Adsorption of methylene blue from aqueous solution on biochar prepared from a K-rich biomass Alternanthera philoxeroides

ABSTRACT

Alternanthera philoxeroides (AP) is a typical invasive plant. The quick spread of AP biomass may cause serious threat to ecological balance and biodiversity of the local area. However, AP has a high content of potassium, making it possible for preparing biochar through a self-activation process. In this study, AP biomass was employed to prepare porous carbon through a simple one-step pyrolysis. The effect of pyrolysis temperature (T) and carrier gas flow rate (v) onto the target carbon was intensively discussed. The obtained carbon were employed as adsorbents for methylene blue (MB) adsorption. Results showed that both of the T and v played great influence on the porous structure of the obtained biochar. Higher pyrolysis temperature and lower carrier gas flow rate were in favor of the formation of micropore and mesopore. The biochar obtained from 900°C pyrolysis temperature and 20 cm³ min⁻¹ carrier gas flow rate (BC/900–20) possessed a satisfying specific surface area (825.6 m² g⁻¹) through the direct one-step pyrolysis, verifying the existence of pyrolysis gas self-activation and inorganic salt template self-activation effect. The maximum adsorption capacities calculated from Langmuir model were 424.9 mg g⁻¹ for BC/900–20, which was comparable to that of the adsorbents reported recently.

KEYWORDS:

• Alternanthera philoxeroides
• Pyrolysis
• Self-activation
• Adsorption
• Methylene blue

Novelty

• Alternanthera philoxeroides, a kind of potassium rich biomass, was employed as precursors to prepare porous carbon material through a simple one-step self-activation pyrolysis process.

• The influence of pyrolysis temperature and carrier gas flow rate among the pyrolysis process on the properties of the obtained carbon materials was intensively discussed.

• The biochar obtained from 900 °C pyrolysis temperature and 20 cm³ min-1 carrier gas flow rate possessed a satisfying specific surface area and sorption capacity for methylene blue.

Acknowledgments

Authors thank for the Analysis and Testing Center, Sichuan University, for the help with FTIR, XRD and SEM analysis.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the National Natural Science Foundation of China [81927809]