Abstract
The present study developed novel functionalized corncobs introducing brushes with dense and active carboxyl groups (–COOH), named MC-g-PAA, for the highly efficient adsorption of Pb2+ from aqueous solutions. MC-g-PAA were synthesized via atom transfer radical polymerization (ATRP) and characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The amount of Pb2+ adsorbed on MC-g-PAA by hydrolysis with t-BuOK was 2.28 times greater than that with NaOH, attributed to the larger steric effect of t-BuOK, which reduced the hydrolysis of the bromo-ester groups. The influence of different parameters including the solid/liquid ratio, working solution pH, sorption temperature, and initial concentration and sorption time on the adsorption of Pb2+ were investigated in detail in batch experiments. Thermodynamic studies have shown that the adsorption process was spontaneous, endothermic, and accompanied by an increase in randomness. A better fit for the isotherm data was obtained using the Langmuir model than for the other four models and the maximum amount () of Pb2+ adsorbed on MC-g-PAA was 342.47 mg/g, which is 21.11 times greater when compared with that of pristine corncobs (16.22 mg/g). The adsorption of Pb2+ on MC-g-PAA was very fast and followed the pseudo-second-order kinetic equation with a correlation coefficient of 0.99999. This monolayer adsorption process was dominated by chemical adsorption, and may proceed according to complexation and electrostatic interactions between Pb2+ and the carboxylate groups. This study indicated that MC-g-PAA could be successfully used as an adsorbent for the removal of Pb2+ from aqueous solutions due to its excellent efficiency.
Highlights
Traditional methods for the removal of Pb2+ from aqueous solutions such as chemical precipitation, ion exchange, oxidation, and membrane processes may be inefficient or extremely expensive, especially when the concentration of Pb2+ in solution is low, resulting in an environmental issue.Adsorption is a more effective and widely adopted method for the removal of Pb2+ with low concentration
The prepared MC-g-poly(methyl acrylate) (PMA) were functionalized through hydrolysis with alkali in order to introduce high densities of carboxyl groups (–COOH) on the corncobs (MC-g-poly(acrylic acid) (PAA))
The brushes with dense and active carboxyl groups (–COOH) was successfully introduced onto the corncobs via the atom transfer radical polymerization (ATRP) technique, obtaining functionalized corncobs (MC-g-PAA) as novel adsorbents, which were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM)
Summary
Traditional methods for the removal of Pb2+ from aqueous solutions such as chemical precipitation, ion exchange, oxidation, and membrane processes may be inefficient or extremely expensive, especially when the concentration of Pb2+ in solution is low, resulting in an environmental issue. Have revealed that carboxylic groups (–COOH) have a strong adsorption affinity of metal ions, which can significantly improve the adsorption capacities of the adsorbent for metal ions It would be ideal if corncobs could be functionalized by introducing polymer brushes with dense and active carboxyl groups (–COOH). Novel functionalized corncobs introducing brushes with dense and active carboxyl groups (–COOH), named MC-g-PAA, were synthesized as adsorbents via atom transfer radical polymerization (ATRP) with the objective to investigate in detail the influence of different parameters including the solid/liquid ratio, working solution pH, sorption temperature, and the initial concentration and sorption time on the adsorption of Pb2+ , which is a hazardous metal ion.
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