Removal of hexavalent chromium by bentonite supported organosolv lignin-stabilized zero-valent iron nanoparticles from wastewater

Abstract

Bentonite supported organosolv lignin-stabilized nanoscale zero valent iron (nominated as BL-nZVI) nanoparticles were fabricated by using organosolv lignin as stabilizer and bentonite as supporter. Results of XRD spectra showed nZVI particles had loaded onto bentonite successfully. Furthermore, addition of organosolv lignin could improve the loaded quantity and dispersity of the nZVI particles effectively. Meanwhile, SEM and TEM images exhibited the stabilizer could decrease the mean size of the product effectively, the mean particle sizes of bare nZVI, B-nZVI and BL-nZVI were 61.3 nm, 53.2 nm and 20.1 nm, respectively. Comparative experiments were carried out to demonstrate the difference of Cr(VI) removal efficiency between the materials. BL-nZVI showed broader suitable pH scope, higher removal efficiency and higher reaction kinetic rate compared with the other two materials, the reaction kinetic rate of Cr(VI) by BL-nZVI was 0.225 min−1 under pH 3.0, which was 2–4 folds higher than that of bare nZVI and B-nZVI. The evolution of iron concentration, pH and DO in the aqueous solution with the increase of reaction time were explored, BL-nZVI reaction system possessed higher iron concentration and equilibrium pH, but lower DO concentration compared with bare nZVI and B-nZVI reaction system under the same initial conditions. Reusability and mechanism analysis were also explored. As an environmental friendly material, BL-nZVI possesses great potential in the treatment of Cr(VI) polluted wastewater.