Removal Of Thallium (?) From Water By Divalent Manganese Enhanced Potassium Ferrate

Thallium is the most stringent element of water quality indicators in China's drinking water standards.The sanitary standard for drinking water GB5749-2006stipulates that the total thallium concentration does not exceed 0.1?g/L.Compared with other heavy metal pollution,the pollution accident is more toxic and more harmful to society.At present potassium ferrate has achieved good results in the oxidation treatment of thallium.However,in view of the high cost and inaccessibility of potassium ferrate,it is particularly important to study a method to reduce the amount of potassium ferrate and improve the removal efficiency of thallium.There are two valence states Tl???and Tl?III?in water,and Tl???is more soluble and harder to remove.Therefore,this study selected Tl??? as the research object.In this paper,a small amount of Mn²⁺is used to enhance the removal of Tl???by potassium ferrate.By comparing the removal rate of Tl???and the particle size change of agglomeration kinetics with potassium ferrate and Mn²⁺-enhanced potassium ferrate.It is proved that the removal of Tl???by Mn²⁺-enhanced potassium ferrate is better,and the removal rate is increased from 58%to 83%.X-ray photoelectron spectroscopy?XPS?analysis,Zeta potential analysis before and after manganese addition,Zeta potential analysis at different pH after manganese addition,scanning electron microscopy-X-ray spectroscopy?SEM-EDS?analysis,FTIR analysis and the removal of Tl???with Mn²⁺-enhanced potassium ferrate in the presence of Na₂SO₃ and Na₂NO₂,these work were did to explore the mechanism of removal of Tl???with Mn²⁺-enhanced potassium ferrate.Under neutral conditions,the in-situ manganese dioxide formed by the addition of divalent manganese to strengthen potassium ferrate has high electronegativity.It can promote the electrostatic adsorption of Tl???onto the surface of the floc,and then replace the hydrogen ions on the surface of the iron-manganese oxide to form the inner layer complex adsorption.At different pH value,the mechanism of Mn²⁺-enhanced potassium ferrate to remove Tl???is different,and the removal effect is optimal under neutral conditions.The effects of ionic strength,Ca²⁺,Mg²⁺,B₄O₇^2-,HPO₄^2-,and humic acid on the removal of Tl???by divalent manganese-enhanced potassium ferrate were also investigated,the application of Mn²⁺-enhanced potassium ferrate to remove Tl???in natural waters was also studied.It was found that ionic strength,Ca²⁺,Mg²⁺,B₄O₇^2-,HPO₄^2-,and humic acid all reduced the removal rate of Tl???in the strengthening system.At high intensity ionic strength,K⁺and Tl???have competition with the binding sites of Fe-Mn oxides;Mg²⁺and Ca²⁺can strengthen the coagulation of new ecological MnO₂ and new ecological Fe?OH?₃,resulting in lower surface area,occupying MnO₂adsorption site and promoting self-decomposition of potassium ferrate.B₄O₇^2-,HPO₄^2-will block the surface-active potential of manganese dioxide and complex with Tl?III?,which makes it difficult to be adsorbed and removed;Humic acid will occupy the surface adsorption site of MnO₂,compete with potassium ferrate oxidant,cause the aggregation efficiency of nMnO₂ to decrease,and complex with Tl?III?,which makes Tl?III?difficult to be adsorbed and removed.In natural water,Mn²⁺can strengthen potassium ferrate to remove strontium,but it is necessary to increase the concentration of potassium ferrate and adjust the ratio of potassium ferrate to divalent manganese.This makes it important to be widely used in practical processes.