Cr(VI) adsorption on binary and ternary composites of raw cocoa shell with magnetic nanoparticle and Prussian blue

Abstract

Binary and ternary composites of raw cocoa shell (CS) were investigated as novel adsorbents for chromate (Cr(VI)) ions adsorption. CS incorporated with magnetite nanoparticle (MNP) and MNP-Prussian blue (MNP-PB) composites of CS were fabricated for the first time in this study. The characterization of the adsorbents was performed by using Fourier-transform infrared (FTIR), BET/N2 surface area analysis, particle size and zeta potential measurements, X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) analysis. The measured zeta potential values are high enough to point out stable aqueous suspensions. The efficiency of Cr(VI) adsorption were examined by evaluating the effects of contact time and initial chromate concentration. The kinetic behaviors of all adsorbents fitted Pseudo Second Order Model. The adsorption capacities were calculated as 23.36, 10.73 and 11.76 mg CrO42?/g adsorbent on CS, MNP-CS and MNP-PB-CS, respectively. Additionally, the pH dependency of the adsorption was investigated by considering surface acidity properties of CS and species distribution of Cr(VI) ions at different pHs. As a result, it was observed that the HCrO4? species was responsible for adsorption at pHs between 2 and 8. © 2021