Saccharide-derived microporous spherical biochar prepared from hydrothermal carbonization and different pyrolysis temperatures: synthesis, characterization, and application in water treatment.

Publication Type:
Journal Article
Citation:
Environ Technol, 2017, pp. 1 - 14
Issue Date:
2017-08-24
Full metadata record
Three saccharides (glucose, sucrose, and xylose) were used as pure precursors for synthesizing spherical biochars (GB, SB, and XB), respectively. The two-stage synthesis process comprised: (1) the hydrothermal carbonization of saccharides to produce spherical hydrochar' and (2) pyrolysis of the hydrochar at different temperatures from 300°C to 1200°C. The results demonstrated that the pyrolysis temperatures insignificantly affected the spherical morphology and surface chemistry of biochar. The biochar' isoelectric point ranged from 2.64 to 3.90 (abundant oxygen-containing functionalities). The Brunauer-Emmett-Teller (BET)-specific surface areas (SBET) and total pore volumes (Vtotal) of biochar increased with the increasing pyrolysis temperatures. The highest SBET and Vtotal were obtained at a pyrolysis temperature of 900°C for GB (775 m(2)/g and 0.392 cm(3)/g), 500°C for SB (410 m(2)/g and 0.212 cm(3)/g), and 600°C for XB (426 m(2)/g and 0.225 cm(3)/g), respectively. The spherical biochar was a microporous material with approximately 71-98% micropore volume. X-ray diffraction results indicated that the biochar' structure was predominantly amorphous. The spherical biochar possessed the graphite structure when the pyrolysis temperature was higher than 600°C. The adsorption capacity of GB depended strongly on the pyrolysis temperature. The maximum Langmuir adsorption capacities ([Formula: see text]) of 900GB exhibited the following selective order: phenol (2.332 mmol/g) > Pb(2+) (1.052 mmol/g) > Cu(2+) (0.825 mmol/g) > methylene green 5 (0.426 mmol/g) > acid red 1 (0.076 mmol/g). This study provides a simple method to prepare spherical biochar - a new and potential adsorbent for adsorbing heavy metals and aromatic contaminants.
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