Bioremediation of Toxic Heavy Metals from Metal Treated Samples Using the Cyanobacterium, Arthrospira maxima

The various stages involved in mining precious metals cause the creation of a number of hazardous byproducts, most of which are toxic to humans, animals and the environment. These waste products fall into two major categories: contaminated mine water and solid mine waste. Both categories involve the accumulation of heavy metal waste. Due to the financial investment involved in cleaning these sites of heavy metal waste, inexpensive novel procedures must be developed to eliminate these toxic byproducts. One such method includes the process of bioremediation by cyanobacteria. Specifically, the cyanobacteria, Arthrospira maxima and/or platensis, commonly called Spirulina. The ability to adsorb or absorb several metals simultaneously would make Spirulina an ideal candidate for bioremediation of heavy metals. Most metals left behind in contaminated sites are bivalent metals. Thus, this study examined the binding of bivalent heavy metals, such as Fe²+, Zn²+, Cu²+, Cd²+ and Pb²+ by the cyanobacterium, Arthrospira maxima, using Fourier Transform Infrared Spectroscopy (FTIR) and Atomic Absorption Spectroscopy (AAS). Initial concentrations of 0.01 M for individual and multi-metal were used for FTIR and AAS analysis. All FTIR data showed differences in energy levels with metal treatments compared to non-treated Spirulina at 30 minutes and two hours of treatment time. All metals showed similar peaks for both time points, with the exception of Cu²+, which showed an additional peak at 1449 cm-¹ two hours after treatment. Percent binding of metals was calculated by using the amount of metal concentration left in the solution compared to basal concentrations. The AAS data revealed that Fe²+ ions showed the highest binding capability with individual and multi-metal treatment. These results suggested that Spirulina was capable of binding heavy metals in both individual and multi-metal solutions. Calculating percent binding of metal ions to the cell surface of Spirulina showed that Spirulina potentially has a high binding capacity for the metals tested. This study showed that Spirulina could potentially be utilized as a bioremediation agent in heavy metal toxic contaminated solutions. The focus of this study applied FTIR to measure the adsorption properties of single and mixed heavy metal in vitro and AAS to confirm results by FTIR. The emphasis of this study was to: (i) analyze the metal adsorption capacity of Spirulina, (ii) adequately understand adsorption properties of Spirulina, (iii) and develop better models for predicting metal adsorption from contaminated environments.