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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.

Table 4

Comparison of adsorption capacities of various polymeric adsorbents with different functional groups for Pb2+, Cu2+, Ni2+, and Cd2+ ions

Adsorption capacity (mg/g)
 
AdsorbentsFunctional groupsPb(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)
 
AdsorbentsFunctional groupsPb(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 

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