Metal composition in the biomass influences the surface properties of activated carbons in the adsorption of different dyes

ABSTRACT Agricultural waste in the form of corn cob (CC), palm kernel (PK) shell, and coconut husk (CH) is a beneficial precursor material in the production of activated carbon, by steam activation, for organic pollutant removal of an aqueous medium. The activated carbons (ACs) were studied using spectroscopic (X-ray fluorescence and diffraction, Fourier transform infrared), and scanning electron microscopy characterization techniques. The surface area of the ACs was determined using the acetic acid adsorption technique to be 577.52, 333.75,, and 246.32 m2/g for PK shell, CC, and CH, respectively. The adsorption equilibrium of each AC was studied with methylene blue (MB) and 8-hydroxyquinoline (8-HQ). The adsorption isotherms best fitted a Freundlich isotherm model using both linearized and non-linearized regressions. Adsorption capacities of as-produced ACs for MB (72–85 mg/g) were higher than those of 8-HQ (33–36 mg/g). The adsorption process suggested that the initial adsorption on the surface of the carbon was driven by electronic tuning through back-donation d-orbital electrons of heavy metals like Fe present in the form of minerals in the biomass, which makes the surface carbon nucleophilic.