University of Tehran

University of Tehran

Adsorption of chromium from wastewater by platanus orientalis leaves


The presence of heavy metals in drinking water can be toxic to consumers; these metals can damage nerves, liver and bones and block functional groups of vital enzymes (Ewan and Pamphlet, 1996). In the recent years, increasing awareness of water pollution and its far reaching effects has prompted concerted efforts towards pollution abatement .Among the different heavy metals from toxic pollutant introduced into natural waters (Donmez and Aksu, 2002). There are two major sources of heavy metals contamination,  astewater metal finishing industries (hexavalent chromium) and tanneries (trivalent chromium). Chromium occurs most frequently as Cr(VI) or Cr(III) in aqueous solutions (Dakikiy et al., 2002). Both valences of chromium are potentially harmful but hexavalent chromium have a grater risk due to its carcinogenic properties (Dakikiy et al., 2002). Hexavalent chromium which is primarily present in the form of chromate(CrO4 2-) and dichromate (Cr2O7 2-), poses significantly higher levels of toxicity than the other valences  states(Sharma and Forester, 1995).The toxicity of hexavalent Chromium, even in small concentrations has been well documented. Since the addition of Chromium ions through industrial waste effluents into natural  bodies of water causes serious environmental disruption, strict wastewater standards have been setup in many countries. In Japan the standard on wastewater quality states that the maximum level permitted in wastewater are 2mg/dm3 for total Cr and 0.05 mg/dm3 for Cr (VI) (Masakazu, 2003). Techniques for removal of heavy metals from industrial wastewater include precipitation, ion exchange, adsorption, electrodialysis and filtration; but these methods have limitations on selective separation and high cost of investment and operation of equipment (Dae et al., 2003).

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