Abstract
In this study, a redox precipitation method was used to load manganese dioxide (MnO2) nanoparticles on biochar (BC) (BC@MnO2) pyrolyzed from the invasive water hyacinth, and the adsorption of Cd(II),Cu(II), Zn(II), and Pb(II) was investigated. Several techniques were used to characterize the adsorbents. The results revealed that the BC surface was covered by many intertwined thin amorphous MnO2 nanosheets, which significantly increased its specific surface area and pore volume. The adsorption of heavy metal ions by BC was negligible, whereas the MnO2-containing adsorbents exhibited a high capacity for adsorbing heavy metal ions. However, the MnO2-normalized adsorption amount decreased with increasing MnO2 load and was largely unchanged at MnO2 loads of 26.6% to 30.2%. The capacity for adsorbing heavy metal ions of BC@MnO2 was pH-dependent, but the adsorption affinity was unaffected by coexisting ions. Column tests revealed that BC@MnO2 with a load of 26.6% had a high capacity for removing heavy metal ions from simulated and real electroplating wastewater. Therefore, BC@MnO2 with a load of 26.6% shows promise as a regenerable adsorbent for removing heavy metal ions from water/wastewater. This study could lay an essential foundation to develop a win-win strategy for heavy metal ions removal from wastewater using biochar derived from water hyacinth.
Highlights
In this study, a redox precipitation method was used to load manganese dioxide (MnO2) nanoparticles on biochar (BC) (BC@MnO2) pyrolyzed from the invasive water hyacinth, and the adsorption of Cd(II),Cu(II), Zn(II), and Pb(II) was investigated
Zhang et al concluded that nanosized manganese oxide demonstrated high adsorption affinity for Pb(II), Cd(II) and Cu(II) ions in aqueous solution and was not significantly affected by coexisting ions (Na+ and Mg2+)[9]
Nanosized MnO2 loaded on materials with a high specific surface area—such as graphene oxide[11], ordered mesoporous silica[15], and ordered mesoporous carbon materials[16] exhibited higher performance in energy storage, catalysis, and adsorption than aggregated nanosized MnO2
Summary
A redox precipitation method was used to load manganese dioxide (MnO2) nanoparticles on biochar (BC) (BC@MnO2) pyrolyzed from the invasive water hyacinth, and the adsorption of Cd(II),Cu(II), Zn(II), and Pb(II) was investigated. Nanosized metal oxides (e.g., zirconium oxides[5], iron oxides[6], aluminum oxides[7], and manganese oxides8) are potential adsorbents because of their large surface areas, abundance of defect sites, and high surface to bulk atom ratios. Compared with their bulk counterparts, nanosized metal oxides exhibit better performance for adsorbing heavy metal ions[4,8]. The loading of nanosized MnO2 onto low-cost supporting materials with large specific surface areas shows promise. The means of enhancing MnO2 loading and reactions among BC, MnO2, and target contaminants have been overlooked
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