Remediation of vanadium-contaminated soils by the combination of natural clay mineral and humic acid

Abstract

Due to the increasingly frequent activities of vanadium mining, soil pollution around the mining area is serious. Remediation of heavy metal contaminated soils using clay minerals is an effectively in-situ remediation technology. In the present study, a novel remediation method by the combination of clay minerals and humic acid to repair vanadium contaminated soils was explored. Results demonstrated that the tourmaline was selected as an effective clay mineral to remediate contaminated soils by comparing the ability of soil pH adjustment, available nutrients retention, and vanadium stabilization. Moreover, the combination of humic acid and tourmaline can further promote the remediation effect. At the dosage of humic acid and tourmaline of 1% and 5%, the soil pH increased slightly by 0.62 units compared with the control, and the retention of the available nutrients in the soil was improved. So the ryegrass germination rate and plant height reached to 95% and 12 cm respectively after two weeks. The analysis of the uniformity and richness of species in the soil repaired by the combination revealed that the Shannon index and McIntosh index increased to 2.023 and 0.968, respectively. Besides, the residual vanadium in the soils increased by 30% compared with the control after 60 days. Furthermore, the Scanning Electron Microscopy-Energy Dispersive Spectroscopy, Fourier Transform Infrared Spectroscopy and X-ray photoelectron spectrometer analysis illustrated the interaction between the combination passivator and vanadium mainly involved complexation, ion-exchange and adsorption. The results of this study can provide a green and effective method for remediation of vanadium contaminated soil.