Dialysis Membrane Assisted Adsorptive Removal Of Trace Rare Earth Ions From Water By Colloidal Graphene Oxide Suspensions

In view of the technological bottleneck in high-efficient separation of trace rare earth ions in wasterwater from Southern China mines, especially nanoadsorbent-derived repollution extensively existing in adsorptive separation technology, a novel route for adsorptive separation of trace rare earth ions has been proposed creatively, which loads grapheme oxide colloid into a dialysis bag to form an adsorption unit based on excellent adsorption capacity of macromolicular grapheme oxide colloid and screening characteristics of dialysis membrane. The dissertation systematically deals with the effects of sorption time, pH, temperature, ion strength, sheet size of graphene oxide on sorption equilibrium, conducts a kinetic and thermodynamic analysis on sorption process, evaluates and regeneration of colloidal graphene oxide suspensions.The results indicated that the maximum sorption capacities of Gd3+, Y3+, Eu3+ and Tb3+ at pH=5.9±0.1,T=303K were 281.03 mg/g, 179.86 mg/g, 267.91 mg/g and265.62 mg/g for micrometer graphene oxide(MGO), and 354.91 mg/g, 340.54 mg/g, 374.32 mg/g and 366.82 mg/g for submicrometer graphene oxide(SMGO), respectively, higher than any other adsorbents reported so far. The pH value of the treated solution is the key factor influencing rare earth ion sorption on graphene oxide. The studies on adsorption thermodynamics and kinetics showed that the adsorption of the above-mentioned rare earth ions on GO was an endothermic, spontaneous and monolayer sorption process, which well fitted the pseudo-second-order model and Langmuir sorption model,The investigation on desorption demonstrated that the desorption of Gd3+、Y3+、Eu3+ and Tb3+ on MGO well fitted the pseudo-second-order desorption model and that the pH value of the treated solution is the key factor affecting the desorption. The maximum desorption rates of Gd3+, Y3+, Eu3+ and Tb3+ on MGO at pH=5.9±0.1,T=303K were 90.00%、92.11%、91.21 and 90.09%, respectively. Significantly, after fourth consecutive sorption–desorption cycle, for Gd3+, 220.23 mg/g, 138.73 mg/g,230.45 mg/g and 216.33 mg/g, and the desorption rates of 85.15%, 74.26%, 76.82% and 75.27%, respectively. In summary, GO is a highly efficient and easily reusable adsorbent with promising application for the enrichment and recovery of lanthanides.More importantly, the combination of colloidal GO suspension with dialysis membrane facilely avoids the re-pollution of the treated solutions, drastically reduces workload in separation and recovery of GO and provides an alternative route for actual application of nanoadsorbents in environmental pollutant removal and valuable resource recovery from wastewater.