Simultaneous adsorption of silver nanoparticles and silver ions on large pore mesoporous silica

Large pore mesoporous silica was synthesized using citric acid as template and modified with mercaptopropyl trimethoxysilane. The MP-Silica exhibited a surface area of 474 m2 g−1 with an average pore diameter of 11 nm (pore diameter ranging from 2 to 30 nm). The material was used in the adsorption of silver ions, AgNPs and simultaneous adsorption of these silver species was also observed. The adsorption of silver ions occurred rapidly and followed a pseudo-second order kinetic model. The adsorption equilibrium of silver ions could be described with a Langmuir isotherm and the maximum adsorption capacity was found to be 114.9 mg g−1. In the mixture of AgNPs and silver ions, the adsorption of AgNPs followed a pseudo-second order kinetic model and took place more slowly compared to silver ions due to their larger size. The MP-Silica exhibited a maximum adsorption capacity of 91.9 mg AgNPs g−1 in the mixture. The adsorption of silver species on MP-Silica occurred through chemisorption via the coordination of these species with thiol groups on the surface. The removal of silver species from wastewater samples and consumer products by MP-Silica was demonstrated.