Remediation of a cyanide contamination using Intramine®
In soils contaminated with wastes from coal carbonization plants, or gasworks, cyanide is a highly toxic contaminant of great concern. It is mainly present in the form of the insoluble ferric ferrocyanide and to a lesser extent in the form of soluble ferrous ferricyanide. The dissolution of these complexes results in mobile iron-cyanide complexes, which are the dominant cyanide species in groundwater.
Iron-cyanide complexes are known to adsorb on iron oxides. For this reason, we developed the colloidal Intramine® iron oxide suspension for effective in situ cyanide adsorption applications. Due to its high surface capacity and high overall surface area, Intramine® is able to effectively immobilize significant amounts of toxic cyanide species in groundwater, with also a strong affinity to metals and metalloids.
The results of the pilot application within site groundwater show that already under pH groundwater conditions (pH = 7.3), a considerable fraction of total available cyanide was adsorbed, respectively between 61 and 87%. The adsorption of cyanides on iron oxides is highly dependent on pH. Lower pH favors the adsorption of CN-anions on positively charged sites at the iron oxide surface, which increase in number with decreasing pH. Indeed, when the pH of the groundwater was lowered from pH = 7.3 to either pH = 6.0, a complete removal of cyanide from groundwater was observed. Considering this exhaustive sorption of available cyanide, the nanogoethite was likely not even saturated with cyanide.
The adsorptive removal of cyanide via Intramine® at the site’s most contaminated area ranged from 61 to 87%.Additionally, the removal of cyanide with Intramine® could be significantly enhanced, until a complete cyanide removal (100%) was reached, by slightly adjusting the aquifer pH.
Thus, the in situ application of Intramine® led to a complete immobilization of CN and removal from downstream groundwater.
Due to its wide pH range of applicability, Intramine® is our new advanced solution especially designed for in situ immobilization of pollutants encountered at mining, coal, gasworks, and steel sites.
The removal mechanisms include adsorption, reduction or precipitation. Target pollutants are heavy metals, metalloids, and cyanides.