Removal of Pb(II) from Aqueous Solution by &amp;lt;i&amp;gt;Portulaca oleracea&amp;lt;/i&amp;gt; Leaves: Kinetic, Equilibrium and Thermodynamic Studies

M A Ackacha

doi:10.4236/ajac.2013.47a004

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.

Highlights

Different toxic heavy metals are frequently discharged into the water environment due to industrial activities of humans
According to Dubinin-Radush Kevich (D-R) isotherm data, the adsorption process is classified as physical adsorption
In order to suggest the mechanism of adsorption, kinetic models such as first-order, pseudo-second-order and intra-particle diffusion are probably used to test the experimental data

Summary

Introduction

Different toxic heavy metals are frequently discharged into the water environment due to industrial activities of humans. There are different industrial sources of heavy metals including mining, plating, textile, storage batteries, electroplating, metal finishing and lead smelting. The presence of these toxic heavy metals in the water environment is of important concern due to their health effects on human and other living organisms. Adsorption onto low cost agriculture materials was studied. These agriculture materials include sawdust [1], olive orange waste [2], almond green hull [3], olive cake ash [4], walnut shell [5] and rice bran [6]. An agriculture material, i.e. Portulaca oleracea leaves were tested as a low cost adsorbent for the elimination of Pb(II) from aqueous solutions

Methods

Results

Conclusion