Biochar produced from pyrolysis of biomass has been used as a sorbent to remove pollutants from water. In this work, hickory chip biochar (HC) produced at different pyrolysis temperatures were ball milled (BMHC) and then post-modified with a 10% hydrogen peroxide (H2O2) solution to obtain a set of novel sorbents BMHC-H2O2. While ball-milling dramatically increased the specific surface area and oxygen-containing functional groups such as hydroxyl and carboxyl groups on the surface of the biochar, H2O2 modification further increased these functional groups. Further, the thermal stability of the ball-milled biochar was not greatly reduced by H2O2 modification and hydrodynamic radius was decreased. Ball milling increased the ability of the biochar to adsorb methylene blue (MB) and this ability was further increased by H2O2 modification, due to the increase in oxygen-containing functional groups to interact with MB. The rate of MB adsorption to BMHC-H2O2 was faster than that of HC or BMHC, reaching equilibrium after about 6 h. Among the adsorbents tested, the 450 oC BMHC-H2O2 had the greatest MB adsorption capacity (310 mg g-1). This study shows that the post-modification of ball-milled biochar with H2O2 may be a low cost and environmentally sustainable sorbent for environmental applications.

Enhanced removal of methylene blue from aqueous solutions employing ball milling and hydrogen peroxide modified biochar

ACS Fall 2021

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