TITLE:
Isotherm, Kinetic and Thermodynamic Studies for the Sorption of Mercury (II) onto Activated Carbon from Rosmarinus officinalis Leaves
AUTHORS:
Mohamed Erhayem, Fatima Al-Tohami, Ragwan Mohamed, Khadija Ahmida
KEYWORDS:
Adsorption, Hg(II), Isotherm, Kinetic, Thermodynamic, Rosmarinus officinalis Leaves
JOURNAL NAME:
American Journal of Analytical Chemistry,
Vol.6 No.1,
January
9,
2015
ABSTRACT: The present work deals with the equilibrium adsorption of Hg(II) onto carbonized Rosmarinus officinalis leaves (ACROL) as a new adsorbent from aqueous solution and it has been investigated. ACROL samples were prepared by physical carbonization at 773 K for 1 h. Titration
method was used to determine the concentration of Hg(II) before and after
adsorption onto ACROL by ethylenediaminetetraacetic acid, EDTA, as chelating
agent. Batch equilibrium studies were carried out under different experimental
conditions such as Hg(II) concentration and temperature. The relationship
between the amount of Hg(II) onto ACROL can be described using four
tow-parameter isotherm models. The equilibrium sorption data were analyzed
using Freundlich, Langmuir, Dubinin-Radushkevich (DRK) and Temkin isotherms.
The experimental results were found to fit the Langmuir isotherm model with a
monolayer adsorption capacity of 588.2 mg/g at 318 K, while they were found to
fit the Freundlich isotherm model at 298 K. The KL was decreased with increasing temperature, indicating a bond strength between Hg(II) and ACROL decreased with increasing temperature
and sorption is exothermic. From DRK isotherm, free energy, E, was higher than 31 kJ/mol suggesting the Hg(II) adsorption onto ACROL chemical sorption. The thermodynamic
studies revealed that the process is spontaneous nature of Hg(II) adsorption by
ACROL and exothermic. The findings from this research show that ACROL has
capability to remove Hg(II) from aqueous solutions.