 mmol L-1, pH 5)/ethanol (90 %, V/V) as the mobile phase; flow rate was 1.00 mL min-1. UV detection at 220 nm was used for quantification. The proposed method showed good linearity in the concentration ranges of 2.20-250.00 μg mL-1 for SUL, 2.50-250.00 μg mL-1 for PARA, and 14.50-250.00 μg mL-1 for AMP. Direct injection of urine samples with no prior extraction was performed. This method was found successful in moving towards greener studies of drugs' urinary excretion, by decreasing hazardous solvent consumption and waste. Moreover, the method was applied to investigate the urinary excretion of the drugs and possible interaction between ampicillin and paracetamol.

The Mechanics of Forming Ideal Polymer-Solvent Combinations for Open-Loop Chemical Recycling of Solvents and Plastics.

The inherent value and use of hydrocarbons from waste plastics and solvents can be extended through open-loop chemical recycling, as this process converts plastic to a range of non-plastic materials. This process is enhanced by first creating plastic–solvent combinations from multiple sources, which then are streamlined through a single process stream. We report on the relevant mechanics for streamlining industrially relevant polymers such as polystyrene (PS), polypropylene (PP), high-density polyethylene (HDPE), and acrylonitrile butadiene styrene (ABS) into chemical slurries mixed with various organic solvents such as toluene, xylene, and cyclohexane. The miscibility of the polymer feedstock within the solvent was evaluated using the Relative Energy Difference method, and the dissolution process was evaluated using the “Molecular theories in a continuum framework” model. These models were used to design a batch process yielding 1 tonne/h slurry by setting appropriate assumptions including constant viscosity of solvents, disentanglement-controlled dissolution mechanism, and linear increase in the dissolved polymer’s mass fraction over time. Solvent selection was found to be the most critical parameter for the dissolution process. The characteristics of the ideal solvent are high affinity to the desired polymer and low viscosity. This work serves as a universal technical guideline for the open-loop chemical recycling of plastics, avoiding the growth of waste plastic by utilising them as a carbon feedstock towards a circular economy framework.

Evaluation of the Adsorption and Desorption Dynamics of Beet Juice Red Dye on Alginate Microbeads

The use of alginate microcapsules has often been mentioned as one of the ways to remove dyes from waste solvents, water and materials from the food industry. In addition, alginate can be used as a wall material for the microencapsulation of food dyes and their further application in the food industry. The aims of this study were to: (i) determine the effect of the alginate concentration (1, 2, 3 and 4%) on the ability of the adsorption and desorption of natural beetroot red dye and (ii) evaluate the kinetic parameters of the adsorption and desorption process, as well as the factors affecting and limiting those processes. According to the obtained results, the viscosity of alginate solutions increased with an increase in the alginate concentration. Based on k2 values (the pseudo-second order kinetic rate constant), when a more concentrated solution of alginate was used in the adsorption process, the beads adsorbed a smaller amount of dye. Furthermore, based on the values for n derived from the Korsmeyer–Peppas model, the dye release rates (k) were higher for beads made with lower alginate concentrations, and this release was governed by a pseudo-Fickian diffusion mechanism (n values ranged from 0.2709 to 0.3053).

Green Stability Indicating Organic Solvent-Free HPLC Determination of Remdesivir in Substances and Pharmaceutical Dosage Forms

A green liquid chromatographic method is considered in this work to minimize the environmental impact of waste solvents. One important principle is to replace or eliminate the use of hazardous organic solvents. Organic impurities in any active pharmaceutical ingredient could arise either during the process of its synthesis, or as degradation products developed throughout the shelf-life. Remdesivir (RDS) is an antiviral drug, approved by the US Food and Drug Adminstration (-FDA), to treat SARS-Cov-2 virus during its pandemic crisis. We studied the stability of remdesivir against several degradation pathways using the organic solvent-free liquid chromatographic technique. Separation was performed on RP-C18 stationary phase using mixed-micellar mobile phase composed of a mixture of 0.025 M Brij-35, 0.1 M sodium lauryl sulfate (SLS), and 0.02 M disodium hydrogen phosphate, adjusted to pH 6.0. The mobile phase flow rate was 1 mL min−1, and detection was carried out at a wavelength of 244 nm. We profiled the impurities that originated in mild to drastic degradation conditions. The method was then validated according to International Conference of Harmonization (ICH) guidelines within a linearity range of 5–100 μg mL−1 and applied successfully for the determination of the drug in its marketed dosage form. A brief comparison was established with reported chromatographic methods, including a greenness assessment on two new metrics (GAPI and AGREE). This study is the first to be reported as eco-friendly, solvent-free, and stability indicating LC methodology for RDS determination and impurity profiling.

