TITLE:
Removal of Pb(II) from Aqueous Solution by Portulaca oleracea Leaves: Kinetic, Equilibrium and Thermodynamic Studies
AUTHORS:
M. A. Ackacha
KEYWORDS:
Portulaca oleracea; Langmuir; Freundlich; Isotherm; Lead; Adsorption
JOURNAL NAME:
American Journal of Analytical Chemistry,
Vol.4 No.7A,
July
2,
2013
ABSTRACT:
Portulaca oleracea leaves are
tested as an agriculture adsorbent material for reducing Pb(II) from aqueous
solutions. The pH of solution, adsorbent dose, shaking speed and particles
size of adsorbent were constants at all adsorption experiments. Effects of contact time on adsorption
capacity of Pb(II) onto Portulaca oleracea leaves were studied. The
adsorption capacity increased as the contact time increased and reached
equilibrium at one hour. Kinetic models including a first-order, pseudo-second-order and intra-particle
diffusion equations were selected to follow the adsorption process. The process
follows a pseudo-second-order kinetic and the intra-particle diffusion is the main step to interpret the mechanism
of adsorption. Langmuir, Freundlich and Dubinin-Radush Kevich (D-R) isotherm
models were applied to describe adsorption equilibrium data. Results proved
that the Langmuir isotherm model gave an acceptable fit to the experimental
data more than Freundlich isotherm model. Maximum adsorption capacities obtained were 192.3, 333.3 and 434 mg/g
at 295, 303 and 310 K, respectively. According to D-R isotherm data, the
adsorption process is classified as physical adsorption. Thermodynamically, the
adsorption process is non spontaneous, endothermic and random in nature.