Table 3.
Adsorption mechanisms for NRFX removal (NRFX pKa1 = 6.22 and pKa2 = 8.51).
| Adsorbent | Optimum pH | pHpzc | Adsorption mechanism | Ref. |
|---|---|---|---|---|
| Montmorillonite-biochar | 11 | 6.9 | Electrostatic interactions, H-bonds, pore-filling | [100] |
| Urea N-doped biochar | 5.0 | 4.0 | H-bonds, pore-filling, π–π EDA | [135] |
| N-doped/activated cocoa shell biochar | 5.0 | 4.1 | Pore-filling, H-bonds, π–π EDA, ion exchange, electrostatic attractions | [98] |
| UIO-66-NH2 nanomaterials | 8.0 | – | Electrostatic interactions, π–π interactions, H-bonds | [9] |
| Ni-Al LDH | 7.0 | 7.3 | Electrostatic interactions, anion exchange, hydrophobic interactions | [34] |
| Silica | 8.2 | 9.0 | Electrostatic interactions | [154] |
| Ferrihydrite nanoparticles | 5.5 | – | Electrostatic interactions, complexation | [155] |
| Bentonite-sludge biochar composite | 6.0 | – | H-bonds, complexation, precipitation, Electrostatic interactions, π–π interactions | [8] |
| Pretreated barley straw | 6.7 | 4.1 | Electrostatic attractions, H-bonds, π–π interactions, π–π EDA | [111] |
| Polydopamine microspheres | 7.0 | 6.3 | H-bonds, electrostatic interactions, π–π interactions | [80] |
| Microplastics | 5.0 | – | π–π conjugation, H-bonds, ion exchange, electrostatic interactions | [7] |
| Dissolved organic matter | 7.0 | – | π–π interactions, electrostatic interactions, H-bonds, van der Waals forces | [4] |
| (Fe/Zn + H3PO4)-modified sludge biochar | 7.0 | 2.2 | H-bonds, π–π interactions, electrostatic interactions, complexation | [133] |
| N rich—Calotropis gigantean fiber | 8.0 | – | Hydrophobic interactions, electrostatic interactions, H-bonds, π–π stacking interactions | [125] |
| Loofah AC | – | – | Physisorption, π–π interactions | [89] |
| Magnetic biochar from furfural residue | 4.0 | 3.4 | Electrostatic attractions, π–π EDA, van der Waals forces | [138] |
| Microplastics | 5.0 | 4.5 | Electrostatic interactions, π–π interactions, H-bonds, polar-polar interactions, van der Waals forces | [12] |
| Rice husk (Oryza sativa) | 6.2 | 5.2 | Electrostatic interactions, H-bonds | [16] |
| Coffee husk (Coffea arabica) | 6.2 | 4.1 | Electrostatic interactions, H-bonds | [16] |
| Montmorillonite | 4.5 | – | Complexation | [157] |
| Functionalized CNTs | – | – | π–π EDA, H-bonds | [145] |
| Iron ore waste | 7.0 | 8.5 | Cation exchange | [15] |
| Magnetic porous carbon-based sorbent | 7.0 | 7.6 | Electrostatic interactions, hydrophobic interactions, H-bonds, π–π EDA | [91] |
| Hematite/biochar composite | 4.0 | 7.7 | π–π EDA, H-bonds, ion exchange, complexation | [139] |
| Pyrite/biochar composite | 10 | 4.0 | π–π EDA, H-bonds, ion exchange, complexation | [139] |
| rGO/magnetic composites | 6.2 | – | π–π interactions, electrostatic repulsion | [134] |
| Potato stem/clay biochar composite | 11 | 7.8 | Electrostatic interactions, hydrophobic interactions, H-bonds, π–π EDA | [10] |
| Layered chalcogenide | 4.0 | – | Electrostatic attractions, π–π stacking interactions | [115] |
| Mg/Fe layered biometallic hydroxide | 6.0 | – | Coordination bonds, H-bonds | [127] |
| Activated magnetic biochar | 7.0 | – | π–π interactions, electrostatic force, pore fillings | [78] |
| Amine-functionalized magnetic bamoboo-based AC | 6.0 | 8.2 | π–π EDA, electrostatic interactions, hydrophobic interactions, H-bonds | [33] |
| KOH-modified biochar | 7.0 | – | Electrostatic interactions, π–π EDA, H-bonds | [158] |
| Chitosan/γ-Fe2O3 composites | 7.0 | – | H-bonds | [86] |
