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As one of global pollutants,mercury in the environment can pose risks to human health.To control mercury pollution has attracted great attentions.There are many methods to remove mercury,such as adsorption,chemical precipitation,oxidation/reduction and ion exchange.Carbon nanotubes(CNTs)modified with silver nanoparticles is one of the efficient methods to remove different forms of mercury.However,the conventional chemical synthesis method for silver nanoparticles can cause secondary pollution for the use of toxic chemicals.Thus,it is necessary to develop an eco-friendly and efficient method for synthesis of silver nanomaterials for mercury removal.In our study,we developed a new biosynthesis method for silver nanoparticles.Algae extract was used as reducing agent and capping agent for synthesis.The experimental conditions including reaction time,reaction temperature,and pH were optimized.The formation process of Ag nanoparticles was monitored by UV-Vis spectrophotometer and characterized by TEM.Later on,the composites,carbon nanotubes(CNTs)loaded with silver nanoparticles were prepared and applied to mercury removal.The composites were also characterized by SEM,TEM and XRD.The adsorption properties of the materials for gaseous elemental mercury were investigated.The conditions including amount of adsorbent,initial concentration of mercury,and temperature were investigated.The highest removal efficiency for mercury was 99.3%.The results indicated that the synthesized nanocomposites could be used as an efficient adsorbent for elemental mercury removal in gas phase.