Magnetically separable porous graphitic carbon with large surface area as excellent adsorbents for metal ions and dye

Abstract

Magnetic porous graphitic carbon (MPGC) materials were fabricated through a facile “Solution-Solid” route and their application as excellent adsorbents for metal ions and dye were also demonstrated. In the preparation, glucose, nickel nitrate and TEOS were selected as carbon resource, catalyst precursor and porogent, respectively. In the first step, the solution contained glucose, Ni²⁺ and TEOS was treated at low temperature to impel polymerization of glucose, coordination of Ni²⁺ with glucose unit and hydrolysis of TEOS simultaneous, leading to the formation of precursor (Solution process). After heating the precursors under N₂ atmosphere, the Ni-SiO₂/carbon composites were formed (Solid process). Followed soaking with NaOH to remove SiO₂ porogent, the corresponding MPGC materials with magnetic nickel particles embedded in the graphitic carbon framework were obtained. The obtained MPGC materials show good chemical stability due to their high graphitic degree. It is noteworthy that they have exceptionally large surface areas up to 918 m² g⁻¹. The adsorption performance of MPGC are evaluated by using metal ions (Cd²⁺, Cu²⁺, Ag⁺, Au³⁺) and dye (Rhodamine B, RhB) in aqueous solutions as the target. The results indicate that MPGC materials exhibit excellent adsorption capacities for metal ions (7.79 mg g⁻¹ for copper for example), which are superior to those of activated carbons and carbon nanotubes. In addition, the materials have also exhibited good ability for adsorption of dye molecular. Notably, MPGC materials could be easily removed for reuse by an external magnet, facilitating separation and reuse of those materials as adsorbents. The adsorption kinetics for these metal ions and dye on MPGC-based adsorbents were well fitted to a pseudo-second order model.