Montmorillonite-alginate films for paraquat adsorption and fluorescent detection

This study explores the ability of montmorillonite (Mt) encapsulated in alginate films (A) to retain and detect the herbicide paraquat (PQ) in situ by molecular fluorescence in aqueous solution. The synthesis of the films (Mt-A) was carried out using a biopolymer in aqueous solution, avoiding organic solvents and thus preventing toxic waste generation. Characterization techniques such as XRD, FTIR, SEM, and EDS demonstrated that Mt. is homogeneously distributed within the film, with only slight changes to its interlayer space. Before evaluating the fluorescence behavior of PQ adsorbed on the films, the robustness of the herbicide's fluorescence signal was confirmed in Mt. dispersions, showing independence from dissolved ions and pH. Fluorescence response as a function of initial herbicide concentration was evaluated under conditions where C_eq ∼ 0. Under these conditions, a linear fluorescence intensity response was observed for the initial PQ concentration in all studied scenarios. The Mt-A composite also exhibited a linear fluorescence response with the initial herbicide concentration within the range of concentrations highly toxic to humans and animals. The simplicity and sustainability of the films synthesis, the ability to preconcentrate the herbicide, the absence of sample preparation, the avoidance of organic solvents, and the simplicity of detection are noteworthy. These findings provide insights for the future development of simple detection systems for PQ in aqueous systems, with montmorillonite as the principal active component.