Insights into the adsorption behavior of tetracycline in various shaped carbon nanopores: Interplay between mass transfer and adsorption

Abstract

Porous carbon is commonly used in the effective removal of antibiotics from water. The geometry of nanopores plays a vital role in determining the adsorption properties of porous carbon. Aiming to reveal the adsorption mechanism and the dependence on the porous geometry, the mass transfer and adsorption performance of tetracycline (TC) in various shaped carbon nanopores was observed in this study by molecular dynamics (MD) simulation. The results show that the molecular diffusion of water and TC in nanopores is confined than that in bulk solution. The mass transfer in cylindrical through pores (THC) is more efficient than that in blind pores. The accumulated presence probability of TCs within the nanopore of THC is over twice as high as in the blind nanopores. THC exhibits the best adsorption rate and capacity in this study, and the adsorption ability of the blind nannopores follows the order BHC-Cy (cylindrical blind pore) > BHC-Co (conical blind pore) > BHC-Sp (spherical blind pore). Both the cylindrical and bottom surface in BHC-Cy are effective adsorption sites, while the adsorption is seldom found in the bottoms of BHC-Co and BHC-Sp. Surface diffusion of adsorbed TC molecules along the carbon surface was investigated. The sphere-shaped blind pore was found unfavorable for the adsorption of TC from water.