Preparation Of LiAlFe-LDHs/Graphene/Sodium Alginate Composite Hydrogel And Its Adsorption Performance For Lithium

An iron-doped lithium aluminum layered double hydroxide/graphene/sodium alginate hydrogel composite material（LiAlFe-LDHs/GBs）was prepared by ultrasonic-assisted precipitation and one-step thermal polymerization reduction methods.Field emission scanning electron microscope（FE-SEM）,X-ray diffractometer（XRD）,Fourier transform infrared spectroscopy（FT-IR）,X-ray photoelectron spectroscopy（XPS）,Thermogravimetric-differential scanning calorime method（TG-DSC）and material universal testing machine were used to characterize the morphology,composition,structure,stability and mechanical properties.The results showed that the flower-like LiAlFe-LDHs were uniformly distributed on the three-dimensional network of GBs.The low doping of Fe³⁺could improve the stability of Li Al-LDHs.The introduction of graphene oxide（GO）could enhance the mechanical strength of GBs.The swelling degree of LiAlFe-LDHs/GBs was always maintained at 100%-250%in acidic and alkaline solution.It illustrated that the present LiAlFe-LDHs/GBs could be used the recovery of Li⁺with excellent stability.The present LiAlFe-LDHs/GBs composite was used to the recovery of lithium under different conditions.The effects of different iron doping,p H,time,temperature,Li⁺initial concentration and coexisting cations were investigated,respectively.In the static adsorption experiment,the adsorption capacity Al:Fe rate of 7:1 was the best.The adsorption was a spontaneous endothermic reaction.The adsorption process conformed to the pseudo-second-order kinetic model with Langmuir isotherm adsorption model.The maximum theoretical adsorption capacity was 8.67 mg·g^-1at p H 7.0,45℃and 12 h.The desorption efficiency could reach 65%after 12 h only using water as an eluent.Moreover,LiAlFe-LDHs/GBs showed better selective adsorption towards the recovery of Li⁺under the interference of Na⁺,K⁺,Ca²⁺,Mg²⁺.The adsorption capacity was more than 5.5 mg·g^-1 after continuous 5 times of the Li⁺recovery,it illustrated that resulting LiAlFe-LDHs/GBs showed good regeneration stability.