LAUSR

Abstract Stabilization technique is regarded effective to control heavy metal pollution in soil. Traditional stabilizers have raised concerns about soil acidification/alkalization, or the stable effectiveness in a long-term. To stabilize vanadium (V) in calcareous purple soil in an environmentally friendly way, Na-bentonite (Na–B) modified by tea polyphenol (TP-B), by FeSO4 (Fe–B), and by TP and FeSO4 (TP-Fe-B) were prepared, characterized and assayed. The tea polyphenol modification loaded –CH2 on TP-B and TP-Fe-B, and ferrous modification introduced rozenite to Fe–B and TP-Fe-B, which supplied reaction sites to V. The effects of stabilizer dosage, soil moisture, and initial V concentration in soil were considered to ascertain the optimum stabilization conditions. Applying 5 wt% Fe–B into the 696.63 mg V/kg soil at 60% field water capacity soil yielded stabilization rates of 19.1%, 37.7% and 20.5% for water-extractable V, bioavailable V, and pentavalent V, respectively. Further study was conducted to assess the stable period of the passivation effect and the stability of the passivation effect under acid rain. The stabilization effect remained functional for at least 4 weeks after TP-B, Fe–B, and TP-Fe-B application. Notably, adding Fe–B could reduce the risk of V transfer from soil into the aquatic environment under acid rain. However, Fe–B resulted in a decrease in soil organic matter and alkali-hydrolyzed nitrogen, thus fertilization should be considered. These results proved that Fe–B was a potential stabilizer for V contaminated soil even under acid rainfall.