Study On The Treatment Of Heavy Metal Wastewater With Sodium Titanate Nano-filler

In recent years,the development of new materials technology provides a new possibility for constructed wetlands to remove heavy metal sewage.Titanium titanate nanofibers have the characteristics of large adsorption capacity and irreversible adsorption.In this paper,a new filler using titanate nanometer is prepared,and a laboratory study on the treatment of heavy metal wastewater by constructed wetland with sodium titanate nano-filler is carried out,which will contribute to solve the problem of the current constructed wetland,such as large area,desorption caused by secondary pollution and other issues.Through laboratory static adsorption experiments,the adsorption process and adsorption capacity of typical heavy metal ions Cu,Pb,Zn,and Cd adsorbed by nano-filler were compared.Adsorption kinetic equations were fitted and isothermal adsorption equations were fitted.The influence of pH on the adsorption of heavy metals by nano-filler was discussed.At the same time,a multivariate competitive adsorption study was carried out to analyze the behavior and mechanism of the treatment of comprehensive heavy metal wastewater.This provides new ideas and references for the application of nano-filler in the treatment of heavy metal wastewater in constructed wetlands.The main findings are as follows:?1?The adsorption process of sodium titanate nano-filler on heavy metals is in accordance with the pseudo second order kinetics equation.The adsorption capacity of the first 30 min can reach about 50%of the equilibrium adsorption capacity.After 6 hours,the adsorption capacity of the unit is about 90%of the equilibrium adsorption capacity.It has the characteristics of"fast adsorption,slow balance".?2?Compared with the traditional zeolite media,the nano-filler has high adsorption performance,witch is 4-12 times of zeolite,and the adsorption process has no adsorption repeated phenomenon.?3?The adsorption of Cu,Pb,Zn and Cd on the nano-filler is mainly chemical adsorption,which can be well fitted by Langumir adsorption model.The adsorption of metal ions on the fillter will be inhibited at pH=2-3,and the best adsorption happens at pH=5-6.When the concentration of ion in the solution is 0-2mmol/L,the maximum adsorption capacity is 1.5²mmol/g when the concentration is 0.3g/L at 25?,pH=5-6.?4?In the single adsorption,the adsorption effect of sodium titanate nano-filler on four heavy metal ions was Pb²⁺>Cu²⁺>Cd²⁺>Zn²⁺,and the maximum unit adsorption capacities were:1.93,1.64,1.63,and 1.55?unit:mmol/g?.When there are many ions in the solution,other competitive ions promote the adsorption of Pb²⁺by nano-filler,while the adsorption of Cu²⁺,Zn²⁺,and Cd²⁺ions in the presence of Pb²⁺will be greatly reduced,and the competitive ability is:Pb>Cu>Zn and Cd.?5?In a certain concentration range,the adsorption capacity of nano-filler for metal ions increases with the initial concentration of the solution.After the maximum equilibrium adsorption capacity is reached,the unit adsorption capacity will decrease with the increasing solution concentration due to the competition between ions.