Table 1.
Chemicals used for synthesizing adsorbents by sol-gel method, adsorbed heavy metals, maximum adsorption capacity, pH and temperature for adsorption of heavy metals from waters.
| Chemicals (interacting group) | Heavy metal [qmax, pH and t (°C)] | Isotherm | Reference |
|---|---|---|---|
| Pyromellitic acid dianhydride/phenylaminomethyl trimethoxysilane (–COOH) | Pb2+ (7.16 mmol/g, 5, room) | Langmuir | [142] |
| Pyromellitic acid dianhydride/phenylaminomethyl trimethoxysilane (–COOH) | Cu2+ (0.28 mmol/g, 4, room) | Langmuir | [143] |
| Pb2+ (1.56 mmol/g, 5, room) | Langmuir | ||
| 3-Thiocyanatopropyltriethoxysilane/TEOS (–SH) | Cd2+ (87.7 mg/g, 5, 25) | Langmuir | [144] |
| 3-[2-(2-Aminoethylamino)ethylamino]propyl-trimethoxysilane (Cd2+– imprinted hybrid sorbent) (–NH2) | Cd2+ (77.2 mg/g, 6, 25) | Langmuir | [145] |
| Cd2+-imprinted mercapto-functionalized silica gel (–SH) | Cd2+ (83.89 mg/g, 6, 27) | Experimental | [146] |
| Non-imprinted mercapto-functionalized silica gel (–SH) | Cd2+ (35.91 mg/g, 6, 27) | Experimental | – |
| Fe3+-imprinted cyanato-functionalized silica gel (–C≡N) | Fe3+ (35.6 mg/g, 3, 20) | Experimental | [147] |
| 3-Glycidyloxypropyltrimethoxysilane/potassium tert-butoxide/titanium isopropoxide (oxygen atoms of adsorbent) | Pb2+ (181.2 mg/g, 5.5, room) | Langmuir | [148] |
| Cu2+ (44.64 mg/g, 5.5, room) | Langmuir | ||
| Cd2+ (35.84 mg/g, 5.5, room) | Langmuir | ||
| Zr(OCH2CH2CH3)4/3-mercapto-1-propanesulfonic acid (–SH) | Pb2+ (0.36 mmol/g, neutral, room) | Experimental | [149] |
| Hg2+ (0.87 mmol/g, neutral, room) | Experimental | ||
| Ti(OCH2CH2CH3)4/3-mercapto-1-propanesulfonic acid (–SH) | Pb2+ (1.24 mmol/g, neutral, room) | Experimental | – |
| Hg2+ (1.41 mmol/g, neutral, room) | Experimental | ||
| 7-Amine-4-aza-heptyltrimethoxisilane/TEOS (amine group) | Pb2+ (36.64 mg/g, neutral, room) | Langmuir | [150] |
| 10-Amine-4-aza-decyltrimethoxisilane/TEOS (amine group) | Pb2+ (30.27 mg/g, neutral, room) | Langmuir | – |
| 3-Chloropropyltrimethoxysilane/TEOS (nitrogen center of sorbent) | Ni2+ (0.47 mmol/g, 4.5, room) | Langmuir | [151] |
| 3-Aminopropyl triethoxysilane/TEOS (–NH2) | Pb2+ (45.45 mg/g, 6, 25) | Langmuir | [152] |
| Cu2+ (35.71 mg/g, 6, 25) | Langmuir | – | |
| 3-Chloropropyltrimethoxysilane/TEOS (nitrogen center of sorbent) | Mn2+ (0.35 mmol/g, 4.5, room) | Langmuir | – |
| Amino-terminated dendrimer-like PAMAM polymer/silica gel (amino content 1.91 mmol/g) (–NH– and –NH2) | Cu2+ (78.7 mg/g, ethanolic, 25) | Langmuir | [153] |
