Lead (Pb²⁺) sorptive removal using chitosan-modified biochar: batch and fixed-bed studies

Area of Science:

• Environmental Science
• Materials Science
• Chemistry

Background:

• Heavy metal contamination, particularly lead (Pb²⁺), poses a significant threat to water quality and ecosystem health.
• Biochar derived from fast pyrolysis of biomass is a promising adsorbent, but its efficiency can be limited.
• Chitosan, a biopolymer, offers functional groups that can enhance the adsorption properties of materials.

Purpose of the Study:

• To synthesize and characterize Chitosan-Modified fast pyrolysis BioChar (CMBC).
• To evaluate the efficiency of CMBC in removing Pb²⁺ from aqueous solutions compared to Non-Modified BioChar (NMBC).
• To investigate the adsorption mechanisms of Pb²⁺ onto CMBC.

Main Methods:

• CMBC was prepared by treating pine wood biochar with a chitosan solution and NaOH.
• Characterization involved techniques such as DRIFTS, SEM, BET surface area analysis, elemental analysis, TGA, DSC, and ζ-potential measurements.
• Batch and column adsorption experiments were conducted to determine Pb²⁺ removal capacity under various conditions.

Main Results:

• Elemental analysis confirmed chitosan constitutes approximately 25% of CMBC by weight.
• CMBC exhibited a Langmuir maximum adsorption capacity of 134 mg g^-1 for Pb²⁺ at pH 5 and 318 K, significantly higher than NMBC (48.2 mg g^-1).
• Column studies showed a CMBC adsorption capacity of 5.8 mg g^-1 for Pb²⁺.

Conclusions:

• Chitosan modification substantially enhances the Pb²⁺ adsorption capacity of biochar.
• The presence of amine groups introduced by chitosan on the biochar surface is responsible for the improved Pb²⁺ adsorption.
• CMBC is a highly effective adsorbent for removing lead ions from contaminated water.