Biomass-derived biosorbents for metal ions sequestration: Adsorbent modification and activation methods and adsorbent regeneration

Heavy metals released from industrial activities pose a significant threat to the environment and public health due to their reported toxicity even at trace levels. Although there are several available methods to treat or remove heavy metals from water and wastewater, the research focuses on development of technological solutions which sound environmental friendly and economically feasible, able to reduce the costs and maximize the efficiency. In this framework, the biosorption process, which uses cheap and non-pollutant materials, may be considered as an alternative, viable and promising, technology for heavy metal and metalloid ions sequestration and ultimately removal technology in the waste water treatment. However, there is as yet little data on full-scale applications for the design and testing of adsorption units using single biosorbents and their combinations to sequester heavy metal ions from multi-metal systems. Immediate research and development is hence earnestly required in this specific direction to further make progress this blooming technology and widen its scope of application to real situations needing heavy metal pollution remediation. This review provides a comprehensive appraisal of the equilibrium modeling of a number of biosorption processes as well as the structural, chemical and morphological modifications and activation of biosorbents. Further the relative merits of the methods used to recover sequestered heavy metal ions and regenerate biosorbents through desorption routes and their future applications are discussed.