Novel biocide multifunctional materials based on mesoporous silicas modified by treatment with guanidine polymers or mercaptopropyltrimethoxysilane: Synthesis, characterization, and applications

Mesoporous thiol and guanidine-modified silicas with narrow pore size distribution have been prepared by the sol-gel technique. The surface area of the silicas was modified by treatment with 3-mercaptopropyltrimethoxysilane (MPTMS) and the guanidine polymers polyacrylate guanidine (PAG) and polymethacrylate guanidine (PMAG). The mesoporous silicas were characterized by nitrogen adsorption-desorption analysis, Fourier transform infrared spectroscopy, and laser diffraction. The materials obtained were used as adsorbents for removing heavy metal ions (Cu²⁺) from water. It was found that modification of the silica surface by treatment with MPTMS and guanidine polymers provides new sorbents with high adsorption capacity compared with unmodified silica. The equilibrium adsorption capacity for Cu²⁺ ions on the surface of silicas modified by PAG and PMAG was 65 and 99.8 mg/g, respectively. Moreover, the modified silicas were tested for antimicrobial activity, in vitro, against the Gram-positive prokaryote Staphylococcus aureus and the Gram-negative prokaryote Escherichia coli. The results showed that only silica modified with guanidine polymers had high antimicrobial activity. To summarize, silica modified by treatment with guanidine polymers is more effective than thiol-modified silica for removing heavy metal ions from aqueous solution and can also be used as a biocide for surface sterilization.