In situ decoration of La(OH)3 on polyethyleneimine-linked dendritic mesoporous silica nanospheres targeting at efficient and simultaneous removal of phosphate and Congo red

Abstract

The simultaneous elimination of phosphorus and dyes is of great significance for the practical treatment of dye-containing wastewater. In this study, a series of novel mesoporous adsorbents were successfully fabricated via the controlled linking of polyethyleneimine (PEI) to 3D dendritic mesoporous silica (DMS), followed by in situ formation of La(OH)₃ through coordination between N-containing functional groups and La³⁺. The synthesis of such adsorbents with different amounts of PEI and La(OH)₃ was optimized towards efficient removal of phosphate (P) and Congo red (CR) with a maximum adsorption capacity of 58.1 mg P g⁻¹ and 926.4 mg g⁻¹, respectively. The optimal adsorbent (DMS-PEI-La2) exhibited excellent simultaneous P and CR removal in a binary-component (P and CR) solution, in which CR adsorption was promoted by the increase of coexisting P concentration. Taken the effects of initial solution pH into consideration, the adsorption mechanisms of P involved electrostatic attraction, hydrogen bonding and ligand exchange. It is noted that LaPO₄ nanodots and nanorods confined in the mesoporous structure were formed via ligand exchange of –OH from La(OH)₃ with P. Meanwhile, the formed LaPO₄ would further act as new active sites for accelerating CR adsorption by hydrogen bonding. In addition, efficient simultaneous removal of P and CR using DMS-PEI-La2 in simulated polluted river water was observed, along with negligible La leaching. The selected adsorbent showed good reusability in four successive cycles of adsorption–desorption, indicating the great potential for practical use in the treatment of dye-containing wastewater. Thus, this work provides a new insight on simultaneous P and CR remediation from wastewater by rationally designing novel porous functional materials.