SELECTIVE CATION REMOVAL VIA GEL POLYMERIZATION IN MARCELLUS FLOWBACK WATER

Alginic acid is a linear copolymer consisting of D-mannuronic and L-guluronic acids that forms hydrogels with many divalent cations, including Ca(II), Ba(II), Sr(II), Cu(II), Pb(II) and others. Calcium is primarily used in the formation of gels for biomass immobilization due to its lack of toxicity, but these cations are known to show differing affinities for alginate. Marcellus flowback water from southwestern PA is of high salinity (37 g/L Na) and contains high concentrations of divalent ions Ca>Ba>Sr>Fe>Mn in the ratio of 1843:479:389:20:1. In this study, we examined the selectivity for sequestration of these ions within alginate gel by polymerization and further diffusion and potential displacement reactions. The gel beads were formed by dropping two percent aqueous sodium alginate directly into Marcellus flowback water. The major divalent ions were concentrated Ba>Sr>Ca in alginate gel relative to in situ values. Applications of this technique for water treatment purposes and improving the accuracy of ICP-MS analysis of rare earth and other elements are presented.