Chromium Removal Using Soil Loaded with Green Iron Nanoparticles

Chromate is considered as a serious environmental problem due its toxicity. Iron nanoparticles produced by green tea polyphenols (GT-nZVI) is a powerful reductant, which can effectively reduce Cr(VI) to Cr(III). Nano ZVI suspension was initially conceived ideal for direct injection in the contaminated aquifers. However GT-nZVI presents limited mobility in calcareous aquifers. For this reason the incorporation of nanoiron in a permeable reactive barrier was investigated as an alternative mode of GT-nZVI application. Namely an amount of soil was loaded with nZVI (0.40 mmol/g of soil) and was evaluated for Cr(VI) removal by conducting batch and column tests. Batch tests were carried out by mixing soil samples, loaded with different levels of nZVI from 0.04 to 0.40 mmol per gram, with contaminated groundwater (GW) containing 1300 ppb Cr(VI). Cr(VI) concentration dropped below detection limit within 1 day using the highest nZVI dose. Soil pre-loaded with nZVI (S-nZVI) presented also high efficiency for chromates remediation, when tested under flow conditions by conducting column tests.