Transition Metal Modified Mesoporous Silica Adsorbents with Zero Microporosity for the Adsorption of Contaminants of Emerging Concern (CECs) from Aqueous Solutions.
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SBA-15 mesoporous silica has been modified in an attempt to develop a platform for adsorbents that can be tailored to target particular contaminants of emerging concern (CECs) present in water sources. Traditionally, mesoporous silicas have exhibited less than desired structural stability in the presence of water, but when carefully grafted with amines and transition metal immobilization (Co2+, Ni2+ or Cu2+) the problem can be minimized in a considerable fashion. We have developed a method that combines blockage of surface micropores and transition metal sources containing less hydration levels to avoid depolymerization of the silica wall. This approach enhanced the materials textural properties and, therefore, the adsorption of CECs. At neutral pH and ambient temperature, a better affinity toward acidic and anionic CECs was observed in M-NH2_g_SBA-15 (M = Co2+, Ni2+ or Cu2+) materials whereas a better affinity toward neutral CECs took place in as-prepared SBA-15. The CuNH2_g_SBA-15 variant displayed the best overall adsorption working capacities, probably due to enhanced steric conditions and specific surface interactions. The latter commensurate well with X-ray photoelectron spectroscopy analyses, which showed that copper underwent the most interactions with the surface environment.