Adsorption And Desorption Of Trace Rare Earth Ions In Mine Wastewater By Graphene Oxide Hydrogel Sealed In Dialysis Membrane

Mine wastewater is discharged without any treatment, will not only destroy the local ecological environment, and even damage to human health, Trace rare earth ions in the treatment of mine wastewater by using nanoadsorbent at present. However, nanoadsorbent derived repollution extensively existing in adsorptive separation technology, and mine wastewater containing a large number of NH₄⁺, there may be a competitive adsorption between rare earth ions in the process of adsorption and separation. In order to find a kind of nanoadsorbent which is not affected by the NH₄⁺ in mine wastewater and has high adsorption separation efficiency and no repollution, a novel route for adsorptive separation of trace rare earth ions has been proposed creatively, which loads grapheme oxide hydrogel into a dialysis bag to form an adsorption unit based on excellent adsorption capacity of macromolicular graphene oxide hydrogel and screening characteristics of dialysis membrane. The dissertation systematically deals with adsorption properties of grapheme oxide hydrogel on NH₄⁺ and the effects of NH₄⁺, sorption time, p H, temperature, ion initial concentration on sorption equilibrium, conducts a kinetic and thermodynamic analysis on sorption process, evaluates and regeneration of graphene oxide hydrogel.The results indicated that NH₄⁺ in mine wastewater had no effect on the adsorption performance of rare earth ions;the maximum sorption capacities of La3+, Ce3+, Ho3+ and Er3+ at p H=5.91,T=303K were 232.06 mg/g?246.15 mg/g?277.43 mg/g and 266.90 mg/g for micrometer graphene oxide hydrogel?GOH?, higher than any other adsorbents reported so far. The p H value of the treated solution is the key factor influencing rare earth ion sorption on graphene oxide hydrogel. The studies on adsorption thermodynamics and kinetics showed that the adsorption of the above-mentioned rare earth ions on GOH 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 La3+?Ce3+?Ho3+ and Er3+ on GOH well fitted the pseudo-second-order desorption model and that the p H value of the treated solution is the key factor affecting the desorption. The maximum desorption rates of La3+, Ce3+, Ho3+ and Er3+ on GOH at p H=1.1,T=303K were 88.01%?85.18%?89.51% and 91.42%, respectively. Significantly, after fifth consecutive sorption–desorption cycle, the maximum sorption capacities of La3+, Ce3+, Ho3+ and Er3+ were 196.11 mg/g, 194.01 mg/g?200.91 mg/g and 207.90 mg/g, and the desorption rates were 72.03%?70.91%?74.68% and 75.60%, respectively. In summary, GOH does not adsorb NH₄⁺ and is a highly efficient and easily reusable adsorbent with promising application for the enrichment and recovery of lanthanides.More importantly, the combination of GOH with dialysis membrane facilely avoids the re-pollution of the treated solutions, drastically reduces workload in separation and recovery of GOH and provides an alternative route for actual application of nanoadsorbents in environmental pollutant removal and valuable resource recovery from wastewater.