International Symposium on
Drylands Ecology and Human Security
Removal of Co and Cd Ions from Aqueous Solutions by Azolla:
Saeid Ghorbanzadeh Mashkani1,* Parisa Tajer Mohammad Ghazvini1, Hossain Ghafourian1, Masoud Ghorbanzadeh Mashkani2, Mohammad Amin Ahmadi1
1 Department of Nuclear Biotechnology, Nuclear Research Center, Atomic Energy Organization of Iran
2 Department of Microbiology, Faculty of Science, Islamic Azad University of Ghom, Iran
The accumulation of heavy metal contaminants in the environment has become a concern due to growing health risks to the public. These contaminants, such as Co and Cd enter the environment through industrial waste, mill tailings, and landfill run off. Exposure to heavy metal contamination has been found to cause kidney damage, liver damage, and anemia in low doses, and in high concentrations, heavy metals can be carcinogenic and teratogenic if not fatal. Although cleanup is necessary to prevent any further discharge of contaminated wastes into the environment, a technology needs to be developed that is cost effective for industry to use. Methods traditionally employed for water remediation consist of removal of heavy metals by filtration, flocculation, activated charcoal, and ion exchange resins. However, because of the high cost of these methods, development of a more cost effective remediation system is necessary. There has been a tremendous amount of attention given to the use of biological systems for removal of heavy metal ions from contaminated areas. Algae, fungi, yeast and bacteria remove heavy metals from wastewaters through functional groups such as ketones, aldehydes, carboxyls on their cell walls. More recently, phytoremediation has emerged as one of the alternative technologies for removing pollutants from the environment. Interest in using plants for environmental remediation is increasing due to their natural capacity to accumulate heavy metals and degrade organic compounds. An Azolla plant is a fern frond consisting of a main stem growing at the surface of the water, with alternate leaves and adventitious roots at regular intervals along the stem. Azolla is found in ponds, ditches, and wetlands of warm temperate and tropical regions throughout the world. In this study we have developed an innovative, patented biological process for the removal of heavy metals from effluents by means of the floating fern, Azolla, suitable for: the removal and possible recovery of Co and Cd. The biosorption capacity of Azolla strongly depends on solution pH, and the maximum Co and Cd sorption capacities of Azolla were obtained at pH 5 and 6, respectively independent of the absence or the presence of increasing concentrations of salt (NaCl). Co and Cd-salt biosorption studies were also performed at this pH values. Equilibrium uptakes of Co and Cd increased with increasing Cr(VI) and Pb(II) concentrations up to 300mg/l for Azolla. Azolla biosorbed 98.5 and 85.6mg/g dry weight of Co and Cd respectively, in 60 min. Uptake of Co and Cd within first 5min of incubation was relatively rapid and the absorption continued slowly there after. The biosorption Co and Cd reached equilibrium within 60 min. Temperature ranging 25-45˚C did not show any significant change in the uptake. An increasing in biomass concentration caused an increase the adsorbed Co and Cd, while specific adsorption decreased. Desorption of Co and Cd from Azolla was completely achieved applying 1mol/l HNO3, and no significant biomass damage took place after 7 sorption–desorption cycles. The maximum Co and Cd uptake was acquired using the small particles of Azolla (0.5mm).