Abstract
Chromium is an extremely toxic metal in the form of Cr(VI) that causes severe environmental and health problems. Therefore, the aim of this study was to remove chromium ions from wastewater by using cost effective and environmentally friendly bio-sorbents; Moringa stenopetala seed powder (MSSP), and banana peel powder (BPP) and to evaluate its adsorption capacities as bio-sorbents. FT-IR characterization of the adsorbents showed that there was a change in the functional groups of the structure of both adsorbents before and after the adsorption that might be due to the adsorption processes taken place on the surface of adsorbent. Adsorption experiments were carried out as batch studies with different contact times, pH, adsorbent dose, initial metal ion concentration, and temperature. Results showed maximum removal efficiency for Cr(VI) at 120 min contact time, adsorbent dose of 20 g/L and pH 2 by MSSP and pH 4 by BPP. The percentage removal of Cr(VI) increased with increasing adsorbent dose (from 5 to 20 g/L) and contact time (from 60 to 120 min). Freundlich isotherm model showed a better fit to the equilibrium data than the Langmuir model. The kinetics of adsorption for chromium was well represented by pseudo-second order kinetic model and the calculated equilibrium sorption capacity of the model showed good agreement with the sorption capacity obtained from experimental results.
Highlights
Chromium is a naturally occurring metal found in the environment commonly in trivalent, Cr(III), and hexavalent, Cr(VI) forms [1, 2]
FT‐IR result for banana peel powder (BPP) and Moringa stenopetala seed powder (MSSP) The Fourier transformer infrared (FT-IR) spectra before and after adsorption of chromium were given for both BPP and MSSP in which the absorption peaks appeared in the wavenumber range of 3500 cm−1to 625 cm−1
The negative values of ΔH° in this study indicates adsorption of Cr(VI) ion onto MSSP and BPP is exothermic in nature
Summary
Chromium is a naturally occurring metal found in the environment commonly in trivalent, Cr(III), and hexavalent, Cr(VI) forms [1, 2]. Badessa et al BMC Chemistry (2020) 14:71 filtration, electrodialysis, polymeric nano particles and activated carbon adsorptions [8,9,10,11,12,13] These conventional and advanced technologies are expensive and non-regenerable materials used, generation of toxic sludge is often ineffective, for the removal of Cr ions at low concentrations and difficult to apply them in developing countries like Ethiopia [14,15,16]. Moringa seeds contain cationic polypeptides with various functional groups, low molecular weight amino acids These amino acids are de-protonated to carboxylate ligands at pH range of 4 to 8 simultaneously protonating the amino group which facilitates the binding of positively charged ions with the carboxylic group [21, 22]. The use of bio-adsorbents like Moringa stenopetala seed powder that are available and effective for removal of metals could be an innovative and economical approach for treatment of industrial wastewater
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