Synthesis and characterization of hydrochar from industrial Capsicum annuum seeds and its application for the adsorptive removal of methylene blue from water Article uri icon


  • Chili seeds (CS) represent one of the most abundant residues in Mexico due to the high production and consumption. In this work, CS were used as raw material for the production of low-cost adsorbents for the removal of methylene blue from water. The adsorbents were synthesized from a hydrothermal treatment (based on a surface response experiment design) and characterized texturally by assessing changes in their properties. The mass yield (%25R), carbon content (%25C), and the second order adsorption rate constant (k2) were derived in relation to a list of input variables (e.g., the reaction temperature, residence time, and water/biomass ratio). Accordingly, those output variables were affected most sensitively by temperature and/or residence time, while changes of the water/biomass ratio were insignificant. Besides, an increase in the reaction temperature favored the degradation of the lignocellulosic material with increases in the carbon fixation. The adsorption capacity of methylene blue (MB) by the hydrochars depended drastically on the oxygen/carbon ratio. As such, the maximum adsorption capacity value of 145 mg g−1 was attained at the initial MB concentration of ~3000 μM (optimal oxygen/carbon value of 0.43). On the other hand, the maximum partition coefficient (KD) was estimated as 2.96 μM−1 mg g−1 with the initial/equilibrium concentrations of 20.5/6.93 μM. The performance evaluation between different studies, when made in terms of KD, suggests that the tested hydrochar should be one of the best adsorbents to treat methylene blue, especially at near-real environmental conditions (e.g., below micromolar levels). © 2020 Elsevier Inc.

publication date

  • 2020-01-01