研究了MnO2离子筛的制备、表征及其提锂性能。通过控制低温水热合成反应条件制备了4种不同晶相的一维纳米MnO2,进一步用浸渍法制备了Li-Mn-O三元氧化物前驱体,并经酸处理后得到对Li^+具有特殊选择性的离子筛。用XRD、吸附等温线、吸附动力学及pH滴定等手段对产物的晶相结构和Li^+吸附性能进行了研究。结果表明,SMO-b和SMO-d离子筛的Li^+平衡吸附量符合Freundlich吸附等温方程。反应物浓度对MnO2不同晶面的生长速率有不同的影响,但(NH4)2SO4对吸附容量并无提高。吸附速率方程符合一级动力学Lagergren方程。MnO2离子筛Li^+的吸附量远远高于Na^+。
The paper presents preparation and characterization of the MnO2 ion sieve for recovering lithium from aqueous media. Different MnO2 polymorphs, produced by low temperature hydrothermal oxidation of Mn2+ by S2O82- with or without (NH4)2SO4 at 393 and 423 K, were employed to prepare 4 MnO2 based ion sieve adsorbents. The structure characteristics, adsorption and ion-exchange properties of the adsorbent were studied by XRD analysis and experimental runs for the Li^+ isotherms, adsorption kinetic data and the effect of initial pH value on the capacity. The capacities of SMO-b and SMO-d adsorbents for Li^+ vs. its equilibrium concentration data were well fitted by the Freundlich adsorption isotherm model. The relative capacity data suggest that (NH4)2SO4 is not necessary for the oxidation. The first order reaction kinetics model is adequate to predict the Li ^+ concentration decay curves of the kinetic runs. The MnO2 based ion sieve adsorbent exhibits an order of magnitude higher capacity for Li^+than for Na^+.