Deep eutectic solvents (DESs) are potential green systems that can be used as reagents, extraction agents and reaction media. DESs are often biodegradable, easy to prepare and have low toxicity. In this work, a recyclable DES formed from aminoguanidine hydrochloride and glycerol (AhG) was used as a reaction medium and reagent (aminoguanidine hydrochloride) for the production of cationic nanocelluloses. Under mild conditions (i.e., a reaction time of 10 min at 70 °C), dialdehyde celluloses (DACs) with two different aldehyde contents (2.18 and 3.79 mmol g) were cationized by AhG DES to form cationic dialdehyde celluloses (CDACs). Both CDACs achieved a similar high charge density of approximately 1.1 mmol g. At 80 °C (for 10 min), a very high cationic charge density of 2.48 mmol g was obtained. The recyclability of AhG DES was demonstrated by reusing it five times without decreasing the reaction efficiency. In particular, due to the low consumption of amoniguanidine hydrochloride, high recycling efficiency could be achieved without the use of any additional chemicals. The cationized celluloses, CDACs, were further mechanically disintegrated to obtain cationic nanocelluloses. According to the initial aldehyde content of DACs, the morphology of the nanocellulose could be tailored to produce highly cationic cellulose nanofibrils (CNFs) or cellulose nanocrystals (CNCs). Transmission electron microscopy confirmed that individual CNFs and CNCs with an average width of 4.6 ± 1.1 nm and 5.7 ± 1.3 nm, respectively, were obtained. Thus, the results presented here indicate that the AhG DES is a promising green and recyclable way of producing cationized CNFs and CNCs.

This article describes the kinetics and capacity of adsorbing condensed conifer tannins onto cationic cellulose nanocrystals (CCNCs). Batch adsorption experiments were carried as a function of pH, contact time, and initial tannin concentration with constant cationic cellulose nanocrystal concentration (0.01%). The adsorption process was highly pH dependent as adsorption capacities ranged from 13.2 mg/g to 112.7 mg/g at pH of 3-10. The amount of tannin adsorbed per unit mass of the cationic cellulose nanocrystals increased with increasing of tannin concentration until equilibrium was attained. The experimental data followed the Langmuir adsorption model, and the maximum experimental and theoretical adsorption capacities for the cationic nanocrystals reached 1,008 mg/g and 1,111 mg/g, respectively. The kinetics of adsorption was described best by the pseudo-second-order kinetics indicating a chemisorption process. The inherent adsorption has interesting applications for CCNC-complexes with natural polyphenolics in green chemical applications for adhesives, adsorbents, preservatives, and packaging materials.

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In search for greener building materials, geopolymer wood composites (GWC) were produced through alkali activation of fly ash, using pine and eucalypt wood particles. The study examined the influence of grinding fly ash, wood species and hot water treatment of wood particles on the physical properties and specific compressive strength of GWC before and after 200 cycles of soaking and drying. Ash-grinding affected particle size distribution, as the hot water pretreatment of the wood affected its extractives. The particle size analysis showed that grinding decreased the mean particle size of raw ash by 55% and played a major role in the composite’s properties, as lower densities and specific strength with high water absorption were recorded for GWC from raw ash than from ground ash. The ash-grinding step doubled the specific strength of the composites before the aging test. A decrease in specific strength (15–32%) was observed for all composites after the soaking and drying cycles. Hot water washing of the wood resulted in a 47% and 67% reduction in the extractive content of the pine and eucalypt particles, respectively. An improvement of 27% and 3% was noted in specific strength values respectively for GWC with treated pine and eucalypt particles. In general, lower specific strength was recorded for pine-based composites than eucalypt ones, due to the fast impregnation and high water absorption from the mixture by pine particles. It was revealed that hot water treatment of wood improves GWC properties less compared to wood species or fly ash particle size.