Preparation via Wet Chemical Method, Characterization, and Antimicrobial and Antifungal Properties of Benzalkonium Chloride-Modified Montmorillonite

This study reports the preparation of benzalkonium chloride-modified montmorillonite (MMT-1227) via a wet chemical method and systematically investigates its structural characteristics and antimicrobial/antifungal properties. The modified montmorillonite was comprehensively characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET) surface area analysis. The results confirmed the successful intercalation of benzalkonium chloride into montmorillonite layers, leading to altered surface morphology, increased interlayer spacing, and enhanced hydrophobicity. Antimicrobial assays demonstrated that MMT-1227 exhibits potent activity against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, with inhibition zone diameters of 15.6 ± 0.2 mm and 17.7 ± 0.2 mm, respectively, and minimum inhibitory concentrations (MIC) of 1 mg/mL and 0.5 mg/mL. When incorporated into latex paint at a mass fraction of 0.3%, MMT-1227 achieved a 99.9% antibacterial rate against both strains after 24 h. Additionally, fungal resistance testing in accordance with GB/T 1741-2020 revealed that the modified paint films completely inhibited the growth of eight common mold strains (e.g., Aspergillus niger, Trichoderma viride), achieving a resistance grade of 0. These findings validate that benzalkonium chloride modification endows montmorillonite with excellent antimicrobial and antifungal properties, highlighting its potential as a high-performance additive for functional coatings and related antimicrobial materials.