期刊
JOURNAL OF HAZARDOUS MATERIALS
卷 403, 期 -, 页码 -出版社
ELSEVIER
DOI: 10.1016/j.jhazmat.2020.123648
关键词
Sewage sludge biochar; Calcium sulfate; Heavy metals; Speciation distribution; Immobilization mechanism
资金
- National Natural Science of China [51638006]
- Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology Fund Projects [Guikeneng1801Z009, Guikeneng1401Z004]
- project of high level innovation team and outstanding scholar in Guangxi colleges and universities [002401013001]
- Guangxi Science and Technology Program Project [2018AD16013-04]
- Special funding for Guangxi 'BaGui Scholar' (Huijuan Liu) construction projects
The study showed that in the co-pyrolysis of sewage sludge and CaSO4 to produce biochar, appropriate dosage of CaSO4, high pyrolysis temperature, and suitable holding time can improve the immobilization rate of heavy metals. Suitable pyrolysis temperature and holding time promote the formation of crystals and particles in biochar, leading to the immobilization of more heavy metals.
The effects of calcium sulfate (CaSO4) dosage (mass ratio of CaSO4 to sludge), pyrolysis temperature and holding time on speciation distribution of Cr, Pb, Cu, Ni and Zn in biochar derived from co-pyrolysis of sewage sludge and CaSO4 were investigated. The appropriate CaSO4 dosages for better immobilization of different heavy metals were 0.075 (Cr), 0.025 (Pb), 0.025 (Cu), 0.025 (Ni), and 0.01(Zn), respectively. The corresponding proportions of heavy metals in stable state (oxidizable and residue fractions) were 96.99%, 89.23%, 99.55%, 87.43%, and 54.33%. The high pyrolysis temperature (750 degrees C) was conducive to immobilization of Cr, Pb and Zn, while the percentages of Cu and Ni in stable state were higher at low pyrolysis temperature (350 degrees C). The suitable holding time was 60 min (Cr, Cu) and 15 min (Pb, Ni and Zn), respectively. The characterization of samples showed that suitable pyrolysis temperature and holding time could promote the formation of crystals and spherical or ellipsoidal particles in biochar, and pyrolysis of aliphatic to form more mesopores and macropores, resulting in immobilization of more heavy metals. During co-pyrolysis process, CaSO4 was easily decomposed and generated CaS, CaO, CaCO3 and Ca(OH)(2), which were beneficial to the immobilization of heavy metals.
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