The systematic characterization of nanoscale bamboo charcoal and its sorption on phenanthrene:A comparison with microscale

- Physical and chemical properties of nanoscale bamboo charcoal were systematically investigated.
- Nanoscale bamboo charcoal was tested for phenanthrene sorption in aqueous and soil-water systems.
- Nanoscale bamboo charcoal had high ability for phenanthrene sorption in soil-water system, even at a low addition rate of 0.2% in soils.
- Nanoscale bamboo charcoal would be more competitive than some biochars in aqueous and soil-water systems.
- This finding increases our knowledge of nanoscale bamboo charcoal for organic pollutants remediation in soil.

This study investigated the characteristics of nanoscale bamboo charcoal (NBC), and made a comparison with microscale bamboo charcoal (MBC) on how they impact on the sorption abilities of different soils. The two charcoals contained similar elemental contents (e.g., high C, low H and low N) and various functional groups on their surfaces (e.g., aromatic structure, carboxyl, and hydroxyl). However, NBC had a larger total pore volume than that of MBC and was more likely to generate multi-layer sorption of phenanthrene. Controlled by van der Waals forces and electrostatic forces, NBC formed meso-and macropores (intra-particle porosity) and a more intricate pore structure. The performance of NBC in aqueous and soil-water systems was conspicuous and impressing. In aqueous system, by virtue of its larger pore volume, surface area and nonprotonated aromatic carbon, the Kd (sorption coefficient) of NBC reached up to 1.24 × 106, almost 10 times higher than that of MBC. In soil-water systems, although it could aggregate and react with compounds in soil, the performance of NBC was not weakened by the complicated soil properties, and was still more capable of phenanthrene sorption than MBC, even at an extremely low addition rate 0.2% in soils. Additionally, in comparison with some other common biochars, NBC still showed a promising capacity for phenanthrene sorption in two systems. This finding increases our knowledge of NBC for the remediation of organic pollutants in soil and indicates that the addition rate of charcoals in soils could be reduced by lessening the particle size. Therefore, NBC provides a new possibility for soil pollutant remediation and deserves further research.

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