Fabrication of Fe-coordinated diamino-functionalized SBA-15 with hierarchical porosity for phosphate removal

Hierarchically macroporous–mesoporous SBA-15 phosphate adsorbent was synthesized via a dual-templating approach, followed by diamino-functionalization and Fe(III) impregnation. The resulting Fe(III)-coordinated diamino-functionalized macroporous–mesoporous adsorbent possessed well-defined and interconnecting macroporous and mesoporous networks. Its maximum adsorption was 12.7 mg/g, which was 86.8% greater than that of Fe(III)-coordinated amino-functionalized mesoporous SBA-15. In the kinetic study of macroporous–mesoporous adsorbent, 92.5% of the final adsorption capacity reached in the first 1 min; and the adsorption followed the pseudo-second-order equation well, suggesting the presence of chemisorption. The pH ranging from 3.0 to 6.0 favored the high phosphate adsorption of hierarchically porous adsorbent; however, the coexistence of other anions, especially F−, retarded the adsorption.

• Fe-coordinated functionalized macro-mesoporous SBA-15 was used to remove phosphate.
• The P adsorption of SBA-NN-Fe-8.6 was 86.8% higher than the mesoporous SBA-NN-Fe-0.
• 92.5% of the adsorption capacity of SBA-NN-Fe-8.6 reached within the first 1 min.
• High phosphate adsorption of SBA-NN-Fe-8.6 was recorded from pH 3.0 to 6.0.
• The coexistence of anions retarded the phosphate adsorption of SBA-NN-Fe-8.6.