Method for the adsorption of surfactants by lignite in a dry condition using mechanical mixing

•The surfactant is adsorbed on the lignite surface by the new methods in a dry condition.•The lignite is mechanically mixed with surfactant in a mill.•The reduction of moisture adsorption is due to the enhancement of surface hydrophobicity.•The moisture content in the treated sample decreased from 25.9% to 11.6%.•The proposed method can be applied after the dry beneficiation process.