Biosorption of Metals and Metalloids

Abstract

Industrial activities such as mining operations, refining of ores and combustion of fuel oils play a relevant role in environmental pollution since their wastes contain high concentrations of toxic metals that can add significant contamination to natural water and other water sources if no decontamination is previously applied. As toxic metals and metalloids, including arsenic, cadmium, lead, mercury, thallium, vanadium, among others, are not biodegradable and tend to accumulate in living organisms, it is necessary to treat the contaminated industrial wastewaters prior to their discharge into the water bodies. There are different remediation techniques that have been developed to solve elemental pollution, but biosorption has arisen as a promising clean–up and low–cost biotechnology. Biosorption is one of the pillars of bioremediation and is governed by a variety of mechanisms, including chemical binding, ion exchange, physisorption, precipitation, and oxide-reduction. This involves operations (e.g. biosorbent reuse, immobilization, direct analysis of sample without destruction) that can be designed to minimize or avoid the use or generation of hazardous substances that have a negative impact on the environment and biota, thus following the concepts of “green chemistry” and promoting the environmental care. Furthermore, it has to be specially considered that the design of a biosorption process and the quality of a biosorbent are normally evaluated from the equilibrium, thermodynamic, and kinetic viewpoints. Therefore, a successful biosorption process can be only developed based on multidisciplinary knowledge that includes physical chemistry, biochemistry and technology, among other fields.

In this chapter, we explain in detail all the aforementioned aspects. State of the art applications of biosorbents for metals and metalloids removal are carefully revised based on a complete analysis of the literature. Thus, it is evidenced in this chapter that the main points to consider regarding biosorption are the type of biomaterial (e.g. bacteria, fungi, algae, plant–derivatives and agricultural wastes, chitin–chitosan based materials) and the presence of a broad set of functional groups on their surface that are effective for the removal of different toxic metals and metalloids. In fact, removal percentages as high as 70–100% can be found in most works reported in the literature, which is demonstrating the excellent performance obtained with biosorbents. Also, biosorbents have evolved with the help of nanotechnology to modern bio–nano–hybrids materials having superlative sorption properties due to their high surface area coming from the nano–materials structures and multifunctional capacity incorporated from the several types of chemical groups of biomaterials. These, as well as other important aspects linked to biosorption are fully covered in the present chapter.