| Thallium（Tl）is a kind of rare and toxic heavy metal element.Plumbum（Pb）is another harmful heavy metal element widely used in industrial production.In recent years,heavy metal pollution in water has become increasingly serious,and thallium and lead pollution incidents have frequently occurred at home and abroad,so their removal technology has attracted much attention.Compared with chemical precipitation method,electrochemical method,ion exchange technology and microbial technology that several kinds of methods to remove the thallium,lead,adsorption method is the most potential practical application of a kind of method,because of its economic efficiency,the craft is simple and not easy to produce pollution,and the adsorption method is the key to develop a new type of economic efficient and stable renewable adsorption material.The adsorption effect of traditional adsorption materials on Tl（I）and Pb（II）in water is better under neutral and alkaline pH conditions,which is determined by the chemical characteristics of thallium and lead cations.And most of the adsorption materials in acidic conditions on the cation adsorption is weak,some materials are poor stability,easy to dissolve metal ions shortcomings.In order to solve the problem of poor adsorption performance of traditional adsorption materials for Tl（I）and Pb（II）at low pH,a new multi-functional adsorption material--Titanium pyrophosphate was developed.The Ti P2O7 material with the best performance was selected by exploring the optimal preparation temperature.The materials were characterized by XRD,TEM,SED-EDS and BET.The adsorption behavior and properties of Tl（I）and Pb（II）by titanium pyrophosphate were analyzed.The adsorption mechanism of Tl（I）and Pb（II）by titanium pyrophosphate was studied.The following research results are obtained:（1）Titanium pyrophosphate prepared at 135℃has the best performance,which is amorphous Ti P2O7.The surface of the material is multi-mesoporous,the aperture range is 2 nm～50 nm,and the specific surface area is 64.4308 m2/g.（2）When pH=7 and 3,the adsorption capacity of 135o C-TiPP on thallium can reach420.72 mg/g and 296.97 mg/g,respectively.The Langmuir model and Freundlich model are more suitable for isothermal curves,respectively.Kinetic results show that the adsorption process of thallium is more suitable to the pseudo-first-order kinetic equation.Its applicable pH range is relatively wide（pH=2～10）;In the coexisting ion experiment,it was found that the material had a high selectivity to thallium,while in the ionic strength experiment,it was found that the background electrolyte had a certain inhibition effect on thallium adsorption,and the inhibition degree increased with the increase of the background electrolyte concentration,which indicated that the adsorption of thallium by this material might have an electrostatic effect.It has good recycling performance and can also treat thallium in acid wastewater in practical application so as to meet the discharge standard.The adsorption mechanism of Tl（Ⅰ）by135℃-TiPP is mainly due to the coordination exchange between Tl（Ⅰ）and-OH in the outer layer of the material surface,resulting in hydroxyl complex reaction.（3）Regardless of pH=7 or pH=3,Freundlich model is more suitable to explain the adsorption behavior of lead at 135℃-TiPP,and the maximum adsorption capacity can reach 1309.28 mg/g and 506.3 mg/g,respectively.The kinetic results show that the adsorption process is more suitable for the pseudo-first-order kinetic equation fitting.In the ionic strength test,it was found that the concentration of the background electrolyte had no effect on the adsorption of lead,and the applicable pH range was relatively wide.In the coexistence ion test,it was found that the selectivity to lead was very high.All these indicated that the adsorption of lead by this material might be mainly caused by the core coordination.The recycling performance is good,and in the actual production application can also be used repeatedly.The mechanism of the high adsorption of Pb on 135℃-TiPP materials is attributed to the coordination exchange reaction between Pb（II）and the-OH in the outer layer of the surface,which is related to the formation of complex complexes（namely core coordination）with the Ti-O bond and the active site of P-O. |
