Synthesis of mesoporous silica-carbon microspheres via self-assembly and in-situ carbonization for efficient adsorption of Di-n-butyl phthalate

Abstract

Mesoporous materials have been widely utilized as adsorbents of environmental refractory organics. However, it is a great challenge to synthesize mesoporous adsorbents with controllable pore structures and surface chemical properties. In this study, mesoporous silica-carbon microspheres, aggregated by silica nanospheres with inner aromatic carbon layers, are synthesized through self-assembly and in-situ carbonization process with triblock-copolymer Pluronic P123 as the structure directing agent, tetraethylorthosilicate as the silica precursor, 1,3,5-trimethylbenzene as the swelling agent, and potassium chloride as the spherical micelle inducer. The synthesized silica-carbon materials possess microspherical morphology made of closely packed nanospheres, faced centered cubic mesostructure with space group of Fm3¯m, large opening mesopores (21.3 nm), high surface areas (491 m2/g) and abundant inner aromatic carbon layers. This microspheres present unique amphiphilic surface that hydrophilic silica of outer layer facilitates well-dispersion in water and helps DBP approach to MSCM by hydrogen bonding, and hydrophobic carbon of inner layer enhances adsorption affinity. Results show an effective adsorption performance in the removal of Di-n-butyl phthalate (DBP) through π-π stacking and hydrophobic interactions. The adsorption of DBP on this adsorbent is an exothermic mono-layer process, fitting to the pseudo-second-order kinetic model, with the maximum adsorption capacity of 57.14 mg/g at 25 °C, the adsorption equilibrium time within 5 min, and DBP removal percentage up to 95% in five cycles. The materials are promising adsorbents of phthalate-like pollutants in water treatment.