Plant tannin immobilized Fe3O4@SiO2 microspheres: A novel and green magnetic bio-sorbent with superior adsorption capacities for gold and palladium

In this paper, a new core-shell nanostructured magnetic bio-based composite was prepared by immobilizing persimmon tannin (PT) onto Fe 3 O 4 @SiO 2 microspheres, and the as designed Fe 3 O 4 @SiO 2 @PT was utilized for adsorptive recovery of Au(III) and Pd(II). The preparation, morphology, composition and magnetic property of Fe 3 O 4 @SiO 2 @PT were characterized. Adsorption parameters of Fe 3 O 4 @SiO 2 @PT towards Au(III) and Pd(II) including initial pH, reaction time, initial concentration of metal ions , effect of acidity and interference of coexisting metal ions were investigated. It is sufficiently confirmed that silica was coated on Fe 3 O 4 and persimmon tannin was immobilized on aminated Fe 3 O 4 @SiO 2 . The thickness of silica and loaded persimmon tannin are around 18 nm and 14 nm, respectively. With only 1.00 wt% of persimmon tannin, however, the maximum adsorption capacities of Fe 3 O 4 @SiO 2 @PT for Au(III) and Pd(II) were as high as 917.43 and 196.46 mg·g −1 , respectively. In addition, after adsorption of Au(III) and Pd(II), the magnetization saturation values ( Ms ) of Fe 3 O 4 @SiO 2 @PT were high enough to guarantee efficient magnetic seperation. Metallic gold could be facilely recovered from wastewaters containing Au(III).