纳米Fe₂O₃和Mn₂O₃及其混合物表面酸碱性质和吸附行为

【作者】 吴震生；

【导师】 孙中溪；

【作者基本信息】 济南大学 ， 无机化学， 2010， 硕士

【摘要】 铁和锰是自然界中常见的变价元素,在沉积环境中带有表面电荷的天然铁锰氧化物和氢氧化物是典型的潜在氧化剂。铁,锰氧化物及氢氧化物矿物是土壤中非常活跃的成分,因为他们对环境变化的敏感性,可以提高许多营养物质的利用率和控制重金属的毒性。用沉淀法制备了Fe₂O₃和Mn₂O₃并对其进行了X-射线衍射（XRD）、比表面测定（BET）、透射电镜（TEM）等表征;并对其在水溶液中的溶解度作了初步分析,发现在Fe₂O₃和Mn₂O₃混合物中Fe₂O₃能使Mn₂O₃更稳定存在;采用自动酸碱滴定法对其表面进行酸碱滴定,利用先进的计算机软件FITEQL模拟计算了平衡常数;试验结果表明实验室制备的纳米Fe₂O₃和Mn₂O₃的表面酸碱常数与其混合物的表面酸碱常数是一种简单的加和关系,但并不是其平均值。然后利用实验室制备的纳米Fe₂O₃和Mn₂O₃作为吸附剂,进行金属离子（Cd2+）的吸附性能的研究,测定了在不同pH值下对金属离子（Cd2+）的吸附的影响,利用先进的计算机软件MEDUSA和WinSGW模拟了溶液组分分布和计算了纳米Fe₂O₃和Mn₂O₃表面吸附重金属离子的平衡常数;并通过表面配合反应平衡常数计算其表面≡XO-上的吸附反应自由能,说明属于化学吸附的范畴。使用Fe₂O₃和Mn₂O₃对As（V）离子作了初步的吸附研究,研究了不同pH值和不同As（V）离子初始浓度对吸附的影响,结果表明Fe₂O₃和Mn₂O₃及其混合物对As（V）离子有很好的吸附效果,可以用来除去废水中的As（V）离子。通过Fe₂O₃和Mn₂O₃对不同As（V）初始浓度的吸附数据得出Fe₂O₃和Mn₂O₃对As（V）的吸附等温线属于Langmuir型,并求得了最大吸附量。并通过Zeta电位分析推断了其吸附后形成的络合物类型。更多还原

【Abstract】 Iron and manganese are common variable valence elements in nature. In the sedimentary environment, the natural Iron and manganese oxides and hydroxides with surface charges is typical of the potential oxidant. Iron and manganese oxides as well as hydroxide minerals are very active constituents in soils because they are sensitive to environmental changes and they could control the availability of many nutrients and the toxicity of heavy metals.Fe₂O₃ and Mn₂O₃ nanoparticles were synthesized by precipitation method. Powder X-ray diffraction （XRD）, and nitrogen adsorption-desorption, transmission electron microscopy （TEM） analysis methods were used to characterize the crystal graphic, structure, morphology and the specific surface area. And we made preliminary analysis about its solubility in aqueous solution, then we found that Iron oxides makes manganese oxides more stable in their mixtures. According to the experimental data of acid base titration of mesoporousα-Fe₂O₃ suspention, using FITEQL computer software and Constant Capacitance Model （CCM）, the protonation and deprotonation constants of Fe₂O₃ and Mn₂O₃ were determined. Base on the acid-base constants the adsorption of heavy metal ions （Cd2+） at the surfaces of Fe₂O₃ and Mn₂O₃ was studied as a function of different pH. The solution components were distributed using computer soft ware MEDUSA and the surface complexation constants of Cd2+ at the surfaces were determined using computer software WinSGW. We calculated the free energies of adsorption reaction through the constants of Fe₂O₃ and Mn₂O₃ which belongs to the scope of chemical adsorption.The adsorption of As（V） at the surfaces of Fe₂O₃ and Mn₂O₃ was studied as a function of different pH and initial concentrations of As（V）. The results showed that Fe₂O₃ and Mn₂O₃ and its mixture have a very strong adsorption capacity for As（V）, which can be used to remove the As（V） ions in waste water. The experimental data from different As（V） initial concentration of the adsorption fitted the Langmuir equation and obtain the maximum adsorption capacity. The type of its adsorption complexes was analysed by testing Zeta potential.更多还原