Synthesis of Thiourea-Graft-Polyethyleneimine and Its Performance in Flocculation of Some Inorganic Particles

In the present study, the synthesis of a new thiourea (TU) derivative of branched polyethyleneimine (PEI) by an aqueous one-pot strategy involving formaldehyde mediated coupling of PEI and TU is reported. The structure of the new polymer, thiourea-g-polyethyleneimine, was confirmed by Fourier transformed infrared spectroscopy, proton nuclear magnetic resonance (NMR), and carbon-13 NMR spectroscopy, as well as by 2D NMR homo- and heteronuclear correlations. The flocculation efficiency of the new polyelectrolyte in kaolin and zirconium silicate (kreutzonit) suspensions, as well as their mixture, was tested in dependence on the polymer dose and suspension pH. A high removal efficiency has been recorded for all of the systems investigated irrespective of the medium pH, namely, more than 97% for kaolin particles and around 95% for the kreutzonit ones. According to the zeta potential values noticed in the optimum dose interval (negative values), the flocculation of inorganic particles has been achieved by the synergistic effect of the electrostatic attraction forces and hydrogen bonding.