Biosorption of metal cations and anions.

There are several chemical groups that would attract and sequester the metals in biomass: acetamido groups of chitin, structural polysaccharides of fungi, amino and phosphate groups in nucleic acids, amido, amino, sulphhydryl and carboxyl groups in proteins, hydroxyls in polysaccharide and mainly carboxyls and sulphates in polysaccharides of marine algae that belong to the divisions Phaeophyta, Rhodophyta and Chlorophyta. However, it does not necessarily mean that the presence of some functional group guarantees biosorption, perhaps due to steric, conformational or other barriers.

Biosorption of heavy metals: Methodology example of uranium removal.

Biosorption process for Heavy metal removal.

Advances in Biosorption of Heavy Metals.

It was concluded that biosorption show good performance for the removal of heavy metal. The effect of pH 4.0 to 5.0 of sample was found to be good. the experimental data points for biosorption of lead, cadmium, nickel and zinc. Lead, cadmium and nickel removal capacities of live biomass were higher than those of pretreated biomass obtained at pH 4.0 and 5.0, but lower at pH 6.0. HNO3 proved to be a more effective elutant than CaCl2 and NaCl, with more than 90% elution for Pb2+, Cd2+, Ni2+ and Zn2+, while deionized water exhibited negligible desorption capability.

Alginate properties and heavy metal biosorption by seaweed biomass.

The NaOH-pretreated M. rouxii biomass showed a high adsorption capability for the removal of lead, cadmium, nickel and zinc from aqueous solution. It exhibited good biosorption capacity in bi- or multi-metal ion systems in terms of total adsorption capability. pH was found to be critical in biosorption, with an optimum pH being 6.0 or higher (Brierley et al., 2009). High recovery of biosorbed metal ions could be achieved with acid elution. Caustic regeneration of eluted biomass rehabilitated the metal ion biosorption capacity of the biomass even after five cycles of reuse (Whistler and Daniel, 2005).

Keywords: biological, biosorption, biomass, chemical, heavy metal

Electrodialysis: In this process, the ionic components (heavy metals) are separated through the use of semi-permeable ion­selective membranes. Application of an electrical potential between the two electrodes causes a migration of cations and anions towards respective electrodes. Because of the alternate spacing of cation and anion permeable membranes, cells of concentrated and dilute salts are formed. The disadvantage is the formation of metal hydroxides, which clog the membrane.

(1995), Adsorption of heavy metals from waste streams by peat.

Ultrafiltration: They are pressure driven membrane operations that use porous membranes for the removal of heavy metals. The main disadvantage of this process is the generation of sludge.

Phd Thesis On Biosorption Of Heavy Metals.

In the (a)– (d) show the experimental data points for biosorption of lead, cadmium, nickel and zinc. Lead, cadmium and nickel removal capacities of live biomass were higher than those of pretreated biomass obtained at pH 4.0 and 5.0, but lower at pH 6.0. For zinc, removal capacity of live biomass was higher than that of pretreated biomass at pH 4.0, but lower than those obtained at pH 5.0 and 6.0 (Tobin and Roux, 2008). The higher adsorption of the live biomass within some pH range might be explained by the fact that biosorption of metal ions on live biomass is due to surface binding followed by intracellular uptake. The intracellular uptake could account for a substantial part in total uptake for some fungal stains of live biomass, while the biosorption of metal ions on dead biomass is achieved via only surface and wall binding, which is non-metabolic. This surface binding involves specific chemical sites or functional groups on the cell wall, performance of which is affected by pH and other ions. This may explain why biosorption capacity of the dead NaOH-pretreated biomass exceeded that of live biomass for certain pH values. Biosorption data for all the four metal ions at pH 4.0 were not described by both models as biosorption capacity at pH 4.0 increased with a decrease in final equilibrium concentration, which is contrary to the condition for favorable adsorption. The Langmuir model was able to describe the experimental data for biosorption of all metal ions at pH 5.0 by live biomass and only Pb ion by pretreated biomass at pH 5.0 and 6.0 (Huang et al., 2010). The Freundlich model explained the data better for biosorption of Cd, Ni and Zn by pretreated biomass at pH 6.0. It was also observed that the final pH of the reaction mixture using live biomass was higher than the initial pH values. This is due to the growth property of M. rouxii which, under aerobic condition, tends to neutralize the medium with pH less than 7.0. Even though no substrate was added to the reaction mixture in the experiment, the biomass was still active to some extent, possibly due to endogenous respiration.