Abstract
Recently, the discharge of metal ions into the aquatic environments has become the main issue because of its role in the ecological system pollution. Herein, a recyclable multifunctional graphene oxide/silica@polyaniline (GO/SiO2@PANI) microspheres composite was synthesized, characterized, and tested for Cu(II) and Cr(VI) ions uptake. The interaction between the studied ions and GO/SiO2@PANI composite was rapid, and the optimum pH values were 5.3 for Cu(II) while pH 3.0 for Cr(VI). The Cu(II)) and Cr(VI) adsorption data at equilibrium reflected proper corrections for traditional Langmuir and Freundlich equations at 30, 40, and 50 °C. Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis revealed that the Cu(II) adsorption onto GO/SiO2@PANI function groups was mainly governed by electrostatic force. Hexavalent chromium was removed in the form of HCrO4−via electrostatic interaction and Cr(III) by the ion exchange. The geometry of the removed ions on the GO/SiO2@PANI receptor sites was deeply interpreted using advanced statistical physics models (ASPM). Single and two-layer with dual-energy sites fitted perfectly with Cr(VI) as well as Cu(II) sorption data. Horizontal and vertical directions were presented in Cr(VI) uptake, indicating the presence of adsorption–reduction coupled mechanism. For Cu(II) ions, only the horizontal position was distinguished, reflecting the participation of various receptor sites of the GO/SiO2@PANI in the removal of copper ion. The adsorption energies for both metals ions were below 40 kJ/mol signifying an endothermic process governed by physical interactions. Removal of both ions in the binary system and regeneration process indicated that the GO/SiO2@PANI composite is a promising adsorbent for metals-bearing water.
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•GO/SiO2@polyaniline microspheres composite was used for Cu(II) and Cr(VI) removal.•Classical and advanced statistical models were used for fitting the experimental data.•Metals adsorption mechanisms were interpreted via statistical physics parameters.•Cr(VI) uptake was mainly governed by adsorption–reduction coupled mechanism.•Cu(II) ions binds via complexation and participation on various receptor sites.