Removal of Hg2+and CH3Hg+ by a polyphosphonate ligand from water

The potential of employing a polyphosphonate ligand, diethylenetriamine-N,N,N′,N″,N″-pentakis(methylenephosphonic) acid (DTPMP), in the removal from water of Hg2+ and (CH3)Hg+ was studied. Metal-ligand systems were investigated by potentiometry in aqueous solution at t = 25°C, 0.1 < I / mol L-1 < 1 for Hg2+, I = 0.1 mol L-1 for (CH3)Hg+. The formation of several complex species was evidenced. The analysis of the results showed that species stability of Hg2+ complex species was significantly higher than that of (CH3)Hg+. The sequestering capacity, determined under typical conditions of natural waters, showed highest potential towards Hg2+, also respect to those of other polyphosphonate ligand, such as etidronic acid ((1-Hydroxy-1,1-ethanediyl)bis(phosphonic) acid, HEDPA). This quantitative study is useful to evaluate the possible employment of this polyphosphonate in the decontamination of natural waters from toxic metals.