Evaluation and selection of biochars and hydrochars derived from agricultural wastes for the use as adsorbent and energy storage materials

The utilization of unconventional agricultural wastes to obtain new porous carbonaceous materials, at mild pyrolysis temperatures and without complex procedures, for either water treatment and energy storage applications is important from the economic and environmental perspective. In this study, biochars and hydrochars were prepared from banana rachis, cocoa pod husks, and rice husks at 600 °C-2 h, under nitrogen flux. The prepared materials were characterized to better understand how their morphological, textural, physical-chemical and/or structural properties correlate with their methylene blue (MB) adsorption capacities. The material with the best properties (mainly SBET > 800 m2/g) and MB adsorption capacity was a novel biochar prepared from banana rachis (BW-BC). This novel material was selected for additional kinetics and equilibrium adsorption tests for lead (Pb) along with its energy storage capacity. In equilibrium test, the novel biochar reached a maximum adsorption capacity for methylene blue of 243.4 mg/g and the highest adsorption capacity for Pb(II) of 179.7 mg/g. In the kinetic adsorption test, the equilibrium adsorption value for methylene blue was 150.4 mg/g and that for Pb(II) was 159.6 mg/g. Most importantly, the performance of the BW-BC material for energy storage in supercapacitors surpassed that of the commercial activated carbon YP50F, reaching specific energy values of 6.66 and 8.52 Wh/kg in acidic and neutral electrolytes, respectively. Among the evaluated hydrochar and biochars derived of agrowastes, the biochar prepared from banana rachis showed the best properties, being potentially useful as adsorbent or as an electrode material for energy storage

Using various techniques to characterize oxidative functionalized and aminosilanized carbon nanotubes for polyamide matrix

The main purpose of this study was to reveal usability of various characterization techniques for certain aspects of surface functionalized multi-walled carbon nanotubes. Surfaces were first oxidative functionalized by sulphuric acid/nitric acid mixture, then aminosilanized by gamma-aminopropyltriethoxysilane. Chemical groups formed on carbon nanotubes due to these surface treatments were characterized by X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy and also energy dispersive spectroscopy. Morphological changes and crystal structure of surface-treated carbon nanotubes were analyzed by scanning electron microscopy and X-ray diffraction, respectively. Thermogravimetric analysis was also used to observe thermal degradation of the chemical groups formed on the nanotube surfaces. In the second part of the study, Polyamide-6 nanocomposites were produced by using unmodified and surface functionalized carbon nanotubes. Transmission electron microscopy indicated that surface functionalization improves distribution of carbon nanotubes in the matrix, while flexural tests revealed that strength and modulus values could be increased as much as 30% and 40%, respectively, due to enhanced interfacial bonding between the matrix and nanotubes