Hierarchically porous graphene-like biochar for efficient removal of aromatic pollutants and their structure-performance relationship: A combined experimental, MD and DFT study

Abstract

Development of high-efficiency adsorbents and exploration of the structure-performance relationship holds exciting implications for removal of aromatic pollutants (APs) from water. Herein, hierarchically porous graphene-like biochars (HGBs) were successfully prepared by K2CO3 simultaneous graphitization and activation of Physalis pubescens husk. The HGBs possess high specific surface area (1406–2369.7 m2/g), hierarchically meso-/microporous structure and high graphitization degree. The optimized HGB-2-9 sample exhibits rapid adsorption equilibrium time (te) and high adsorption capacities (Qe) for seven widely-used persistent APs with different molecular structures (e.g., phenol: te = 7 min, Qe = 191.06 mg/g; methylparaben: te = 12 min Qe = 482.15 mg/g). HGB-2-9 also shows a wide pH (3–10) suitability and good ionic strength (0.01–0.5 M NaCl) resistance properties. The effects of the physicochemical properties of HGBs and APs on the adsorption performance were deeply investigated by the adsorption experiments, molecular dynamics (MD) and density functional theory (DFT) simulation. The results demonstrate that the large specific surface area, high graphitization degree and hierarchically porous structure of HGB-2-9 can supply more active sites on accessible surface and facilitate the transport of APs. And the aromaticity and hydrophobicity of APs play the more crucial roles during the adsorption process. Besides, the HGB-2-9 presents good recyclability and high removal efficiency for APs in various real water, which further confirms its potential for practical applications.