Abstract
The synergistic adsorption of heavy metal ions and humic acid can be very challenging. This is largely because of their competitive adsorption onto most adsorbent materials. Hierarchically structured composites containing polyethylenimine-modified magnetic mesoporous silica and graphene oxide (MMSP-GO) were here prepared to address this. Magnetic mesoporous silica microspheres were synthesized and functionalized with PEI molecules, providing many amine groups for chemical conjugation with the carboxyl groups on GO sheets and enhanced the affinity between the pollutants and the mesoporous silica. The features of the composites were characterized using TEM, SEM, TGA, DLS, and VSM measurements. Series adsorption results proved that this system was suitable for simultaneous and efficient removal of heavy metal ions and humic acid using MMSP-GO composites as adsorbents. The maximum adsorption capacities of MMSP-GO for Pb(II) and Cd (II) were 333 and 167 mg g−1 caculated by Langmuir model, respectively. HA enhances adsorption of heavy metals by MMSP-GO composites due to their interactions in aqueous solutions. The underlying mechanism of synergistic adsorption of heavy metal ions and humic acid were discussed. MMSP-GO composites have shown promise for use as adsorbents in the simultaneous removal of heavy metals and humic acid in wastewater treatment processes.
Highlights
PEI molecules played bilateral roles one of them serving as the binding bridge for conjugation and the other to improve the adsorption affinity of the magnetic mesoporous silica (MMSP) microspheres to the pollutant matter. [28]
The results showed that Langmuir model with R2 higher than 0.99 fitted better than Freundlich model, indicating that Pb(II) and Cd(II) adsorption on magnetic mesoporous silica and graphene oxide (MMSP-graphene oxide (GO)) can be considered to be a monolayer adsorption process
Adsorption of Pb(II)/Cd(II) by MMSP-GO Influenced by humic acid (HA) We investigated the influence of HA at an initial concentration of 10 mg L221 on the adsorption of heavy metal ions onto MMSP-GO composites within a pH range of 2.0 to 9.0
Summary
Heavy metal ions and humic acid (HA) in underground water pose a severe threat to public health and ecological systems.[1,2,3] A great deal of effort has been made to develop effective adsorbents with different chemical compositions, microstructures, and surface functionalities for the removal of heavy metal ions and organic pollutants from water.[4,5,6,7,8,9] In this way, the development of adsorbents with high adsorption capacity, low toxicity, and efficient separation has attracted considerable interest. [10,11]. [24] synergistic adsorption of heavy metal ions and humic acid molecules is still a challenge because of their competitive adsorption onto most adsorbents.[25–. 27] To the best of our knowledge, there have been few studies that have evaluated the use of functionalized magnetic mesoporous silica and graphene oxide in the synergistic adsorption of two kind of pollutants. The high surface-to-volume ratio and surface functionalities of the graphene oxide (GO) and PEI-grafted magnetic mesoporous silica (MMSP) microspheres can be both used to this effect. We report a facile method for preparation of magnetic mesoporous silica-graphene oxide (MMSP-GO) composites and describe our investigation of the synergistic adsorption of HA and heavy metal ions, Pb(II) and Cd(II). The functionalization of the mesoporous silica microspheres containing PEI molecules was found to both facilitate the adsorption of HA and provide sites for chemical reaction with graphene oxide sheets. The magnetic cores of MMSP microspheres were embedded to facilitate easy separation using magnetic fields
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