3 - Macroalgae Biomass as Sorbent for Metal Ions

Abstract

Seaweeds play a key role in the aquatic environment, but over the last years algal blooms have increased on maritime coasts, fouling beaches and threatening tourism. Biosorption has captured scientific interest in the last decades as a possible way to manage biowaste and to develop a cost-effective technology to detoxificate heavy metal–bearing waters and recover the metals. Algae, in their native or modified forms, especially from the brown division, have proven to be good sequestrants for different cationic heavy metals (Pb, Zn, Cr(III), Ni, Cd), although they are not as effective for anionic species such as arsenic and antimony. The present chapter presents the state-of-the-art of the potential use of dead marine macroalgae as a low-cost biosorbent for removal of heavy metals and metalloids from water. Physical and chemical characterization of the algae are reviewed; biosorption mechanisms summarized and the biosorption capacities of some brown, green, and red algae analyzed; studies in continuous mode and using industrial effluents are also covered. The chapter also describes pretreatments reported in literature that can be applied to the seaweeds to enhance their biosorption ability and properties, namely, protonation, saturation with cations, aldehyde treatment, oxidation, encapsulation, and the use of algal waste.