Abstract
BackgroundDischarge of heavy metals such as hexavalent chromium (Cr (VI)) and nickel (Ni (II)) into aquatic ecosystems is a matter of concern in wastewater treatment due to their harmful effects on humans. In this paper, removal of Cr (VI) and Ni (II) ions from aqueous solution was investigated using an amino-functionalized magnetic Nano-adsorbent (Fe3O4-NH2).MethodsAn amino-functionalized magnetic Nano-adsorbent (Fe3O4-NH2) was synthesized by compositing Fe3O4 with 1, 6-hexanediamine for removal of Cr (VI) and Ni (II) ions from aqueous solution. The adsorbent was characterized by Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), powder X-Ray Diffraction (XRD), and Vibrating Sample Magnetometry (VSM). Also, the effects of various operational parameters were studied.ResultsAccording to our finding, Fe3O4-NH2 could be simply separated from aqueous solution with an external magnetic field at 30 s. The experimental data for the adsorption of Cr (VI) and Ni (II) ions revealed that the process followed the Langmuir isotherm and the maximum adsorption capacity was 232.51 mg g−1 for Cr (VI) at pH = 3 and 222.12 mg g−1 and for Ni(II) at pH = 6 at 298 °K. Besides, the kinetic data indicated that the results fitted with the pseudo-second-order model (R2: 0.9871 and 0.9947 % for Cr (VI) and Ni (II), respectively. The results of thermodynamic study indicated that: standard free energy changes (ΔGɵ), standard enthalpy change (ΔHɵ), and standard entropy change (ΔSɵ) were respectively −3.28, 137.1, and 26.91 kJ mol−1 for Cr (VI) and −6.8433, 116.7, and 31.02 kJ mol−1 for Ni (II). The adsorption/desorption cycles of Fe3O4-NH2 indicated that it could be used for five times.ConclusionsThe selected metals’ sorption was achieved mainly via electrostatic attraction and coordination interactions. In fact, Fe3O4-NH2 could be removed more than 96 % for both Cr (VI) and Ni (II) ions from aqueous solution and actual wastewater.
Highlights
Discharge of heavy metals such as hexavalent chromium (Cr (VI)) and nickel (Ni (II)) into aquatic ecosystems is a matter of concern in wastewater treatment due to their harmful effects on humans
Discharge of heavy metals into aquatic ecosystems is a matter of concern in wastewater treatment due to their harmful effects on humans even at low concentrations [1, 2]
In order to determine the effects of various factors, the experiments were performed at different Fe3O4-NH2 doses (0.1 to 0.3 g/L), initial concentrations of Cr (VI) and Ni (II) (5 to 100 mg/L), and temperatures (298.15 to 338.15 °K)
Summary
Chemicals Anhydrous sodium acetate, iron (III) chloridehexahydrat (FeCl3 · 6H2O), potassium dichromate, ethanol, 1,6-hexanediamine, ethylene glycol, nickel (II) chloride hexahydrat (NiCl2.6H2O), sodium hydroxide, hydrogen chloride, which were of analytical grade, were purchased from Merck, Germany and were used without further purification. The above mixture was stirred at 50 °C under vigorous stirring for 30 min This solution was heated at 198 °C in a Teflonlined autoclave for 6 h. Fe3O4-NH2 with adsorbed Cr (VI) and Ni (II) was separated from the solution under the external magnetic field. The concentrations of Cr (VI) and Ni (II) ions in the solutions were measured by an Inductive Coupled Plasma (ICP-OES, Spectro arcos, Germany (Company: SPECTRO)). In order to determine the effects of various factors, the experiments were performed at different Fe3O4-NH2 doses (0.1 to 0.3 g/L), initial concentrations of Cr (VI) and Ni (II) (5 to 100 mg/L), and temperatures (298.15 to 338.15 °K). The removal of Cr (VI) and Ni (II) by Fe3O4-NH2 and removal efficiency have been figured by equations in Table 1 [18]
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