Effects of zinc on the growth of Bulrush (Schoenoplectus californicus) and its distribution between different sediment fractions

Biosorption of Cr(III) and Pb(II) by Schoenoplectus californicus and Insights into the Binding Mechanism

Biosorption and desorption of chromium and lead on shoots biomass of Schoenoplectus californicus were investigated by performing batch sorption tests in different conditions of pH, biosorbent dose, and initial concentration in simple and binary solutions. Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models were employed to describe sorption equilibrium. Filters and biomass were characterized before and after treatments by environmental scanning electron microscopy and X-ray energy-dispersive spectrometry. The optimal conditions for biosorption were found to be pH 5 for both metals. The contact time to reach pseudoequilibrium changed as a function of pH and the metal studied. The highest optimisation of biosorbent dose was 5 g L−1 at pH 7 and 15 g L−1 at pH 5 for both metals. The most effective extracting agents for lead and chromium proved to be HNO3 and NaOH, respectively. The recovery of lead was greater than of chromium because the Cr(III) sorption mechanisms involve a stronger binding energy than the mechanisms for Pb(II), such as in intern sphere complexes. Both metals accounted for a high % removal (>90%) under the best sorption conditions. The use of Schoenoplectus californicus proved to be an efficient and economical alternative for the treatment of effluents contaminated with lead and chromium.