Advances in preconcentration/removal of environmentally relevant heavy metal ions from water and wastewater by sorbents based on polyurethane foam

An increased interest in the removal of heavy metal ions from aqueous media is encountered due to their toxicity and negative impacts on ecosystems, human health and economic activities. A variety of processes may be used for the removal of heavy metal ions from water and wastewater, such as chemical precipitation, ion exchange, adsorption, membrane processes, etc. How- ever, the removal efficiencies of heavy metals by adsorp- tion depend on several factors such as initial loads of heavy metals in the influent, purpose of treatment (drink- ing/industrial water production, wastewater treatment for disposal or recycling), costs of the overall process, and properties and conditions for regeneration of the sorbent materials. In this context, the use of polyurethane foams as heavy metal ion sorbents is of a special interest because they provide versatile applications in heavy metal efflu- ent management. This study reviews relevant published researches that are concerned with new sorbents based on polyurethane foams applied in batch and dynamic systems for separation and/or preconcentration of heavy metal ions in environmental aqueous media. This review is divided into the following sections: synthesis of polyu- rethane foams; physical and chemical properties of polyu- rethane foams; preconcentration of pollutant metal ions from environmental aqueous media by different types of polyurethane foam (untreated, loaded, reacted and com- posite polyurethane foams); the applicability of sorbents based on polyurethane foams for water and wastewater treatment; comparison of sorbents based on polyurethane foam with other sorbents for heavy metal ion removal.