Research On The Adsorption Behavior And Mechanism Of Lanthanum Zeolite To Organophosphorus

Lake eutrophication has seriously affected the ecological environment function and social and economic benefits of lakes in China.Phosphorus is a limiting factor of eutrophication.The control of phosphorus in and out of lakes has been studied extensively.A large number of studies have confirmed that organophosphorus occupies a considerable proportion in the total phosphorus pool of lakes.Organophosphates can be converted to orthophosphates through hydrolysis,thus contributing to the algae bloom.Therefore,more attention should be paid to the control of organophosphorus in lakes.Adsorption method has been widely used in phosphorus control in lakes because of its simple,easy to operate and low cost.Lanthanide adsorbents have attracted extensive attention in recent years because of their superior phosphorus removal efficiency and controllable ecological security risks.However,the adsorption of organophosphorus by lanthanide passivators has not been studied.The adsorption behavior and mechanism of adenosine triphosphate(ATP),adenosine monophosphate(AMP)and glycerine phosphate(GP)on the surface of lanthanum zeolite were studied.The effect of humic acid(HA)on the adsorption of organophosphorus by lanthanum zeolite was also studied.The conclusions are as follows:(1)The maximum Langmuir adsorption capacities of lanthanum zeolite for adenosine triphosphate(ATP),adenosine monophosphate(AMP)and glycerine phosphate(GP)were 17.79mgP/L,3.98mgP/L and 7.63mgP/L,respectively.The maximum adsorption capacity of phosphorus compounds on lanthanum zeolite is related to its unit molecular weight and molecular structure.The adsorption rate of lanthanum zeolite on organophosphorus is faster,and the adsorption capacity of ATP,AMP and GP at 0.5h can reach 83%,85%and 73%of the adsorption equilibrium,respectively.Organophosphorus forms an inner ring complex on the surface of lanthanum zeolite,the reaction is less affected by the change of ionic strength,and acidic conditions are conducive to the adsorption of organophosphorus by lanthanum zeolite.Organic acids will compete with organophosphorus for adsorption sites on the surface of lanthanum zeolite.The smaller molecular weight of citric acid was stronger than the larger molecular weight of humic acid.(2)With the adsorption reaction of lanthanum zeolite to organophosphorus,the pH of the solution keeps rising,indicating the occurrence of chemical adsorption process.The changes of XPS La 3d and P 2p fine spectrum before and after adsorption further confirmed the above conclusion,and also indicated that the adsorption of organophosphorus by lanthanum zeolite mainly depended on lanthanum hydroxide component.Raman spectrum analysis results show that the non-phosphate groups in the organophosphorus peak after the reaction shift,proving that the non-phosphate groups in the organophosphorus will interact with lanthanum zeolite,may be an important reason for the relatively low adsorption of organophosphorus.(3)HA can form effective competition for the adsorption of organophosphorus;The adsorption sequence of HA and organophosphorus significantly affected the adsorption capacity and rate of lanthanum zeolite to organophosphorus,and the adsorption of organophosphorus was more strongly inhibited after the pre-adsorption of HA.The adsorption affinity of lanthanum zeolite for the four adsorbents is SRP>>HA>AMP/GP;SRP can replace a large amount of humic acid adsorbed on lanthanum zeolite,but the two organophosphates can not replace the humic acid adsorbed on lanthanum zeolite on a large scale.