Metal Ion Binding by Biomass Derived From Nonliving Algae, Lichens, Water Hyacinth Root and Sphagnum Moss
Many types of microorganisms are known to strongly bind metal ions under certain conditions.1–8 Higher plants have also been studied.9 Although several potential binding groups are thought to exist on the complex cell wall structures of proteins and polys
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Metal Ion Binding by Biomass Derived From Nonliving Algae, Lichens, Water Hyacintli Root and Sphagnum Moss Gerald J. Ramelow, Hua Yao and Wei Zhuang
Introduction
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any types of microorganisms are known to strongly bind metal ions under certain conditions.1-8 Higher plants have also been studied.9 Although several potential binding groups are thought to exist on the complex cell wall structures of proteins and polysaccharides, binding is thought to involve primarily COOH groups at pH values less than 2,1° while diamine groups may be involved at pHs greater than 6. 11 Thus, binding of most metal ions is very pH dependent.12 Generally, optimum binding is observed at a pH of around 5. Little binding is seen below pH values of 2 for most metal ions, but gold (in the form of the AuCI4- ion) usually binds most strongly at a pH of 2. Darnall and coworkers found that certain algae were able to bind many metals, and especially precious metals such as gold, to a high degree. 13,1 4 Some metals such as silver and mercury seem to be less affected by pH than other metals. The metal binding properties of algae and other microorgansims have been exploited by immobilizing biomass in inert polymeric materials such as silica gel,13 styrene divinylbenzene15 and polysulfone.16 Thus, it might be possible to prepare adsorbent materials by immobilizing biomass in inert supports and use the sorbents thus prepared to either concentrate metal from aqueous streams or remove potentially harmful metal ions from waste streams. In order to better utilize the metal-binding properties of microoganisms for practical purposes, it is important to: 1) survey the metal-binding properties of a wide variety of organisms to assess both the degree of binding of each metal by each organism with the aim of selecting eventually the organisms with the maximum ability to bind certain metals; 2) observe differences in metal-binding behavior Wastewater Treatment with Algae, edited by Yuk-Shan Wong and Nora F.Y. Tam. Springer - Verlag and Landes Bioscience 1998.
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Wastewater Treatement with Algae
between organisms with the ultimate aim of completely understanding the nature of the metal binding process; and 3) enhance the natural metal binding of biomass types by subjecting them to chemical and physical pretreatments. Marine and freshwater algae are among the organisms that have been widely studied for metal-binding properties. Kuyucak and Volesky made a survey of several marine algae for ability to bind cobale7 and gold.18 They found marked differences between algal species in their metal binding powers. living algal specimens have been used as monitors of marine pollution by metalS.19,20 However, the nature of the metal-binding process is not well understood. An understanding of metal binding by marine micro and macro algae is important first of all to elucidate the chemistry of dissolved metals and relationships between dissolved metals in the sea and marine algae. It has been found that nonliving biomass can also bind metals very efficiently. In fact
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