Abstract
To adsorb hexavalent chromium (Cr(VI)) in polluted water, this paper prepared a UiO-66 (Zr6O4(OH)4(BDC)12) modified granular corncob composite adsorbent by hydrothermal method with in situ loading of UiO-66 on pretreated corncob particles. The physicochemical properties of the synthesized samples were characterized. Batch adsorption experiments were conducted to investigate the adsorption process of aqueous Cr(VI) under various conditions (different ionic strength, pH and co-existing anions). The results showed that UiO-66 was successfully loaded on the modified corncob particles. The isothermal adsorption data of Cr(VI) adsorption by the UiO-66 modified corncob fit well with the Langmuir model with the maximum adsorption capacity of Cr(VI) on UiO-66@Corn+ being 90.04 mg/g. UiO-66 loading could increase Cr(VI) adsorption capacity of Corn+. The kinetic study showed that the equilibrium time for Cr(VI) adsorption on UiO-66 modified corncob was about 180 min and the kinetic data followed the pseudo-secondary kinetic model. The Cr(VI) adsorption capacity on UiO-66@Corn+ decreased with the increasing solution pH, and the optimum pH range was 4–6. The ionic strength has little effect on the Cr(VI) adsorption capacity, but the coexistence of CO32−, SO42− and PO43− in the solution could significantly decrease the equilibrium adsorption capacity of Cr(VI). The adsorption mechanism analysis showed that Cr(VI) was adsorbed on the surface of adsorbents through electrostatic attraction and was reduced further to the less toxic Cr(III) by the electron donor on the surface of adsorbent. The electrostatic interaction was the main force affecting the adsorption of Cr(VI) by UiO-66. UiO-66@Corn+ had an excellent removal efficiency of Cr(VI) and excellent reusability. UiO-66@Corn+ could effectively remove Cr(VI) from water and have a promising application.
Highlights
The surface of the UiO-66@Corn− was loaded with a small amount of fragments and particles (Figure 1c), and the pore structure was more abundant than the virgin corncob (Figure 1d)
The UiO-66 showed irregular agglomeration, which was consistent with a previous study [27]
The results indicated that the process of Cr(VI) adsorption on UiO-66 and UiO-66 modified corncobs tend to be monolayer adsorption, the adsorption capacity of Cr(VI) is closely related to the number of adsorption sites and the specific surface area of the adsorbent
Summary
Chromium (Cr) usually exists as Cr(III) or Cr(VI), and the toxicity of Cr(VI) is much greater than that of Cr(III) [1]. Cr(VI) is commonly found in industrial wastewater such as textiles, electroplating, leather production, cooling towers and metal processing. A small amount of Cr(VI) could have the risk of carcinogenesis and teratogenesis to humans and animals. Cr(VI) has been recognized as one of the most toxic heavy metals by the International Agency for Research on Cancer (IARC) [2].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
