MnO2/FeOOH复合材料对水中U(Ⅵ)的去除及机理试验研究

采用化学沉积法制备了二氧化锰/羟基氧化铁(MnO2/FeOOH)复合材料,并将其用于吸附去除水中的放射性重金属铀。通过静态吸附试验,考察了Fe/Mn物质的量比、pH值、吸附时间和干扰离子等因素对MnO2/FeOOH吸附U(Ⅵ)效果的影响,利用扫描电镜-能谱分析(SEM-EDS)、X射线衍射(XRD)、拉曼光谱(Raman)、红外光谱(FT-IR)和X射线光电子能谱(XPS)对材料结构和形貌进行表征,并分析其吸附机理。结果表明,在投加量为150 mg/L、温度为30℃、U(Ⅵ)初始质量浓度为10 mg/L、pH值为5、Fe/Mn物质的量比为1/2及吸附时间为120 min的条件下,MnO₂/FeOOH对U(Ⅵ)的去除率最大可达97.7%,且pH值对铀去除效果的影响最为明显。MnO₂/FeOOH对U(Ⅵ)吸附动力学符合准二级动力学模型,吸附等温线均能符合Langmuir和Freundlich模型,且最大吸附容量达260.34 mg/g。干扰离子试验表明,SO₄^2-、CO₃^2-和Fe³⁺对MnO₂/FeOOH吸附U (VI)几乎没有影响,而Ca²⁺和Cu²⁺具有明显的抑制作用,且抑制随浓度的增大而增强。FTIR和XPS分析表明MnO2/FeOOH对U(Ⅵ)的主要作用机制为表面羟基、Mn-O与铀的配位作用。因此,MnO2/FeOOH可作为一种潜在的铀吸附材料。

Adsorption of U(Ⅵ)fromaqueous so-lution by composite material known as MnO2/FeOOH and mechanism con-cerned

The purpose of this paper is to synthesize a low-cost,environmentally friendly and efficient adsorbent for adsorption of the radioactive uranium in the aqueous solution.For the said purpose,we have been trying to take some familiar raw materials,say,KMnO₄,MnSO₄ and FeCl₃ to prepare for manganese dioxide/hydroxyl oxidize iron composite materials (MnO₂/FeOOH) through a simple chemical deposition method.To achieve the purpose,through the static adsorption experiments,we have done an investigation of the effects of the Fe/Mn molar ratio,the p H value,the reaction time,the interfering ions and some other factors on the adsorption of uranium by MnO2/FeOOH.The structure and morphology of the adsorbent we have adopted can be assessed and judged by way of scanning the electronic microscopy,such as the energy dispersive spectrometer(SEM-EDS),X-ray diffraction (XRD),Raman spectroscopy(Raman),Fourier Transform infrared spectroscopy (FT-IR),and X-ray photoelectron spectroscopy (XPS).In addition,we have also analyzed the adsorption mechanism of U (VI) by MnO₂/FeOOH,which can be expected to provide us for a theoretical basis of its application to the practical sewage treatment.The experimental results show that,when the temperature reaches 30℃,the dosage would be 150 mg/L.And,at the situation,the Fe/Mn molar ratio would turn to be 1 to 2.And,the initial U(VI) mass concentration rate may turn to be 10 mg/L at pH=5 for 120 min.In such a case,the maximum removal efficiency of MnO₂/FeOOH for U(VI) can be made so high up to 97.7%,with the effect of p H on the uranium removal being the best.Besides,the adsorption kinetics of MnO2/Fe OOH for U(Ⅵ) should be getting to conform to the quasi-second-order kinetic model,whereas the adsorption isotherms can be made to be integrated to the Langmuir and Freundlich models,with the maximum adsorption capacity being 260.34 mg/g.Moreover,the interfering ions experiment can also show that the Fe³⁺,SO₄^2- and CO₃^2- have almost dissipate their own impacts on the adsorption of U(VI) on MnO₂/Fe OOH,whereas Ca²⁺ and Cu²⁺ can produce obvious inhibitory effects,which enhances with the increase of their concentration.And,the FTIR and XPS analysis can also indicate that the adsorption mechanism of U(VI) on MnO2/FeOOH is mainly due to the coordination among the surface hydroxyl groups,the Mn—O bonds and the U(VI).Thus,eventually,comparing the U(VI) adsorption effect of MnO2/FeOOH with other adsorbents,it can be concluded that it is a very promising adsorbent for U(VI) adsorption in the water bodies.