Remediation Of Mercury-contaminated Soil With Sodium Thiosulfate System

As one of the most important but also most predisposed resources,soil contamination in particular mercury pollution is a significant problem found at many mining and industrial sites.Mercury in soil can go through an extensive array of biological and chemical conversion.As more and more concerns have been focused on the mercury contamination to the eco-system,international regulations on mercury emission,supply and demand are being tightened.In order to detoxify and purify the mercury-contaminated soil,the sodium thiosulfate syetem was used in the experimentals.The simple sodium thiosulfate system was used to remove Hg from solid phase to liquid phase,and the single factor experiment method was chosen to optimize the leaching conditions at room temperature.The optimum conditions of leaching are:the initial pH 1.30,the sodium thiosulfate concentration 0.02mol/L,the ratio of soil to thiosulfate 1g:200mL,leaching time 120min.Under this condition,the total removal of Hg is 47.1%when the Hg content is about 1100mg/kg.Hydrogen peroxide and sodium persulfate acted as oxidants pertreatmenting soil samples are not efficient when selecting the proper oxidizers at room temperature.The total removal of Hg is about 50%after employing sodium thiosulfate to leach the residual samples.Comparised with the simple sodium thiosulfate system,the initial objective is not achieved.Potassium permanganate acted as oxidant pertreatmenting soil samples can significantly enhance the Hg removal process.Thorough a series of the single factor experiments at room temperature,the optimum conditions of leaching are:the mass fraction of acidic potassium permanganate 2.5%,the ratio of soil to liquid 2g:2mL,leaching time 60min,and the removal of the oxidizing step can reach up to 63.0%,and the removal of leching with sodium thiosulfate can obtain 79.0%.Sodium hypochlorite acted as oxidant pertreatmenting soil samples works pretty well.Thorough a series of the single factor experiments at room temperature,the optimum conditions of leaching are:the available chlorite 10%,the ratio of soil to liquid 2g:20mL,leaching time 60min,and the removal of the oxidizing step can reach up to 75.1%,and the removal of leching with sodium thiosulfate can obtain 83.0%.