title: Dye removal from aqueous solution by cobalt-nano particles decorated aluminum silicate: kinetic, thermodynamic and mechanism studies.
abstract: This article describes the preparation of a nanoadsorbent containing Co-nanoparticles decorated functionalized SiO2-Al2O3 mixed-oxides as a scavenger toward removal of methyl orange. SiO2-Al2O3 mixed-oxides were functionalized with pyridine-2-carbaldehyde and thereafter, in the next step, Co-nanoparticle was prepared over the modified mixed-oxides. The as-prepared nanoadsorbent was characterized by Fourier transform infrared (FTIR), UV-visible diffuse reflectance spectra (UV-vis DRS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Results showed that Co-nanoparticle with average size of about 5-25 nm was immobilized successfully on the surface of modified mixed-oxides and was widely dispersed. EPR and CV of Si/Al-PAEA=PyCA@CoNP confirmed that most of the covalently bond active sites of the nano-adsorbent are in the form of Co(II) ions. The supported cobalt is a suitable and efficient adsorbent for the removal of methyl orange from aqueous solution. The heterogeneous Co-NPs were found to be effective adsorbent for the removal of methyl orange ions from solution. The adsorption process was spontaneous and endothermic in nature and followed pseudo-second-order kinetic model. The CV and EIS of the Co-NPs-MO indicates an easily oxidizable environment, this being in agreement with the FTIR data, where the electron density at Co-NPs is higher due to the presence of a donor-electron ligand (methyl orange), that is, reduction of Co-NPs from +3 to +2 oxidation state is more favored.
authors.affiliation: Department of Chemistry, Shiraz Branch, Islamic Azad University, P.O. Box 71955-149, Shiraz, Fars, Iran. Electronic address: m-arshadi@ch.iut.ac.ir.
authors.forename: M
authors.initials: M
authors.lastname: Arshadi
authors.affiliation: Young Researchers and Elite Club, Pharmaceutical Sciences Branch, Islamic Azad University, Tehran, Iran.
authors.forename: A R
authors.initials: AR
authors.lastname: Faraji
authors.affiliation: Department of Chemistry, Faculty of Science, University of Zabol, Zabol, Iran.
authors.forename: M
authors.initials: M
authors.lastname: Mehravar
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry*; D004396:Coloring Agents / Q000302:isolation & purification*; D058266:Dielectric Spectroscopy; D004578:Electron Spin Resonance Spectroscopy; D007700:Kinetics; D053768:Metal Nanoparticles / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
chemical_list: D000538:Aluminum Silicates; D004396:Coloring Agents; D012996:Solutions; D014867:Water
keywords: Adsorption; Cobalt nanoparticle; Cyclic voltammogram; Electrochemical impedance spectroscopy; Mechanism; Methyl orange