Water containing excess heavy metals poses a health risk to humans but can be purified effectively using adsorbents. As such, identifying novel and efficient adsorbents to remove heavy metals such as Pb(II) and Cr(VI) is vital. We report a new metal-organic framework (MOF), {[Cd 1.5 (btc)(bibp)·2H 2 O]·H 2 O}n, capable of capturing Pb(II) and Cr(VI) from water. The adsorbent has a high density of exposed active sites, with maximum adsorption capacities of 537.634 mg/g for Pb(II) (pH = 7) and 787.402 mg/g for Cr(VI) (pH = 6). Adsorption equilibrium was reached after 60 and 120 min with Pb(II) and Cr(VI), respectively, and the adsorbent was regenerated effectively using an ethanol-acetic acid eluent. Analysis of the adsorption kinetics using Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy showed that the abundant –OH groups (hard base) and the Pb(II)/Cr(VI) (soft acid) behave according to the hard-soft acid-base principle. In addition, electron pairs are shared between the imidazole N atoms and Pb(II)/Cr(VI). This study provides new insights into the design of three-dimensional MOFs for removing pollutants from industrial wastewaters, with the potential to mitigate health risks to humans and natural ecosystems.
Three Fe3O4magnetic solvent-free nanofluids with different amine-based coronal layer structures are synthesized and characterized by using magnetic Fe3O4as the core, silane coupling agent as the corona, and polyether amines with different graft densities and chain lengths as the canopy. The concentration of heavy metal ions after adsorption is measured by atomic absorption spectrometry (AAS) to study the effect of Fe3O4magnetic solvent-free nanofluids on the adsorption performance of the heavy metal ions lead (Pb(II)) and copper (Cu(II)) in water. The adsorption of Fe3O4magnetic solvent-free nanofluid was explored by changing external condition factors such as adsorption contact time and pH. Additionally, the adsorption model is established. The magnetic solvent-free nanofluid is separated from water by applying an external magnetic field to the system, and desorption and cyclic adsorption tests are carried out. Based on the adsorption mechanism, the structure design of Fe3O4magnetic solvent-free nanofluid was optimized to achieve optimal adsorption performance.
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