Specific investigation for adsorption nature of iodine, reactive dye or wastewater model over low-priced bio-char derived from biomass waste

In this research, low-priced bio-chars produced from biomass waste (fiddle-leaf fig seed) via physical and chemical activation processes were applied for selective removals of iodine and reactive dyes. The adsorption natures and capabilities were systematically considered from isotherms, kinetic and thermodynamic parameters. As achieved results, activated bio-char (ABC) prepared via phosphoric activation and carbonization at 400 °C for 2 h presented good capabilities for adsorptions of iodine (q_max = 420.47 mg/g) and reactive red 22 (RR22, q_max = 15.17 mg/g). The fast adsorption natures of iodine and RR22 using each adsorbent exhibited monolayer physisorption, which were identified by Langmuir, Dubinin–Radushkevich, Redlich–Peterson, Toth and pseudo-second order, while intra-particle diffusion with 2 steps could be obtained from Weber–Morris model. Thermodynamic nature also displayed that iodine and reactive dye adsorption procedures were endothermic and spontaneous styles, supporting by standard enthalpy/entropy/Gibbs free energy at temperature range about 303–328 K. Moreover, the capability for selective removal of wastewater models (mixed dyes) over all adsorbents was in order of reactive blue 19 (RB19) > RR22 > reactive yellow 3 (RY3). This work methodically focused on adsorption manners of dye molecules using low-priced bio-char and gave possible/green way for wastewater treatment under practical process.