Capacitive removal of Pb ions via electrosorption on novel willow biochar–manganese dioxide composites

ABSTRACT

Biochar derived from lignocellulosic biomass has been used as a low-cost adsorbent in wastewater treatment applications. Due to its rich porous structure and good electrical conductivity, biochar can be used as a cost-effective electrode material for capacitive deionization of water. In this work, willow biochar was prepared through carbonization of shrub willow chips, activated with potassium hydroxide, and loaded with manganese dioxide (WBC-K-MnO₂ nanocomposite). The prepared materials were used to electrochemically adsorb Pb²⁺ from aqueous solutions. Under the applied potential of 1.0 V, the WBC-K-MnO₂ electrode exhibited a high Pb²⁺ specific electrosorption capacity (23.3 mg/g) as compared to raw willow biochar (4.0 mg/g) and activated willow biochar (9.2 mg/g). KOH activation followed by MnO₂ loading on the surface of raw biochar enhanced its BET surface area (178.7 m²/g) and mesoporous volume ratio (42.1%). Moreover, the WBC-K-MnO₂ nanocomposite exhibited the highest specific capacitance value of 234.3 F/g at a scan rate of 5 mV/s. The electrosorption isotherms and kinetic data were well explained by the Freundlich and pseudo-second order models, respectively. The WBC-K-MnO₂ electrode demonstrated excellent reusability with a Pb²⁺ electrosorption efficiency of 76.3% after 15 cycles. Thus, the WBC-K-MnO₂ nanocomposite can serve as a promising candidate for capacitive deionization of heavy metal contaminated water.

GRAPHICAL ABSTRACT

KEYWORDS:

• Electrosorption
• activated biochar
• manganese dioxide
• lead
• capacitive deionization

Acknowledgements

The authors would like to acknowledge the Cornell Center for Materials Research for their assistance with BET and Raman analysis supported by the NSF Award Number DMR-1719875. The authors also thank Shuya Li for her assistance with the XRD and TEM analyses.

Disclosure statement

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

Data availability statement

Data available upon request.

Additional information

Funding

This work was supported by the research funding received from the New York State Department of Environmental Conservation (NYSDEC) under Grant No. 87652 and 87231.