Biochar produced from oak sawdust by Lanthanum (La)-involved pyrolysis for adsorption of ammonium (NH4+), nitrate (NO3−), and phosphate (PO43−)

• Published in: Chemosphere (Oxford) 2015-01, Vol.119, p.646-653
• Main Authors: Wang, Zhanghong, Guo, Haiyan, Shen, Fei, Yang, Gang, Zhang, Yanzong, Zeng, Yongmei, Wang, Lilin, Xiao, Hong, Deng, Shihuai
• Format: Article
• Language: English
• Subjects: Adsorption; Ammonium Compounds - metabolism; Approximation; Biochar; Charcoal - chemistry; Functional groups; Hot Temperature; Isotherms; Lanthanum; Lanthanum - chemistry; Microscopy, Electron, Scanning; Models, Chemical; N & P adsorption; Nitrates; Nitrates - metabolism; Oak; Phosphates - metabolism; Pyrolysis; Pyrolytic temperature; Quercus - chemistry; Sawdust; Spectrometry, X-Ray Emission; Spectroscopy, Fourier Transform Infrared; Surface chemistry; Thermogravimetry; Wood - chemistry
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2014.07.084

•It was feasible to employ the LaCl3 in slow pyrolysis for producing La-biochars.•Biomass pyrolysis behaviors were not significantly changed by La-involvement.•Readily soluble NH4+, NO3− and PO43− releases from La-biochars were greatly weakened.•NH4+, NO3− and PO43− maximum adsorption capacity of La-biochars was greatly improved. A series of biochars were prepared by pyrolyzing oak sawdust with/without LaCl3 involvement at temperature of 300–600°C, and approximate and ultimate analyses were carried out to check their basic characteristics. Meanwhile, the releases of readily soluble NH4+, NO3− and PO43− from biochars and the adsorption of NH4+, NO3− and PO43− by biochars were investigated. Results indicated that the involvement of LaCl3 in pyrolysis could advance the temperature of maximum mass loss by 10°C compared with oak sawdust (CK), and potentially promoted biochar yield. Overall, the releases of readily soluble NH4+, NO3− and PO43− from biochars were negatively related to pyrolysis temperature, and the releases were greatly weakened by La-biochars. Additionally, the adsorption to NH4+ can be promoted by the biochars produced at low temperature. On the contrary, the NO3− adsorption can be improved by increasing pyrolysis temperature. The highest PO43− adsorption was achieved by the biochars produced at 500°C. According to the results of adsorption isotherms, the maximum adsorption capacity of NH4+, NO3− and PO43− can be significantly promoted by 1.9, 11.2, and 4.5 folds using La-biochars. Based on the observations of FT-IR, SEM–EDS, and surface functional groups, the improvement of NH4+ adsorption was potentially associated with the existing acidic function groups (phenolic-OH and carboxyl CO). The increased basic functional groups on La-biochars were beneficial to improve NO3− and PO43− adsorption. Besides, PO43− adsorption was also potentially related to the formed La2O3.