Ligand Adsorption on an Activated Carbon for the Removal of Chromate Ions from Aqueous Solutions

Abstract

The results presented in this work are related to the design of a guideline to develop specific properties at the surface of an activated carbon (AC). For this, two model aromatic compounds have been synthesized and their electrolytic behavior in aqueous solutions was studied by a potentiometric method. The textural characteristics of the activated carbon were determined by porosimetry methods. The nature of oxygen-carrying functions and the acid-base behavior of the AC surface were characterized by TPD and potentiometric titration methods, respectively. The adsorption and desorption equilibria of the aromatic compounds on activated carbon were measured in aqueous solutions, and the hysteresis between adsorption and desorption, which reveals irreversible adsorption, was discussed on the basis of the frontier orbital theory. HOMO and LUMO orbitals of the adsorbent and adsorbates were calculated, and irreversible adsorption was attributed to the small energy difference between HOMO and LUMO of the aromatic adsorbates and the adsorbent. Adsorption equilibria of K2CrO4 in aqueous solution on the AC alone and on the AC-aromatic ligand adsorbents, respectively, prove the efficient development of specific chemical functions at the carbon surface provided by the adsorbed aromatic compounds.

New hybrid materials based on the grafting of Pd(ii)-amino complexes on the graphitic surface of AC: preparation, structures and catalytic properties

“…A commercial activated carbon, AC, Merck K24504014 (Merck hereinafter), previously characterized, 11,13,14 was used as-received. All solvents and other chemicals were of analytical grade and used as received.…”

“…[11][12][13] Moreover if the majority of the Ar-S-F molecules are adsorbed into open pores (meso-and macropores) the strong π-π interactions give rise to stable AC/Ar-S-F hybrid materials. In these hybrids the functional groups conjugated with the pyrimidine (plane) residue are blocked (due to the plane to plane interaction) whilst, should the character of S-F residues are non-aromatic, the properties of F (free) functions are efficiently transferred to the AC surface.…”

Adsorption of Metal Ions on an Activated Carbon/L‐Lysine Derivative Hybrid Compound

“…This bipolar character means that the energy differences between their HOMO and LUMOs are small and that the energy of these orbitals is close to the energy values calculated for the frontier orbitals of modelled arene active sites present on the surface of an activated carbon (AC). [9] This suggests that the observed irreversible adsorption of the above molecular receptors on the AC is probably due to some electron donation, through a π-π interaction, from the arene centres of the carbon to a vacant π orbital of the pyrimidine moiety.…”

“…[9][10][11] These molecular receptors contain a planar pyrimidine moiety (Ar), which acts as an anchor to attach the receptors onto the arene centres of the activated carbon. This pyrimidine fragment is connected through a polymethylene aliphatic arm (S) to a Lewis base function (F), which acts as an active site for complexation of the metal centres (Scheme 1).…”

Study of protonation and Zn(II), Cd(II), Cu(II) and Mn(II) complexation with a glutamic acid N-pyrimidine derivative: Crystal structure of a neutral Cd(II) complex of the bianionic ligand

“…Activated carbons have been extensively used for the purification or recovery of pollutant metals in waste waters [1][2][3]. In recent works [4,5], we have described a new method to add chemical functionality to the surface of an active carbon based on adsorbing the above-mentioned model compounds on it. That adsorption, which takes place when pyrimidine residues interact with carbon arene centres, favours adsorbed compounds acting as metal-ion receptors.…”