Removal of Cr(VI) from aqueous solutions using montmorillonite-biochar composites

Montmorillonite, attached to paralyzed biochar, was used to develop novel biochar for removing Cr(VI) from aqueous solution. The biochar feedstock was pyrolyzed at 250 degrees C for 2 h and then stirred with montmorillonite in distilled water. The structure and surface morphology of biochar, montmorillonite, and composite materials were characterized by scanning electron microscopy with energy-dispersive X-ray spectroscopy and transmission electron microscopy. The composite materials inherit the properties from both montmorillonite and biochar. The fitting results of adsorption kinetics and isotherms analysis show that modified biochar is more in line with the pseudo-second-order and Langmuir adsorption model. The maximum adsorption capacity of montmorillonite-modified biochar is 21.75 mg/g. The adsorption effect of SO42- and HCO3- on the materials is relatively noticeable. The research of this work shows that a modified material with low operational cost and favorable removal efficiency was prepared to remove Cr(VI) from aqueous solution compared with other adsorbents.