ABSTRACT
Due to natural sources or human activities, heavy metal ions are found in surface water, wastewater, waste and soils. Attention is being given to the potential health hazard presented by heavy metals in the environment. Various industries use heavy metals due to their technological importance and applications: metal processing, electroplating, electronics and a wide range of chemical processing industries. Biosorption is a physico-chemical mechanism including sorption, surface complexation, ion exchange and entrapment, which is relevant for living and dead biomass as well as derived products. Biosorption capacities of microorganisms for metal ions generally depend on the metal concentration, the pH of the solution, the contact time, the ionic strength and the presence of competitive ions in the solution. The microbially-catalyzed reactions, which occur in the natural sulfur cycle, were integrated in a microbiological process to remove toxic metals from contaminated soils or solid wastes.
