Mechanism of sonication time on structure and adsorption properties of 3D peanut shell/graphene oxide aerogel

A 3D pretreated peanut shell-supported graphene oxide (PPS/GO) aerogel has been facilely prepared through a brief sonication + freeze-shaping technique, avoiding the traditional application of hydrothermal method which suffered from high temperature and long reaction time as well as significant loss of oxygen-containing functional groups. It was then employed to efficient norfloxacin (NOR) removal from aqueous medium. The mechanism of sonication time on the structure and adsorption properties of as-obtained PPS/GO aerogels was emphatically discussed via combining instrumental analyses, batch adsorption experiments and density functional theory (DFT) calculations. Results showed that the 3D PPS/GO aerogel with a decrease in oxygen functional groups and an increase in sp²-derived sp³ hybridization regions was observed as sonication time provided in excess, causing the worse removal efficiency towards NOR. The resulting PPS/GO(5:1) aerogel obtained at sonication of 2 min and GO loading content of 200 mg/(PPS)g exhibited the optimal NOR adsorption capacity (pH 6.2, 228.83 mg g^-1). DFT calculations further identified that the sp³-hybridized areas in PPS/GO aerogel had much lower adsorption energy (ΔE, -6.69 kcal/mol) towards NOR as compared with that of sp²-hybridized zones (-12.45 kcal/mol). In addition, multiple interactions were involved in the adsorption of NOR by 3D PPS/GO aerogel, including electrostatic attraction, H-bonding, π-π conjugation and hydrophobic effect.