Heteroatom nitrogen and oxygen co-doped three-dimensional honeycomb porous carbons for methylene blue efficient removal

[Display omitted] •Carbon disulfide extract of coal tar pitch as raw material.•Melamine sponge as structural framework and nitrogen-doped precursor.•N and O co-doped three-dimensional honeycomb porous carbons (HPCs) were prepared.•HPC-3 had excellent methylene blue adsorption capacity of 631.0 mg g−1. High carbon content and low-priced coal tar pitch (CTP) was a suitable precursor to prepare porous carbon. However, the porous carbon directly prepared by CTP showed an amorphous two-dimensional structure, which limited its subsequent applications in certain respects. In this paper, under the oxidation of H2O during KOH activation, nitrogen and oxygen co-doped three-dimensional honeycomb porous carbons (HPCs) were prepared with carbon disulfide extract of CTP as raw material and melamine sponge as structural framework and nitrogen precursor. HPCs exhibited a unique three-dimensional honeycomb structure, which was able to prevent the stacking of nano materials and provide larger effective specific surface area (2246 m2 g−1) to supply more adsorption space for pollutants in wastewater. In addition, HPC-3, prepared by an impregnation ratio (char:KOH) of 3, displayed excellent adsorption performance of methylene blue, the maximum adsorption capacity was 631.0 mg g−1, which was 2–5 times higher than most of biomass porous carbons previously reported. The adsorption process conformed to Langmuir and pseudo-second order kinetic model. As can be clearly seen from the adsorption results, HPC-3, as a kind of adsorbent, effectively contributed to removing synthetic dyes from wastewater.