Use of Organic Waste from Coffee Capsules in the Adsorption of Cu(II), Co(II), Ni(II) and Cd(II) Ions in Aqueous Systems

Abstract

The present work aims to use organic residues of coffee capsules as adsorbent material for adsorption of Cu(ІІ), Co(ІІ), Ni(ІІ) and Cd(ІІ) ions in aqueous systems. In order to know the properties of the adsorbent, it was subjected to characterization by dispersive energy X-ray fluorescence (EDXRF), Absorption Spectroscopy in the Infrared Region (IR) and determination of pH at the Zero Charge Point (pHPCZ). The analysis by EDXRF after the adsorption procedure revealed an increase in the intensity of the peaks related to the cooper and the appearance of peaks related to the cobalt and nickel. The IR spectra showed bands referring to the main functional groups present in the organic residue of coffee capsules. pHPCZ revealed a neutral surface in a range of 6 to 8. The factors that influence the adsorption process, such as pH, adsorbent mass and adsorption time, were evaluated in a univariate manner, with the optimal values of 9, 80 mg and 60 minutes being obtained, respectively. The kinetic evaluation of the adsorption process was performed, indicating that the Ni(II) and Co(II) ions were better adjusted to the Avrami model, the Cd(II) ion to the pseudo-second order model and the Cu(II) ion fit the Avrami and pseudo-second order models, which can be explained by both.