Removal of Ni²⁺ Ions from Aqueous Solution by Sorption into Poly(Acrylamide–co–Sodium Acrylate) Hydrogels

Abstract

In this study, removal of Ni (II) ions from aqueous solution by sorption into poly(acrylamide–co–sodium acrylate) hydrogels has been examined by a batch equilibration technique at 30°C. The sorption process follows a Langmuir–type behavior, with the extent of sorption of Ni (II) ions depending upon composition of the co–polymeric gels, presence of other ions in the solution, and temperature of the system. Low temperature favors the sorption process. The various kinetic and absorption parameters, such as rate constant for sorption, intraparticle diffusion rate constant, Langmuir constant, and absorption capacity have been evaluated. The activation energy was found to −3.556 kJ mol⁻¹. Finally, various thermodynamic parameters have also been calculated to elucidate the mechanism involved in the sorption process. The negative values of enthalpy change and the free energy change indicate the exothermic and spontaneous nature of the sorption process, respectively. Similarly, negative entropy change suggests faster interaction with the active sites of sorbent.

Keywords:

• sorption
• Langmuir isotherm
• ion–exchange
• activation energy

5 Acknowledgement

The authors are thankful to Dr. S.L. Dengre, Head of the Chemistry Department for providing work facilities.