Lignosulfonate/N-butylaniline hollow microspheres for the removal of Cr(VI): Fabrication, adsorption isotherm and kinetics

Lignosulfonate, a byproduct from biomass pretreatment spent liquor, was used to fabricate lignosulfonate/N-butylaniline (LS-NBA) hollow microspheres at room temperature. The fabricated LS-NBA was used as biosorbent for remediation of hazardous Cr(VI). When the mass fraction of LS was 10%, LS-NBA-10 with N content of 7.73% showed the maximum adsorption capacity (840.42 mg g−1) of Cr(VI). The adsorption process of Cr(VI) by LS-NBA-10 was in line with the Langmuir isotherm model and pseudo-second-order kinetic model. The calculated thermodynamic parameters showed that the adsorption of Cr(VI) on LS-NBA-10 was a spontaneously endothermic process. In addition, LS-NBA-10 exhibited splendid removal ability of Cr(VI) in real industrial wastewater, of which the residual concentration was decreased from 255 mg L−1 to 0.005 mg L−1 that is below the permission value of drinking water recommended by the Environmental Protection Agency (EPA). The mechanism of Cr(VI) remediation was also discussed. The results are conducive to the application of lignin-based biosorbents in the treatment of Cr(VI)-containing wastewater.