Heavy metal pollution causes irreversible damage to plants, animals, and humans. Therefore, it is meaningful to develop facile, fast, and efficient strategies for heavy metal ion (HMI) detection. Here, a portable composite film (CPSE) was designed for HMI detection with high sensitivity and wide detection range. The CPSE was prepared by using cellulose nanofibers (CNF)/polyvinyl alcohol (PVA) as the matrix and utilizing modified starch (HPS) to assist disodium calcium ethylenediaminetetraacetate (EDTA-Ca) to form stable complexes with HMI. The R, G and B values (the three primary colors of light) were captured using an image acquisition system to produce an HMI standard color card successfully. Specifically, the composite film can effectively distinguish Cu2+, Pb2+ and Fe3+. The response time of the composite film to HMI was 2–4 s, and the detection ranges of Cu2+ and Fe3+ were 5–700 ppm and 10–1000 ppm, respectively. Additionally, the synergistic effect of HPS and EDTA-Ca led to the increase in tensile strength (1.59–1.71 times), tear strength (3.29–3.57 times), and glass transition temperature (~ 6 °C) compared to CNF/PVA/HPS and CNF/PVA/EDTA-Ca films. This study confirms the value of CPSE films as materials for HMI detection and suggests innovative ideas for designing similar biomass detection materials in the future.
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