Enhancing the Phosphate Adsorption of a Polyallylamine Resin in Alkaline Environments by Lanthanum Oxalate Modification

Xiaofeng Xu; Ruonan Li; Jinglin Chen; Jie Yang; Yukai Wu; Junrui Liu; You-Gui Huang; Shaohua Chen; Xin Ye; Wei Wang

doi:10.1021/acsomega.2c01520

Enhancing the Phosphate Adsorption of a Polyallylamine Resin in Alkaline Environments by Lanthanum Oxalate Modification

ACS Omega. 2022 May 28;7(23):19743-19753. doi: 10.1021/acsomega.2c01520. eCollection 2022 Jun 14.

Authors

Xiaofeng Xu^{1

2

3}, Ruonan Li^{2

3}, Jinglin Chen⁴, Jie Yang^{1

2

3}, Yukai Wu⁴, Junrui Liu^{1

2

3}, You-Gui Huang^{2

3}, Shaohua Chen⁴, Xin Ye⁴, Wei Wang^{2

3}

Affiliations

¹ College of Chemistry and Materials Science, Fujian Normal University, Fuzhou 350002, China.
² CAS Key Laboratory of Design and Assembly of Functional Nanostructures, and Fujian Provincial Key Laboratory of Nanomaterials, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China.
³ Xiamen Institute of Rare Earth Materials, Haixi Institute, Chinese Academy of Sciences, Xiamen 361021, China.
⁴ Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.

Abstract

Sevelamer hydrochloride (SH), originally developed as an oral pharmaceutical for controlling blood phosphate levels, is a polyallylamine resin that could be used in water treatments. Although it binds phosphates effectively, its adsorption capacity suffers from a significant loss at high pH. Here, we modify SH with lanthanum oxalate to improve its phosphate adsorption in alkaline environments. With less than 6.00 wt% in La content, the composite adsorbent (SH-1C-1La) exhibits an adsorption capacity of 109.3 mg P g^-1 at pH 8.0 and 100.2 mg P g^-1 at pH 10.0, demonstrating significant enhancement from the original SH (86.3 mg P g^-1 at pH 8.0 and 69.4 mg P g^-1 at pH 10.0). Besides its high adsorption capacity and rapid adsorption kinetics, SH-1C-1La is capable of maintaining more than 78% of its capacity after four regeneration cycles, showing good durability in long-term applications. Zeta-potential measurements and XPS analysis reveal that the lanthanum oxalate species increase the surface potential to enhance the electrostatic adsorption while introducing chemical binding sites for phosphate ions. Both factors lead to the improved adsorption properties. The modification by lanthanum oxalate species might provide a new alternative for improving the phosphate adsorption properties of anion-exchange resins.