| Iron-doped activated alumina | 6.5 | 6.5 | Cation bridging, surface complexation | [110] |
| Lotus stalk-based AC | 5.5 | 5.4 | Hydrophobic interactions, cation exchange, π–π EDA | [110] |
| Carboxylated WMCNTs | 5.4 | 3.5 | Electrostatic interactions, H-bonds | [121] |
| Macroporous resin | 5.4 | – | Hydrophobic effect | [121] |
| Hypercrosslinked resin aminated polystyrene resin | 5.4 | 4.8 | Micropore fillings, electrostatic interactions, H-bonds, π–π EDA, hydrophobic effect | [121] |
| Fe-MCM-41 | 3.0 | 3.3 | Hydrophobic effect, surface complexation, π–π interactions, electrostatic interactions | [101] |
| Pretreated barley straw | 7.0 | – | π–π EDA, H-bonds, electrostatic interactions, hydrophobic interactions | [90] |
| Pomelo peel-based biochar | 3.0 | 11 | Cation exchange, H-bonds | [104] |
| γ-Fe2O3/biochar | 5.0 | 5.9 | Cation exchange, H-bonds, hydrophobic interactions | [104] |
| H2SO4-treated termite feces | 8.0 | 1.7 | π–π interactions, H-bonds, electrostatic interactions | [5] |
| Fe/Cu oxides nanocomposites | 7.0 | 3.7 | Electrostatic interactions, surface complexation, H-bonds, π–π EDA | [103] |
| Shaddock peel-derived N-doped AC | 7.0 | 8.0 | π–π EDA, hydrophobic effect, H-bonds, electrostatic interactions, Lewis acid-base effect | [102] |
| Carbon/montmorillonite hybrid | 7.0 | 2.0 | H-bonds, electrostatic interactions, π–π EDA | [2] |
| MCM-41 mesoporous silica | 7.0 | – | π–π interactions, hydrophobic interactions | [130] |
| Graphene oxide | 7.0 | 3.9 | Van der Waals force, π–π interactions, hydrogen bond donor and acceptor | [17] |
| Fe/mesoporous silica | 7.0 | 3.6 | Electrostatic interactions, n- π EDA, H-bonds, surface complexation | [128] |
| Cu/mesoporous silica | 7.0 | 5.1 | Electrostatic interactions, n- π EDA, H-bonds, surface complexation | [128] |
| Polydopamine microspheres | 6.0 | 6.3 | Electrostatic interactions, H-bonds, π–π stacking interactions | [80] |
| 3D pretreated peanut shell/graphene oxide | 6.2 | – | Electrostatic interactions, H-bonds, π–π conjugation, hydrophobic effect | [118] |
| Pomelo peel-derived AC/phosphoric acid | 7.0 | 6.3 | Electrostatic H-bonds, hydrophobic interactions | [126] |
| Luffa sponge biochar | 6.0 | 1.8 | Cation exchange, electrostatic interactions | [3] |
| Temperature-switchable graphene oxide | 7.0 | – | π–π EDA, H-bonds | [159] |
| MOF/graphene oxide composite | 7.0 | – | Electrostatic interactions, π–π interactions, H-bonds | [83] |
| Carbon/montmorillonite hybrids | 5.0 | – | π–π EDA, electrostatic interactions | [116] |
| Magnetic biochar from salix mongolica | 9.0 | 5.8 | π–π dispersion, hydrophobic interactions, H-bonds, electrostatic interactions | [120] |
| Hydroxyapatite/polymeric nanocomposite | 7.0 | 7.2 | Physisorption | [6] |
| Iron-trimesic MOFs | 7.0 | 3.6 | Coordination bonds, pore filling, π–π stacking interactions | [112] |
| Cassava dreg biochar | 7.0 | – | H-bonds, π–π interactions | [160] |
| Fe/Cu oxides composite particles | 8.1 | 4.0 | h-bonds, π–π stacking interactions, surface complexation, hydrophobic interactions | [148] |
| Humic acid | 3.0 | – | Cation exchange | [161] |
| MgO/chitosan/graphene oxide | 7.0 | 5.5 | Electrostatic interactions, π–π EDA | [92] |
| MIL-101(Cr)-SO3H | 7.0 | – | Electrostatic interactions | [99] |
| UiO-66-NH2@TpTGcl | 8.0 | – | Electrostatic interactions | [117] |
| ZIF-8 | 6.0 | – | Electrostatic interactions, π–π stacking interactions | [147] |
| Mg-Al-CO3-LDH | 8.7 | 8.7 | Electrostatic attraction | [136] |
| Mg-Al-Cl-LDH | 8.0 | 9.5 | Electrostatic attraction, anion exchange | [136] |