Comparison of Microflow and Analytical Flow Liquid Chromatography Coupled to Mass Spectrometry Global Metabolomics Methods Using a Urea Cycle Disorder Mouse Model.

Microscale-based separations are increasingly being applied in the field of metabolomics for the analysis of small-molecule metabolites. These methods have the potential to provide improved sensitivity, less solvent waste, and reduced sample-size requirements. Ion-pair free microflow-based global metabolomics methods, which we recently reported, were further compared to analytical flow ion-pairing reagent containing methods using a sample set from a urea cycle disorder (UCD) mouse model. Mouse urine and brain homogenate samples representing healthy, diseased, and disease-treated animals were analyzed by both methods. Data processing was performed using univariate and multivariate techniques followed by analyte trend analysis. The microflow methods performed comparably to the analytical flow ion-pairing methods with the ability to separate the three sample groups when analyzed by partial least-squares analysis. The number of detected metabolic features present after each data processing step was similar between the microflow-based methods and the ion-pairing methods in the negative ionization mode. The observed analyte trend and coverage of known UCD biomarkers were the same for both evaluated approaches. The 12.5-fold reduction in sample injection volume required for the microflow-based separations highlights the potential of this method to support studies with sample-size limitations.

Investigating the processing capacity of batch distillation by applying a second, smaller column

Increasing the processing capacity is important, especially in the pharmaceutical industry, where a given amount of waste solvent must be processed in a specific time period, else the remaining amount of waste solvent must be incinerated, which results in organic solvent loss and considerable environmental impact. In this paper, the possibility of increasing the processing capacity of batch distillation by using a second, already available, smaller batch column in addition to the original one is studied. The size of the columns is not changed during the calculations performed. Two case studies are presented. In the first one (Mixture 1), acetone, in the second one (Mixture 2), acetic acid must be recovered in high purity from their aqueous mixtures by operating either the larger column only or both columns simultaneously. The smaller column serves for preliminary separation, and its main-cut (Mixture 1) or residue (Mixture 2) is further processed in the larger one. The goal of this work is to maximise the processing capacity of the two-column process with the same recovery as in the single-column process. Both processes are modelled with a professional flow-sheet simulator. For the single-column process, the only independent variable is the reflux ratio. For the two-column process, the independent variables are the reflux ratios of both columns and the amount of intermediate product (distillate or residue) of the first column transferred to the second one. The ranges of the independent variables are determined by sensitivity studies for different charge compositions (20–50-80 mass% acetone or acetic acid), and each case is optimised by a genetic algorithm coupled to the flow-sheet simulator. It is also shown in this work that the processing capacity maximum of the two-column process is not always at the equality of the processing times of the two columns.

Method for Efficient Regeneration of Solvent Mixture: Extractive Heterogeneous-Azeotropic Distillation

Abstract The fine chemical and pharmaceutical industries use large amounts of various organic solvents in their manufacturing processes. By reusing them, production costs can be significantly reduced. If we can regenerate waste solvent mixtures, we have the opportunity to reuse them in the production process or in other production processes. Our study illustrates an efficient regeneration process using the example of a four-component solvent mixture. Calculations were performed in a professional process simulator to demonstrate that the highly non-ideal Water-Ethyl Alcohol-Methyl Ethyl Ketone-Ethyl Acetate solvent mixture can be efficiently decomposed into azeotropic pairs and thus regenerated by the extractive heterogeneous-azeotropic distillation technique.

