Study Of Adsorption Treatment And Mechanism Of Prussian Blue Compound On Lead-containing Wastewater

As a highly toxic heavy metal ion,lead pollution and its harm to the environment and human body have aroused great concern.The discharge of lead-containing wastewater is an important way to cause lead pollution in water and soil,and it poses a serious threat to the ecological environment and the safety of human life.Therefore,research on efficient and economical treatment technologies is essential for treating lead-contaminated wastewater.The adsorption has attractive advantages such as low cost,high removal efficiency,and simple operation.It is one of the best methods for treating heavy metal pollution.As the prototype of the early Metal Organic framework?MOF?,Prussian Blue?PB?and its analogs?PBAs?,it is very suitable as a sorbent to remove heavy metal lead ions from wastewater,due to its open frame and three-dimensional mesoporous structure.In this paper,the iron-iron Prussian blue?Fe-Fe PB?and manganese-iron Prussian blue?Mn-Fe PBA?,referred to as KFFC and KMFC were synthesized by liquid precipitation.Comparison of the adsorption effect of two sorbents on Pb???and optimal the structural characterization to further analyze the mechanism of Pb???adsorption by KMFC.At 25?,KMFC synthesized by choosing suitable inorganic ion exchanger and has an adsorption capacity of four times on Pb???,compared with KFFC.Combined with transmission electron microscope?TEM?,scanning electron microscope?SEM?,specific surface area?BET?,X-ray diffractometer?XRD?,X-ray photoelectron spectroscopy?XPS?,Zeta potential analysis,Fourier-transform infrared spectroscopy instrument?FT-IR?and other characterizations,the structure of KMFC and the mechanism of lead adsorption were studied and discussed.The chief conclusions of this study are as follows:?1?The KFFC was synthesized by a precipitation reaction,with potassium ferrocyanide trihydrate?K₄Fe?CN?₆·3H₂O?and ferrous sulfate?Fe SO₄?.Under room temperature conditions with a lead solution concentration of 400 mg/L and a p H of5.0,the maximum adsorption quantity of Pb²⁺by KFFC was achieved 245.31 mg/g,and the adsorption equilibrium time was 180 min.The adsorption process of Pb²⁺onto KFFC conforms to the Langmuir adsorption isotherm model and the quasi-second-order kinetic model.The adsorption process appears as a single layer adsorption on a uniform surface,and the main step to control the reaction rate is chemical adsorption.Thermodynamic parameters indicate that the adsorption is spontaneous and endothermic.?2?The KMFC prepared by a precipitation reaction with potassium ferrocyanide trihydrate?K₄Fe?CN?₆·3H₂O?and manganese chloride tetrahydrate?Mn Cl₂·4H₂O?,which is overall an open large void cubic crystal structure.The specific surface area of KMFC is 42.24 m²/g,and the surface is negatively charged.At room temperature with a lead ion concentration of 800 mg/L and a p H of 5,the maximum adsorption capacity of Pb²⁺onto KMFC was reached 1075.27 mg/g.The adsorption process of lead ions onto KMFC conforms to the Langmuir isotherm adsorption model,which is a monolayer adsorption;at the same time,it also conforms to the quasi-second-order kinetic model,the reaction rate is controlled by the chemical adsorption mechanism.Thermodynamic data analysis shows that the adsorption is a spontaneous and endothermic reaction.The adsorption mechanism of Pb???by KMFC is that the negatively charged on the surface of KMFC and positively charged Pb²⁺undergoes electrostatic adsorption firstly,and then Pb²⁺enters into the large void and cubic lattice structure of KMFC internally exchanges with K⁺to complete the adsorption process.The research in this paper not only provides a new perspective for the design and evolution of heavy metal sorbents,but provides insights into the mechanism of Prussian blue and its analogues for adsorption of heavy metal ions.