Prepration Of Lanthanum-modified Carbon Nanotube Materials And Study On Adsorptive Phosphorus Removal Efficiency

Water is the source of life.The problem of the biological safety of drinking water has seriously threatened the development of today's society and the survival of humankind.Phosphorus,as an important nutrient,is an essential element for the growth of organisms.The biological stability of drinking water has been raised and concerned since the last century.Controlling the phosphorus content in water is an efficient and easy method to suppress bacterial regeneration in the pipe network.Therefore,if we can control the phosphorus content in drinking water,we can effectively control the biological stability of drinking water quality.There are many methods for removing phosphorus from water,which have different advantages and disadvantages.As a relative ly efficient and economical method,adsorption method has received extensive attention.The core of adsorption phosphorus removal method lies in the choice of adsorbent.Therefore,this study has studied the adsorbent with relatively high adsorption capaci ty,and conducted a series of experimental studies on the adsorption and removal of phosphorus by the adsorbent.In this study,firstly,lanthanum were loaded on the carbon nanotubes by simple and easy wet immersion method The characterization of lanthanum-loaded carbon nanotubes was performed using conventional characterization techniques.The measurements of the lanthanum-loaded carbon nanotubes,such as XPS,XRD,and FTIR,showed that the lanthanum was successfully loaded onto the carbon nanotubes in the form of lanthanum hydroxide during the preparation process.The preliminary study of the removal efficiency of lanthanum-loaded carbon nanotubes show that adsorption of phosphorus on water by lanthanum-loaded carbon nanotubes is suitable for the description of pseudo-secondary adsorption kinetic model,but physical adsorption may occupy relatively more part of the main part of the whole adsorption process under high temperature conditions.The mechanism of adsorption behavior is less affected by pH.Both two adsorption isotherm models are suitable for,and the theoretical adsorption capacity reaches 160 mgP/g.By thermodynamic analysis,it can be indicating that the adsorption reaction process is an exothermal reaction with spontan eous entropy increase.Subsequently,the carbon nanotubes film was prepared by suction filtration.Through single-factor experiments,it was found that among the adsorption conditions,the adsorption time,the concentration of initial phosphorus element and the adsorbent adsorption amount were positively correlated,and the adsorbent dosage was negative correlated.The removal effect of the adsorbent material decreases slowly as the pH value increases first and then decreases rapidly.The maximum adsorption capacity is at pH=5,and can be stabilized at 80 mgP/g when pH=2-8;all four kinds of coexisting anions have a certain inhibitory effect on the removal of phosphorus,of which the inhibition of carbonate ions is the most significant.Finally,experimental studies were carried out on the adsorption efficiency of lanthanum-loaded carbon nanotubes thin films.According to the experimental results of adsorption kinetics,the adsorption of phosphorus on the lanthanumloaded carbon nanotube film has a good correlation with the two adsorption kinetic models at 25 degrees.The pseudo-first-order kinetics fitting correlation coefficient is slightly.High,this is different from the powdered adsorbent.Under the conditions of temperature increase or pH increase,the adsorption of phosphorus on the carbon nanotube film loaded with helium is more suitable to be described by quasi-second order kinetics.Through the adsorption isotherm experimental analysis,the adsorption process of the lanthanum-loaded carbon nanotubes adsorbent is more in line with the Freundlich adsorption isotherm model,and the theoretical saturated adsorption capacity reaches 140 mgP/g.The thermodynamic analysis indicates that the adsorption process is an exothermal reaction with spontaneous entropy increase.Through the characterization of the material before and after adsorption,it was proved that the phosphate is adsorbed on the adsorbent by replacing the-OH group on the surface of the material to form an inner complex.For the low concentration of phosphorus,the lanthanum-loaded carbon nanotubes film can still play a very good adsorption effect.