Kinetic study of adsorption of phenol on the novel polymer prepared AUFP from aqueous solution

Abstract

This work includes the synthesis and characterization of new adsorbent of
attapulgite-urea-formaldehyde polymer (AUFP). The Chemical structural formula of
this adsorbent was confirmed by FTIR spectroscopy and XRD diffraction technique.
The results showed that the urea was linked to attapulgite by hydrogen bonds through
the NH2 moieties. The disappearance of NH2 stretching band from the IR spectrum of
the complex during polymerization with formaldehyde gave good indication of polymer
formation. The adsorption ability of attapulgite and AUFP toward phenol has been
studied using UV-Visible spectrophotometry. This technique has been utilized to
construct the relation between the amount of the adsorbate (phenol) and the equilibrium
concentration (isotherms).

The shape of the isotherm obtained from the adsorption of phenol on the
attapulgite and AUFP were found to be comparable in all cases to the Freundlich
equation and were similar to S-curve type according to Gilles’s classification. Ability of
the adsorbents to adsorb the phenol is in the following order AUFP > A.
The adsorption phenomena on these adsorbents were studied at different
temperatures 298, 308 and 318 K. The above sequence in activity of the adsorbents
surfaces remained unchanged as the temperature changed.
The extent of the adsorption found to decrease as the temperature increased, i.e.,
exothermic adsorption. The thermodynamic functions ΔH, ΔG and ΔS were calculated
and were explained in the mean of the chemical structure of the adsorbate. Kinetic of
adsorption was studied using Lagergren’s equation and the adsorption rate constant Kad
was calculated. The kinetic results indicated that the adsorption was pseudo first order
and the rate determining step was demonstrated.

Activation energy was calculated using Arrhenius equation and was found to be
dependent on the nature of the adsorbents surfaces.