Insights into interfacial interaction mechanism of dyes sorption on a novel hydrochar: Experimental and DFT study

In this experiment, the interfacial interaction mechanism associated with the sorption of methylene blue (MB) and methyl orange (MO) on Fe-doped porous graphite hydrochar (Fe@PGHC) was studied. The characterization results indicated that Fe@PGHC was fabricated successfully and possessed a well-distributed pore size, graphene-like properties and a large surface area (2340 m 2 /g). The sorption results demonstrated that the pseudo-second-order kinetics and Sips isotherm models matched well with the MB/MO uptake behaviour. The results of density functional theory (DFT) calculations revealed that increasing the number of oxygen-containing functional groups improved the sorption capacity of MB and decreased the sorption capacity of MO. MB was regarded as an electron acceptor, MO was regarded as an electron donor, and the interaction between adsorbent and MB/MO included π-π, electrostatic and hydrogen bond interactions. The above results demonstrated that Fe@PGHC was a green and promising adsorbent for the sorption of organic dyes from aqueous solutions.