Preparation Of Titanium Dioxide Nanomaterials And The Properties For Thallium Adsorption

Thallium concentration in the natural environment is low,which will not pose a threat to human health.Recently,thallium?Tl?pollution in surface water has frequently occurred,mostly due to the mining and smelting of Tl-containing minerals,which present a serious threat to aquatic ecosystem and human health.Therefore,more and more attention has been paid to the treatment of thallium-containing wastewater.Adsorption is extensively used to removal thallium from wastewater because of its high efficiency,economy and very low secondary pollution.In recent years,various adsorption materials such as activated carbon,biomass,metal oxides,have been applied for the removal of thallium from wastewater.However,reported adsorbents have low Tl?I?adsorption capacities or low chemical stability or need complicated processes to be synthesized,which limits their wide applications.Therefore,it is very essential to develop adsorbents possessing high adsorption capacity,high stability and easy preparation.TiO₂ is widely used as catalyst and adsorbent,due to its high catalytic activity and high stability.Nevertheles,its application in Tl?I?removal is less reported and TiO₂ reported with high crystallinity has low Tl?I?adsorption capacity.Amorphous TiO₂ has high specific surface area and abundant metal hydroxyls,which is probably beneficial for its adsorption for Tl?I?.In this study,different TiO₂ were prepared by ammonia co-precipitation,sodium hydroxide co-precipitation and titanium source with titanium sulfate,and Tl?I?was adsorbed well by TiO₂?1?and TiO₂?2?.To study the adsorption properties of TiO₂?1?and TiO₂?2?under different pH conditions,background ion strength and coexisting ions.XRD,SEM,bet,zeta potential and surface hydroxyl content were used to explore the characteristics of four different titanium dioxide nanomaterials,such as morphology,pore size,specific surface area,isoelectric point and surface hydroxyl content.And analyzed the factors affecting the adsorption of titanium dioxide nanomaterials on Tl?I?.Based on the analysis of XPS,we discussed the before and after Tl?I?adsorption by TiO₂?1?and TiO₂?2?and the adsorption mechanism.The results are as follows:?1?TiO₂?1?and TiO₂?2?had strong adsorption properties for Tl?I?.Under the condition of pH=7.0,the saturated adsorption capacities could reach 301.54mg/L and217.93mg/L,and the removal rates of Tl?I?solution with the initial concentration of30mg/L could reach 94.13%and 93.22%.?2?The adsorption capacity of TiO₂?1?and TiO₂?2?on Tl?I?was greatly affected by the pH of the solution,and increased with the increase of the pH of the solution.Tl?I?has a strong selective adsorption ability under the conditions of higher background ion strength and different coexistence ions.Zn²⁺,Cd²⁺,Mg²⁺,Ca²⁺,K⁺,Ni²⁺at different concentrations?0.1,1.0,10mmol/L?had no effect on Tl?I?adsorption performance of TiO₂?1?under neutral conditions.?3?TiO₂?1?and TiO₂?2?are all amorphous materials.The adsorption and removal mechanism of Tl?I?may be as follows:Tl?I?reacts with hydroxyl group?-OH?on the surface of the material to form O-Tl,which is absorbed on the surface of titanium dioxide in the form of ion exchange.?4?The higher content of hydroxyl on the surface of titanium dioxide and the lower isoelectric point on the surface of the material has a positive effect on the ability of titanium dioxide nanomaterials to absorb Tl?I?.?5?TiO₂?1?and TiO₂?2?can be applied to the Tl?I?polluted water treatment,the Tl?I?in the river has a good adsorption effect.For example,TiO₂?1?can adsorb and remove97.78%Tl?I?in polluted river water.After treatment,the concentration of thallium in river water decreases from 100 g/L to 2.09 g/L.In conclusion,the TiO₂?1?and TiO₂?2?materials studied in this study have good adsorption performance for Tl?I?in water.It has wide application prospect in treatmenting to the thallium-containing water.