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Physical, Chemical and Biological Characterization of Six Biochars Produced for the Remediation of Contaminated Sites
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Surface Structure Analysis and Formaldehyde Removal Mechanism of Lotus Shell Biochar: An Experimental and Theoretical
Wenchao Ji1, Manping Zhang1, Xingjun Fan1
1College of Resource and Environment, Anhui Science and Technology University, Fengyang 233100, China.
Langmuir : the ACS Journal of Surfaces and Colloids
|July 27, 2023
Summary
Lotus shell biochar, especially when carbonized at 700°C, effectively removes formaldehyde (HCHO) through chemical adsorption. This study highlights the role of carboxyl groups and inorganic crystals in biochar for air purification applications.
Area of Science:
- Environmental Science
- Materials Science
- Chemistry
Background:
- Formaldehyde (HCHO) is a common indoor air pollutant with significant health implications.
- Biochar derived from biomass offers a sustainable and cost-effective adsorbent for air pollutants.
- Understanding the adsorption mechanisms of biochar is crucial for optimizing its environmental applications.
Purpose of the Study:
- To investigate the adsorption of gaseous formaldehyde by lotus shell biochar carbonized at different temperatures (500, 700, and 900 °C).
- To elucidate the roles of internal crystal structure and surface functional groups in formaldehyde adsorption.
- To explore the adsorption kinetics, isotherms, and mechanisms using experimental and computational methods.
Main Methods:
- Experimental adsorption studies of formaldehyde onto lotus shell biochar.
- Characterization of biochar properties, including crystal structure and surface functional groups.
- Density Functional Theory (DFT) calculations to model adsorption energies and mechanisms.
- Kinetic and isotherm analyses (pseudo-second-order, Langmuir).
Main Results:
- Lotus shell biochar carbonized at 700 °C exhibited the highest formaldehyde removal rate (87.64%) at a concentration of 10.50 ± 0.30 mg/m³.
- Adsorption followed pseudo-second-order kinetics and Langmuir isotherm, indicating chemical, monomolecular layer adsorption.
- DFT calculations confirmed chemical adsorption of formaldehyde onto CaCO₃ and KCl surfaces, with energies ranging from -64.375 to -87.554 kJ/mol.
- Carboxyl groups on the biochar surface were identified as the primary functional groups responsible for formaldehyde adsorption.
Conclusions:
- Lotus shell biochar, particularly at 700 °C, is a highly effective adsorbent for formaldehyde.
- The adsorption mechanism is primarily chemical, driven by electron transfer facilitated by inorganic components and carboxyl groups.
- This research enhances the understanding of biochar's environmental remediation capabilities and guides the development of advanced biochar-based air purification materials.
