title: Formation of chukanovite in simulated groundwater containing [Formula: see text].
abstract: Chukanovite (Fe2(OH)2CO3) is one of the secondary mineral precipitates on the surfaces of zero-valent iron (ZVI) barriers in groundwater containing carbonates. Synthesizing experiments were conducted in FeCl2, NaOH, and Na2CO3solutions to investigate the effect of carbonate concentration on the formation of Fe2(OH)2CO3and estimate the stability field of Fe2(OH)2CO3on the potential-pH diagram. Results revealed that Fe2(OH)2CO3is a unique product based on X-ray diffraction. The [Formula: see text], OH-, and Fe2+concentrations and the ratios (R = [Fe2+]/[OH-] and R' = [[Formula: see text]]/[OH-]) are important parameters in the formation of the Fe2(OH)2CO3. Fe2(OH)2CO3was better formed in the R = 1.1, R' = 0.9 system than in the R = 1.1, R' = 0.7 system. The crystallization of Fe2(OH)2CO3was increased with the concentration of [Formula: see text] increased from 0.018 to 0.18 mol/L. The standard Gibbs free energy of the formation of Fe2(OH)2CO3was -1151.1 ± 5.3 kJ/mol from the equilibrium conditions between Fe2(OH)2CO3and Fe2+, [Formula: see text]. Potential-pH diagram of iron, including Fe2(OH)2CO3, was drawn in the Fe-C-H2O system. In this diagram, the stable domain of Fe2(OH)2CO3was 7.87 < pH < 10.34, -740 mV < Eh < -400 mV, which can be converted into FeCO3in low pH value in the 0.18mol/L carbonate solution. This work will aid in predicting the potential for mineral precipitation, as well as estimating the reactivity, porosity, and hydraulic performance of ZVI permeable reactive barriers.
authors.affiliation: a Key Laboratory of Groundwater Resources and Environment, Ministry of Education , Jilin University , Changchun , People's Republic of China.
authors.forename: Ri
authors.initials: R
authors.lastname: Chen
authors.affiliation: a Key Laboratory of Groundwater Resources and Environment, Ministry of Education , Jilin University , Changchun , People's Republic of China.
authors.forename: Juan
authors.initials: J
authors.lastname: Chen
authors.affiliation: a Key Laboratory of Groundwater Resources and Environment, Ministry of Education , Jilin University , Changchun , People's Republic of China.
authors.forename: Mei
authors.initials: M
authors.lastname: Hong
authors.affiliation: b Chinese Academy for Environmental Planning (CAEP) , Beijing , People's Republic of China.
authors.forename: Wenjing
authors.initials: W
authors.lastname: Zhang
keywords: Chukanovite; carbonate; potential–pH diagram; stable domain; standard Gibbs free energy