Kinetic and isotherm studies of empty fruit bunch biochar on Ammonium adsorption

Abstract

Empty fruit bunch (EFB) was utilized into biochar using pyrolysis method and being used as adsorbent for ammonium removal. Different temperatures were used to produce the EFB biochar at temperature 350°C, 450°C, 500°C and 550°C. The characteristics of the EFB biochar were studied by analyses on the moisture content, ash content, Fourier Transform Infrared (FTIR) Spectroscopy and pH zero charge of the produced EFB biochar. As the pyrolysis temperature increases, the moisture content of the EFB biochar decreases while the ash content increases. Several peaks or bands diminished from the FTIR spectra of EFB biochar as the temperature rises. The FTIR spectra of EFB biochar showed the presence of functional groups such as primary and secondary amines and amide, carbonyl compound, alkenes and aromatic groups for the ammonium adsorption. The pH zero charge of the EFB biochar was found at pH 7.0. The optimum dosage of the absorbent was 0.05 g and the adsorption process and reached equilibrium at minutes of 200 with initial adsorbate concentration of 2.5 ppm. For kinetic studies, pseudo-second-order model indicates better agreement with the experimental data so that it is more preferable for chemical adsorption which involved valence forces by sharing or exchange the electrons between the EFB biochar and ammonium ions. The applicability of adsorption isotherms reveals that Freundlich isotherm is more preferable as compared to Langmuir isotherm, indicate that it is a multi molecular layer of adsorption and the adsorption sites are heterogeneous on the EFB biochar.