A novel NH2-rich polymer/graphene oxide/organo-vermiculite adsorbent for the efficient removal of azo dyes

A multifunctional polyethyleneimine-graphene oxide/organo-vermiculite composite (PGO/OVt) was successfully fabricated by introducing OVt (modified by dodecyl dimethyl benzyl ammonium chloride, 1227) and polyethyleneimine (PEI) onto GO. For PGO/OVt, the proportion of GO was 25%, while OVt accounted for 75%, which can not only effectively reduce the cost of GO-doped adsorbents, but also ensure a high adsorption efficiency. Various analyses, including FT-IR, XPS, AFM, SEM, TEM, TG-DTG, and XRD were used to characterize the structures and surfaces of PGO/OVt. The surface properties of graphene oxide (GO), the hydrophobicity of OVt, and abundant amino functional groups in polyethyleneimine made PGO/OVt an excellent, versatile adsorbent of Congo Red (CR) and Acid Red 1 (AR-1) in single and binary-dyes system. In single-dye systems, due to the existence of hydrogen bonding, π-π, hydrophobic, and electrostatic interactions between adsorbent and dyes, PGO/OVt exhibited excellent adsorption capacities of 570 mg/g and 365 mg/g for CR and AR-1, respectively. The adsorption processes were well described by pseudo-second-order kinetics ( R 2  > 0.99) and the Langmuir isotherm model ( R 2  > 0.98). The thermodynamic parameters demonstrated that the adsorption processes were nonspontaneous and endothermic. In the binary-dyes system, the maximum adsorption amount of CR was 491 mg/g, and that of AR-1 was 384 mg/g. The influence intensity factor ( φ ) revealed that the effect between the two components changed from competition to synergy with the variation of initial concentration. The synergistic effect indicated the possible presence of a π-π stacking effect between the molecules of adsorbed and dissociative dyes. Based on the obtained results, the resulting PGO/OVt was an efficient, and a lower cost adsorbent containing GO (GO-doped adsorbent). This work provided a reference for the development of GO composite adsorbents.