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

Misapplication of chemical water treatment inhibition technologies results in the formation of water-formed scale deposits (notably, CaCO 3 and BaSO 4 ) that interfere with proper system operation. These are removed by chemical additives through dissolution. Herein, we report the efficient dissolution of CaCO 3 at pH 4 by 2-phosphonobutane-1,2,4-tricarboxylic acid (H 5 PBTC). 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(H 3 PBTC)(H 2 O) 2 ·2H 2 O] n . It is the first metal−PBTC complex reported to date. In the structure of polymeric [Ca(H 3 PBTC)(H 2 O) 2 ·2H 2 O] n Ca 2+ is seven-coordinated, bound by two phosphonate oxygens, three carboxylate oxygens, and two water molecules. [Ca(H 3 PBTC)(H 2 O) 2 ·2H 2 O] n was also prepared by designed synthesis by reacting various Ca 2+ sources and H 5 PBTC. Studies of anticorrosion properties of Ca 2+ /H 3 PBTC 2- combinations are also reported.