SORPTION OF AMMONIA NITROGEN ON SUSPENDED SEDIMENTS IN LANZHOU SECTION OF THE YELLOW RIVER, CHINA

To explore the mechanism of water self purification, the adsorption properties of ammonia nitrogen on the suspended sediment with different particle sizes in the Lanzhou section of the Yellow River, China were studied. The effects of sediment amount, concentration of ammonia nitrogen, sediment size and chemical components on the ammonia nitrogen adsorption, were analyzed. The results indicated that the Langmuir model provides a better description of equilibrium adsorption capacity of ammonia nitrogen, and the adsorption kinetics fits well to the pseudo-second-order kinetic model. Sediment amount has a significant effect on the adsorption of ammonia nitrogen, and both the adsorption capacity and equilibrium time have remarkable inverse relationships with the sediment amount. The initial concentration of ammonia nitrogen is positively correlated with ammonia nitrogen adsorption capacity and equilibrium time. In addition, the decrease of sediment size leads to increase in the ability to absorb ammonia, the adsorption capacity and the degree of reaction spontaneity. Moreover, the contents of organic matters, Fe2O3, Al2O3 and MgO in the sediment increase with the decrease in particle size, which has a positive effect on the maximum adsorption capacity of sediment. In summary, the sediment adsorption of ammonia has a positive effect on water self-purification in Lanzhou section of the Yellow River, China.