Preparation Of A Phosphate-modified Flower-like α-FeOOH Composite And Its Application For Aqueous U(Ⅵ) Removal

Goethite is a stable and widespread mineral in soil.It has strong adsorption ability and complexation effect on heavy metal ions,which affects the transportation and immobilization of heavy metal in the soil environment.It is significant to study the removal and immobilization of uranium on goethite by using synthetic goethite under the simulation pH conditions of uranium containing aqueous solution and its contaminated sites.To improve the adsorption performance of goethite,Here,the goethite and the modified goethite were synthesized.The effect of removal uranium by adsorption materials was compared in aqueous solution,and the removal mechanism of uranium was discussed respectively.This paper mainly consists of the following contents: The three-dimensional flower-like goethite（TDFLG）was prepared by refluxing precipitation method,the modified three dimensional flower-like goethite（MTDFLG）was prepared by NaH₂PO₄ with dipping method,and the obtained samples were characterized by SEM,EDX,BET and XRD.The effects of adsorption time,sorbent dose,solution pH and initial uranium concentration on the uranium adsorptionbehaviors were investigated using the two materials as adsorbent for the treatment of uranium-containing wastewater.The adsorption kinetic model and the adsorption isotherm model were used to fit the experimental data,and the adsorption mechanism of uranium on these materials was discussed.The conclusions could be obtained as follows:（1）The modification of phosphoric acid has little effect on the morphology of the original goethite,and its flower morphology still exists.The crystallinities of the two materials are not high.The TDFLG and MTDFLG were prepared with large specific surface area（229.96 and 203.17m²/g,respectively）.（2）The results of single factor experiment showed that the adsorption performance of modified flower goethite on uranium was obviously better than that of flower goethite under the same experimental conditions.The optimal was pH = 4,C₀ = 5 mg/L,2 h of the contact time and 0.5 g/L of the solid-liquid ratio,the adsorption rate of the MTDFLG to uranium could reach over 94 %.The reason is that in addition to the ion-exchange and complexation reactions between the hydroxyl of the modified goethite itself and uranyl ion,a ternary complex（≡FePO₄UO₂）was formed between uranium and phosphate modified goethite.（3）TDFLG and MTDFLG followed the Pseudo-second-order kinetic model and the Langmuir adsorption isotherm model,which indicated that uranium adsorption on TDFLG or MTDFLG is mainly based on monolayerchemisorption,and the maximum adsorption capacity of two adsorbents is48.24 mg/g and 112.36 mg/g,respectively.