Ultraviolet Radiation in the Remediation of Cr(VI)-Contaminated Soil by Corn Stover

Ultraviolet (UV) radiation was selected in this study to evaluate its assistant remediation effects on Cr-contaminated soil. Various remediation materials, including corn stover (CS), corn stover biochar (CSB), polypyrrole-modified 44 corn stover (PPy-CS), and polypyrrole-modified corn stover biochar (PPy-CSB), were employed to evaluate their synergistic effects with UV radiation. The results showed that UV radiation increased the toxicity characteristic leaching procedure (TCLP) Cr(VI) when no other remediation was added to the contaminated soil. However, when the remediation materials were added, with UV radiation, the contents of TCLP-Cr(VI) decreased, while the contents of Cr(III) increased, and the removal rates of TCLP-Cr(VI) in contaminated soil treated by CSB, PPy-CSB, CS, and PPy-CS were 18.7%, 7.6%, 11.0%, and 8.2% higher than those of the non-irradiated groups, respectively. Notably, the CS group demonstrated superior efficacy in Cr(VI) removal compared with CSB under UV irradiation. Meanwhile, characteristic analysis including electron paramagnetic resonance (EPR), Fourier-transform infrared spectroscopy(FTIR) and X-ray photoelectron spectroscopy(XPS) assisted us in finding reaction mechanisms, which implied that UV irradiation could enhance the content of oxygen free radicals on the material surface and effectively activate the reactions between Cr(VI) and remediation materials. This study verified that UV irradiation could also be a promising tool in the remediation of heavy-metal-contaminated soil.