A Review on Biosorption of Potentially Toxic Metallic Pollutants from Wastewaters by Bacterial Adsorbents

Nowadays potentially toxic metal removal from the environment, particularly wastewater, is moving from the use of conventional techniques to the use of biosorption, which utilizes diverse natural materials of biological basis, including bacteria, fungi, algae and yeast, for the binding and concentration of these metal ions or other pollutants. These biomaterials contain functional groups such as hydroxyl, carboxyl, amido and sulphydryl, which make it feasible for them to attach potentially toxic metal ions from wastewaters. The binding mechanism involved in biosorption process has been found to be quite complex. It consists of several phenomena comprising precipitation, physical adsorption, complexation and ion-exchange. The binding mechanism between the potentially toxic metal ions and these biosorbents will be discussed, including the key functional groups implicated in metal binding process.