Effect of adsorption materials on adsorption-desorption of ammonia-nitrogen in riparian sediments in Lanzhou section of the Yellow River
The use of in-situ cover technology can effectively enhance the adsorption of land-based pollutants by riparian sediment and effectively control the release of endogenous pollutants in sediments.In this study,zeolite,concrete slag,and activated carbon were used as representatives of cover materials(inorganic/activated),combined with BET,SEM-EDS,FTIR,XRD,and other characterization means,to comparatively analyze the ammonia nitrogen adsorption effect and mechanism of the cover materials through adsorption kinetic and thermodynamic experiments,mixed experiments and in-situ covering experiments,the effect of the materials on the adsorption and desorption of ammonia nitrogen in the sediment of the riparian zone was also studied.The results showed that the adsorption kinetics of ammonia nitrogen in 20 mg·L-1 ammonia nitrogen solution on the three materials were following:zeolite and biochar could reach the adsorption-desorption equilibrium in 180 min,while concrete slag took 720 min.With the increase of the ambient temperature,the adsorption capacity of the material increased,and the theoretical adsorption value of zeolite was the largest.The adsorption of ammonia nitrogen on the three materials was a spontaneous endothermic process,and the physical adsorption mainly occurred on activated carbon,while the chemical adsorption adsorption also accompanied on zeolite and concrete slag.The results of characterization analysis showed that the hydroxyl functional groups of zeolite and concrete slag could form hydrogen bonds with ammonia nitrogen or produce electrostatic attraction during the adsorption of ammonia nitrogen,which was conducive to the adsorption of ammonia nitrogen,of which the silica-oxygen and aluminum-oxygen bonding functional groups of concrete slag also took part in the adsorption of ammonia nitrogen.After adsorption,no changes happened in the crystal structure of zeolite,but some changes appeared on the surface structure of concrete slag.The results of the mixed adsorption/release experiments showed that with comparison to the control experimental group with no material addition,the adsorption efficiencies of ammonia nitrogen in overlying water with an initial concentration of 20 mg·L-1 increased by 23.04％,9.41％,and 15.72％after the addition of zeolite,concrete slag,and activated carbon to the sediment and 12 h absorption,respectively.However,there were differences in the release control of endogenous ammonia nitrogen from the sediments after the three materials were added to the sediments,the release control effects of ammonia nitrogen from the overlying water were 6.24％and 0.80％for the addition of zeolite and activated carbon groups,respectively,while the addition of concrete slag group increased the release of ammonia nitrogen from the sediments.Through comprehensive comparison,the best effect of adsorption ammonia nitrogen was zeolite,then was activated carbon,and the worst effect was concrete slag.Further in-situ covering experiments were carried out,and the results showed that zeolite as in-situ covering material could increase the adsorption efficiency of ammonia nitrogen by about 21.58％,and the risk of induced release of ammonia nitrogen from sediment was low,it can be used as in-situ covering material for non-point source pollution control in the riparian zone of Lanzhou section of the Yellow River.
万方数据
维普
