Equilibrium Isotherms and Kinetic Studies of Removal of Methylene Blue Dye by Adsorption onto Miswak Leaves as a Natural Adsorbent

Taha M Elmorsi

doi:10.4236/jep.2011.26093

Abstract

In this research miswak leaves, agriculture wastes, available in large quantity in Saudi Arabia, was used as low-cost adsorbent for removing methylene blue (MB) dye. Equilibrium behavior of miswak leaves was investigated by performing batch adsorption experiments. The effects of [MB] 0, pH, contact time and adsorbent dose were evaluated. An alkaline pH (10.6) was favorable to the adsorption of MB dye. Adsorption isotherm models, Langmuir, Freundlich and Temkin were used to simulate the equilibrium data. Langmuir equation was found to have the highest value of R2 compared with other models. Furthermore, it was found that miswak leaves have a high adsorptive capacity towards MB dye (200 mg/g) and show favorable adsorption of MB dye with separation factor (RL < 1). In addition, pseudo-first- order, pseudo-second order and intra-particle diffusion were used to study the kinetics of MB adsorption onto miswak leaves. Adsorption process undergoes pseudo-second order kinetic as proved by the high value of R2 and the low value of sum of squared error (SSE percentage). Results indicated that intra-particle diffusion is not the limiting step, and the adsorption process is spontaneous as indicated by the negative value of the .

Highlights

Presence of many pollutants in water and wastewater has increased recently due to high increase in various industrial activities
The results showed that the uptake of methylene blue (MB) dye by miswak leaves depends on [MB]0 and contact time
This may be because the constant number of available sites in miswak leaves is saturated by the increase of [MB]0, which would lead to a decrease in the removal percentage of MB dye

Summary

Introduction

Presence of many pollutants in water and wastewater has increased recently due to high increase in various industrial activities. Using dyes in many industries [1] such as textile, paper, plastics, leather, food and cosmetic, represent a large group of chemicals that get mixed in wastewater among many aqueous pollutants. There is a dramatic increase in the annual production of different synthetic dyes representing more than 10,000 dyes [2]. It was reported that incomplete degradation of dyes by bacteria in the sediment resulted in production of some carcinogenic and harmful amines [4]. Presences of color substances in the water body may decrease the light transmission which decreasing the photosynthesis activity, leading to decrease growth of bacteria and decreasing the biodegradation of impurities in water [5]. It is essential that wastewater contaminated with MB dye to be given some treatments before discharge

Methods

Results

Conclusion