Effect of coexisting ions on Cr(VI) adsorption onto surfactant modified Auricularia auricula spent substrate in aqueous solution

Abstract

In this paper, the effect of coexisting cations and anions on Cr(VI)(in the form of Cr2O72-) adsorption onto Auricularia auricula spent substrate (AASS) modified by cetyl trimethyl ammonium bromide (CTAB) was investigated in batch adsorption experiment. The Cr(VI) adsorption capacity of 9.327 mg/g, obtained at pH 3.0, 303 K, adsorbent dosage of 2 g/L, initial Cr(VI) concentration of 20 mg/L, rotational speed of 150 r/min for 120 min, was decreased in the presence of coexisting cations and anions, among which Pb2+ and PO43- affected most by 21.79% and 12.43%, respectively. XRD, XPS and FTIR detection found that coexisting Pb2+ and PO43- would not only interfere Cr(VI) to form crystals and reduce to Cr(III), but also compete with Cr(VI) for oxygen-containing and amino groups to form Pb-O and P-NH2, respectively. In addition, the single Cr(VI) adsorption fitted with Langmuir isotherm model, while the competitive adsorption was well described by Freundlich isotherm model. Both single adsorption and competitive adsorption were in line with the pseudo-second-order kinetic model.