Microporous nanocarbon spheres were prepared by using a microwave assisted solvothermal method. To improve the carbon dioxide adsorption properties, potassium oxalate monohydrate and ethylene diamine (EDA) were employed, and the influence of carbonization temperature on adsorption properties was investigated. For nanocarbon spheres containing not only activator, but also EDA, an increase in the carbonization temperature from 600 °C to 800 °C resulted in an increase of the specific surface area of nearly 300% (from 439 to 1614 m2/g) and an increase of the CO2 adsorption at 0 °C and 1 bar (from 3.51 to 6.21 mmol/g).
The aim of this work was to prepare sugar alcohol-based deep eutectic solvents (DES) and test them as starch plasticizers. Thermoplastic starch (TPS) films were obtained via a simple and convenient thermocompression method. Influence of starch/DES premixtures conditioning (preheating, storage time) on TPS properties was investigated. TPS/sorbitol (S)-based DES exhibited similar tensile strength (TS) (8.6 MPa) but twice higher elongation at the break (ε) (33%) when compared with TPS plasticized only with S. Extra treatment, i.e., heating or prolonged storage time, facilitated starch/DES plasticizing. Starch with selected DES was also extruded and the influence of preconditioning and extrusion rotational speed were subsequently studied on thermocompressed films. Extrusion at 100 rpm led to films with TS up to ca. 10 MPa and ε up to 52%. Some differences in film samples morphology obtained via two processing methods were observed. X-ray diffractograms revealed that extruded samples exhibited a V-type peak at 18.2°, with intensity depending on plasticizer total molecular size. Applied techniques (mechanical tests, XRD, Dynamic Mechanical Analysis (DMA), FTIR-Attenuated Total Reflection (ATR), and moisture sorption) indicated that S-based DES forms stronger interactions with starch than glycerol (G) only used as conventional plasticizer, thus leading to better mechanical properties and inhibited tendency to starch recrystallization (studied up to one year).
For the first time, low transition temperature mixtures – LTTM based on sugars: fructose (Fruc), glucose (Gluc) or sucrose (Suc), and glycerol (G) are prepared, characterized by DSC and applied as potato starch plasticizers. Sugar‐based LTTM exhibits good plasticizing activity leading to homogenous transparent, flexible thermoplastic starch (TPS) materials. Mechanical, dynamic mechanical (DMA), X‐ray diffractometry (XRD), and FTIR analysis of obtained TPS/LTTM films are performed for their relative comparison. For TPS/Fruc:G films, tensile strength (TS) and Young's modulus (YM) decreases and elongation at break (EB) increases with increase of G. However, for TPS/Gluc:G molar ratio of Gluc to G did not affect significantly on films mechanical properties. Comparing two monosugars, i.e., Gluc and Fruc, TPS/Gluc:G materials exhibit slightly higher TS (4.8–5.8 MPa) but lower EB (44–61%) in comparison with TPS/Fruc:G films (TS 3.2–5.0 MPa; EB 90–115%) at 25 °C, RH 50%. LTTM as whole mixture of components led to TPS products with not only higher TS, YM but even EB in comparison with films where sugars and G were added separately into starch. Mutual interaction between sugar, polyol and starch is confirmed by DMA. XRD reveals that starch with LTTM undergone amorphization and TPS/Suc:G 1:6 is the most amorphous among investigated TPS films.
This paper examines the synthesis of the ZnO/carbon spheres composites using resorcinol—formaldehyde resin as a carbon source and zinc nitrate as a zinc oxide source in a solvothermal reactor heated with microwaves. The influence of activation with potassium oxalate and modification with zinc nitrate on the physicochemical properties of the obtained materials and CO2 adsorption capacity was investigated. It was found that in the case of nonactivated material as well as activated materials, the presence of zinc oxide in the carbon matrix had no effect or slightly increased the values of CO2 adsorption capacity. Only for the material where the weight ratio of carbon:zinc was 2:1, the decrease of CO2 adsorption capacity was reported. Additionally, CO2 adsorption experiments on nonactivated carbon spheres and those activated with potassium oxalate with different amounts of zinc nitrate were carried out at 40 °C using thermobalance. The highest CO2 adsorption capacity at temperature 40 °C (2.08 mmol/g adsorbent) was achieved for the material after activation with potassium oxalate with the highest zinc nitrate content as ZnO precursor. Moreover, repeated adsorption/desorption cycle experiments revealed that the as-prepared carbon spheres were very good CO2 adsorbents, exhibiting excellent cyclic stability with a performance decay of less than 10% over up to 25 adsorption-desorption cycles.
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