Do All Carbonized Charcoals Have the Same Chemical Structure? 2. A Model of the Chemical Structure of Carbonized Charcoal

Abstract

Charcoals and carbonized charcoals (i.e., biocarbons) were prepared from a wide variety of biomass substrates, including pure sugars containing five- and six-membered rings with furanose and pyranose configurations, lignin, agricultural residues (corncob and nut shells), and a hard wood. These biocarbons were subject to proximate and elemental analysis, gas sorption analysis, and analysis by inductively coupled plasma mass spectroscopy (ICP-MS), scanning electron microscopy (SEM), X-ray diffraction (XRD), electron spin resonance (ESR), 13C cross-polarization magic-angle spinning (CPMAS) NMR, and matrix-assisted, laser desorption ionization coupled with time-of-flight mass spectroscopy (MALDI-TOF MS). All the carbonized charcoals contained oxygen heteroatoms, had high surface areas, and were excellent conductors of electricity. Doping the biocarbon with boron or phosphorus resulted in a slight improvement in its electrical conductivity. The XRD analysis indicated that the carbonized charcoals possess an aromaticity of about 71% that results from graphite crystallites with an average size of about 20 Å. The NMR analysis confirmed the highly aromatic content of the carbonized charcoals. The ESR signals indicated two major types of carbon-centered organic radicals. MALDI-TOF spectra of the charcoals and carbonized charcoals greatly differed from those of synthetic graphite. The biocarbons contained readily desorbed discrete ions with m/z values of 317, 429, 453, 465, 685, and 701. These findings were employed to develop a model for the structure of carbonized charcoal that is consistent with the biocarbon's oxygen content, microporosity and surface area, electrical conductivity, radical content, and its MALDI-TOF spectra.

Dynamic Molecular Structure of Plant Biomass-Derived Black Carbon (Biochar)

“…Bourke et al (23) found that the lack of atomic pore space within the crystallite carbon layers as well as recondensation and trapping of VM in pores reduces the SA.…”

Effects of Biochar Amendment on Chloropicrin Adsorption and Degradation in Soil

“…In the process of pyrolysis, the biochar surface forms many free radicals [16] that are generated by oxygen atoms and inorganic impurities of the feedstock [36]. The free radical content varies with pyrolytic temperature.…”

Extraction of hydrocolloids from Pereskia Aculeata Miller: reuse of process residue as activated carbon for the pigment-removal phase

“…Thermogravimetric studies show that during the carbonization of a lignocellulosic material, carboxyl groups are the most thermolabile oxygen groups, as they can be decomposed as CD 2 at temperatures in the range of 100 to 400 °C, while carboxylic anhydrides and lactones decompose in the range of 430 660 °C. The other types of oxygen groups (phenols, ethers, carbonyls and quinones) are decomposed thermally as either CD or CD 2 at temperatures above 600 °C, the pyrone structures being the most thermally stable (decomposing at 900 to 1,200 °C) (Bourke et al, 2007). Thus, to control the acidic or basic nature of the activated carbon produced, except for the intrinsic properties of the precursor material, the temperature and heating rates must be carefully controlled in the carbonization and activation process (Dliveira & França, 2008).…”