No abstract

Solvents constitute a major portion of a chemical laboratory's waste and cause immediate costs for proper disposal and reordering. Next to reducing solvent usage, the recycling of used solvents by distillation is an obvious measure. In practice, commercially available equipment for distillation often offers insufficient separation and is inappropriately sized, overly costly, or simply not solvent-resistant. We constructed and put into service two distillation units for 6 L batches to recover analytical grade solvents−ethyl acetate and toluene for preparative chromatography and N,N-dimethylacetamide for analytical size exclusion chromatography. The systems separate fractions automatically at freely programmable vapor temperatures with high accuracy (0.1 K). The recovered solvents are therefore highly pure and are reused for analytical applications without any problems. Common laboratory glassware and standard electric components were used for construction. All wetted parts of the distillation systems are solvent-resistant and have withstood the distillation of corrosive, high-boiling solvents on a daily basis. Even highboiling N,N-dimethylacetamide (164 °C) was conveniently recovered from waste GPC eluent. To verify the recovered solvents' purity, a GC-MS method was developed, which encompassed both possible target solvents and impurities. UV/vis spectroscopy, Karl Fischer titration, and the chromatographic performance of the solvents were used as critical quality parameters. Typically, the recycled solvents were of higher purity than commercial ones. Additionally, several safety features were included in the distillation setup to prevent uncontrolled escape of solvent vapors with possibly catastrophic consequences. Both the construction of the distillation unit and its everyday operation are described in detail, offering an affordable, easily accessible, and reliable facility for greener solvent usage in common student and research laboratories.

In the past two decades, research on electrospinning has boomed due to its advantages of simple process, small fiber diameter, and special physical and chemical properties. The electrospun fibers are collected in a non-woven state in most cases (electrospun non-woven fabrics, ESNWs), which renders the electrospinning method an optimum approach for non-woven fabric manufacturing on the nano-scale. The present study establishes a convenient preparation procedure for converting water-soluble dialdehyde cellulose (DAC) into DAC-based electrospun non-woven fabrics (ESNWs) reinforced with poly(vinyl alcohol) (PVA). The aldehyde content, which was quantified by colorimetry using Schiff’s reagent, was 11.1 mmol per gram of DAC, which corresponds to a conversion yield of ca. 90%. DAC is fully water-soluble at room temperature between 10 and 30 wt%, and aqueous solutions turn into hydrogels within 24 h. To overcome gelation, NaHSO3, which forms bisulfite adducts with aldehyde functions, was added to the DAC and its concentration was optimized at 1 wt%. The electrospun (ES) dope containing 5 wt% DAC, 5 wt% PVA, and 1 wt% NaHSO3 in an aqueous solution was successfully transformed into ESNW, with an average fiber diameter of 345 ± 43 nm. Post-spinning treatment with excess hexamethylene diisocyanate was performed to insolubilize the ESNW materials. The occurrence of this chemical conversion was confirmed by energy-dispersive X-ray elemental analysis and vibrational spectra. The cross-linked DAC/PVA ESNW retained its thin fiber network upon soaking in distilled water, increasing the average fiber diameter to 424 ± 95 nm. This suggests that DAC/PVA-ESNWs will be applicable for incorporation or immobilization of biologically active substances.