Experimental simulation of urea adsorption on sediments in different sea areas, China

Typical sea areas of Bohai Sea, Yellow Sea and East China Sea were selected, and the sediments were collected to simulate experiment on adsorption and desorption of urea. The Freundlich adsorption model and the Henry adsorption model were used to analyze the thermodynamic properties of urea adsorption on different sediment surfaces. The effect of temperature, particle size and organic matter content on the adsorption of urea on the surface of sediments was studied. The results showed that three typical stages, which were quick adsorption stage(0-5 h), slow adsorption stage (5-12 h) and equilibrium stage(after 12 h), were obviously showed in adsorption and desorption curves of urea on sediments. When the urea concentration is low, the sediment desorbs and releases urea, and the sediment adsorbs the urea in the overlying water when the urea concentration gradually increases. The adsorption capacity of urea from strong to weak is the Bohai Sea, East China Sea and Yellow Sea, which may be related to the types of sediments. The Freundlich equation and the Henry equation can accurately simulate the adsorption of urea by sediments. Temperature, particle size and organic matter content all affect the adsorption of urea on the sediments. With the increase of temperature, the adsorption of urea on the sediments becomes smaller. The smaller the particle size of sediments and the higher the organic matter content, the stronger the adsorption capacity. Therefore, when revealing the environmental behavior of urea on the sediment surface, it is necessary to fully consider the influence of the above factors.