Performance comparison between solid phase extraction and magnetic carbon nanotubes facilitated dispersive-micro solid phase extractions (Mag-CNTs/d-\xb5SPE) of a cyanide metabolite in biological samples using GC\u2013MS

Dispersive-micro solid phase extraction (d-µSPE) has gained increasing attention due to its convenience, effectiveness, and flexibility for sorbent selection. Among a various selection of materials, magnetic carbon nanotubes (Mag-CNTs) is a promising d-µSPE sorbent with excellent separation efficiency in addition to its high surface area and adsorption capability. In this work, two different surface-modified Mag-CNTs, Mag-CNTs-COOH and Mag-CNTs-SO3H, were developed to facilitate d-µSPE (Mag-CNTs/d-µSPE). The cyanide metabolite, 2-aminothiazoline-4-carboxylic acid (ATCA), was selected to evaluate their extraction performance using gas chromatography–mass spectrometry (GC–MS) analysis. The Mag-CNTs-COOH enabled a one-step derivatization/desorption approach in the workflow; therefore, a better overall performance was achieved. Compared to the Mag-CNTs-SO3H/d-µSPE and SPE workflow, the one-step desorption/derivatization approach improved the overall extraction efficiency and reduced solvent consumption and waste production. Both Mag-CNTs/d-µSPE workflows were validated according to ANSI/ASB 036 guidelines and showed excellent analytical performances. The limit of detection (LOD) and limit of quantitation (LOQ) of ATCA in synthetic urine were 5 and 10 ng/mL, respectively, and that in bovine blood were achieved at 10 and 60 ng/mL. The SPE method’s LOD and LOQ were also determined at 1 and 25 ng/mL in bovine blood samples. The Mag-CNTs/d-µSPE methods demonstrated great potential to extract polar and ionic metabolites from biological matrices. The extraction processes of ATCA described in this work can provide an easier-to-adopt procedure for potential routine forensic testing of the stable biomarker in cyanide poisoning cases, particularly for those cases where the cyanide detection window has passed.

Fabrication of PDMS/GA Composite Materials by Pickering Emulsion Method and Its Application for Oil-Water Separation

With the intensification of human activities, a large amount of oil and organic solvent waste has been created, resulting in serious ecological and environmental pollution. Therefore, how to balance environmental benefits and economic benefits control a large number of organic solvent and oil pollution is an urgent problem. To solve this problem, a highly efficient oil-water separation material was designed and prepared in this paper. Graphene oxide aerogels were synthesized by the Pickering emulsion and hydrothermal method, and then hydrophobically lipophilic polydimethylsiloxane (PDMS) reduced graphene oxide aerogel composites (PDMS/GA) were obtained by modification of PDMS. The surface functional groups, hydrophobicity, thermal stability, and micromorphology of the materials were tested by various characterization methods. Their properties were tested by an oil absorption test and repeated experiments. The oil absorption performance experiments and repeated performance experiments of PDMS/GA are reported. The number of oxy-gen-containing functional groups of the modified graphene oxide (GO) decreased, and the contact angle of water was 134.4°. The adsorption capacity of n-hexane was up to 18.5 times its own weight. The material has the advantages of being lightweight, easy to recover, good hydrophobicity and lipophilicity, and has the potential for large-scale applications in the field of oil-water separation.

Tea Bags for Fmoc Solid-Phase Peptide Synthesis: An Example of Circular Economy.

Peptide synthesis is an area with a wide field of application, from biomedicine to nanotechnology, that offers the option of simultaneously synthesizing a large number of sequences for the purpose of preliminary screening, which is a powerful tool. Nevertheless, standard protocols generate large volumes of solvent waste. Here, we present a protocol for the multiple Fmoc solid-phase peptide synthesis in tea bags, where reagent recycling steps are included. Fifty-two peptides with wide amino acid composition and seven to twenty amino acid residues in length were synthesized in less than three weeks. A clustering analysis was performed, grouping the peptides by physicochemical features. Although a relationship between the overall yield and the physicochemical features of the sequences was not established, the process showed good performance despite sequence diversity. The recycling system allowed to reduce N, N-dimethylformamide usage by 25–30% and reduce the deprotection reagent usage by 50%. This protocol has been optimized for the simultaneous synthesis of a large number of peptide sequences. Additionally, a reagent recycling system was included in the procedure, which turns the process into a framework of circular economy, without affecting the quality of the products obtained.

