| Popis: |
Spinel type lithium manganese oxides (LMOs) are promising adsorption materials for selective recovery of lithium from salty brines. In this work a lithium-ion sieve material, H$_{1.6}$Mn$_{1.6}$O$_{4}$, derived from Li$_{1.6}$Mn$_{1.6}$O$_{4}$4, a spinel type LMO, was successfully prepared via hydrothermal synthesis. This lithium-ion sieve, H$_{1.6}$Mn$_{1.6}$O$_{4}$, was then used in laboratory tests to adsorb Li+ from a generic LiCl solution and geothermal brine from Bruchsal geothermal power plant. Desorption experiments were performed with the following desorption solutions: ammonium peroxydisulfate ((NH$_{4}$)$_{2}$S$_{2}$O$_{8}$), sodium peroxydisulfate (Na$_{2}$S$_{2}$O$_{8}$), acetic acid (CH$_{3}$COOH), sulfuric acid (H$_{2}$SO$_{4}$), carbonic acid (H$_{2}$CO$_{3}$), ascorbic (C$_{6}$H$_{8}$O$_{6}$) and hydrochloric acid (HCl). The results showed that C$_{6}$H$_{8}$O$_{6}$ led to adsorbent destruction and only small amount of lithium was desorbed with H$_{2}$CO$_{3}$. CH$_{3}$COOH and (NH$_{4}$)$_{2}$S$_{2}$O$_{8}$ showed the best desorption performance with high lithium recovery and low Mn dissolution. The kinetic experiments indicate that more than 90% of equilibrium was reached after 4 hours. A decline in the adsorption/desorption capacity was measured for all desorption agents after eight cycles in the long-term experiments. These long-term tests revealed that higher lithium recovery in desorption with HCl and CH$_{3}$COOH was achieved compared to (NH$_{4}$)$_{2}$S$_{2}$O$_{8}$. On the other hand, the use of CH$_{3}$COOH and (NH$_{4}$)$_{2}$S$_{2}$O$_{8}$ seems to be advantageous to HCl because of lower Mn dissolution. According to the XRD results, the spinel structure of the treated adsorbents was preserved, but a weakening of the peak intensity was observed. Analyzing the adsorbent composition after eight cycles, an accumulation of competing ions was observed. This was especially remarkable when acetic acid was used. |
