Synthesis and characterization of pecan nutshell-based adsorbent with high specific area and high methylene blue adsorption capacity

Abstract In this work, a pecan nutshell was used as a precursor to prepare activated hydrochar (HPN-ATV) with a high specific area. HPN-ATV was engineered as an adsorbent for the removal of methylene blue (MB) from aqueous environments. The obtained materials were characterized using textural, morphological, and chemical analysis techniques. HPN-ATV showed a BET specific area of 2342 m 2  g −1 and an average pore diameter of 2.24 nm. Boehm titration and FTIR spectral analysis indicated the presence of acidic and basic functional groups on the surface of HPN-ATV, which rendered the removal of cationic molecules more favorable. The kinetic experimental data better correlated with the pseudo-second-order kinetic and Elovich equations, and the Langmuir model showed a better fit for the data of MB adsorption. The adjusting parameters indicated a monolayer with an adsorption capacity of 1190.62 mg g −1 , which is higher than that of the other adsorbents reported in literature. In addition, the thermodynamic data suggested a spontaneous adsorption process with endothermic characteristics.