Recovery of scandium from red mud by leaching with titanium white waste acid and solvent extraction with P204

Recovery of scandium (Sc) from various wastes is generally one strategy to solve potential supply shortage problems of Sc. This work proposes a synergistic process for co-recovery of Sc by using the acid titanium white waste acid (TWWA) to leach the basic red mud, to which the acidity was adjusted with concentrated sulfuric acid when necessary. First, the effect of adjusted acidity of TWWA on Sc leaching from red mud was studied when the acidity of TWWA was adjusted to 5 mol/L H2SO4, which inhibited the formation of silica gel in the leachate with a Sc recovery of 70%. Then, the volume fraction of 10% P204 (di-(2-ethylhexyl) phosphate)-5% TBP (tributyl phosphate)-85% sulfonated kerosene was used to extract Sc from the leachate under the most suitable conditions. Specifically, at an A/O (volumetric liquid phase over oil phase) ratio of 10 for 30 min at room temperature, over 99% Sc was extracted and almost no Fe and Al were co-extracted. The selective scrubbing of 99% Ti was achieved via 5 mol/L H2SO4–1% H2O2 at 60 °C with almost no scrubbing towards Sc. A solution of 3 mol/L NaOH was then used as the stripping agent, which resulted in solid Sc enrichment with a high stripping efficiency of 99%. The process generated a final Sc-enrichment product with a purity of 17.4% and a total recovery yield of 68.6%.

Use of Portable Capillary Liquid Chromatography for Common Educational Demonstrations Involving Separations

High-performance liquid chromatography is one of the primary techniques covered in the undergraduate analytical chemistry curriculum. This technology report describes the use of a portable capillary-scale instrument that can provide similar performance to a benchtop instrument but generates less solvent waste and enables operation in nonlaboratory settings. Comparisons between the two instrument types were made for single-standard calibration analysis of caffeine in diet soda and aspirin content in over-the-counter tablets, with relative percent differences between the standards and samples under 5% for both instrument types and both samples. The capability to use the instrument in lecture and outreach demonstration activities was also explored. Portable instruments can serve similar pedagogical purposes to traditional instruments as well as provide a platform to introduce discussions on green analytical chemistry based on differences in solvent waste generation and power consumption.

Amphiphilic Polymer Nanoreactors for Multiple Step, One-Pot Reactions and Spontaneous Product Separation.

Performing multiple reaction steps in “one pot” to avoid the need to isolate intermediates is a promising approach for reducing solvent waste associated with liquid phase chemical processing. In this work, we incorporated gold nanoparticle catalysts into polymer nanoreactors via amphiphilic block copolymer directed self-assembly. With the polymer nanoreactors dispersed in water as the bulk solvent, we demonstrated the ability to facilitate two reaction steps in one pot with spontaneous precipitation of the product from the reaction mixture. Specifically, we achieved imide synthesis from 4-nitrophenol and benzaldehyde as a model reaction. The reaction occured in water at ambient conditions; the desired 4-benzylideneaminophenol product spontaneously precipitated from the reaction mixture while the nanoreactors remained stable in dispersion. A 65% isolated yield was achieved. In contrast, PEGylated gold nanoparticles and citrate stabilized gold nanoparticles precipitated with the reaction product, which would complicate both the isolation of the product as well as reuse of the catalyst. Thus, amphiphilic nanoreactors dispersed in water are a promising approach for reducing solvent waste associated with liquid phase chemical processing by using water as the bulk solvent, eliminating the need to isolate intermediates, achieving spontaneous product separation to facilitate the recycling of the reaction mixture, and simplifying the isolation of the desired product.

Optimization of Hybrid Distillation-hydrophilic and Organophilic Pervaporation Systems

The hybrid distillation-pervaporation process is an efficient method for the removal or recovery of volatile organic compounds from their aqueous mixtures. The hybrid distillation-pervaporation process has not only shown its excellent performance in the purification of solvent mixtures but also proven to have a potential of saving energy. In this study, the hybrid distillation-pervaporation process is optimized for the treatment of low-alcohol waste solvents. Three combinations are examined: distillation with hydrophilic pervaporation, distillation with organophilic pervaporation and distillation with both pervaporation methods. The hybrid systems result in a better performance in term of energy-use compared to conventional distillation. It is observed that a combination of distillation and hydrophilic or/and organophilic pervaporation is suitable for the separation of ethanol-water mixtures and the most recommended is the third layout.Keywords: hybrid distillation-pervaporation process, pervaporation, ethanol-water separation, azeo

