Removal Of Uranium Contaminant In Groundwater By Dielectric Material Of PRB

To explore an efficient dielectric material of PRB for removing uranium contaminants in groundwater, the author based on the latest domestic and foreign researches and choosed reduced iron powder(Fe0), Hydroxyapatite(HAP), nanoscale Zero-Valent Iron(nZVI) and the composite material of HAP and nZVI to remove uranium(Ⅵ). We used scanning electron microscopy(SEM), X-ray diffraction(XRD), particle size analysis to research four materials’ characterization. Then the effect factors such as solution pH value, dosages of reactive material, contact time and initial U(Ⅵ) concentration on removal of U(Ⅵ) by the four materials with batch experiments was investigated. In addition, we studied adsorption isotherms and adsorption kinetics for each materials.(1) The reduced iron power with loose structure and uniform particle size, the average particle size was 18.964 μm. When pH value of solution was 4.0, the dosage of reduced iron powder was 1.6 g/L, contact time was 60 min, initial U(Ⅵ) concentration was 10 mg/L, the U(Ⅵ) removal rate and adsorption capacity reached 92.81% and 5.80 mg/g respectively. Langmuir adsorption isotherm model could describe adsorption U(Ⅵ) by reduced iron powder and the maximum adsorption was 26.042 mg/g. Under the conditions of different reaction time, the remove U(Ⅵ) process by reduced iron powder fited pseudosecond-order kinetic equation.(2) The Hydroxyapatite with loose structure and large surface, the average particle size was 30.060 μm. When pH value of solution was 3.0, the dosage of HAP was 1.0 g/L, contact time is 60 min, initial U(Ⅵ) concentration was 10 mg/L, the U(Ⅵ) removal rate and adsorption capacity reached 95.04% and 9.50 mg/g respectively. Both Langmuir and Freundlich adsorption isotherm model could describe adsorption U(Ⅵ) by HAP and the maximum adsorption was 47.847 mg/g. Under the conditions of different reaction time, the remove U(Ⅵ) process by Hydroxyapatite fited pseudo-second-order kinetic equation.(3) The nanoscale Zero-Valent Iron with close particle and smooth surface, but the particle got together and formed a chain, the average particle size was 10.769 μm. When pH value of solution was 4.0, the dosage of nZVI was 1.2 g/L, contact time was 60 min, initial U(Ⅵ) concentration was 10 mg/L, the U(Ⅵ) removal rate and adsorption capacity reached 90.40% and 7.53 mg/g respectively. Langmuir adsorption isotherm model could describe adsorption U(Ⅵ) by nZVI and the maximum adsorption was 31.25 mg/g. Under the conditions of different reaction time, the remove U(Ⅵ) process by nanoscale ZeroValent Iron fited pseudo-second-order kinetic equation.(4) The composite material with fluffy and smooth surface, the average particle size was 20.798 μm. When pH value of solution was 3.0, the dosage of composite material was 1.0 g/L, contact time was 60 min, initial U(Ⅵ) concentration was 10 mg/L, the U(Ⅵ) removal rate and adsorption capacity reached 91.33% and 9.13 mg/g respectively. Langmuir adsorption isotherm model could describe adsorption U( Ⅵ) by composite material and the maximum adsorption was 41.67 mg/g. Under the conditions of different reaction time, the remove U(Ⅵ) process by composite material fited pseudo-second-order kinetic equation.(5) Through research, experimental results show that under relative condition, Hydroxyapatite can remove U(Ⅵ) in aqueous solution effectively. The removal rate is higher than 95%. Moreover, when the reaction reached equilibrium, the adsorption capacity of Hydroxyapatite was better than the other three reaction materials.