Cd(II), Zn(II) and Cu(II) Bioadsorption on Chemically Treated Waste Brewery Yeast Biomass: The Role of Functional Groups.

Szende Tonk

doi:10.17344/acsi.2014.1265

Abstract

Here we study the role of functional groups from waste brewery yeast Saccharomyces cerevisiae cells in the bioadsorption of Cd(2+), Zn(2+) and Cu(2+) ions. In order to clarify the role of these functional groups, the brewery yeast was pretreated chemically, thereby helping to determine the mechanisms responsible for binding the target metals. SEM studies were performed to examine the surface microstructure of the adsorbent in pure as well as pretreated forms. The biomass was characterized using FTIR analysis, which indicated that hydroxyl, carboxyl and amid groups are present on the biomass surface. When carboxyl groups were modified by various chemical treatments, the adsorption capacity decreased dramatically, showing that carboxyl groups play a fundamental role in the bioadsorption process. The residual metallic ion concentrations were determined using an Atomic Absorption Spectrophotometer (AAS). Pseudo-first and second-order kinetic models were used to describe the bioadsorption process.

Highlights

The extensive use of heavy metals in industrial activities resulted in a dramatic increase of such residues in wastewaters
In the adsorption of heavy metals, the surface chemistry of the biosorbent plays a key role since adsorption is favored by the presence of oxygen-containing functional groups which can be vary different according to the nature of the biosorbent.[6,7]
Our results confirm that the removal of surface impurities, rupture of cell membrane and exposure of available binding sites after pretreatment may cause an increase in metal bioadsorption

Summary

Introduction

The extensive use of heavy metals in industrial activities resulted in a dramatic increase of such residues in wastewaters. The bioadsorption mechanisms involve several processes, including ion exchange, coordination, complexation, chelation, adsorption, and microprecipitation.[2,3] Metal uptake by bioadsorption is reported to occur through interactions with functional groups native to the biosorbent cell wall.[4,5] In the adsorption of heavy metals, the surface chemistry of the biosorbent plays a key role since adsorption is favored by the presence of oxygen-containing functional groups which can be vary different according to the nature of the biosorbent.[6,7] The cell walls of Saccharomyces cerevisiae consisting mainly of polysaccharides, proteins and lipids, offer many functional groups that can bind metal ions, such as carboxylate, hydroxyl, sulphate, phosphate, and amino groups. Depending on the chemical activation method, partial oxidation takes place, and the biomass surface becomes rich in a variety of functional groups whose nature and concentration depend on the method of activation, chemicals used and temperature of preparation

Objectives

Results

Conclusion