Ferrous Carbonate Nucleation and Inhibition

Abstract In this research, the nucleation kinetics and inhibition of ferrous carbonate (siderite) were investigated in a batch reactor under rigorously anoxic conditions in the absence of reducing agents. The nucleation kinetics of ferrous carbonate in 0.01 m NaCl solutions was measured from 25°C to 65°C at constant supersaturation. A decrease in temperature slows down ferrous carbonate nucleation rate. Similarly an increased ionic strength and a decreased saturation index result in a slower ferrous carbonate nucleation. Then, citrate and two common calcite (CaCO3) scale inhibitors such as phosphinopolycarboxylic acid (PPCA) and bis-hexamethylene triamine-penta(methylene phosphonic) acid (BHPMP) were examined in inhibition experiments. Our results reveal that common calcite scale inhibitors are not effective at preventing ferrous carbonate precipitation, whereas citrate is. The effectiveness of citrate as a ferrous carbonate nucleation inhibitor depends strongly temperature. This work suggests that citrate may have important implications in municipal, industrial, and natural waters in controlling ferrous concentrations.