Influence of mixed alkali on the preparation of edible fungus substrate porous carbon material and its application for the removal of dye

•The agricultural waste EFS was used as raw material for preparation porous carbon.•The mixed alkali was the first time used for producing porous carbons based on EFS.•Three porous carbons exhibited the high surface area and total pore volume.•The porous carbons shown the excellent adsorption performance of Rhodamine B.•The probable mechanism of adsorption was analyzed for four possible forces.