| 2-Aminoethyl-3-aminopropyltrimethoxysilane/poly(dimethyl siloxane) (–NH/NH2) | Cu2+ (1.2 mmol/g, ethanolic, 25) | Langmuir | [154] |
| Ni2+ (0.37 mmol/g, ethanolic, 25) | |||
| Fe3+ (1.3 mmol/g, ethanolic, 25) | |||
| Bis[3-(triethoxysilyl)propyl]disulfide/TEOS (–S–S–) | Cd2+ (26.8 mg/g, 6, 25) | Langmuir | [155] |
| Pb2+ (56.7 mg/g, 6, 25) | Langmuir | ||
| Cu2+ (13.3 mg/g, 6, 25) | Langmuir | ||
| Salen(NEt2)2/silica gel (–OH and –N(C2H5)2) | Cu2+ (4.36 mg/g, 11, room) | Langmuir | [156] |
| Mn2+ (2.34 mg/g, 11, room) | Langmuir | ||
| Pb2+ (10.06 mg/g, 11, rom) | Langmuir | ||
| Zn2+ (11.3 mg/g, 11, room) | Langmuir | ||
| 2-Acrylamido-2-methylpropanesulfonic acid/silica gel (–OH, –NH– and –SO3H) | Cu2+ ( 0.66 mmol/g, ethanolic, 25) | Langmuir | [157] |
| Amino-terminated dendrimer-like polyamidoamine polymer/silica gel (–NH2) | Pd2+ (0.7 mmol/g, neutral, room) | Experimental | [158] |
| Pt4+ (0.41 mmol/g, neutral, room) | Experimental | ||
| Au3+ (0.12 mmol/g, neutral, room) | Experimental | ||
| Polyethylene glycol/3-mercaptopropyl trimethoxysilane (–SH) | Cu2+ (0.4 mmol/g, 4, 40) | Langmuir | [159] |
| Polyvinilalcohol/3-(2-aminoethylamino)propyl trimethoxysilane (–NH/NH2) | Pb2+ (67.6 mg/g, 5, 30) | Langmuir | [160] |
| Activated alumina/3-mercaptopropyl trimethoxysilane (–SH) | As(III) (9.28 mg/g, 7, room) | Experimental | [161] |
| N-[3-(trimethoxysilyl)propyl]-ethylenediamine/TEOS (–NH2) | Pt2+ (139 mg/g, 3.05, 25) | Langmuir–Freundlich | [162] |
| Escherichia coli/TEOS (immobilized E. coli cells) | Cd2+ (79.9 mg/g, 5.7–6.2, 25) | Langmuir | [163] |
| N,N-(dipropylcarbamothioyl)thiophene-2-carboxamide/TEOS (–S–, C=O and amine groups) | Cd2+ (3.89 mg/g, 7, 30) | Langmuir | [164] |
| SiNSSH/TEOS (via sulfur or nitrogen atoms of sorbent) | Hg2+ (8.52 mmol/, neutral, 25) | Langmuir | [165] |
| Pb2+ (1.90 mmol/g, neutral, 25) | Langmuir | ||
| Cu2+ (1.66 mmol/g, neutral, 25) | Langmuir | ||
| Ni2+ (1.44 mmol/g, neutral, 25) | Langmuir | ||
| Co2+ (1.26 mmol/g, neutral, 25) | Langmuir | ||
| 3-Aminopropyltriethoxysilane/TEOS (–NH2) | Ni2+ (31.29 mg/g, 4.5, 25) | Langmuir | [166] |
| Cd2+ (40.73 mg/g, 4.5, 25) | Langmuir | ||
| Pb2+ (96.79 mg/g, 4.5, 25) | Langmuir | ||
| 3-Chloropropyltrimethoxysilane/aniline/TEOS (–NH–) | Co2+ (0.32 mmol/g, 4.5, 25) | Experimental | [167] |
| Zn2+ (0.34 mmol/g, 4.5, 25) | Experimental | ||
| Cd2+ (0.12 mmol/g, 4.5, 25) | Experimental |