Abstract
Many efforts have focused on the adsorption of metals from contaminated water by microbes. Synechococcus PCC7002, a major marine cyanobacteria, is widely applied to remove metals from the ocean’s photic zone. However, its ability to adsorb cesium (Cs) nuclides has received little attention. In this study, the biosorption behavior of Cs(I) from ultrapure distilled water by living Synechococcus PCC7002 was investigated based on kinetic and isotherm studies, and the biosorption mechanism was characterized by Fourier-transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectrometry, and three-dimensional excitation emission matrix fluorescence spectroscopy. Synechococcus PCC7002 showed extremely high tolerance to Cs ions and its minimal inhibitory concentration was 8.6 g/L. Extracellular polymeric substances (EPS) in Synechococcus PCC7002 played a vital role in this tolerance. The biosorption of Cs by Synechococcus PCC7002 conformed to a Freundlich-type isotherm model and pseudo-second-order kinetics. The binding of Cs(I) was primarily attributed to the extracellular proteins in EPS, with the amino, hydroxyl, and phosphate groups on the cell walls contributing to Cs adsorption. The biosorption of Cs involved two mechanisms: Passive adsorption on the cell surface at low Cs concentrations and active intracellular adsorption at high Cs concentrations. The results demonstrate that the behavior and mechanism of Cs adsorption by Synechococcus PCC7002 differ based on the Cs ions concentration.
Highlights
The risks posed by radionuclides in water have attracted considerable attention since the Fukushima Daiichi Nuclear Power Plant in Japan was damaged by an earthquake [1]
To reduce the hazards of heavy metals to cyanobacteria, generally speaking, Extracellular polymeric substances (EPS) first binds to the metal ions; EPS plays a significant role in the resistance of microorganisms to heavy metals [34]
The equilibrium Cs uptake process was well described by the Freundlich model, indicating heterogeneous adsorption with monolayer binding
Summary
The risks posed by radionuclides in water have attracted considerable attention since the Fukushima Daiichi Nuclear Power Plant in Japan was damaged by an earthquake [1]. Radioactive fallout from nuclear plants and the nuclear industry can cause great damage to human health upon entering the environment [2,3]. Previous studies have applied solvent extraction, ion exchange, and chemical precipitation to remove radionuclides from contaminated wastewater. These methods are regarded as inefficient and costly for the removal of Cs [5]. Many efforts have focused on identifying materials (e.g., alum and ferric chloride) for removing Cs from aquatic environments [6]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
