Study of simultaneous adsorption efficiency of metals using modified organic and synthetic adsorbents

ABSTRACT

Water contamination by heavy metals represents a high risk of environmental pollution and a precursor of several human diseases. The presence of these metals at high levels in wastewater treatment plants and industrial effluents motivated the search for remediating these pollutants. Among remediation methods, adsorption is extensively used to decontaminate waters containing these metals. Thus, this study prepared, characterized, optimized, and applied two types of adsorbents to a prepared metal ion solution (PMS): a bioadsorbent based on banana peel flour (BPF) and a synthetic adsorbent based on magnetite encapsulated by chitosan (MEC). A systematic study was performed with PMS containing Al (III), Ba (II), Pb (II), Cu (II), Cr (III), Fe (II), Mn (II), and Zn (II) to determine the best conditions for simultaneous metal ion adsorption Adsorption studies evaluated the experimental adsorption isotherms according to the variation in pH values, the mass of adsorbents, and contact time, and the kinetic study applied pseudo-first- and pseudo-second-order models. The best parameters were the pH of 6, a mass of adsorbents of 25 mg, and fast saturation time of around 10 minutes. The kinetic model that best fitted the process was the pseudo-second-order for all metals in both adsorbents. The PMS adsorption capacity achieved by MEC was higher than BPF. The removal by MEC was Al=Fe=Pb=Cu=Cr> Zn>Mn>Ba, in the percentages of 100, 100, 100, 100, 100, 98, 88, and 76%, respectively. The BPF showed Pb>Fe>Cr>Cu>Al>Zn>Ba>Mn, in the percentages of 97, 67, 63, 50, 46, 45, 44, and 5%, respectively. The results suggest that the affinity between adsorbents with certain metal ions is due to the characteristics of the adsorbent surface and the number of chemical species available in the solution, which may interfere with the adsorptive process. Above all, the percentage of simultaneous removal of metal ions by both adsorbents was relevant, making them promising for remediating heavy metal ions in sanitary sewage after conventional treatment and industrial effluents containing mixed metal ions.

Keywords
Adsorption; Musa spp; Heavy Metal; Magnetite; Chitosan