Peroxidase mimics through DEHP-rich plastic wastes upcycling for colorimetric sensing neonicotinoid insecticides

Pesticide residues in agricultural products are closely related to people's daily dietary health, and the detection for pesticide residues is always a concern. Simple and sustainable methods for real-time monitoring and screening of pesticide residues still faced challenges. The dechlorination and plasticizers decomposition to achieve high-value recycling of waste plastics was urgent demand. Herein, diethylhexyl phthalate (DEHP)-rich polyvinyl chloride (PVC)/iron filings were dechlorinated in subcritical water at low temperatures while DEHP was decomposed, resulting in waste plastics upcycling to simulated enzyme materials for colorimetric detecting pesticides. The recycled materials (CM-FeOOH/Fe₃O₄-dPVC) were different from the previous treatment for PVC without plasticizers (CM-Fe-dPVC). In subcritical water treatment, decomposition of DEHP led to the formation of FeOOH and magnetic Fe₃O₄ nanoparticles. Mechanism studies revealed that the flocculation of FeOOH and multi-layer or sheet-like C matrix double increased the specific surface area, resulting in strong catalytic activity of Fe₃O₄ nanocomposites for 3,3',5,5'-tetramethylbenzidine (TMB)-H₂O₂ reaction. Acetamiprid and imidacloprid interacted with CM-FeOOH/Fe₃O₄-dPVC to change microscopic electron distribution of the materials and increase Fermi level (E_F), thereby weakening materials' mediated electron migration and inhibiting the generation of ·OH free radicals. The colorimetric analysis for neonicotinoid pesticides was constructed by inhibiting simulated enzyme activity of CM-FeOOH/Fe₃O₄-dPVC, and the detection limit of neonicotinoid pesticide combinations was 8.6 × 10^-8 M. The developed paper-based colorimetric sensor was extremely easy to operate and could complete pesticides detection within 30 min at ambient temperatures. LCA (life-cycle assessment) results indicated that this strategy had significantly small environmental impact. This work pioneered environmentally friendly and inexpensive method for detecting pesticides based on the decomposition and transformation of waste plastics, and also provided insights for high-value recycling of organic solid wastes co-processing.