Design of bionic amphoteric adsorbent based on reed root loaded with amino-functionalized magnetic nanoparticles for heavy metal ions removal

Renewable and cheap reed roots are rich in polysaccharide and lignin and naturally possesses wastewater purification ability. However, if applied as industrial adsorbent, the active sites of reed roots need further enhancement to fit realistic amphoteric ion adsorption requirement and its recovery also request for optimization to avert secondary pollution caused by adsorbent residues. Under this background, a novel adsorbent based on reed root loaded with magnetic amino-functionalized nanoparticles (Rr(H)@Fe3O4 @SiO2-NH2) with a bionic dendritic structure and a pleated surface was designed. The reed roots were firstly pretreated with hydrogen peroxide solution with strong oxidizing properties under UV light irradiation to expose more oxygen-containing functional groups, which then condensed with the amino groups on the surface of Fe3O4 @SiO2-NH2 nanoparticles, leading to the formation of the final adsorbent. The carboxyl, hydroxyl and methoxy and amino groups on the surface of the adsorbent synergistically contribute to the adsorption of both anions and cations. The maximum adsorption capacity for Pb (II) and Cr (VI) ions per unit mass of reed root in Rr(H)@Fe3O4 @SiO2-NH2 reached 99.1 and 106.5 mg g(-1), much higher than those obtained with raw reed roots (24.8 and 30.6 mg g(-1)). The superior adsorption performance was ascribed to its physicochemical properties as characterized by a series of characterization methods. The adsorption process followed pseudo-second-order kinetic and Freundlich isotherm model, indicating a chemical multi-layer endothermic adsorption process. The addition of magnetic Fe3O4 endows the easy recovery of the adsorbent by applying a magnetic field, and after five cycles, the adsorption capacity can still reach 82% of that of the first time. In summary, the desirable adsorption performance, easy recovery, and low cost make the bionic RrH@Fe3O4 @SiO2-NH2 a promising amphoteric adsorbent for eliminating heavy metal ions from wastewater.

Automated summary

A novel adsorbent based on reed root loaded with magnetic amino-functionalized nanoparticles was designed, which showed superior adsorption performance, easy recovery, and low cost for eliminating heavy metal ions from wastewater.