磷酸铁锂/石墨烯复合材料的制备及锂回收应用

Preparation of lithium iron phosphate/graphene composite electrode and its application in lithium recovery

以溶胶−凝胶法制备了磷酸铁锂(LiFePO_(4),简称LFP)。将LFP和胺基化石墨烯(GNs)制成悬浮液,以滴涂法制备了磷酸铁锂和胺基化石墨烯修饰钛网电极(LFP/GNs/Ti)。采用场发射扫描电镜(FE-SEM)和X射线衍射仪(XRD)表征了电极的形貌和微观结构,结果显示:LFP和GNs混合物均匀地分散在钛网电极表面,LFP纳米球颗粒的平均直径为(20±2)nm。以LFP/GNs/Ti电极,采用电化学辅助吸附−脱附法研究了盐溶液中锂离子(Li^(+))的分离行为,考察了pH、电位、时间等因素对Li^(+)分离效果的影响。恒电位静态吸附过程中,LFP/GNs/Ti电极对Li^(+)的吸附符合准二阶动力学模型。在Li^(+)初始浓度75 mg/L、pH 6、25℃、−0.3 V、6 h的条件下,Li^(+)的吸附容量为30.1 mg/g。在循环伏安法脱附过程中,以pH为4的0.5 mol/L NH4Cl盐酸溶液作为脱附液,在25℃、+0.8 V至−0.8 V的范围内扫描300圈,Li+的脱附率可达90%,LFP/GNs/Ti电极得到同步再生。

LiFePO_(4)(LFP)was synthesized by sol–gel method,and then used to prepare a suspension with aminated graphene(GNs).A LFP and GNs modified titanium mesh electrode(LFP/GNs/Ti)was fabricated by drop coating method.The morphology and microstructure of LFP/GNs/Ti composite electrode were characterized by field-emission scanning electron microscopy(FE-SEM)and X-ray diffractometry(XRD).The mixture of LFP and GNs was uniformly dispersed on the surface of the titanium mesh electrode,and the average diameter of LFP nanoparticles was(20±2)nm.The separation behavior of Li^(+) in brine solution at LFP/GNs/Ti electrode was studied by electrochemically assisted adsorption/desorption method.The effects of pH,potential,and time on the recovery of Li^(+) were discussed.In a potentiostatic adsorption process,the adsorption of Li^(+) at LFP/GNS/Ti electrode conformed to the quasi-second order kinetic model.The adsorption capacity for Li^(+) was 30.1 mg/g under the following conditions:initial Li+mass concentration 75 mg/L,temperature 25℃,pH 6,potential−0.3 V,and time 6 h.The desorption was conducted in a 0.5 mol/L NH_(4)Cl/HCl solution at 25℃ and pH 4 by cyclic voltammetric scanning in the potential range of+0.8 V to−0.8 V.The desorption efficiency of Li+reached to 90%within 300 cycles,and then the LFP/GNs/Ti electrode was regenerated.