Advances in Automated Piston Liquid-Liquid Microextraction Technique

A new automated micro liquid-liquid extraction technique was successfully developed. This novel syringe-based technique capitalizes on the advantages of vigorous fluid agitation and the shearing effect of two fluids with different properties to achieve high extraction efficiency. The technique is at least 20 times faster than mechanical shaking or sonication in achieving a similar recovery even with a hydrophilic probe molecule such as 1,4-dioxane in an aqueous medium. Excellent repeatability with a relative standard deviation as low as 0.56% over a five-day test, n = 2 per day, was demonstrated with 1,4-dioxane. Other model compounds in aqueous matrices evaluated, including phenolics and extraction solvents like chloroform and hexane, showed similar performance in repeatability. An added advantage of this technique involves performing multiple extractions. Its capabilities in conducting complicated extraction steps and minimizing the use of organic solvents as low as 200 µL to achieve a preconcentration effect were demonstrated. The technique is suitable for use with emulsion-forming samples without further sample manipulation by incorporating a demulsifier such as acetone during the extraction process. The technique was found to be efficient and environmentally friendly with low solvent waste. This technique is ideal for implementation in automated high throughput and cost-effective quality assurance laboratory environments.

Comparative study of novel green UV-spectrophotometric platforms for simultaneous rapid analysis of flumethasone pivalate and clioquinol in their combined formulation

Flumethasone pivalate (FP) and clioquinol (CL) formulation was developed as a prodigious remedy to cure the external ear inflammatory disorders. So, the current research introduces five smart and novel UV-spectrophotometric platforms relying on minimal mathematical manipulation steps for simultaneous green analysis of FP and CL with no preliminary separation in their formulation that suffered from the high difference of their ratio and severe spectral overlapping. These platforms involved dual-wavelength, first derivative ratio, Fourier self-deconvolution, area under the curve, and bivariate methods. The suggested platform’ linearity was observed over the concentration range of 3–42 µg/ml for FP and 1.5–8 µg/ml for CL. All suggested platforms were validated according to ICH recommendations regarding accuracy, precision, repeatability, and selectivity producing satisfactory results within the accepted limits. These platforms were represented as rapid, green, and cheap alternatives to the reported chromatographic method due to lower solvent consumption and waste generation. Furthermore, they improved the determination sensitivity of the studied drugs and enhanced the recorded data signals or its spectral resolution by the newly introduced Fourier self-deconvoluted method. The statistical comparison between the results of the suggested platforms with each other and with those of the reported method showed no significant differences between them.

SOLVENT-FREE SYNTHESIS OF AMIDE: A NOVEL TECHNIQUE OF GREEN CHEMISTRY

Objective: Amide is one of the most important functional group presents in the chemicals, pharmaceuticals, and foods. Conventionally, it has been synthesized from the carboxylic acid and amines. This conventional reaction is lengthy and involves hazardous chemicals and solvents. Hence, it poses waste management, solvent removal, and environmental issues to the industries. To overcome this limitation, we have reported the green chemistry-based method for the synthesis of amide from carboxylic acid and urea.
 Methods: In this reaction, we have used boric acid as a catalyst, it is a simple and readily available compound. It is simple, efficient, and solvent-free procedure which involves the trituration of the reactant mixture and subsequent, direct heating of the triturated mixture.
 Results: The rate of reaction is very high and can synthesize the amide quickly.
 Conclusion: Various amides were prepared in good yield by this technique.

One-Step Synthesis of a Durable and Liquid-Repellent Poly(dimethylsiloxane) Coating.

Coatings with low sliding angles for liquid drops have a broad range of applications. However, it remains a challenge to have a fast, easy, and universal preparation method for coatings that are long-term stable, robust, and environmentally friendly. Here, a one-step grafting-from approach is reported for poly(dimethylsiloxane) (PDMS) brushes on surfaces through spontaneous polymerization of dichlorodimethylsilane fulfilling all these requirements. Drops of a variety of liquids slide off at tilt angles below 5°. This non-stick coating with autophobicity can reduce the waste of water and solvents in cleaning. The strong covalent attachment of the PDMS brush to the substrate makes them mechanically robust and UV-tolerant. Their resistance to high temperatures and to droplet sliding erosion, combined with the low film thickness (≈8 nm) makes them ideal candidates to solve the long-term degradation issues of coatings for heat-transfer surfaces.