Induced crystallization for the simultaneous removal of hardness-iron-manganese in groundwater: An experimental study

Kaihong Li; Ruizhu Hu; Shichang Li; Tinglin Huang; Gang Wen

doi:10.1016/j.envres.2023.117988

Induced crystallization for the simultaneous removal of hardness-iron-manganese in groundwater: An experimental study

Environ Res. 2024 Mar 15:245:117988. doi: 10.1016/j.envres.2023.117988. Epub 2023 Dec 23.

Authors

Kaihong Li¹, Ruizhu Hu², Shichang Li¹, Tinglin Huang¹, Gang Wen¹

Affiliations

¹ School of Environment and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, PR China; Shaanxi Key Laboratory of Environmental Engineering, Key Laboratory of Northwest Water Resource, Environment and Ecology, MOE, Xi'an, 710055, PR China; Collaborative Innovation Center of Water Pollution Control and Water Quality Security Assurance of Shaanxi Province, Xi'an University of Architecture and Technology, Xi'an, 710055, PR China.
² School of Environment and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, PR China; Shaanxi Key Laboratory of Environmental Engineering, Key Laboratory of Northwest Water Resource, Environment and Ecology, MOE, Xi'an, 710055, PR China; Collaborative Innovation Center of Water Pollution Control and Water Quality Security Assurance of Shaanxi Province, Xi'an University of Architecture and Technology, Xi'an, 710055, PR China. Electronic address: huruizhu@xauat.edu.cn.

PMID: 38145734
DOI: 10.1016/j.envres.2023.117988

Abstract

Hardness, iron, and manganese are common groundwater pollutants, that frequently surpass the established discharge standard concentrations. They can be effectively removed, however, through induced crystallization. This study has investigated the effectiveness of the simultaneous removal of hardness-iron-manganese and the crystallization kinetics of calcium carbonate during co-crystallization using an automatic potentiometric titrator. The impacts pH, dissolved oxygen (DO), and ion concentration on the removal efficiency of iron and manganese and their influence on calcium carbonate induced crystallization were assessed. The results suggest that pH exerts the most significant influence during the removal of hardness, iron, and manganese, followed by DO, and then the concentration of iron and manganese ions. The rate of calcium carbonate crystallization increased with pH, stabilizing at a maximum of 10^-10 m/s. Iron and manganese can be reduced from an initial level of 4 mg/L to <0.3 mg/L and 0.1 mg/L, respectively. The removal rate of iron, however, was notably higher than that of manganese. The DO concentration correlates positively with the removal of iron and manganese but has minimal impact on the calcium carbonate crystallization process. During the removal of iron and manganese, competitive interactions occur with the substrate, as increases in the concentration of one ion will inhibit the removal rate of the other. Characterization of post-reaction particles and mechanistic analysis reveals that calcium is removed through the crystallization of CaCO₃, while most iron is removed through precipitation as Fe₂O₃ and FeOOH. Manganese is removed via two mechanisms, crystallization of manganese oxide (MnO₂/Mn₂O₃) and precipitation. Overall, this research studies the removal efficiency of coexisting ions, the crystallization rate of calcium carbonate, and the mechanism of simultaneous removal, and provides valuable data to aid in the development of new removal techniques for coexisting ions.

Keywords: Co-crystallization; Coexisting ions; Hardness-iron-manganese; Induced crystallization; Simultaneous removal.

MeSH terms

Calcium Carbonate / chemistry
Crystallization
Groundwater* / chemistry
Hardness
Iron / chemistry
Manganese / chemistry
Manganese Compounds / chemistry
Oxides / chemistry
Water Pollutants, Chemical*
Water Purification* / methods

Substances

Manganese
Manganese Compounds
Iron
Oxides
Calcium Carbonate
Water Pollutants, Chemical