Competitive adsorption of Cr(III) and Cr(VI) by sugarcane bagasse magnetic nanocomposite in water matrix

Biosorption is an eco-friendly process with low cost, high speed, and efficiency in removing contaminants, among which chromium stands out due to its various industrial applications. Due to its adverse effects and the large number of industrial effluents containing chromium, new techniques have been proposed to decontaminate aquatic environments. The present work proposes to use sugarcane bagasse as a biosorbent, a residue from the sugar and alcohol industry, in natura (SB) and nanomodified (SB-NP), in order to evaluate the chromium removal capacity, in their most abundant forms, Cr(III) and Cr(VI), in aqueous matrices. The potential of these materials in water decontamination is evaluated in a batch process to investigate the effect of pH individual or competitive sorption of Cr(III) and Cr(VI) ions. Chromium was determined by Flame Atomic Absorption Spectroscopy (FAAS) or Ultraviolet-Visible Molecular Absorption Spectrophotometry (UV/VIS). In the individual sorption of these metal ions, the best Cr(VI) result for SB and SB-NP occurred at pH 1, with the removal of 85 and 84% of this contaminant, respectively. For Cr(III) sorption, the best sorption pH value was 6, reaching up to 60% and 40% removal for SB and SB-NP, respectively. In simultaneous studies, the highest removal efficiency was obtained at pH 4, with the removal of 27% and 52% for SB and SB-NP, respectively. Depending on the pH, Cr(III) and Cr(VI) may change their oxidation state, and hexavalent chromium can be reduced to Cr(III) due to the oxidation of organic matter on the surface of the biosorbent.