离子交换与吸附

Li_1.6Mn_1.6O₄是一种性能优良的锰系锂离子筛，具有较高的锂离子吸附容量，但鉴于该材料本身为粉状，含锂溶液在其中流动性差、渗透率低，故在工业应用中需对该粉状材料进行造粒、成膜等加工后才能应用。文章以表面改性后的Li_1.6Mn_1.6O₄粉体、苯乙烯和二乙烯苯(聚合基体)和甲苯(致孔剂)为原料，采用悬浮聚合造粒工艺制备得到粒状锰系锂离子筛，研究了甲苯添加量对材料表观形貌以及吸附性能的影响，并对所制样品的结构和吸附性能进行表征。结果显示，以甲苯为致孔剂有助于形成多孔结构，且比表面积与甲苯添加量呈正相关。当甲苯添加量为苯乙烯体积的60%时，所制得样品的比表面积可达261.14 m²·g^-1，远超未加甲苯时所制得样品的比表面积(0.17 m²·g^-1)；但过量甲苯会导致孔洞增大，使得颗粒强度降低、易破碎。将多孔锰系锂离子筛颗粒经酸化转型后进行吸附实验，发现多孔结构的粒状锰系锂离子筛吸附容量最高可达4.76 mg·g^-1，相比于未致孔的对照组提高了92.13%。此外，吸附过程符合Langmuir等温吸附模型和准二级动力学模型，表明对Li⁺的吸附过程属于单层的化学吸附。该多孔粒状锰系锂离子筛具有优异的循环性能，经过30次吸附/解吸循环后，吸附容量保持率达94.37%。

Li_1.6Mn_1.6O₄ is a high-performance manganese-based lithium ion sieve(LIS) with a considerable lithium ion adsorption capacity. Nevertheless, its intrinsic powdery morphology leads to poor fluidity and low permeability of lithium-containing solutions within the material. Consequently, in industrial applications, this powder must undergo processing steps such as granulation and film formation prior to practical use.In this work, granular manganese-based LISs were fabricated via a suspension polymerization granulation method. The raw materials employed included surface-modified Li_1.6Mn_1.6O₄ powder, styrene and divinylbenzene(as the polymer matrix), and toluene(as the porogen). The influence of toluene dosage on the apparent morphology and adsorption performance of the resultant granular LISs was systematically investigated. Granular manganese-based LISs with distinct pore structures were successfully prepared, and their apparent structure and adsorption properties were characterized using relevant analytical techniques. The results indicate that toluene, as a porogen, effectively facilitates the formation of a porous structure in the granular LISs. Moreover, the specific surface area(SSA) of the pores exhibits a positive correlation with the toluene dosage. When the volume of toluene added was 60% of that of styrene, the SSA of the prepared sample reached 261.14 m²·g^-1, which was significantly higher than that of the sample prepared without toluene(0.17 m²·g^-1). However, excessive toluene addition resulted in the enlargement of pore size within the granules, which compromised the mechanical strength of the manganesebased LIS particles and increased their brittleness. After acidification and phase transformation, the porous granular LIS particles were subjected to lithium ion adsorption experiments. It was found that the maximum adsorption capacity of the porous granular LISs reached 4.76 mg·g^-1, representing a 92.13% increase compared to the non-porogen control group. Furthermore, the adsorption process was well-fitted by the Langmuir isothermal adsorption model and the pseudo-second-order kinetic model, suggesting that the Li+ adsorption onto the granular LISs followed a monolayer chemical adsorption mechanism. Additionally, the porous granular manganese-based LISs exhibited excellent cyclic stability: after 30 consecutive adsorption-desorption cycles, the retention rate of the adsorption capacity remained as high as 94.37%.