Sorption of Methylene Blue onto Ionic Composite Hydrogels Based on Polyacrylamide and Dextran Sulfate: Kinetics, Isotherms, and Thermodynamics

Abstract

Ionic composite hydrogels based on polyacrylamide (PAAm) and dextran sulfate (DxS) have been prepared by radical polymerization at two temperatures: +20°C and −18°C, using DxS as physical entrapped polymer, acrylamide (AAm) monomer, N,N^’-methylenebis(acrylamide) (BAAm) as cross-linking agent, ammonium persulfate as radical initiator, and N,N,N’,N’-tetramethylethylenediamine as accelerator of free-radical polymerization. The PAAm/DxS composite hydrogels were tested as sorbents for Methylene Blue (MB) from aqueous solution by the batch procedure. The effect of contact time, initial dye concentration, and temperature on the dye sorption onto composite hydrogels has been investigated. The modeling of the experimental data by applying different kinetic and isotherm models was also performed.

Keywords:

• hydrogels
• isotherms
• Methylene Blue
• polyacrylamide
• sorption

ACKNOWLEDGEMENTS

This work was supported by CNCSIS-UEFISCSU, by the project PNII-IDEI ID 981/2008. M.V. Dinu is very grateful for the financial support by the European Social Fund – ‘‘Cristofor I. Simionescu'’ Postdoctoral Fellowship Programme (ID POSDRU/89/1.5/S/55216), Sectoral Operational Programme Human Resources Development 2007–2013.

Notes

^a Swollen state porosity estimated by Eq. (1);

^b Dry state porosity estimated by Eq. (2).

^c Swelling ratio determined by Eq. (3).