Phosphonopolycarboxylates as Chemical Additives for Calcite Scale Dissolution and Metallic Corrosion Inhibition Based on a Calcium-Phosphonotricarboxylate Organic−Inorganic Hybrid

Abstract

Misapplication of chemical water treatment inhibition technologies results in the formation of water-formed scale deposits (notably, CaCO3 and BaSO4) that interfere with proper system operation. These are removed by chemical additives through dissolution. Herein, we report the efficient dissolution of CaCO3 at pH 4 by 2-phosphonobutane-1,2,4-tricarboxylic acid (H5PBTC). We also report the identity of the Ca-containing dissolution product, characterized by single-crystal X-ray crystallography and a variety of spectroscopic techniques, as [Ca(H3PBTC)(H2O)2·2H2O]n. It is the first metal−PBTC complex reported to date. In the structure of polymeric [Ca(H3PBTC)(H2O)2·2H2O]n Ca2+ is seven-coordinated, bound by two phosphonate oxygens, three carboxylate oxygens, and two water molecules. [Ca(H3PBTC)(H2O)2·2H2O]n was also prepared by designed synthesis by reacting various Ca2+ sources and H5PBTC. Studies of anticorrosion properties of Ca2+/H3PBTC2- combinations are also reported.