Poly [2,5-(1,3,4-thiadiazole)-benzalimine] (TDPI) resin was prepared as a new adsorbent for removing Pb2+, Cu2+, Ni2+, and Cd2+ ions from an aqueous solution. The maximum adsorption capacities of TDPI adsorbent for all four metal ions calculated from the Langmuir isotherm were found to be 437.2 mg/g for Pb2+, 491.6 mg/g for Cu2+, 493.7 mg/g for Ni2+, and 481.9 mg/g for Cd2+, respectively, which are higher than other polymeric chelating adsorbents (Table 4). The adsorption process for the metal ions onto TDPI fits well to pseudo-second-order kinetic model, and the best adsorption isotherm was found to be the Redlich–Peterson model. The adsorption process is spontaneous (ΔGads < 0), exothermic (ΔHads < 0), and reversible (ΔSads < 0). For regeneration purposes, 0.1 N H2SO4 was found to be sufficient. Due to its good thermal, chemical stability, high adsorption capacities, and re-usability, TDPI exhibits potential application for efficient removal of Pb2+, Cu2+, Ni2+, and Cd2+ ions from aqueous effluents.
Comparison of adsorption capacities of various polymeric adsorbents with different functional groups for Pb2+, Cu2+, Ni2+, and Cd2+ ions
| . | . | Adsorption capacity (mg/g) . | . | |||
|---|---|---|---|---|---|---|
| Adsorbents . | Functional groups . | Pb(II) . | Cu(II) . | Ni(II) . | Cd(II) . | Reference . |
| SBA-15 | 3-Aminopropytriethoxy silane | – | – | 14.10 | 23.70 | Shahbazi et al. (2011) |
| NH2–MCM–41 | –RNH2 – | – | – | 40.50 | 79.80 | Lam et al. (2007) |
| NH2–MCM–41 | –NH2 | 57.74 | – | 12.36 | 18.25 | Heidari et al. (2009) |
| NH2–SNHS | 3-Aminopropyltriethoxy-silane (APTES) | 96.79 | – | 40.73 | 31.29 | Najafi et al. (2012) |
| Mercerized cellulose (DIPCI) | Triethylenetetramine | 147.1 | 56.8 | – | 68.0 | Gurgel & Gil (2009) |
| Present work | Thiadiazole, imine | 437.2 | 491.6 | 493.7 | 481.9 | TDPI |
| . | . | Adsorption capacity (mg/g) . | . | |||
|---|---|---|---|---|---|---|
| Adsorbents . | Functional groups . | Pb(II) . | Cu(II) . | Ni(II) . | Cd(II) . | Reference . |
| SBA-15 | 3-Aminopropytriethoxy silane | – | – | 14.10 | 23.70 | Shahbazi et al. (2011) |
| NH2–MCM–41 | –RNH2 – | – | – | 40.50 | 79.80 | Lam et al. (2007) |
| NH2–MCM–41 | –NH2 | 57.74 | – | 12.36 | 18.25 | Heidari et al. (2009) |
| NH2–SNHS | 3-Aminopropyltriethoxy-silane (APTES) | 96.79 | – | 40.73 | 31.29 | Najafi et al. (2012) |
| Mercerized cellulose (DIPCI) | Triethylenetetramine | 147.1 | 56.8 | – | 68.0 | Gurgel & Gil (2009) |
| Present work | Thiadiazole, imine | 437.2 | 491.6 | 493.7 | 481.9 | TDPI |