Modeling of phosphate speciation on goethite surface: Effects of humic acid

Yu Liang; Jiezi Jin; Hongfeng Chen; Jinling Xu; Mingxia Wang; Wenfeng Tan

doi:10.1016/j.chemosphere.2024.142351

Modeling of phosphate speciation on goethite surface: Effects of humic acid

Chemosphere. 2024 May 16:359:142351. doi: 10.1016/j.chemosphere.2024.142351. Online ahead of print.

Authors

Yu Liang¹, Jiezi Jin², Hongfeng Chen³, Jinling Xu⁴, Mingxia Wang², Wenfeng Tan²

Affiliations

¹ Tropical Crops Genetic Resources Institute, Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101, PR China.
² State Environmental Protection Key Laboratory of Soil Health and Green Remediation, College of Resources and Environment, Huazhong Agricultural University, Wuhan, 430070, PR China.
³ College of Hydraulic & Environmental Engineering, China Three Gorges University, Yichang, 443002, PR China. Electronic address: chenhongfeng@ctgu.edu.cn.
⁴ College of Geography and Environment, Shandong Normal University, Jinan, 250358, PR China.

PMID: 38761821
DOI: 10.1016/j.chemosphere.2024.142351

Abstract

Iron (hydr)oxides and humic acid (HA) are important active components in soils and usually coexist in the environment. The effects of HA on the adsorption and subsequent immobilization of phosphate on iron (hydr)oxide surface are of great importance in studies of soil fertility and eutrophication. In this study, two types of goethite with different particle sizes were prepared to investigate the phosphate adsorption behaviors and complexation mechanisms in the absence or presence of HA by combining multiple characterization and modeling studies. The adsorption capacity of micro- (M-Goe) and nano-sized goethite (N-Goe) for phosphate was 2.02 and 2.04 μmol/m², which decreased by ∼25% and ∼45% in the presence of 100 and 200 mg/L HA, respectively. Moreover, an increase in equilibrium phosphate concentration significantly decreased the adsorption amount of goethite for HA. Charge distribution-multisite surface complexation (CD-MUSIC) and natural organic matter-charge distribution (NOM-CD) modeling identified five phosphate complexes and their corresponding affinity constants (logK_P). Among these phosphate complexes, FeOPO₂OH, (FeO)₂PO₂, and (FeO)₂POOH species were predominant complexes on the surface of both M-Goe and N-Goe across a wide range of pH and initial phosphate concentrations. The presence of HA had little effect on the coordination mode and logK_P of phosphate on goethite surface. These results and the obtained model parameters shed new lights on the interfacial reactivity of phosphate at the goethite-water interface in the presence of HA, and may facilitate further prediction of the environmental fate of phosphate in soils and sediments.

Keywords: ATR-FTIR; CD-MUSIC; Humic acid (HA); Iron (hydr)oxides; NOM-CD model; Phosphate adsorption.