Impact of modification on the properties of Eucheuma biochar and its adsorption of phenanthrene from aqueous solution

Abstract

Biochar was derived from Eucheuma (EBC) at a temperature of 500 °C and the resulting biochar was modified using NaOH, KOH, NaOH + KOH and HNO₃ + HCl. This study investigated the impact of these modifications on the characteristics of the biochar and its effectiveness in adsorbing phenanthrene (Phe) from an aqueous solution. The results indicated that the surface roughness increased, leading to an increase in the specific surface area, and the development of complex pore structure, leading to a decrease in the polarity and increase in hydrophobicity of biochar modified by a mixture of KOH and HNO₃ + HCl (EBC-K and EBC-H). The EBC-K and EBC-H samples exhibited superior surface areas (272.76 and 289.60 m² g⁻¹) and adsorption capabilities for Phe (removal rates of 99.8% and 99.4%). The pseudo-first order, pseudo-second order and intraparticle diffusion Kinetic model demonstrated that the adsorption process is determined by both physicochemical and intra-particle diffusion. The adsorption process was well described by the Langmuir model. The maximum adsorption capacity of EBC-K and EBC-H was increased by approximately 2.4 times compared with the original biochar. Batch adsorption experiments indicated that the removal rate increases with the increase of dosage. Additionally, EBC-H regenerated from n-hexane removed 85.52% of the Phe solution.

Graphical abstract

Keywords:

• Eucheuma
• biochar modification
• structural characterization
• Phe
• adsorption

Disclosure statement

The authors declare no competing interest.

Data availability

The datasets used and analyzed during the current study are available from the corresponding author upon reasonable request.

Additional information

Funding

The work was supported by the National Key R&D Program of China (2020YFD0900903), Science Foundation of Donghai Laboratory (DH-2022KF0218), Zhoushan Science and Technology Plan Project (2019F12004), Zhoushan Science and Technology Plan Project (2021C41004).