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-CN) 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 [Formula: see text] by Langmuir modeling g-CN showed superior adsorption spontaneity of MB >MO. With linear and exponential modeling, gCN 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-CN surface after optimization during low concentration. And both MB and MO molecules were inclined to orient in perpendicular position at g-CN 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-CN. 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-CN interface, which can provide fundamental basis for operation removal of organic dye pollutants by g-CN.