In-situ investigation of dye pollutant adsorption performance on graphitic carbon nitride surface: ATR spectroscopy experiment and MD simulation insight

The adsorption performances on graphitic carbon nitride (g-C 3 N 4 ) surface were investigated for organic dye pollutants by both experimental and calculation methods. For experimental investigation, adsorption thermodynamics and kinetics results were in-situ obtained and evaluated. With Δ G MB + = − 31.78 < Δ G MO − = − 17.38 kJ mol − 1 by Langmuir modeling , g-C 3 N 4 showed superior adsorption spontaneity of MB + >MO - . With linear and exponential modeling, g - C 3 N 4 showed only adsorption process for MB + but both diffusion and adsorption processes for MO - . For simulation insight, all MB + molecules but only parts of MO - molecules were inclined to orient in parallel position at g-C 3 N 4 surface after optimization during low concentration. And both MB + and MO - molecules were inclined to orient in perpendicular position at g-C 3 N 4 surface after optimization during high concentration. Combined with experimental and calculation results, a molecular-orientation and force-dominance mechanism adsorption model are proposed to explain the surface interaction processes between dyes and g-C 3 N 4 . Electrostatic interaction and π-π stacking interaction were revealed to dominate for MB + adsorption, and π-π stacking interaction and van der Waals force were revealed to dominate for MO - adsorption. This work obtained ‘localized’ interfacial information and elucidated in-situ intermolecular interactions at g-C 3 N 4 interface, which can provide fundamental basis for operation removal of organic dye pollutants by g-C 3 N 4 .