Study On The Preparation Of Fe-Ce@CG Composite And Its Fluoride Removal Performance

Fluorine content of groundwater exceeding the standard in North China and Northwest China is the most significant,which seriously hinders the improvement of people's quality of life in these areas.Therefore,it is necessary to study effective methods of defluorination in drinking water.Due to its high removal efficiency,easy operation and great economic benefits,the adsorption method emerges among many defluorination methods and is considered to be the most potential defluorination technology at present.Previous studies have found that bimetallic composite oxides have a better fluorine removal effect than single metal oxides,but the metal oxides are in the form of fine powder under normal conditions,and have the disadvantages of easily agglomerating during the reaction and difficultly recycling.In this study,cellulose and graphene oxide containing a large number of active functional groups were combined to form a carrier(CG),and a bimetallic oxide was loaded to prepare the Fe-Ce@CG composite to solve the above problems.It provides a new idea for the removal of fluorine in water.The research content and main results are as follows:(1)The Fe-Ce@CG composite was prepared by the coprecipitation method and characterized.The results showed that the specific surface area and pore size of the Fe-Ce@CG composite reduced significantly compared with those of CG composites due to distribution of metal oxides.The results of EDS demonstrated that Fe and Ce were successfully loaded on the carrier,and the atomic ratio of Ce-Fe was 1.2:1.Through electron microscopy,it can be seen that the surface of the Fe-Ce@CG composite is uneven,with short and cluster-like protruding structures,and the pore distribution is relatively uniform.There are multi-layers of thin lamellar structure with hollow slender holes,and attached with Fe and Ce oxides with a diameter of approximately 50 nm in the middle.(2)Based on a series of experiments,the influence of various factors on the adsorption effect was explored.It can be shown that the adsorption effect reached the best with 1.0 g/L of Fe-Ce@CG dosage and 3.0 of p H value when the fluoride ion concentration is 10 mg/L in fluoride containing water,the adsorption capacity is 9.2 mg/g,when the p H value is 7,the adsorption capacity is 6.8 mg/g.Because the electrostatic attraction caused by protonation causes the adsorption capacity of the adsorbent under acidic conditions to be greater than that under alkaline and neutral conditions.Anions inhibit the adsorption of fluoride ions,and SO₄^2-,HCO₃^-,and PO₄^3-inhibit the adsorption of fluoride ions more obviously and their effects increase successively.(3)The Fe-Ce@CG composite has excellent regeneration performance and still reaches80%of the adsorption capacity after four time regenerations when using 5 wt%Na OH solution as the desorption agent.The stability of the Fe-Ce@CG composite is great,and the metal leaching concentration under different p H conditions is less than 8?g/L.The defluorination effect of well water collected from certain village of Xi'an by Fe-Ce@CG was remarkable,and after treatment,the fluoride concentration of the well water were up to the national limit standard.It can be seen that the adsorption material used has a good application prospect.(4)The Fe-Ce@CG composite has a higher degree of fitting with the pseudo-second-order kinetic model,and the adsorption process is mainly chemical adsorption;it has a higher degree of fitting with the Freundlich model,and the adsorption process is multi-layer adsorption;the?G⁰fitted by adsorption thermodynamics is less than 0,?H⁰and?S⁰are both greater than 0.The adsorption reaction is a spontaneous endothermic reaction,and the adsorbent has a stronger attraction for fluoride ions.(5)Through the comparative analysis of the XRD,FT-IR,SEM and EDS characterization results of the Fe-Ce@CG composite before and after adsorption,the possible defluorination reaction mechanism of the Fe-Ce@CG composite was proposed.In the range of p H 2-6,the reaction mechanism is ligand exchange and electrostatic attraction.In the range of p H 7-12,the reaction mechanism is ligand exchange,and Ce(?)plays a major role in ligand exchange.