Equilibrium of methylene blue removal onto crayfish shell biochar

Abstract This work was aimed to establish the adsorptive properties of crayfish shell biochars for methylene blue dye removal. The adsorbents were prepared via pyrolysis at 650 and 800 °C and yield the surface area of 665 and 635 m 2 /g, respectively. The latter biochar, designated as CFB800, exhibits a dye adsorption capacity of 50.5 mg/g, which is nearly double that of the former (CFB650), with a capacity of 23.0 mg/g. The equilibrium capacity decreased with increasing adsorbent mass, but increased with increasing initial concentration and temperature. The equilibrium data fitted well with Langmuir model. The methylene blue adsorption onto crayfish shell biochars is favourable and spontaneous. Hence, crayfish shell is a promising resource of biochar to treat dye-containing wastewater.