Compositions and sorptive properties of crop residue-derived chars.
Chars originating from the burning or pyrolysis of vegetation may significantly sorb neutral organic contaminants (NOCs). To evaluate the relationship between the char composition and NOC sorption, a series of char samples were generated by pyrolyzing a wheat residue (Triticum aestivum L.) for 6 h at temperatures between 300 degrees C and 700 degrees C and analyzed for their elemental compositions, surface areas, and surface functional groups. The samples were then studied for their abilities to sorb benzene and nitrobenzene from water. A commercial activated carbon was used as a reference carbonaceous sample. The char samples produced at high pyrolytic temperatures (500-700 degrees C) were well carbonized and exhibited a relatively high surface area (>300 m2/g), little organic matter (<3%), and low oxygen content (< or = 10%). By contrast, the chars formed at low temperatures (300-400 degrees C) were only partially carbonized, showing significantly different properties (<200 m2/g surface area, 40-50% organic carbon, and >20% oxygen). The char samples exhibited a significant range of surface acidity/basicity because of their different surface polar-group contents, as characterized by the Boehm titration data and the NMR and FTIR spectra. The NOC sorption by high-temperature chars occurred almost exclusively by surface adsorption on carbonized surfaces, whereas the sorption by low-temperature chars resulted from the surface adsorption and the concurrent smaller partition into the residual organic-matter phase. The chars appeared to have a higher surface affinity for a polar solute (nitrobenzene) than for a nonpolar solute (benzene), the difference being related to the surface acidity/basicity of the char samples.
Department of Crop, Soil, and Environmental Sciences, University of Arkansas, Fayetteville, Arkansas 72701, USA.
Yuan
Y
Chun
Guangyao
G
Sheng
Cary T
CT
Chiou
Baoshan
B
Xing
D000327:Adsorption; D001554:Benzene / Q000737:chemistry / Q000302:isolation & purification; D002606:Charcoal / Q000737:chemistry* / Q000592:standards; D018556:Crops, Agricultural / Q000737:chemistry*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D009578:Nitrobenzenes / Q000737:chemistry / Q000302:isolation & purification; D012015:Reference Standards; D012989:Soil Pollutants / Q000302:isolation & purification; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D014908:Triticum / Q000737:chemistry
D009578:Nitrobenzenes; D012989:Soil Pollutants; D002606:Charcoal; C036077:nitrobenzene; D001554:Benzene