Cu(II) removal from aqueous solution by Spartina alterniflora derived biochar

A cost-effective biochar (SABC) was prepared from Spartina alterniflora by pyrolysis at low temperatures (⩽500 °C) under anoxic conditions. The obtained biochar was examined for its ability to adsorb copper ions from aqueous solution and the Cu(II) removal mechanisms were explored. Cu(II) adsorption on SABC was found to fit well with Langmuir isotherm and pseudo-second-order kinetic model. The maximum Cu(II) adsorption capacity of SABC reached 48.49 mg g−1, which is about 5 times higher than the raw biomass. Ion exchange had negligible effect on Cu(II) removal. Based on FTIR spectra and potentiometric titration, a complexation model including two acidic and one basic functional groups was proposed. However, metal ions complexation with the surface sites could not account for the uptake amounts of Cu(II) by SABC, alternative binding mechanisms might involve simultaneously.

► Biochar prepared from an invasive plant – Spartina alterniflora.
► 5 times higher removal capacity for Cu(II) was obtained.
► Surface complexation other than ions exchange contributes the Cu(II) removal.
► A 3-site model was proposed to characterize the complex surface of the char.
► Other mechanisms, such as Cπ–metal interaction, metal (hydr)oxide precipitation may involve.