Freundlich model assumes a heterogeneous adsorption whileLangmuir model assumes a homogeneous adsorption (Foo andHameed, 2010). Therefore, the removal of Pb by the rice husk biocharsmay have different mechanisms. The calculated maximumremoval capacity (Qmax) values for RH300, RH500, and RH700 are14.1, 21.7, and 26.7 mg/g respectively.