Adsorption and precipitation of myo‐inositol hexakisphosphate onto kaolinite. (12th July 2019)

• Record Type: Journal Article
• Authors: Hu, Zhen; Jaisi, Deb P.; Yan, Yupeng; Chen, Hongfeng; Wang, Xiaoming; Wan, Biao; Liu, Fan; Tan, Wenfeng; Huang, Qiaoyun; Feng, Xionghan
• Is Part Of: European journal of soil science. Volume 71:Number 2(2020)
• Page Start: 226
• Page End: 235
• Publication Date: 2019-07-12
• Subjects: 31P NMR -- clay minerals -- dissolved Al(III) -- inner‐sphere complexes -- interfacial reaction -- organic phosphorus -- Phytate (IHP); Soil science -- Periodicals; 631.4
• DOI: 10.1111/ejss.12849
• Languages: English
• ISSNs: 1351-0754

Abstract

Abstract: Sorption of myo ‐inositol hexakisphosphate (IHP), a common type of organic phosphorus in soils, largely controls its mobility and bioavailability. Research on the interaction between IHP and phyllosilicate minerals such as kaolinite, which is commonly present in highly weathered soils, has often been neglected, probably due to the common assumption that negatively charged phyllosilicate minerals have low sorption capacity and binding affinity to IHP and thus do not play any significant role in its fate. Here, the interaction between IHP and poorly crystallized kaolinite (KGa‐2) was investigated in batch experiments using Zeta ( ζ ) potential measurement and 31 P nuclear magnetic resonance (NMR) spectroscopy. The results showed that dissolved Al(III) concentration at the adsorption initiation stage increased with increasing IHP concentration at pH 4.0. From pH 2.5 to 9.0, IHP presented a maximum sorption capacity (50 μmol g −1 ) at pH 4.0 at 24 hr. With IHP sorption, the ζ potential of kaolinite first decreased sharply to a negative value, then gradually increased with resorption of Al(III) released from kaolinite dissolution at acidic pH, and finally approached the original value of the pure kaolinite. 31 P NMR spectroscopy and ζ potential analyses revealed that IHP formed inner‐sphere surface complexes and aluminium phytate precipitated on kaolinite at low pH (2.5 and 4.0), whereas the formation of inner‐sphere surface complexes was the dominant sorption mechanism at pH ≥ 5.5. This study implies that various mechanisms, depending on ambient pH condition, can dominate the IHP sorption onto kaolinite, which impacts the mobility and bioavailability of phosphorus in highly weathered soils. Highlights: IHP promotes the dissolution of kaolinite mainly through the formation of aluminium phytate complex. IHP sorption presents a sharp maximum at pH 4.0. IHP forms inner‐sphere complexes at the surface of kaolinite. Formation of aluminium phytate surface precipitates is favourable at relatively low pH.