Abstract
Nanocomposites containing magnetic iron oxide (magnetite) nanoparticles and layered double hydroxide (LDH) nanosheets were prepared by two different methods, exfoliation-reassembly and coprecipitation, for aqueous chromate adsorbent. According to X-ray diffraction, scanning electron microscopy, and atomic force microscopy, both nanocomposites were determined to develop different nanostructures; LDH nanosheets well covered magnetite nanoparticles with house-of-cards-like structure in exfoliation-reassembly method, while coprecipitation resulted in LDH particle formation along with magnetite nanoparticles. Zeta-potential measurement also revealed that the magnetite surface was effectively covered by LDH moiety in exfoliation-reassembly compared with coprecipitation. Time, pH, concentration dependent chromate adsorption tests, and magnetic separation experiments exhibited that both nanocomposites effectively adsorb and easily collect chromate. However, exfoliation-reassembly nanocomposite was determined to be slightly effective in chromate removal by ~10%. Chromate adsorbed nanocomposites could be regenerated by treating with bicarbonate and the regenerated nanocomposites preserved ~80% of chromate adsorption efficacy after three times of recycling.
Highlights
Fabrication of nanocomposites is a subject of great importance in developing functional nanomaterials such as catalysts [1], nanomedicines [2], electronic materials [3], and pollutant scavenger [4]
At the time points 0, 0.5, 1, 2, 3, 4, 6, 12, and 24 hours, nanocomposites were collected by magnetic separation and chromate concentration in supernatant was quantified with ultraviolet-visible spectrophotometer (UV-Vis; Shimadzu UV-1800, Shimadzu Corporation, Kyoto, Japan) at λmax = 372 nm
The removal efficacy of magnetite nanoparticles (Mag)@layered double hydroxide (LDH)-CO at 24 h was determined to 16.07, 31.83, and 50.65 mg Cr(VI)/g nanocomposite at 50, 100, and 200 ppm of chromate, respectively. These results showed that the chromate removal efficacies of current nanocomposites were comparable or higher than previous reports as we described in Introduction [16, 17]
Summary
Fabrication of nanocomposites is a subject of great importance in developing functional nanomaterials such as catalysts [1], nanomedicines [2], electronic materials [3], and pollutant scavenger [4]. 2-dimensional nanosheets have attracted interests to prepare nanocomposites for catalysts [9], electrodes [10], and energy storage [11], due to their high specific surface area, unusual physicochemical property resulting from anisotropic structure, and controllable compositions. Among the 2-dimensional nanosheets, layered double hydroxides, LDHs: M(II)1−xM(III)x(OH)2(An−)x/n ⋅ mH2O, (M(II): divalent metal cation; M(III): trivalent metal cation; An−: anionic species with n− charge, 0 < x < 1; m: interlayer water quantity) have been widely studied in biomedical or environmental applications, as they have been reported to have biocompatibility [12], high anionic exchange capacity [13], tunable composition [14], and easy surface modification property [15]. Yu et al studied the removal of As(V) and Cr(VI) with MgAl-LDH whose three-dimensional hierarchical structure affected removal efficiency showing maximum ∼150 mg Cr(VI)/g LDH and ∼200 mg As(V)/g LDH [18]
Sign-in/Register to view highlights & summary 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.
