Novel magnetic lignin composite sorbent for chromium(VI) adsorption

A novel magnetic lignin composite was prepared and modified with diethylenetriamine. The properties of the composite were characterized by SEM, FTIR, XRD, TGA and VSM. Then, the adsorption of chromium(VI) from aqueous solutions using this magnetic lignin composite was investigated. Chromium(VI) removal is pH dependent and the optimum adsorption was observed at pH 2.0. The pseudo-second-order model and the Langmuir adsorption isotherm model were applied to describe the adsorption kinetics and adsorption isotherm, respectively, for the chromium(VI) adsorption. Thermodynamic parameters were calculated, which revealed the adsorption process to be spontaneous and exothermic. Regeneration of the magnetic lignin composite was achieved by using 0.4 M NaCl and 0.2 M NaOH, more than 87% efficiency retention was obtained after 5 cycles.