Adsorption performances and antimicrobial activity of the nanosilver modified montmorillonite clay

Abstract

The synthesis and adsorption potential of Cy-npAg, obtained by modification of raw montmorillonite clay (raw-Cy) with silver nanoparticle (npAg), was studied in this work. Optimization procedure, with respect to time, temperature and amount of deposit npAg, obtained either by reductive precipitation or ultraviolet irradiation, was performed using response surface methodology (RSM). The most efficient adsorbent, obtained by chemical reduction of silver ion with sodium borohydride, named Cy-npAg, was characterized in detail using Brunauer-Emmett-Teller, scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction techniques, and point of zero charge determination. The Cy-npAg showed good adsorption capacity with respect to non-systemic organophosphate insecticide (diazinon) as well as of heavy metals ions (Cd2+ and Ni2+ ions), that is, 74.26, 62.33, and 35.49 mg g(-1), respectively, obtained from Langmuir model fitting. Temperature dependent kinetic study allowed determination of pseudo-second rate constant (10(3) g mg(-1) min(-1))/activation energies (kJ mol(-1)): 1.45/14.48 for diazinon, and 1.27/6.59 and 0.7/7.35 kJ mol(-1) for Cd2+ and Ni2+ ions, respectively. Thermodynamic parameters indicated feasible and spontaneous adsorption with main participation of physisorption. Antibacterial potential of npAg deposit for water disinfection was confirmed by the moderate reduction of bacterial growth of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, by 64%, 39%, and 70%, respectively. Thus, two synergistic effects contribute to water purification processes using Cy-npAg: pollutants removal with a simultaneous decrease of the microbial contamination contributing to overall water quality improvement.