Feasibility of using ammonium iron (II) sulphate to passivate hexavalent chromium in polluted soil

ABSTRACTThe use of ammonium iron (II) sulphate ((NH4)2Fe(SO4)2) to remediate soil contaminated with Cr (VI) was assessed. (NH4)2Fe(SO4)2 effectively remediated soil contaminated with Cr (VI) and, acted as a fertilizer by supplying nitrogen because it contains ammonium. The effects of the (NH4)2Fe(SO4)2 dose, water content, pH of the soil and the contact time were investigated. The amount of Cr (VI) leached from the most-polluted soil, determined using a leaching toxicity procedure using optimized conditions, was 347.64 mg kg-1 when the soil was untreated and 6.74 mg kg-1 when the soil was treated with (NH4)2Fe(SO4)2. Bio-utilizable Cr contributed 59.44% and 0.16% of the total Cr contents of the untreated and treated soil, respectively. The relatively stable Cr species contributed 24.92% and 98.38% of the total Cr contents of the untreated and treated soil, respectively. The results indicated that adding (NH4)2Fe(SO4)2 markedly decreased the risk of Cr being released from heavily contaminated soil by decreasing the availability of Cr in the soil. Overall, the results indicated that adding (NH4)2Fe(SO4)2 causes some Cr (VI) in contaminated soil to be reduced to Cr (III), and to form a precipitate, which decreases the risk of Cr being released. (NH4)2Fe(SO4)2 can be applied to soil contaminated with Cr (VI) on a large scale because it is cheap and simple to achieve.