Lead removal in aqueous solution using polyacrylamide-based cryogels as adsorbent: Balance study in batch mode

Abstract

The objective of this research was to remove lead (Pb²⁺) ions from aqueous solutions using macroporos polyacrylamine gel (MPAAG) called cryogels as an adsorbent material. The MPAAG, were prepared by a free radical co-polymerization reaction of acrylamide (AAm) and allyl glycidyl ether (AGE) and N, N-methylene-bis (acrylamide) (MBAAm) bonded to epoxy functional groups (epoxy-pAAm) at a concentration of 7,5%, the reaction was carried out at -12 ^oC for 1 hour. After the preparation process, MPAAG was evaluated by binding the tris (2aminoethyl) amine (TREN) ligand groups followed by bromoacetic acid (BA). The presence of the amide and carboxyl group in the structure of the cryogels allowed the removal of lead to apply in aqueous solutions. The ability to remove lead on the MPAAG-TBA has been determined at different pH, metal concentrations and contact times. The technique used for the determination of lead in the aqueous solution was the Atomic Absorption Spectrophotometer (AAS). The maximum adsorption capacity of lead on the MPAAG-TBA was 10,78 mg/L at pH5 in 30 minutes. Adsorption equilibrium was performed at concentrations of 20,72; 41,44; 82,88 and 165,75 mg/L respectively of lead ions on the MPAAG-TBA results obtained were adjusted with the Langmuir and Freundlich model. The maximum adsorption capacity was determined by the Lagmuir model, the adsorption intensity (R_L) values ​​were lower than one, indicating that the adsorption of lead on the MPAAG-TBA is favorable; however it did not fit the model in the first two concentrations. The regression coefficient (R²) was used the Freundlich model and the intensity values ​​(n) were found in the range of 1 to 10 considering the process of lead removal on the MPAAG-TBA was favorable. The results indicate that MPAAG-TBA criogels could be used as adsorbent material to remove ions Pb²⁺ present in aqueous solution at low concentration.