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Comparative study of mercury(II) removal onto natural and iron-modified zeolite

The contamination of soil and water bodies with mercury from the anthropogenic sources such as mining and industry activities causes negative effect for living organisms due to the process of bioaccumulation and biomagnification through the food chain. Therefore, the need for remediation of contaminated areas is extremely necessary, especially if it is effective by using low-cost sorbents. This paper compares the sorption abilities of natural and iron-modified zeolite towards mercury(II) ions from aqueous solutions. The influence of pH, initial concentration, solid/liquid ratio and contact time on the sorption efficiency onto both sorbent materials was investigated. At the optimal pH=2, the maximum amount of sorbed mercury(II) is 0.28 mmol g -1 of natural zeolite and 0.54 mmol g -1 of iron-modified zeolite. It has been observed that a minimum contact time of 600 minutes is required to achieve the maximum sorption capacity for both sorbents. In addition, to achieve the same sorption efficiency, the twice solid/liquid ratio of natural zeolite than that of iron-modified zeolite is needed. The results showed that the iron- modified zeolite has a better sorption ability compared to the natural zeolite. For a possible application of sorbents for in situ remediation of soil or groundwater contaminated with mercury, the leaching of mercury from saturated sorbents was examined according to the standard leaching method DIN 38414. In a wide pH range, 4.01<pH<9.09, the leaching of mercury(II) was observed in the amount of only 0.28 % – 0.78 % from natural zeolite and 0.07 % – 0.51 % from iron-modified zeolite. At extreme pH conditions, pH<3 and pH>11, leaching of mercury(II) in an amount of 4–7 % occurs on both sorbents. In conclusion, both sorbent materials could be used in remediation purposes while the results suggest that modification significantly improves the sorption properties of zeolite.

natural zeolite ; iron-modified zeolite ; mercury(II) ; sorption ; leaching

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