Insect-derived biochar-organically modified vermiculite composite enabling synergistic adsorption and analysis of insecticides in water samples.

Background

The widespread application of insecticides has raised concerns about environmental persistence and risks to non-target organisms, calling for efficient adsorbents and reliable analytical methods for residue monitoring. Biomass-derived carbon-based materials show promise but often suffer from limited capacity and poor reusability. While biochar-clay composites and organically modified clays have been studied separately for pollutant removal, their integration into a synergistic adsorption system remains largely unexplored.

Results

A novel insect-derived biochar-organically modified vermiculite composite (1.5VB400-91) was developed using fall webworm biomass and vermiculite for the adsorption and determination of five insecticides. The composite achieved a maximum adsorption capacity of 956.06 mg g-1 for thiacloprid and over 80% removal of chlorbenzuron at low concentrations. A dispersive solid-phase extraction method coupled with gas chromatography-electron capture detection was established for garden water samples, showing good linearity (0.30-8000 μg L-1, R2 ≥ 0.9991), low detection limits (0.080-5.4 μg L-1), and satisfactory recoveries (81-91%). Mechanistic studies revealed a synergistic Capture-Transfer-Immobilization process, in which biochar acts as an adsorption entry and mass-transfer accelerator, while organically modified vermiculite serves as the terminal immobilization domain.

Significance

This work demonstrates the first successful integration of biochar-vermiculite compositing with organic modification to create a synergistic adsorption system enabling both rapid capture and deep fixation of pesticide molecules. The use of pest-derived biomass offers a sustainable and cost-effective fabrication route, while the elucidated Capture-Transfer-Immobilization mechanism provides insights for designing advanced adsorbents for environmental analysis and remediation. The developed method also offers a reliable and sensitive analytical tool for monitoring insecticide residues in environmental water samples.