Abstract
In this work, four types of nanosponges were prepared from pyromellitic dianhydride (PMDA) and D-glucose (GLU) with different molar ratios (1.5:1, 2:1, 2.5:1 and 3:1). The obtained PMDA/GLU nanosponges were then pyrolyzed at 800 °C for 30 min under N2 gas flow. The prepared polymeric nanosponges were investigated by FTIR spectroscopy, elemental and thermogravimetric analyses to unravel the role played by the different molar ratio of the precursors in the formation of the polymer. The pyrolyzed nanosponges were investigated by means of porosity measurements, X-ray diffraction analysis, Raman spectroscopy and high-resolution transmission electron microscopy. Notably, no significant correlation of the amounts of used precursors with the porous texture and structure was evidenced. The results corroborate that PMDA and GLU can be easily combined to prepare nanosponges and that the carbon materials produced by their pyrolysis can be associated with glassy carbons with a microporous texture and relatively high surface area. Such hard carbons can be easily obtained and shrewdly used to segregate relatively small molecules and organic contaminants; in this study methylene blue adsorption was investigated.
Highlights
Porous carbons are synthesized by various methods such as: chemical and physical activation [1]; catalytic activation of carbon precursor using metal salts or organometallic compounds; carbonization of polymer blends; carbonization in presence of inorganic templates [2]
Four nanosponges were synthesized by reacting pyromellitic dianhydride (PMDA) with GLU in different molar ratios (1.5:1, 2:1, 2.5:1 and 3:1)
Spectrum of PMDA showed very strong absorption bands at 1764 cm−1 and 919 cm−1, assigned, respectively, to υ (C=O) and υ (C–O) of the five-membered rings [29], while the GLU spectrum exhibited a broad band in the 3000–3500 cm−1 range due to υ (O–H) of hydroxyl groups, and signals in the region of an 800–1200 cm−1 interval originate from coupling of stretching and bending vibrations of C–O and C–C bonds [30]
Summary
Porous carbons are synthesized by various methods such as: chemical and physical activation [1]; catalytic activation of carbon precursor using metal salts or organometallic compounds; carbonization of polymer blends; carbonization in presence of inorganic templates [2]. The obtained porosity can be classified according to the origin (interparticle, intraparticle pores), state (open, closed pores) and dimension of pores [3]. IUPAC [4] classifies pores in micropores (diameter less than 2 nm), mesopores (diameter between 2 and 50 nm) and macropores (diameter larger than 50 nm). Porosity and surface functional groups influence carbon adsorption capacity [5]. Due to the possibility to tailor their properties, porous carbons are widely applied. They can be employed in pollutant removal from water and soil [6] and in gas adsorption [7,8]
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