Core-Shell MnO2-SiO2 Nanorods for Catalyzing the Removal of Dyes from Water

Wei Gong, Xianling Meng, Xiaohong Tang, Peijun Ji
2017 Catalysts  
This work presented a novel core-shell MnO 2 @m-SiO 2 for catalyzing the removal of dyes from wastewater. MnO 2 nanorods were sequentially coated with polydopamine (PDA) and polyethyleneimine (PEI) forming MnO 2 @PDA-PEI. By taking advantage of the positively charged amine groups, MnO 2 @PDA-PEI was further silicificated, forming MnO 2 @PDA-PEI-SiO 2 . After calcination, the composite MnO 2 @m-SiO 2 was finally obtained. MnO 2 nanorod is the core and mesoporous SiO 2 (m-SiO 2 ) is the shell.
more » ... ) is the shell. MnO 2 @m-SiO 2 has been used to degrade a model dye Rhodamine B (RhB). The shell m-SiO 2 functioned to adsorb/enrich and transfer RhB, and the core MnO 2 nanorods oxidized RhB. Thus, MnO 2 @m-SiO 2 combines multiple functions together. Experimental results demonstrated that MnO 2 @m-SiO 2 exhibited a much higher efficiency for degradation of RhB than MnO 2 . The RhB decoloration and degradation efficiencies were 98.7% and 84.9%, respectively. Consecutive use of MnO 2 @m-SiO 2 has demonstrated that MnO 2 @m-SiO 2 can be used to catalyze multiple cycles of RhB degradation. After six cycles of reuse of MnO 2 @m-SiO 2 , the RhB decoloration and degradation efficiencies were 98.2% and 71.1%, respectively. Catalysts 2017, 7, 19 2 of 11 compatibility, manganese oxides-for example, acid-activated MnO 2 [26], α-MnO 2 nanowires [27], manganese dioxide nanosheets [28], and manganese oxides with hollow nanostructures [29]-have been investigated for oxidative degradation of dyes. In this work, a novel core-shell catalytic material MnO 2 @m-SiO 2 for oxidative degradation of dyes has been developed. Scheme 1 illustrates the preparation route for the composite MnO 2 @m-SiO 2 . MnO 2 nanorods were first coated with polydopamine to form MnO 2 @PDA, and then polyethyleneimine (PEI) was bound to MnO 2 @PDA, forming MnO 2 @PDA-PEI. Further silicification of this material formed MnO 2 @PDA-PEI-SiO 2 . After calcination under 400 • C, MnO 2 @m-SiO 2 was prepared. This material has been utilized to degrade a model dye Rhodamine B (RhB). The mesoporous m-SiO 2 layer on the surface of the composite adsorbed and enriched RhB; the RhB molecules were transported through the mesoporous m-SiO 2 layer by diffusion, and then the MnO 2 nanorods catalyzed the degradation of RhB.
doi:10.3390/catal7010019 fatcat:xmc3hwbbtjavjotvr3r5kv47ei