Table 5.
Technologies Directly Considered for Extraction of Valuable Metals from Saline Aqueous Sources.
| Technology | Target Metals | Limiting Factor/Barrier/Gap | References |
|---|---|---|---|
| Selective Capacitive Deionization (CDI) | Lithium, Uranium, Cesium | CDI Electrode Selectivity and Capacity | 58 |
| Selective Solvent Extraction | Lithium | Low Recovery, Alterative Solvents | 59 |
| Biosurfactant-Ligand Complexation | REEs, Uranium | Low Selectivity Among REEs | 60,61 |
| Ionic liquids (ILs) Extraction | REEs | IL Extraction Mechanism, Functionality of ILs | 62 |
| Specific Ion Exchange (IX) Resins | Lithium | Presence of Interfering Cations; Incomplete IX Regeneration | 63 |
| Fractionation Crystallization Process | Magnesium | Mg Salt Product Purity | 64 |
| Polymeric Adsorbents | Uranium | Decreased Capacity with Increasing Desorption Cycles | 65 |
| Chelating Resins and Membrane Adsorbers | Copper, Cobalt, Platinum, Palladium, Silver, Gold, Uranium | Expense of Dendrimers as Chelating Agents | 36 |
| Polymeric Adsorbent | Uranium | Significant Impact of Capacity Degradation on Cost | 66 |
| Carbon Nanotube-Iron Oxide Adsorbent | Cobalt | Reduced Capacity by Background Organic Matter | 67 |
| Functionalized Adsorbents | Europium | Competition by Divalent Cations | 49 |
| Magnetic and Functionalized Nanoparticle Sorbents | Uranium | Limited Work Done on Desorption | 68 |
| Selective Sorbents and Exchangers | Cesium, Rubidium, Lithium, Uranium | Constituent- and Sorbent-Specific Capacity | 69 |
| Bio-Electrochemical Systems (BES) | Chromium, Selenium | Application of BES to metalloids (chromate, selenate) | 70 |
| Membrane Crystallization (MCr) | Barium, Strontium, Magnesium, Lithium, Manganese, Copper | Requires NF Reject Stream from SWRO Brine | 71 |
| Nanofiltration (NF) Fractionation of Multi- and Poly-Valent Cations | Lithium versus Magnesium | Fate of Non-Targeted Mono- and Poly-Valent Ions | 72 |
| Bipolar Membranes | Lithium | Improved Membrane Performance | 73 |