ABSTRACT
Metals are ubiquitous in our environment, and humans have been using them for thousands of years from the development of metal mining and smelting techniques, increasing metal distribution. Zinc is a common trace metal in natural waters; and it is also essential for the proper growth and development of humans, animals, and plants. Several treatment techniques have been used and developed over the years to remove dissolved metals from wastewaters. The most conventional technologies are based on chemical precipitation, adsorption, coagulation/flotation, sedimentation, filtration, membrane processes, electrochemical techniques, ion-exchange, and chemical reactions. Although these methods are simple and relatively cheap, most of them present some disadvantages such as a difficult separation of the solid, the need of an adequate disposal of the resulting toxic sludge, and the ineffectiveness for low metal concentration as in industrial wastewaters. The presence of soluble ligands in industrial wastes directly influences Zn(II) availability and its consequent interaction with the sorbent surface. Zn(II) can be efficiently removed by biosorption processes using both mineral and microbiological matrices as sorbents. The implementation of industrial-scale treatments using biosorption techniques will still require a deeper analysis to make them commercially viable, not discarding the combination with other technologies.
